Let's say a friend is struggling to calculate the difference in total diameter between a 26" rim with a 2.1" tyre and a 700c rim with a 32c tyre on (and lets say he knows he could just measure/compare them, but he's at work, the wheels are at home and it's bugging him).
What's the difference between the two setups?
don't forget that the effective diameter of the wheel in the bike will be decreased by the amount of 'give' that the 26" tyre has due to running lower pressures. Or does that not matter?
Let's assume that doesn't matter.
Er, to my friend.
About 673mm for the 26x2.1 (so maybe 670-675 if it's a treaded tire), vs 690mm for the 700x32. That's making assumptions about casing height vs width etc but using the same rules to compare is usually close enough.
I'm guessing IHN's friend wants to put 700c wheels into a mtb frame
I have no measurements but I've done it with no problems
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this much, then.
Or maybe more or less depending on the size of the screen you're viewing this on, obviously. HTH.
Can he not use the ETRTO numbers on each tyre?
[url= http://sheldonbrown.com/tire-sizing.html#isoetrto ]Sheldon[/url] to the rescue.
[i]I'm guessing IHN's friend wants to put 700c wheels into a mtb frame
[/i]
Bingo, and he's wondering how any subsequent effective change in the geometry will affect how the bike 'feels'. He's aware that it's all probably pretty subjective...