You will get the most accurate measurements by carefully measuring your roll out and using a cyclecomputer that counts wheel revolutions.
I find the easiest way to measure roll out is to lay out a 50' cloth tape (using bricks or rocks to weight the ends helps), line up the valve stem at the 1 foot mark, then roll along the tape and stop with the valve stem at the bottom and read off the distance (don't forget to subtract the 1 foot for where you started). Alternatively you can use chalk to mark the road next to the valve stem and measure between the marks. Either way have the tire inflated to normal pressure and sit on the bike as you roll. I find it's easiest to do this right next to the sidewalk curb out in front of my house, but any parking lot should suffice. If that's more trouble than you want to deal with, just linearly interpolate between 25.35 in. for a 32mm tire and 25.84 in for a 45mm tire. Those are values I got with 650B GB Cypres, and 650B Schwalbe "fatty" respectively. On Saturday, December 20, 2014 6:21:29 AM UTC-8, lungimsam wrote: > > Which method is more accurate for getting more accurate cyclecomputer > data? I am mostly interested in the miles ridden being accurate, if that is > even possible on a cyclecomputer. I don't know how accurate these things > are. My cycling app shows very different speed reads than my cycle computer. > Also, which is more accurate? An iPhone cyclecomputer app, or an > actual cycle computer? I am guessing the app is using GPS, but I have heard > that GPS isn't so accurate either. > > *Rivcontent:* > > 1.Only one 650b size is available on cyclecomputers I have, so unless I > have 37mm tires, I can't get an accurate read using that. > 2. I find it difficult to accurately measure from ground to hub axle > center accurately. Is that tire *really* standing vertical? > 3. Roll out may be easier better? > > Lastly, if I have been using the one and only 650b x 37mm default wheel > size setting on my cycle computer with my 42mm wide tires, I am guessing > that the distances are being represented as shorter and the speeds shown > as slower since the bigger actual tire is taking longer to make one > revolution than the computer is expecting for the wheel size setting of > 650b x 37mm? > -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/rbw-owners-bunch. For more options, visit https://groups.google.com/d/optout.
