TRACOMP TECHNOLOGY

When developing the Tracomp technology, our goal was to significantly improve the global performance of a wheel intended to climb the highest mountain passes. Not just incremental changes, but massive and disruptive improvements that provide tangible and impactful benefits.

A thorough analysis of cyclists needs made it obvious that we had to tackle three parameters simultaneously. None of these needs were optional in engineering a new benchmark for the ultimate alloy wheel.

Those parameters are:

At the end of our journey, we created a technology that enabled the wheel to have significantly improved stiffness while reducing weight and maintaining the durability Mavic is known for. Here is how.

1. LATERAL STIFFNESS

1.1.    Parameters influencing lateral stiffness

What are the parameters that influence lateral stiffness of a bicycle wheel?
Here is a list of the parameters that have the greatest impact on the lateral stiffness of any bicycle wheel, their level of impact and the downside for the cyclist:

So, to reach our goal of significant improvements, we have to act on spoke stiffness and wheel dish. But we also have to take into account the downside of playing with those elements.

1.2.    Lateral stiffness measurement

First, lets explain, quickly, lateral stiffness. To have an efficient wheel there must be a resistance to the lateral (side-to-side) flex when force is applied. The stiffer the wheel, the more efficient. So, a high degree of lateral stiffness is desired in order to have the most efficient power transfer to the road.

Second, let’s have a look at how to accurately measure lateral stiffness. The wheels needs to be locked by the hub in a solid and infinitely stiff fixture. Then, we progressively apply a load on the side of the rim at the point that represent the contact of the wheel on the ground. The load applied must represent the power of a solid rider while sprinting, This is the condition where you need to count on your wheel. We typicaly apply a lateral load of 20 décanewton (DaN) representing the lateral load achieved during a sprint by a high level cyclist. This process results in a graph which represents the amount of deflection with 0 to 20kg of side load.

1.3.    Interpreting the result

The graph drawn when applying the load is this one :

The red circle shows that at a point (sooner or later depending on the wheel), the deflection increases very rapidly for just a small incremental amount of side load.

This happens when a spoke becomes lose. Then, he does not support the integrity of the wheel anymore. The consequences for the cyclist :

1. The wheel deforms: the rider will feel the wheel flexing
2. The wheel is noisy
3. Complete loss of tension affects the wheel’s durability

So, to increase the lateral stiffness, it becomes obvious that we must

• prevent spokes from losing tension under high load
• At any load minimize the amount of deflection

That would mean that the slope on the graph becomes steeper and with no inflection point.
The usual solution used by many wheelbuilder to avoid those sudden loss of tension is to increase the spoke tension
If we do so and put the same wheel with higher spoke tension on the same bench here is what you get:

Indeed, there is a delay in the moment where the spoke will lose tension: more load is needed to cause that spoke loosening.

BUT we’ve created more issues:

1. More stress is applied on the wheel components which limits:

• durability
• Opportunity to save weight

2. The wheel is less stiff : at reasonable load, you have more distortion for the same force as the wheel buckles more easily as the result of higher tension throughout the whole wheel (the curve is flatter).

1.4.    The 2 most effective solution to increase lateral stiffness

Solution #1: stiffer spokes
The spoke is the 1^st wheel component which is responsible for wheel deflection. Its elasticity is much higher than that of the rim or hub flange.
A stiffer spoke will bring less elasticity:

Solution #2: larger bracing angle with no spoke loosening
Rear wheels are asymmetrical because spokes have to make room for the cassette on one side, and have plenty of space on the other side.

When applying the load, we get:

When the spoke tension gets down to 0, we have the extra deflection talked about in the section above.

1.5.    How TRACOMP solves the issue of higher lateral stiffness

As seen above, we need stiffer spokes
The spokes of a Tracomp wheels are made of carbon. When tensioned (the TRAction mode), carbon doesn’t stretch as much as steel or alloy and the wheel deflection is reduced :

Then, when a regular spoke will lose its tension under high load, the Tracomp spoke will enter into its COMPression mode to maintain the lateral stiffness at a constant level, avoiding the sudden loss of stiffness :

1.6.    How does a Tracomp wheel achieve this?

The spoke is clamped on both ends :

1. At the rim thanks to Fore® technology
2. At the hub thanks to the Tracomp ring

The spoke is rigid and does not flex when compressed :

1. Material : multidirectional carbon fiber (intermediate module) for the highest impact resistance
2. Shape :

Tubular
External diameter : 4mm
Internal diameter : 2,6mm

Spokes don’t stretch (Traction) and cannot lose tension (Compression)
The wheel is STIFF whatever the load and even with low spoke tension

1.7.    Stiffness comparison

A Tracomp wheel offers a very high level of stiffness (less deflection at equal loads.
A Tracomp wheel will never have spokes losing tension, so there will be no sudden loss of stiffness even under the highest load.

Tracomp wheel lateral stiffness :

• Front: 56 N/mm
• Rear: 56 N/mm

30% STIFFER THAN A TRADITIONAL WHEEL WITH TENSIONED SPOKES ONLY

2. LIGHTWEIGHT & DURABLE

2.1.    The benefits of lower spoke tension

As seen on the stiffness section above, on a Tracomp wheel spokes never lose tension, so the tension can be reduced with no negative impact on lateral stiffness.
Less tension means less stress on the hub, spokes and rim. The weight of the wheel components can be lowered with no impact on durability.
Here are CFD simulations of wheels in a static situation (no load applied):

We can clearly see that, even in a static mode, because of the constant spoke tension, a traditional wheel is under moderate stress.
A Tracomp wheel however, thanks to lower spoke tension, is under very low stress.
Of course, once in a dynamic mode (ride), the stress difference is even higher.

2.2.    The use of the best material for the function

Aluminum rims:
Light, durable, convenient, stiff
sub 370g rims (clincher weight)

Aluminum hubs:
Lighter than any redundant composite application

Carbon spokes:
Light and much stiffer than anything other option, if shaped correctly,
5g per spoke/nipple (VS 7g on Zicral spoke, 8g on steel spoke)

R-SYS SLR : 1295g per set
Ksyrium Pro Exalith SL : 1355g per set
=>Lighter than most carbon clincher wheels

3.    About the carbon Tracomp spokes
Since 2010, carbon Tracomp spokes are made from multidirectional, reinforced carbon layers consisting of multiple layers of unidirectional carbon fibers that are oriented in a specific pattern designed for increased strength.

3. ABOUT THE CARBON TRACOMP SPOKES

Since 2010, carbon Tracomp spokes are made from multidirectional, reinforced carbon layers consisting of multiple layers of unidirectional carbon fibers that are oriented in a specific pattern designed for increased strength.

A pin has been inserted between the spoke and its 2 ends to reinforce this area and disperse stress over a larger surface area. This greatly improves the failure resistance of the spoke when a 3^rd party object like a pedal or derailleur intrudes into a spinning wheel. The resistance behavior is similar to that of a Ksyrium wheel with Zicral spokes.

The spoke impact resistance has been multiplied by 5x.
Its torsional stiffness is now 3.5x higher.
Tracomp shows the same crash resistance behavior than that of any other Mavic wheel.