Originally Posted by bh20
The manual it came with gave my size tire (700 x 35c) a 2205 mm circumference. I did a roll-out test myself and came out with 2159. I put 2159 in my computer, but as I looked around at all other brands of cyclometers every company has differenct mm circumference measurements for the same size tire. Why is that? is a 700 x 35c tire not the same size for other companys? Just curious.
There are differences in sizes between "same sized" tires between companies. One reason (supposedly) is that it allows the manufacturer to claim a lighter weight. Knubby tires should also have a larger diameter than slick tires.
You should also do your measurement more than once. Three's a good number to use. If you get numbers that are close, you can average them. If one is way off, you can drop it and measure again.
(The Sigma computers are well-liked.)
If you have knee problems, you might want to be careful not to use too high a gear (fairly common for people starting out). Generally speaking, you should be pedalling at no slower than 60 RPM (as a rough starting point). If you can't turn the pedals at that RPM (called "cadence"), use a lower
gear. If your legs are moving too fast (more than is comfortable), shift to a higher
gear. Note that it's possible that 60 RPM will seem too fast for you. It's OK if you have to work up to that but it's a good target for somebody starting out. (You don't have to be neurotic about it being "exactly" 60 RPM.)
Probably the best bet for increasing your performance is to ride with other people (who can push you a little)!
Last edited by njkayaker; 09-11-09 at 05:28 PM.