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Gates claims their belts do not stretch over their life, so theoretically speaking you should not have to adjust the tension (which appears finicky).

I'm interested in anyone with real world experience. Do you ever have to adjust the tension of the belt, apart from when you have to move the back wheel for another reason, such as to change a tyre?

Gates, who make the belts have a FAQ. I can't get a direct link, but if you go to http://www.carbondrivesystems.com/support.php under the question "What are the benefits to the Carbon Drive systems?" this is part of their answer.

No Stretch – The Carbon Drive belt does not stretch over time like a chain. This means you don’t have to re-tension the belt, or replace the belt due to stretch. This also means no excessive wear on pulleys due to stretch.

Does this claim hold up in practice?

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Have you had problems with yours? My partner's bike has not required any adjustment at all in about six months of daily commuting. –  DC_CARR Aug 23 '11 at 20:30
Many car engines use "timing belts" which are fundamentally the same concept. They last 70-100 thousand miles. In much more difficult conditions. –  Daniel R Hicks Sep 10 '13 at 11:28

2 Answers 2

up vote 2 down vote accepted

Once the system is set up correctly you will not need to tension it again until it is time to replace the system. There will be a slight drop in tension over the life of the system but it is not enough to require adjusting the tension. When performing a tire change using a bike with sliding vertical drop outs or an eccentric bottom bracket it is not necessary to re-tension the system, just pop the wheel in and out as you would with a chain.

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I have a Gates belt drive. After getting tension right (using the iPhone app) initially I did not touch it for a year and was surprised to find it had not changed. For me at least, no stretch.

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