Converting tire length into mm?

[SadieKate]

What computer do you have? The manufacturers usually provide a chart or you can do the rollout method for measuring (which at the moment I can't articulate because the brain is still on vacation).

[suhollyberry]

I think it's called cyclomaster. They had the layouts, but none of them fit my tires. I guess I can try to do the rollout method. I think they have instructions included.

[suhollyberry]

I have a giant road bike, with the standard tires that came with it.

So by having it set at 2085, that means it is underestimating my miles?

[DeniseGoldberg]

If you don't want to do the rollout, Sheldon Brown also has a calibration chart on his site that you can use as a starting point: http://www.sheldonbrown.com/cyclecom...ation.html#ccc

Of course 700x29 is not included in the chart. That sounds like a very odd size. And wow - this is a first for me. I just did a search on google for
bicycle tire 700x29c
and came up with only 1 document. I've never done a search before that matched only one thing. (If you're interested, the document that matched was a catalog for mountain bike tires (or tyres, as they spelled it) from a company called Geax. Of course that doesn't help with your tire calibration, but I thought it was interesting).

--- Denise

[Geonz]

Come on out to ILlinois, where there are scads of places to ride a mile (the standard distance between roads on the prairie) and see how your odometer compares, and adjust accordingly :-)

[HillSlugger]

I wrapped a string around my tire (700x32c) and then got the length from a tape measure. On my first ride my distances were all about 5% higher than what my car odometer had said. I decreased the setting by 5% and ended up short on my next ride. I ended up nearly perfect with a -2.25% adjustment. I don't know why this is necessary. Who can be sure that the car odometer is right either?

[DebW]

I wrapped a string around my tire (700x32c) and then got the length from a tape measure. On my first ride my distances were all about 5% higher than what my car odometer had said. I decreased the setting by 5% and ended up short on my next ride. I ended up nearly perfect with a -2.25% adjustment. I don't know why this is necessary. Who can be sure that the car odometer is right either?

The tire circumference is probably different with a rider on the bike. You should have your weight on the bike when you do a roll-out. That probably accounts for your difference. Of course, the car odo may not be that accurate either.