MDcatV
02-05-08, 11:15 AM
If I switch tires from a 23 to a 25, which results in a change in wheel circumference, does my power go up, down, or stay the same?
Road Bike Racing - wheel circumference ?
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bdcheung
02-05-08, 11:35 AM
I don't think changing the circumference of a wheel alters the power in your guads.
kudude
02-05-08, 11:36 AM
it effectively makes your gears a bit harder -- like going from a 39 tooth to a 40 tooth up fron (although not that dramatic). Like he said ^^ no effect on guads
Homebrew01
02-05-08, 11:47 AM
23 to 25 affects the tire WIDTH. I wouldn't expect any significant change in diameter. Do a roll-out and measure each to see.
waterrockets
02-05-08, 11:54 AM
23 to 25 affects the tire WIDTH. I wouldn't expect any significant change in diameter. Do a roll-out and measure each to see.
Average 700x23c is 2096mm, where 700x25c is 2105mm. Tire cross sections are round, so when they get wide, they get tall too :)
Average 700x23c is 2096mm, where 700x25c is 2105mm. Tire cross sections are round, so when they get wide, they get tall too :)
bdcheung
02-05-08, 11:55 AM
23 to 25 affects the tire WIDTH. I wouldn't expect any significant change in diameter. Do a roll-out and measure each to see.
http://www.sheldonbrown.com/cyclecomputer-calibration.html#iso
http://www.sheldonbrown.com/cyclecomputer-calibration.html#iso
merlinextraligh
02-05-08, 12:21 PM
Average 700x23c is 2096mm, where 700x25c is 2105mm. Tire cross sections are round, so when they get wide, they get tall too :)
so on your PT, it will make your speed be slightly underestimated if you don't recalibrate, but it won't affect the power reading.
so on your PT, it will make your speed be slightly underestimated if you don't recalibrate, but it won't affect the power reading.
MDcatV
02-05-08, 12:49 PM
so on your PT, it will make your speed be slightly underestimated if you don't recalibrate, but it won't affect the power reading.
thank you
thank you
waterrockets
02-05-08, 02:29 PM
so on your PT, it will make your speed be slightly underestimated if you don't recalibrate, but it won't affect the power reading.
Actually, I think it would affect the power reading since the hub just takes a torque and multiplies by distance to get power. I think it would actually read lower power, but only by 0.5%.
Actually, I think it would affect the power reading since the hub just takes a torque and multiplies by distance to get power. I think it would actually read lower power, but only by 0.5%.
TurboTurtle
02-05-08, 06:07 PM
Actually, I think it would affect the power reading since the hub just takes a torque and multiplies by distance to get power. I think it would actually read lower power, but only by 0.5%.
It uses angular velocity so all it needs is the rpm. - TF
It uses angular velocity so all it needs is the rpm. - TF