In TOUR 04/2019 we tested 16 road bike wheelsets with rims between 40 and 58 millimetres high (tested models at the end). Conclusion: sensitivity to heat remains the Achilles heel of carbon wheels for rim brakes. Many wheels are damaged on steep descents. How does TOUR actually test carbon wheels for rim brakes? These are our test procedures:
Aerodynamics
Tested in the wind tunnel. The wheels are subjected to airflow at angles between -20 and +20 degrees, and we measure the air resistance experienced by the entire system. Share of the overall score: 20 per cent.
Crosswind stability
Tested in the wind tunnel. We use a steering torque balance to determine how much crosswind can be felt in the steering. This is where the wheels differ more than in drag. Share of the overall score: 15 per cent.
Brake test
Test bench run in the TOUR laboratory, based on real-world data. The brake test on the test bench is based on riding tests with a system weight of 100 kg on a short, steep descent (13% average, winding) with a final emergency stop. The real thing tends to be harder than the test bench run - so it's by no means a broken test. The only special thing about the TOUR test is that the road is somewhat steeper than is usual on large mountain passes. Defects occur on this descent during normal, speedy riding - no scary braking! But not only with weak CFRP rims, but also with discs that are too small. Aluminium rims master the descent without any problems. The good carbon rims also pass this practical test.
On the test bench, we analyse the friction values in dry and wet conditions, check whether the braking effect diminishes during continuous braking and how the rims withstand continuous braking as it occurs in practice. In addition, we record modulability and pad wear. Five disciplines are assessed and the braking performance in dry and wet conditions is specified. Proportion of the overall score: 20 per cent - additional devaluation in the event of damage.
Stiffness
Determined in the TOUR laboratory. High stiffness values represent a direct, precise ride feel. Share of the overall score: 15 per cent.
Endurance run
The wheels, each fitted with 25 mm tyres, rolled almost 5,000 kilometres on Schwalbe drum test rigs. For the spokes, this meant around nine million impacts in addition to the load changes at the wheel contact point. Overall rating downgraded in the event of damage
Weight and acceleration
In the TOUR laboratory, we determine weights, analyse the inertia of the wheel, which counts when accelerating, and examine concentricity after heavy loading of the spokes. Share of the overall score: 15 per cent.
Impact resistance
Carbon is strong, but also brittle. Is the wheel ruined when you hit a pothole? We test this with an impact test in the TOUR laboratory. A plastic hammer is used to hit the rim flange. We worked with three impact energies:
Drop height 1 = 3.2 joules
Drop height 2 = 6.3 joules
Drop height 3 = 9.5 joules
At least eight rims were unaffected, an improvement on the last test. The weakest rim was already damaged at level one. For comparison: an optimally designed CFRP rim does not suffer any damage even at level 7 (22 J) and is therefore much stronger than any aluminium rim! We know this from MTB tests. So, as with brakes, there is a world of difference between the strongest and weakest rims.
Share of the overall grade: 15 per cent
Practical test
The wheels are ridden on the road and various loads are simulated
You can find the carbon wheels in the TOUR test:
Bike Components Braiding
Zipp 302 Carbon Clincher
Giant SLR 1 Aero
Mavic Cosmic Pro Carbon UST
Swiss Side Hadron Classic 485
Vision SC 55
Bikebeat high flyer
Veltec Speed Pro 5.0 TR
Rose RC-Fifty
Equator 50 TLR
Aerycs C55 SL
Leeze CC 58 Road WASO
Bontrager Aeolus Pro 5 TLR
The following models were not rated due to failure in the test:
Venn VAR 45 TCC
Hunt 50 Carbon Wide Aero
Acros Road SP
Kristian Bauer
Editor
