Today, we hear a lot about “modern rim shape”. What’s behind this is simply wider rims. Some have succeeded in convincing cyclists that a wide rim makes a better wheel and nowadays, each brand launching a new wheel has to make sure its rims are at least 1mm wider than their competitors.

But what they have forgotten in their equation is the tyre. Nobody talks about the shape that the tyre takes when the rim width increases. Nobody talks about what is the right size tyre to put on those wide rims and everybody forgets about safety standards and norms.

So, talking about rim width alone is only doing half the job and it becomes pointless. It’s only when you look at both variables of the equation (tyre + rim) that it makes sense. Performance and safety are also at stake.


2.1 Rim Width

Rim width is measured at 2 points :

  • Outer width (A): most often measured at the brake track
  • Inner width (B): measured inbetween the rim hooks

The outer width (A) will mostly have an influence on the look of the rim, but also on the aerodynamics of the wheel-tyre system. But it has zero influence on the comfort, rolling efficiency or tyre shape.

The inner width (B) is the one that defines the tyre shape, by pinching its sidewalls. It influences the air volume and tyre width.

So, this is really the one measurement we have to look at when discussing rim width to tyre width in the respect of rolling efficiency, comfort and air volume.


2.2 Tyre Width

As we just mentioned, the width (section) of a tyre is directly linked to the rim on which it is mounted. It is also linked to the amount of air pressure.

To neutralise those variables, a norm defines how a tyre section should be measured. This norm called ETRTO (European Tyre and Rim Technical Organisation) has defined all the safety and performance parameters that a tyre and rim should respect to be compatible with one another. Although the name says “European”, this organisation’s work is the reference for all international and national norms in the bike industry (ISO, CEN and their national declination).

To measure a tyre section, ETRTO has defined:

  • The rim width on which each tyre section must be measured
  • The pressure at which it must be measured, taking into account that the casing of a brand new tyre will stretch within the first 24 hours of inflation, so the measurement should be done after those 24 hours

For example, a tyre said to be a section of 23mm should be measured on a rim of 15mm internal width at 6 bars (87 PSI) after 24 hours.
A tyre said to be a section of 28mm should be measured on a rim of 17mm internal width at 6 bars (87 PSI) after 24 hours.
Only the casing of the tyre should be measured. If the tyre has side knobs or an extra rubber layer down on its shoulder, this should not be taken into account.

But at the end of the day, it’s the manufacturer’s responsibility to indicate the right dimension of the tyre and one should always be able to rely on those indications so the tyre choice can be made safely.


3.1 How the tyre section influences the rolling resistance and the tyre pressure

To increase your speed for the same effort, the Rolling Resistance Coefficient (Crr) must be as low as possible.
Our measurement shows that the Crr decreases when the tyre pressure increases:

However, the Crr decreases when the tyre section increases. The graph bellow shows that at equal tyre pressure and rim width, the Crr gap between a 23mm and a 25mm tyre (for a given tyre) is about 0.3/1000:

So, when reading the 2nd graph in light of the 1st one, you can see that this 0.3/1000 gap is equivalent to a pressure difference of 1.5 bars / 22PSI.

In short, the Crr of a 23mm inflated at 100PSI, is the same as that of a 25mm tyre inflated at 80 PSI.
While increasing the tyre section, the rolling resistance is maintained, while hugely improving your comfort.
And if your goal is to lower your rolling resistance, you can just go for a wider tyre and keep the same riding pressure.

The same would go with even bigger tyres (28mm) but then weight and inertia will come into account and there will be a trade off between rolling resistance, low inertia and weight.


3.2 Better ride quality with both wider rims and wider tires

The “ride quality” is influenced by many factors and cannot be reduced to just one single number. It’s more a question of “feeling” and, as such, it is a personal matter and doesn’t have just one universal definition.

However, in most instances, cyclists refer to ride quality in terms of comfort and high “speed to effort” ratio.

The air volume is a good way to look at it.
More air volume means a stronger protection against snakebite, by increasing the distance of the gap between the ground and the rim edge.
As a result tyre pressure can be lowered to improve comfort and traction without increasing the chances of pinch flats.


So, how to increase the air volume? Here are few measurements:

Width Width change Air volume difference (mL) Difference
17mm rim Tyre 23–>25 144,25 15,0%
25mm tyre Rim 17 –> 19 24,04 2,2%

A 2mm increase of the tyre width alone has a much higher impact (+15%) than a 2mm increase of the rim width alone (+2.2%).
And of course, the combination leads to both air volume increases, which is even better.


3.3 Better aerodynamics with wider rims

For a long time the general thinking was that to be faster a part (let’s say a wheel) had to be narrow to reduce its frontal area. It’s true, but this doesn’t take into account real world conditions where the wind doesn’t always blow right in front of the cyclist.

With deep section rims becoming more and more popular it also became obvious that the ease of handling of such wheels had to be improved.

Based on those 2 factors research began to improve the wheel’s aerodynamic performance. Very soon, two facts became obvious:

  1. The tyre had to be part of the equation: you can spend hours developing the right wheels but as soon as you change the tyre the behaviour of the system in the wind changes dramatically.
  2. The best way to achieve amazing aerodynamic performance is to define a rim-tyre shape that is as close as possible to a NACA airfoil profile.

The widest point of such a profile is quite far from its leading edge. On a bicycle wheel, that means that the widest point of the rim-tyre combination must be below the tyre itself. In short, the rim has to be wider than the tyre.

Doing that, the trailing edge radius gets rounder to the benefit of the wheel’s stability in a crosswind.

The frontal drag (at 0° of yaw angle) becomes higher but at every other yaw angle this design lowers the drag and improves the stability of the wheel.

The graph bellow compares two 40mm wheels fitted with the same 23mm tyre. The blue curve is a 19mm wide rim, whereas the pink one is a 25mm wide rim.

The gap is 2,5 Watts in favour of the wide rim, based on our yaw angle weighted law (

But, if you use a 25mm tyre on the 25mm wide rim you’ll be back to the blue curve and even higher since the frontal area has become bigger!

So, widening the rim for aero benefits is really efficient as long as the tyre remains narrower than the rims widest point.

If you think I have a wide rim, so I can ride a wide tyre, thats true but means that youll annihilate the aero benefits of the wide rim. But maybe youre pursuing another goal, like more comfort or lower rolling resistance


Tyre width and rim width have to be made for each other.

If the tyre is too wide relative to the rim width, it will not be well supported by the rim and the ride may feel flimsy. There is also a higher chance of pinch flats.

Equally, if the tyre is too narrow relative to the rim width, it will get a flat shape that is bad for rolling efficiency and ride feel. For a MTB tyre this can result in the side knobs constantly coming in contact with the ground even in a straight line. The tyre will not deform as it is supposed to and the grip and rolling efficiency is no longer guaranteed.

But most importantly, there is a safety issue.

Some tests performed by several tyre manufacturers, including Mavic, have shown that a narrow tyre on a wide rim has a higher chance of severely coming off the rim.

Norms are setting barriers and rules to ensure rider safety. ISO 4210 refers to the ETRTO manual that provides a chart to show which combinations are possible and safe :

This chart says for a given tyre width (left column) which rim widths can be used (middle column for hookless rims, right column for regular rims).

Example of reading: a 23mm tyre can be safely mounted on traditional rims of 13mm to 16mm (internal width). On any rim wider than 16mm, it is not possible to use a 23mm tyre safely.

On the other hand, a rim that is 21mm wide internally, can only accept tyres from 35mm and above.

This is where Mavic and our Wheel-Tyre System helps the rider make the best choice. We deliver our wheels with the tyre that perfectly matches the rim in terms of performance, safety and dimensions.


  • A wider tyre and rim allow for better rolling efficiency while improving comfort
  • A wider rim improves aerodynamic performance (low drag and high stability) as long as the tyre width doesnt increase at the same time
  • Safety is a key item. Norms have defined the working parameters of tyre to rim widths and should always be respected

For safety matters always make sure your wheel and your tyre bear the ETRTO mention and that their sizes match according to the chart in this article.


To find out the best combination for rim and tyre, taking into account who you are and what kind of ride and road you’re riding, download the MyMavic app for iOS and Android.


  • Fascinating!

    But what do you offer at the wider outer rim dimensions to compete with the new fashion of wide section rims.

    I have Cosmic Carbone SLE and i am a big fan. However I see a lot of negative comments about you preference for narrow rim profile and I wonder why. See example below:

    “Although admirably quick in calm winds, the Cosmic Carbone’s antiquated aero profile – it was introduced back in 2008 – is also easily blown around in crosswinds, plus the tyre bed is inordinately narrow. Whereas more modern rims now come with nearly 20mm of width between the bead hooks (thus yielding better ride quality, handing, and aerodynamic performance), the Cosmic Carbone carries on with just 13mm. Unless Mavic has a dramatic redesign coming for 2016, we’d much rather see something more progressive like a HED Jet.”

    That is damning criticism but it seems from your analysis that he has a point…

    • Hopefully you love your wheels and they haven’t become more unstable since you read the Bike Radar article 
      This article is mainly about air volume and tyre / rim compatibility. In that respect, the only rim dimensions that matters, is the inner rim width, as this is the one that condition the tyre shape and air volume.
      When it comes to outer dimension, as we say in the article also, this has only an impact on aerodynamics, and mostly on crosswind stability. But also on weight, in a bad way.
      However, in 2012 and 2013, we’ve been busy designing the fastest aerodynamic wheel-tyre system on the market, the CXR family.
      In 2014 and 2015, we’ve focused our R&D resources on stepping up our Endurance and Performance wheel line, known as the Ksyrium family.
      So, you can imagine what our engineers are busy with at the moment…

  • I use a pair of R system SLR wheels on a full titanium Merlin. (yes forks as well) which gives a superb ride and performance. Can someone tell me if Rim tape is required for these wheels ?I am using 23 mm tyres at the moment but will try a pair of 25mm soon. will give an update later

    • Sweet bike and great match with the R-Sys SLR wheels ! No, rim tape is not needed on those wheels since the rim bed has no holes. Another 15g saved, and exactly where it matters most. 🙂


      • Thank you so much for your very quick reply. They are a delight to ride and I still can’t get over how much more comfortable they are to ride than my old very light wheels. I also have a pair of Elites on my old 531 Brian Rourke which is 80’s but you can’t believe how much difference it made to the performance and the comfort of the bike. They also look GREAT as well

  • Does this take tubular rims and tires into account?
    I currently use two sets of wheels (tubulars). 26mm at brake track (and widest point)/38mm deep and set two is 28mm at brake track (30mm aero width)/56mm deep.
    On the widest rim i use a 23mm tubular and there is no issue holding the tire even though erto must be high. Both these sets rides more stabile than my previous CCU which i found to be best with 22mm tubulars, but still more twitchy.
    Real world riding seems to tell me the widest and deepest of them handles more stabile than my previous shallower and less deep rims. I might be off here, but i find crosswinds and side winds to be the what affects steering and handling the most. Stability seems to be almost as important as aero for reasons of safty and holding speed!? I read as much technical as i can to get an insight of how this works, but for true riding i have nothing negative to say about any of these two sets. The widest and deepest set is my favorite to my surprise.

    •  The topic of compatibility between rim width and tyre width is only a clincher one. Tubular is not affected by this and there is no “internal width” on a tubular rim (no hooks for holding the tyre beads). Indeed, what’s important in a tubular set up is the gluing surface. If the rim is really wide, then, the gluing surface will be dictated by the tubular tyre itself, not that much the rim. Now, if the rim gets too narrow, there might be issues. But we are not aware of any tubular rim that would be that narrow nowadays.
      As far as aero is concerned, only the outside rim width matters and it should be considered relative to the tyre width. From our studies in CFD, wind tunnel and field testing, we found the optimal combination being a 23mm tyre with a 27mm rim (outside width) at its widest point that should be just below the brake track. This is the design we use on our CXR wheels. It has proven to offer super low drag and great side wind stability. Because you’re right, low drag is nothing if you can’t control the bike !
      23mm tyre and 27mm outside width is fairly easy to design on a tubular set up. But much more difficult on a clincher set up. Indeed, the inner rim width for a 23mm tyre should not exceed 16mm (safety concerns, as defined by the ETRTO). As the outside width, needs to be 27mm, this means +11mm, so each rim sidewalls must be 5.5mm thick. Which becomes a tricky and possibly heavy design… Of course, we could use 25mm tyres, but that would increase the aero drag and to maintain the same stability, the rim would need to be even wider (29mm) and the design complexity will still be the same. Not even talking here about frame clearance and brake caliper compatibility…


  • Hi, great article and well written! I’m just a little confused as to the contradicting information regarding the tyre/rim combination benefits when compared to the ETRTO table accepted combinations.

    i.e. Its mentioned at the end of the article ‘For safety matters always make sure your wheel and your tyre bear the ETRTO mention and that their sizes match according to the chart in this article’, however in the aero /yaw angle test you used a 23mm wide tyre on 25mm and 19mm wide rims, both of these combinations are deemed ‘unsafe’ by the ETRTO chart?

    For instance, according to the chart , a 28mm tire is the smallest you can safely use with a 19mm rim and a 23mm tire can only be safely used with a 13-16mm rim?

    I currently have upgraded to wider rims (17mm) and have been researching this topic a lot, according to the ETRTO chart the smallest tires I can safely use on this rim are 25mm, however I prefer using 23mm, which I have read that some cyclists have no problem with but again this contradicts the safety measure.

    I have found it very hard to find a clear answer on what exactly can be used with my new 17mm rims and would love some expert advice on what the generally accepted tolerances are outside of the ETRTO chart?

    Is using 23mm tires on a 17mm rim actually ok as it is only one ‘movement’ outside the ETRTO paraments etc? (i.e. you can safely use 23mm tires on a 16mm rim according to ETRTO)

    In general is one movement outside the ETRTO parameters accepted, or do is there actually a much wider range that can be combined outside the chart with no real ill effects re: safety?

    Thanks and I would love your insight/clarification on this topic, much appreciated.


    • Thank you for your comment.

      First, we have to differentiate inner and outer width :

      • Outer width is used on our aero chapter as this is the parameter that influences drag. So, in that chapter, when we speak about 19mm or 25mm, we refer to the outer rim width
      • Inner rim width is what defines the compatibility with the tyre and the combination with the different tyre width. And this is what the ETRTO chart is all about.

      There is no direct link between inner and outer width. In general, the outer width is about 4mm wider than the inner width. But, in some cases, it can be very different. For example, our CXR Ultimate 60C is 13mm internal and 27mm outer.

      Your reading of the ETRTO chart is correct. When using a 17mm inner rim width, the minimum tyre width allowed is 25mm. It’s the same with a 16mm inner rim width.
      This norm is about safety and guarantees 100% safety if all conditions are fulfilled. It’s been proven that using a 23mm tyre on a 16mm inner rim width can, in some conditions, lead to the tyre coming off the rim suddenly.
      As a responsible and liable company, Mavic cannot put its customer in an unsafe situation, although it might be only a very small proportion of them. So, we cannot recommend set up that are out of the ETRTO / ISO requirements.
      That said, riders can freely decide to take their chance on this…

      But keep in mind that you have many benefits in using 25mm tyres : they roll faster, provides more grip and more comfort. The only drawback is they’re about 15 grams heavier (on the case of Mavic tyres). There is an interest in using a 23mm tyre for your front wheel (if your rim allows it) for getting more aerodynamism. Here is a magnitude order: for a rim with a high of 60mm (so aero-typed), the difference related to the aerodynamism between 23mm and 25mm for a front wheel is about 2W at 40km/h. This difference is reduced at lower speeds and lower rims.

      Best Regards


      • Thanks for clarifying re: external rim width on aero test, makes perfect sense (and very obvious in hindsight on my part!)

        After reading all of the science it certainly looks to be proven that 25mm tires have a benefit over 23mm re: speed/roll faster, although I must admit after trialling 25mm and 23mm tires in similar conditions on the same stretch of road x3 times each, the 25mm tires still felt ‘sluggish’ especially during acceleration and it ‘feels’ like I am working harder at speed. This very well may all be in my head after riding 23mm tires for many years, but I would be interested to know if you have had any anecdotal evidence of riders having the same experience when transitioning from 23mm to 25mm? (Note: Without doubt the ride is more comfortable)

        To confirm, the new wheels I have purchased have a 17mm inner width and 22mm external width.

        Good to know I was on the right track re: 25mm tires are the recommended minimum for 17mm inner rim width wheels re: ETRTO. Although then I guess you need to be sure that the tires you are buying are labelled correctly which as I understand from research can be another big problem re: incorrect labelling/non-standardised measuring re: PSI etc.

        Above in your response you mention that a 25mm tire is also the minimum recommended for a 16mm inner rim width (which in turn would mean that a 23mm tire could only be used safely with a 15mm inner rim width maximum), however the ETRTO chart appears to indicate that a 23mm tire can be used safely on a 16mm inner rim width? Confirming this is correct?

        When you mention that it has been proven that a 23mm tire can come off a 16mm inner rim width, is this referring to testing done outside the ETRTO testing? (by Mavic I assume?)

        I agree that a wheel company should only recommend combinations based on safety etc. and I commend Mavic for producing an article such as this to help educate riders, after much research on the topic this is by far the best/easiest to understand summary of the topic I have read re: wheel/tire combinations. I must say I am surprised that a number of major wheel companies appear to recommend combinations far outside the ETRTO chart, including the company I purchased my wheels off who actually state on their website that a 23mm tire can used on their wheels with an inner rim width of up to 19mm(!), which while may be possible, is hardly the right way to educate riders of the risk they may be taking by doing this.

        Thanks again for taking the time to respond, it is much appreciated. This is indeed very fascinating science!


  • OK but what’s the point of testing a 23mm tyre on a 25mm wide rim if according to the ISO 4210 chart that is not recommended? It does make sense to have a smooth transition from tyre sidewall to rim sidewall, therefore usually installing tyres the same size or smaller than the external width of the wheel set… but apparently that is unsafe? I asked Veloflex and Challenge and they do not recommend to use 23-622 on a 17C rim, for instance.

    I’ve seen some companies recommend different size ratios, say, OK to use 23mm tyres on our new super wide rim. Maybe this also depends on if the wheelset has been specifically designed to work with 23mm tyres no matter how wide they are? This is a bit confusing.

    • Once again, there is confusion between inner width and outer width of the rim (please see the last comment).

      In the aero section of this article, the rim width is the external one, as this is the one that defines the transition from the rim to the tyre.
      Our CXR tubular rims are 27mm wide (internal width doesn’t apply on tubular rims) and can safely be used with 23mm tubular tyre.
      Our new Cosmic Pro Carbon are 25mm wide outside and 17mm inside and indeed, ETRTO doesn’t recommend to use them with tyre smaller than 25mm, rules that we strictly follow.
      Our CXR Ultimate 60 Clincher is 25mm outer width, but 13mm inner width. Hence, it can safely be used with 23mm tyre. And this is the configuration that provides the lowest drag and highest crosswind stability, in full safety as long as tyre fit is concerned.

      We find it hard to understand how some companies can safely recommend configurations that are out of the norm, unless their rim would only be compatible with their own tyre. This the the only way for them to eventually guarantee the match.
      But if the rim can be used with any other tyre, then it is a big risk taken by this companies as they have no way to know what kind of tyre their consumer is going to use. Hence, how to guarantee safety ?

      Norms are here for this reason : when 2 different companies / manufacturers design and manufactures 2 items that are made to fit each other, it is only if BOTH OF THEM respect the norm that the consumer safety can be guaranteed.

  • 1- Where is your methodology?

    2- When you make graphs, don’t forget to give them a name and a number. The results you got in the second one could be very well attributed to the error margin of your testing instrument. With no methodology it is very hard to attribute any validity to your results. Have you tested multiple times? What are the conditions of testing, etc.?

    3- Again graph 2, what was the pressure? That’s the kind of thing you put in the graphic title…

    To me, it looks like a college student with excel spent a couple of hours to produce this article that is far from what an engineer talk should be like.

    • Dear reader,

      We agree with you: the scientific rigor that may require a thesis or a research paper is missing in this article. But the goal of this blog is not to be an engineer’s white paper, but rather a collection of our deliberately popularized methods.

      We can actually specify methodologies and explain our measurement protocols, with the sensitivity and precision of our instruments. But the article would be 5 times longer! Many readers would not read the article to the end.

      On the other hand, we do not want to publicly disclose some elements of our methodology that we want to keep confidential. For example, the way we measure our rolling coefficients (Crr).

      Hope you understand our desire.


  • Mavic Ksyrium Pro Exalith Clincher Wheelset.
    Hello, I am looking to purchase this wheel set, belive they are 15mm internal width, I would like to put 28mm tyres on, is this possible? and how much will I loose going to the 28mm as oposed to the 25 mm they are supliled with. is it worth the 28mm loss in performance to gain comfort on longer rides? thanks. Guy

    • Hello Guy,

      28mm tyre are totally compatible with Ksyrium Pro Exalith and their 17mm rim width.
      28mm tyre can roll fast if inflated high, but that’s probably not your objective if you’re trying to achieve a better comfort.
      They are 15 to 30 grams heavier than 25, depending on brands.
      But the added comfort they bring is very noticeable in longer rides even if it’s impossible to put a number on the performance gain passed the 4th hours for instance.

      So if your objective is to improve your performance on long rides, go for it, that should easily offset the extra few grams.

      Enjoy your rides !


  • Very interesting article thanks.
    Question: I have mavic a ksyrium equipe s wheelset that I believe are 15mm internal width and was looking to upgrade the tires to 25mm is this a good setup?


    • Hello,
      On your 15C Ksyrium Equipe you can safely use tyres up to 32mm.
      But the best performance will be reached using either a 23 or a 25mm.
      So, yes, you can use a 25mm tyre in full confidence !

  • Thanks for the chart it a very helpful
    It appears the 16mm rims can take 23 to 32
    And 17mm can take 25 to 52 mm tires is there a reason why the range of the 17 mm rim is so much bigger

    • Hello Jason,
      Thanks for your comment.
      The Engineering Design Information (EDI) of ETRTO is using formulas to calculate the possible tyre section + rim width combination, and ensure safety in all conditions.
      According to those formulas, the wider the rim gets, the broader the range of possible tyre gets, linked to lower tyre pressure.
      Furthermore, there are years of experience backing up those formulas, since 17mm wide rim has been the standard for MTB rims for decades.
      Have a nice day.

  • Most of the pro’s apparently run 25mm tires on rims of an internal width of 19mm. If this is true, does this mean that what they are riding is unsafe?

    • Hello Steve,
      Indeed, most Pros have now switched to 25mm tyre width, all season long.
      However, 95% of them are riding tubular tyres and in that case, the rule for rim and clincher tyre width combination doesn’t apply.

  • Hi, I just recently bought a set of Cosmic carbon pro exalith wheels. On the specs listed it said that, you can run 23mm-28mm tires. The rims are 13mm inside, but according to the chart in this article the min rim width for 28mm should be 15mm. So, which one is it? Can I safely and efficiently run 28mm on those wheels?


  • Hi. I have a pair of 2013 R-Sys SL with internal measurement (B) of 15mm and external (A) 20mm. Can I safely run 25mm clinchers or should I rather use 23mm tyres? Would there be any benefit besides ride comfort by fitting 25mm tyres?

    Thank you in advance.
    Osman, South Africa.

    • Hi Osman,
      It is totally safe to use 25mm on your R-Sys SL.
      Doing so, you’ll benefit from better comfort and slightly better rolling efficiency. The only drawback will be the additional 10 to 20g per tyre.

  • Thank you for the comprehensive review and report.

    I am really surprised that the Hed’s Ardennes Plus should be used with 31mm+ tires according to the ETRTO’s manual.

    One thing to ask: In the 2nd graph, what are the air pressures for 23mm tire and 25mm tire? In reality, wider tires are filled with lower pressure, because the same pressure gives the uncomfortable rides.

    • Hello,

      ETRTO and ISO defines the general safety conditions in which products can be used. They have to make sure, that under no circumstances, the consumer will be at risk. In the case of wheel and tyre combination, the technical expert within those norms have identified that some combination, in some circumstances, can be unsafe.

      In this second graph, this is the same air pressure (7 bars) in order to see the influence on the Rolling resistance (Crr).
      Of course, in the real life, we recommend to put lower pressure in the wider tire (here 25mm) to have the same Crr and a better comfort.


  • Hi, I am building a new bike and width the new R-SYS SLR , may I know your thoughts if I place 28mm tires with regards to the recommended PSI, roll resistance, aero quality, weight increase? Thanks, Rory

    • Hello Rory,

      It is totally safe to use a 28mm tyre with your R-Sys SLR.

      Recommended tyre pressure will depend on your personal weight, on the type of roads you’re riding on and on your personal preference (comfort vs speed). If you weight around 75kg, are riding on reasonably nice roads and want to find the good balance between comfort and rolling efficiency, we recommend you inflate at 95 PSI.

      The rolling resistance will depend on the tyre pressure and of course on the tyre brand / model you’re using. If you use our Mavic Yksion Pro in 28mm instead of the 25mm delivered with the wheels, the rolling efficiency will be the same but with a better comfort and cornering (because you can put a lower air pressure in a 28mm tyre than in a 25mm).

      Aerodynamically, of course, a 28mm tyre having more frontal surface will not be as fast as a 25mm. But if you’re going for R-Sys SLR it’s probably because you spend most of your time in mountainous area. The aerodynamic disadvantage in the downhill should easily be offset by the confidence you’ll get from the extra grip given by the wider tyre.


      • Thank you for your reply, since a 28mm tyre has more frontal surface, will a 25mm front and 28mm back setup on a R-SYS SLR be more advantageous or it’s better to stay with a 25 mm front and back set up?

  • Thank you for your reply, since a 28mm tyre has more frontal surface, will a 25mm front and 28mm back setup on a R-SYS SLR be more advantageous or it’s better to stay with a 25 mm front and back set up?

  • Dear Sir,

    I have Trek, USA Hybrid Bicycle Model = 7.3 FX.
    I currently have 700*32 C Tyre and Rim size=622*15C

    Can I change my tyre to 700*25C???? for Speed?? and what will be the impact if I change 700*32C to 700*25C.

    Pls do let me know. Waiting for your response.

    • Dear Hassan,

      Of course, you can mount a 25mm tyre on your rim (15C) instead of the 32mm tyre.
      It will depends on what you are looking for and which tyre you’ll use. When you compare the rolling resistance of 2 similar tyres (same compound, same thickness…), the wider will be the faster ! The deformation of the tyre on the ground is different and the wider is losing less energy. Nevertheless, the wider is also a bit heavier, an less aerodynamic. And often, the wider will have more rubber in the tread and so finally, the rolling resistance will be very close to a narrower one.
      So, it’s always a balance to find. If you are looking for comfort and ride quality, the wider will be a good solution, if you are more looking for speed, a 25mm is a good compromise.

      To give you some data, the difference of rolling resistance between the MAVIC Allroad (32mm) mounted tubeless at 5 bars and the Yksion Pro (25) at 7 bars is very weak : 0,3 Watts better for the Allroad at 30km/h for a 80kg rider. But the Yksion Allroad will be less aerodynamic (about 1W). So it really depends on the feeling you are looking for and of course the kind of road you’ll ride.



  • So you’re saying that tire widths that match the rim width are less aerodynamic but have lower rolling resistance? Then why would the slightly worse aerodynamic profile be a factor to consider?

    • There must be a misunderstanding : rim width matters both for rolling efficiency and aero.

      But :
      – internal rim width is related to air volume and tire shape, so it matters for rolling efficiency, but doesn’t have a direct influence on aero
      – outer rim width only matters for aero : the optimal aero performance will be reached if the outer rim width is slightly larger than the tyre width (but there are plenty of other criteria to take into account).

      We say that inner and outer rim width are necessarily linked with each other.
      For instance at Mavic, on the CXR 60 clincher, we had to use a 13mm inner rim width to be able to fit our CX01 Blades on the rim wall tips, but the outer rim width is 27mm which is substantially larger than the 23mm tire we’re using on that wheel. And this what dramatically improves the aero performance of the whole wheel tire system.


  • Am I correct that the tire width limitations apply to MEASURED actual tire width rather than the width marked on the tire sidewall? The marked 25mm width tires I use generally measure 26mm or 27mm wide on 17mm inner width rims (Mavic Ksyrium Pro). I’ve read reports of them measuring up to 28mm wide. The same brand tire at a marked 23mm width has the reputation of measuring 25mm wide — but I haven’t gone to the trouble of measuring them yet. Is the MEASURED tire width the important number?

    • Hello Bill,
      Yes, you’re correct, it applies to measured width. But a consumer should be able to rely on the information provided by the manufacturer. So, here is how it works :
      First, according to those norms (ISO & ETRTO), each tyre size must be measured on a defined rim size. For instance, a claimed 23mm tyre must be measured on a 15c rim and must measure 23mm +/- 1mm on this rim. If you mount the same tyre on a wider rim, you will measure it wider than written on its sidewalls, but that doesn’t mean that the tyre is wrong.
      It is the tyre manufacturer’s responsibility to ensure that what he writes on the sidewalls represents the reality, within the requirements of the norm. Again with 1mm of tolerances.
      So, let’s say that you use a claimed 23mm tyre on a 15c rim, hence respecting the norm. But if this tyre actually measures 25mm on this rim, then you’re consequently outside the norm that says that a 25mm tyre cannot be used on a 15c rim. If you have a problem, you can go back to the tyre manufacturer to complain as he’s been the one in violation of the norm in the 1st place.

      • Thank you for the quick response. I am considering the Mavic Cosmic Pro Carbon SL C. It appears that the 25mm tire spec is right at or beyond the maximum width of that rim. My favorite 25mm tire measures wider than that on a 17mm inner rim. If the tire is as wide or wider than the widest point on the rim, to what extent are the benefits of the 40mm deep rim compromised?

  • Hi, I’m very interested in the actual width measurement of the 25c tyre on both the 2016 Ksyrium Pro (17mm internal rim) and the 2016 Ksyrium Pro SL (15mm internal rim).
    I’m currently running 25c Vredestein Fortezzas on a pair of 2007 Ksyrium Elites (13mm internal rim) and the rims are nearly used up, so I’ll need to replace shortly.
    I’m fairly sure that a lot of the newer wide rims won’t fit my 2007 cervelo fork, but I don’t live near to a store where I can check for myself.
    – Thanks

    • Hi Dan,

      Our 25mm tyre on our 17mm rim measures on average 25.1mm, when just mounted. It will stretch after the 1st 48hours inflated at 7 bars and settle at around 25.3mm.
      On our 15mm rim, it will be down to 24.5 when new, 24.7 after 48 hours.

      Hope one of those configuration will fit in your frame and you’ll be able to enjoy the ride quality of the Mavic Wheel-Tyre System.

      Thanks !


      • Hi, i have cosmic c40 elite wheels, they came in 13c inner rim.
        I used 25mm tyre on them but they make a ballon, they feel slugish when i use less pressure.
        I have some problems with flats, i want to make the best performance.

        Now im running 23mn tyre, they feel fast and responsive, i dropped to 100psi 105psi back

        I ride cobbles some times. Should i continuous use 23mm on this wheels or go to 25mm(make a ballon and the tyre is not weel suportted)

        • Hi,
          First of all, it is totally safe to use a 25mm tyre on your 13mm rim. There is no risk of the tyre coming off the rim.
          To ride on cobbles or poorly paved road, for sure 25mm tyres will offer more comfort and pinch flat protection.
          But you should always ride with what you feel works well for you. If you don’t like the performance of 25mm tyres on your CC40 Elite, then, use 23mm ones.

          • But what is the best width for this rim by the engineers? I know that 25mm is superior for confort and less rolling resistance at the same pressure.
            But there is s better choise,my idea is to choose a better tyre 23c with good performance and flat protection and choose the right pressure for the ride.

            Or buy 25mm tyre and ignore the ballon effect , because they will rolle better anyway

          • This rim has been designed around a 23mm. This is the combination that will deliver the best performance for the use that this wheel has been designed for: traditional road racing.

      • Thanks guys!
        – Dan

  • Dear Admin,

    I have a tubular 20mm rim width wheelset.
    What size of tyre are the fastest for 20mm rim width? 22-23-25 mm tyre width?
    Thanks for your help!

    • Hi,
      Given the specs of your rims (max width 23mm according to the website and 20mm at the tyre bed according to you), the best aerodynamic performance would be achieved with a 21mm wide tubular, or slightly narrower.
      However, “best aero” doesn’t necessary mean “fastest”. Indeed, a 21mm tubular tyre will have a significantly higher rolling resistance than a wider one. Not even talking about comfort and traction.
      There are so many variables that it’s hard to give precise numbers: your wheel would need to go in the tunnel with different tyres to tell what the exact savings can be. And the tyre would need to be tested for rolling efficiency too, as there is not 1 single truth that tells how much faster is a 25 over a 21mm. It all depends on the tyre construction itself.

  • Hi I,m a 30 year tyre veteran and love your article. I always think their is a balance between tyre and wheels whether it’s bikes cars etc..
    I use Ksyrium Equipe and want to upgrade. Can you please make a suggestion. Thanks Clem

    • Hi Clem,
      Thanks for your comment. Much appreciated.
      For your wheel upgrade, it all depends on your riding style and preference and, we have to say, you’re budget.
      If you favor long distance comfort over stiffness and high speed, you should remain within our Ksyrium family. But if you want to race and ride hard and fast, check out our Cosmic family. To upgrade from your current Ksyrium Equipe, anything in the Elite range or even better, the Pro range, will make a difference.
      Don’t hesitate to call our customer service to get personalized advises. You’ll find its phone number at the top of our homepage, after you chose your country and language.
      Thanks for your loyalty with Mavic.

      • Hello,

        I ride actually on 23mm wide Tubulars with the Mavic CCU, old version rim 21mm width.

        There are a lot of articles, talking about the new benchmark 25 mm width tyres but forgot to talk cleverly as a Wheel-tyre combo-design as on piece as you do.

        During the next change of tubulars, I shall like to test wider tubulars of 25mm to win in comfort and inflate them in 7 bars instead of 8 bars at present with 23mm. Or to stay with 23mm tubular but with softer compounds and latex inner tube.

        But is there a big loss at the aerodynamic level in watts from a certain speed and according to different yaw angles? Will i loose a lot of reactivity for accelaration?

        I really hesitate to keep riding with 23mm or to change to 25mm.

        For which tubulars width are the first model CCU best designed for?

        If riding with a 23 mm front tubular and a 25 mm rear tubular, which pressure would be good? I suppose it’s not good to ride in the front 8 bars and 7 bars on the back?

        Your advices would be very appreciated cause you articles are very well explained!

        Happy New Year 2017!
        Best Regards

        • Good question, has anyone answered this?

          • Dear Stephen,

            The width of a tubular rim has very limited impact on the tubular tyre shape. On your Cosmic Ultimate, you can use either 23 or 25mm.

            As for the pressure, we just released an app called MyMavic that will very precisely answer your question. You can download it from the AppStore (iOS) or the Playstore (Android).

            In a few steps and a few basic question about you wheel, your tire size, your body weight, the type of ride quality you expect, the road surface, the weather conditions… you’ll get a precise answer to your question.

            In your case and with the data you’re giving us and assuming you’re leaning toward performance, riding on mixed weather conditions, on a 25mm tubular tyre and your bike weighs about 7kg, the recommended pressure is 119psi front, and 123 psi rear.

            Thank you,


  • In my mavic c40, i got a flat again, maybe is because i use low pressure for 23mm, 100psi front 105psi rear, i weigh 80kg plus 8kg bike plus 2kg gear bottle watter.
    Whats the best tyre pressure in my case to prevent pinch flat?

    Right now im using 25mm vittoria pro slick. Mounted they measure 25mm at 8bar pressure.

    In harsh roads and cobbles is better to keep 25mm ?
    The tyre is making a little ballon with 25mm.
    Whats the right pressure for 25mm?

    • Mavic’s C40 are 13C rims which is not suitable for 25 mm tyres.
      Get rid of them and buy a decent set with at least 17C rims.
      Then you can safely ride 25 mm tyres at 6 bar pressure , with great stablity in corners and very little risk of pinch flats.

      • Hello,
        There are norms that defines what’s safe or not. They’re called ETRTO and ISO.
        Those people are industry representatives who conducts testing to asses what’s safe and what’s not. And that’s how they’ve defined the rim and tyre combination that can be ridden safely, and those who can’t. What’s safe to ride is illustrated in the black table above. And you’ll read that a 25mm tyre on a 13mm rim is totally safe to ride.
        Hundred thousands of cyclists have been using those kind of combination for decades and none have ever reported any safetyissues, specific to the this combination of rim and tyre.
        Now, whether the ride quality is good or not and the performance at its highest level is a different story.

        • The question was not if it’s safe, the question was about which pressure to use on cobbles with a 13C rim and 25 mm tyres.
          My advice is : don’t do that , at 8 bar you will be thrown out of the saddle and at 6 bar you’get pinch flats, so this combination is not suitable.
          Progress comes not by following ETRTO tables , unfortunately….

  • I have a Ksyrium SLS wheelset. I’m currently using 700 x 23c tires. Will 700 x 25c tires fit also? I’d like to see how a wider tire changes the feel of the ride. Please advise.

    • Yes , they will fit.
      You can save yourself the cost though, because it won’t bring any advantage on narrow rims.

    • Hi Philip,
      Your Ksyrium SLS have 15mm internal rim width, which can be safely fitted with tyres up to 32mm (as per the table above).
      So, using 25mm is not only safe, but will greatly improve your ride quality: lower rolling resistance and improved comfort. We suggest that you decrease your tyre pressure by 5 to 10 PSI.

  • Absolutely fantastic article! I really appreciate the fact that you reply to your reader’s questions because I had all of my own questions answered by going through the comments. My next wheelset is coming from you guys. Cheers!

  • The key information chart has been left out of this article, and I can’t understand why?
    1) Best rim width for 25mm tyre
    2) Best rim width for 23mm tyre

    Come on guys!

    • Hi Dan,

      Thanks for your comment.

      Based on the data in this article, we can say that the wider the rim, the better (for more air volume, lower rolling resistance, better comfort…), as long as you respect the safety requirement described in norms.

      – the best rim for a 25mm tubetype tyre is 17mm wide
      – the best rim for a 23mm tubetype tyre is 15mm wide
      – the best rim for a 28mm tubetype tyre is 19mm wide



      • Hi
        I have the 22 mm wide tubular CCU rims. Which tubular width do you recommend? ANd which pressure with that tubular? My weight is 73kg if thaat matters.

      • – the best rim for a 25mm tubetype tyre is 17mm wide
        – the best rim for a 23mm tubetype tyre is 15mm wide
        – the best rim for a 28mm tubetype tyre is 19mm wide

        Sorry , I don’t agree
        Add 2 mm for each of these tyre sizes , THAT’s the best rim size.
        No safety issues at all.

  • I find that the information overload is quite overwhelming sometimes. What it boils down to me is the overall feel of the ride, and I will leave all the technical stuff to the experts. I have raced on and ridden Mavic wheels for the past 30 plus years. What I trust in is that the RD departments are doing their best to improve the equipment we ride on and the safety there of, so for me I stay with the companies that have a long history of specializing in certain areas of the sport i.e: Sidi shoes, Look pedals, Shimano group sets, Fizik saddles, Castelli clothing and now Giant frames – previously Colnago. Thank you Mavic for your continued research. My last SLR wheels have 35000Km on them in 2 years and still going strong. Now replacing them with R-SYS. Regards Stephen

  • I have a set of wheels which I bought for a third bike in my workshop. It states on the rim that it is a 6063 T6 622×13. According to your graph above, ( if I have read it correctly ) a 25 mm tire will fit. I have also read that a standard 700x23c tire will also fit. I have managed to fit a 23 mm tire on the rims, but not without the use of a crow bar ( metaphorically speaking ) The 25 mm is the same. Okay in a workshop situation you can work on it, but on the road with only small tire levers its virtually impossible. I just want a plain answer to a plain question, which tire fits these rims with ease.

    • Hi Thomas,

      The ease of installing a tyre has no direct link with the rim width or tyre width.
      The purpose of this article is to explain how to match rim and tyre width for performance and safety.

      The problem you’re describing is related to the rim diameter and/or the tyre beads stiffness and diameter.
      You seem to be an experienced cyclist, so I would eliminate the fact that you miss technics and experience in mounting tyres 🙂 So, the problem is either the rim or the tyre, or both.
      622 refers to the rim bead seat diameter, which, according to the norm mentioned in this article is 621,95mm +/-0.5 (this is measured inside the rim, just at the bottom of the sidewalls). If your wheel has a diameter that is bigger than this, this makes tyre mounting more difficult.
      According to the same norm, the tyre which will fit this rim should have beads diameter of 619mm (it’s intentionally smaller than the rim since the tyre beads are stretchable). If the tyres you’re trying to install have beads smaller than this, this makes for a difficult mounting as well.
      If you’re really unlucky, you have both “big rim” and “small tyre”, which makes mounting even more difficult, if not impossible.

      This is why those norms exist and must be respected : for safety and ease of use.

      Since, there are no tools available to consumers to perform rim or tyre bead measurement, only experimentation can tell what’s wrong:
      – If you can assemble those tyres on another rim, then, your rim is to be blamed (they are too big).
      – If you can mount other tyres on this rim, then the tyres are to be blamed (they are too small).


  • Hi, I have cosmic elite c40 elite 13c inner rim. With Gp4000 23c they measure 24mm

    A friend has same wheels with same wheels but Michelin power 25c and they measure almost 27mm

    In chart says 25mm is safe, but 27mm is good or bad on performance?

    • If you keep the pressure as high as with your 23’s you will get slightly less rolling resistance, but less comfort because the increased volume of the 25 mm tyre.
      Lowering the pressure is bad for the cornering so there is not much to win with 13C rims and 25 mm tyres.
      For 25 mm tyres you need at least 17C rims.
      (but they will be wider than 25 mm, so it depends on the frame)

  • On your Ksyrium Elite UST Disc wheels spec page, the rim’s internal width is 19mm so using your table, you recommend a 28-62mm tire yet the wheels ship with 25mm which should be too small. Does this mean this table does not apply to disc brake rims?

    • The table in this article does not take into consideration Road Tubeless configurations. With Road Tubeless wheels (as the new Ksyrium Elite UST Disc), the conditions are changing. Indeed, the rim profile has the ability to lock the tyre bead more firmly than a conventional tube-type rim design.

      Therefore, mounting a 25mm tyre on a 19mm rim is now possible, providing a maximum tyre pressure is respected. This pressure is 87 PSI for a tubeless tyre and 102 PSI if used with a tube.
      We have to apologize, as this article has not been updated yet. Work in progress 🙂

      Also, come back soon on our website to learn more about the right tyre pressure.


      • Yes – it seems with tubeless and disc brakes the tire to rim width has become more complex. For example your Open Pro UST (also a 19mm rim with UST tubeless) specify a 28mm minimum and not 25 like the Ksyrium Elite so I’d be interested in seeing an updated table or article explaining these differences as well.

  • I fail to see any functional difference between conventional hooked rims for tubed tyres and tubeless ready rims with regard to rim width.
    The air pressure keeps the tyre in place regardless tube or no tube.
    A 19C rim can safely be ridden with 23 mm tyres ,countless riders proof it every day all over the world.

    • Hi Kees,
      The tube makes most of the job on holding the tyre on the rim.
      Once it’s gone (tubeless system), all the forces go on the tyre beads. Which then needs to be very carefully designed and become very sensitive to rim width.
      We’ve identified conditions (rim in the lows of the diameter’s tolerance, tyre on the highs of the diameter’s tolerances and the lows of the bead stiffness, narrow tyre, wide rim) where tyre can come off the rim. We’ve also measured some wheels and tyres, bought from dealer’s shelves, that were out or on the very edge of the norm tolerances.
      So, indeed, in most instances, coupling narrow tyres with wide rim doesn’t create any big risks and we are aware thousands of consumers are riding like that. However, as a responsible company, if we can find one instance, being in very extreme conditions, where rider’s safety would be put at stake, we simply cannot support or recommend it.
      Everything is safe, until something goes wrong…
      Maxime – Road product manager

      • Thanks, Maxime, for a very clear summary of the official technical position. One further thought is that if the bike is being used at its limit, then you’re more likely to have a catastrophic failure. I assume that hot weather and tight bends and descending are 3 factors to watch out for? Or have I guessed wrong with the hot weather? Richard (old and safe approach)

        • Weather is a factor, but also and mostly tyre pressure. The initial tyre pressure out of your garage is then influenced by the weather, but also the speed and the braking force (in the case of a rim brake bike).
          Also note that riding a tubeless profile that incorporates some kind of bead lock system (like the hump on each side of the inner channel on the Mavic UST profile) helps keeping the beads in place.
          Maxime – Road product manager

  • Thanks for an excellent discussion and explanations, Mavic.
    Am I right in thinking that the scenario where a tyre could just possibly come off the rim (due to a narrow tyre on a just slightly wide rim) is most likely with a tight turn, descending road and hot weather? Or is the hot weather not a factor?

  • Can I run 28mm tyres on 13c inner rim?i want confort and commute and do some sportive rides in my mavic cosmic.

    I tried vittoria in the back 28c. They measure 27mm
    At 6 bar

    • Hi Nuno,
      It’s totally safe to run your 13mm rim with 28mm tyre.
      The added volume compared to the 23 or 25mm will already offer more comfort, grip, and rolling efficiency.
      Maxime (Product Manager)

  • I’m looking for a carbon wheelset that will last, a common failure point is the carbon rim surface and the spoke nipple contact point. The forces are too great over time in the carbon/nipple area, what you often see is small cracks and buldging in the rim area.

    how to better manage these forces through better design?

  • I assume this also applies to car wheels. Is there a similar chart to car wheels? Also, i do not understand how rolling efficiency increases with wider the tyre, doesn t the friction increase?
    Thank you for answers.

    • Hi Alex,
      Thanks for your comment.
      This applies slightly differently for cars, but we cannot give you precise advice here as this goes beyond our competences.
      As for the lower rolling resistance with bigger tyre, it’s a question of tyre footprint and air volume. With a narrow tyre, the footprint is long and narrow as where with a wider tyre, the footprint gets wider but shorter and in the end, this is more efficient way to transfer power.
      Stay tuned on as a new article will be published in the coming weeks and will go more into the details of rolling efficiency related to tyre width and pressure.
      Maxime (Product manager)

  • Hi, i bought some mavic yksion tyres 28c

    Mounted in my mavic cosmic 13c inner rim measure 26mm

    In width chart, its not safe at 28mm
    So its safe to ride them right? Im looking for conforts.

    I had once 25c Gp4000 Mounted and they measure 27mm and they were fine with a little bit more pressure.

    • Hi Nuno,
      As indicated on the black table of section 4 above, on a 13C rim, for safety reasons, the maximum allowed tyre size is 25mm.
      So, in theory, you cannot ride a tyre wider than 25mm on this wheel.
      Concerning actual / measured tyre width :
      – You have to refer to the advertise width written on the tyre
      – 25mm tyre should be 25mm on a 15mm rim. On a narrower rim, the same tyre can be measured narrower
      – There are of course tolerances on the advertised width, than can vary from +/- 1mm (by norm. Any wider tolerances is the manufacturers responsibility)
      – With time, the casing of the tyre will stretch, hence measuring wider than advertised.
      – In the end, it is the tyre manufacturer’s responsibility to ensure that, whether new or used, the tyre width he advertises will be safe to ride on a given rim width
      Finally, keep in mind, that the bigger the tyre, the lower the pressure. For instance, a MTB tyre inflated at 3bars will feel as hard/stiff as a road tyre inflated at 8bars. You would not inflate your MTB tyre at 8bars, would you ?
      Maxime (Product Manager)

  • In that case, seems better to use 23c tyre in this wheels for better handling, performance and aerodinamics

    Most 23c tyres I put measure 24mm +-

    Maybe is always better to use tyre width most close to rim width e use right pressure instead of using big tyre and wrong pressure to avoid pinch flat