Mostly agree, Easiest thing is no cyclometer, Next easiest is gps only cyclometer (no calibration), Then comes the various ways of calibrating a wheel rev counting cyclometer.
The standard value typically given for 700x23 is 2096mm circumference, which works out to about 26.26 inch diameter. Measuring roll out with Schwalbe 650B "fatties" (aka HS315) which measure about 45mm wide, I came up with a 25.84 inch diameter, which is ~1.5% less than the 26.26 value. My guestimate for the soma GRs is ~25.72" which is ~2% less than the 26.26 value. Is 1 or 2 percent worth bothering with? Thats up to each rider. Though cue sheets may be no more accurate than your own cyclometer, if you are consistently reading ~2% over the cue sheets, and you would like to agree with them, then adjusting your circumference setting to match is a reasonable thing to do. On Saturday, December 20, 2014 10:31:57 AM UTC-8, Bill Lindsay wrote: > > The easiest thing is no cyclometer. The second easiest thing is to use > the 700x23 default number for your 650bx42 (both have a nominal radius of > 334mm) Then ride a known distance and adjust accordingly. I've used the > track at the high school. 4 laps = 1 mile. I've used the painted mile > stripes at the bike path. Deacon is right about load affecting things, but > your tire pressure also can. A 1% error in radius means a 1% error in your > distance and 3mm of extra drop because you are running your tires softer > than usual is a 1% error in radius. Getting better than 1% accurate is > probably not worth the effort. > > On brevets, a 1 mile discrepancy between your computer and the cue sheet > can EASILY be partially due to the cue sheet. A very noble, very generous > volunteer made that cue sheet, using his cyclometer. S/he is not perfect > either. > > On Saturday, December 20, 2014 10:08:05 AM UTC-8, ted wrote: >> >> If you want to eliminate the discrepancy, just reduce the wheel >> circumference setting on your cateye by 2% (1 mile in 50 is 2 in 100 is 2%). >> >> On Saturday, December 20, 2014 8:15:38 AM UTC-8, Tim wrote: >>> >>> Good question. I set my CatEye up as 700x32 (Compass Stampede Pass). The >>> computer gains about 1 mile in 50 during every brevet I've ridden. So I'm >>> guessing if it shows that I've gone 51 when th cue sheet reads 50, that >>> probably means I'm riding slightly slower than the computer shows. I always >>> reset at controls so it's not a huge issue but I've often wondered if other >>> riders have similar experiences. Turn to turn distances are accurate and >>> I'm sure there is some margin of error on cue sheets but my reading is >>> consistently long. >> >> -- 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 rbw-owners-bunch+unsubscr...@googlegroups.com. To post to this group, send email to rbw-owners-bunch@googlegroups.com. Visit this group at http://groups.google.com/group/rbw-owners-bunch. For more options, visit https://groups.google.com/d/optout.
