Why do we need to do impact resistance testing?
The impact resistance test shows the overall structural performance of the wheels. Our impact test is performed on wheels without tires mounted. Eliminating the tire as a variable gives us cleaner results and helps to mimic bottoming out the rim on trail obstacles. With repeat strikes on test models, we’ll see how much impact force the bare wheels can endure.
What is the test goal?
The aim of this test is to predict the behavior of bicycle wheels under normal and also extreme impacts. We need to make sure that the wheel remains unaffected by regular impacts that could occur during normal riding conditions. We gradually raise the striker height to increase the force, and hit the rim repeatedly until it eventually breaks. These are called destructive tests as they are designed to get more and more extreme until a failure occurs.
Test Standard
The impact energy required by the UCI is 40 Joules (J), after which the wheel must remain intact and usable (no cracks & lateral/radial run-outs within 0.5mm). At Winknow Bike, we raise the minimum level to 80J, and the ultimate impact our wheel can endure is well over 100J.
Test Method
UCI testing consists of a vertical drop. The wheel is firmly secured without a tire. A rubber pad is fitted to a block of steel which is them dropped onto the wheel. The wheel is hit at a right angle from the valve hole. For a wheel to pass, in addition to there being no damage to the rubber pad, there must be the following:
No visible cracks or delamination
No change in lateral profile or in lateral run out in excess of 0.5mm
No change in radial profile or in radial run out in excess of 0.5mm
Test Conditions
| Test Method | Vertical drop |
| Wheel State | Without tires |
| Energy Level |
Starting level: 40J Usability level: 80J (5J increment per round) |
| Test Positions |
90° position from the valve hole on the wheel |
| Impact Striker | Flat steel-plated weight with block at impact point (85+/-5 HA Shore A) Weight: 20kg |
Wheel Sample Profile
| Model | Width | Depth | Spoke | Spoke Tension | Wheel Condition |
| FC50 | 28mm | 50mm | Carbon | 130kgf | Well trued& stress relieved |
Test Results
Conclusions
After the FC50 wheel was subjected to a 100J impact, there was no crack or breakage on the rim. Vertical vibration: 0.18mm (+0.10mm/-0.12mm) before the test → no change after the test. Transverse vibration: 0.20mm (+0.13mm/-0.14mm) before the test → 0.23mm (+0.13mm/-0.15mm) after the test. All changes were controlled within 0.50mm. However, when the impact force reached 105J, visible cracks appeared at the impact point of the rim. The impact test results have confirmed that the wheel can withstand an impact force of more than 100J.
