TPU inner tubes are gaining attention as the third force in bicycle tires. We summarize its features, advantages and disadvantages of using it on Road bikes and MTBs, and major manufacturers.
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Standards set by ASTM, the world’s largest international standardization and standard-setting organization
The ASTM standard for wheels refers to the standard set by ASTM (America Society for Testing and Materials), the world’s largest international standardization and standard-setting organization.
ASTM standards for wheels are not very familiar in Japan, but in other countries where extreme sports are popular, they are considered important when selecting wheels.
ASTM standards by category and ASTM standards
ASTM standards for bicycle wheels are divided into five condition categories according to “Condition of use”.
|CONDITION1||paved road||most road wheels|
|CONDITION2||Paved road + clean gravel road||Some road wheels and gravel wheels|
|CONDITION3||Rough dirt roads and small obstacles||MTB wheels|
|CONDITION4||Rough dirt roads at high speed||MTB downhill wheels|
|CONDITION5||downhill and jumps||for extreme riding|
Most road bike wheels are Condition 1. Some wheels that are “can be used on road and gravel” are Condition 2.
Some wheels for gravel road use fall into Condition 2 and Condition 1. Since this varies from product to product, it is best to contact the manufacturer to confirm.
Surprisingly, Condition 2 is intended for “clean gravel roads. This means that gravel wheels are not designed for MTB tracks.
For Condition 3 and beyond, there are three levels depending on the hazard of the ride, from MTB to extreme sports such as downhill and jumps. If you ride in this area, you may have already purchased wheels to ASTM standards.
What happens if the wheel is used outside of ASTM standards?
The ASTM standards for wheels are only “driving conditions under which the manufacturer can guarantee performance and quality,” so there is no problem if the wheels are used in other applications. However, if a wheel with a low condition level is used in high condition applications such as MTB courses, the risk of damage increases.
We often see reports of “road wheels that ran fine on gravel,” but it could just be that nothing happened by chance. In fact, there have been cases of carbon rims breaking on gravel with condition 1 road carbon wheels.
Considering this, it is better to use them in the expected conditions as much as possible.
Especially when the ride itself, such as MTB course or trails, has a risk of accidents, it is advisable to firmly match the wheel to the intended use.