i have brand new bfg 315/70/17's (H2's).

for input into the attitude, what circumfrence do you use? or... what method do you use to measure?

i used a piece of chalk, rolled back one rev at an indexed spot on tire, measured, came up with 2667. but... i'm wondering what happens at highway speed? does the circumfrence change? seems like edge could have easily put in a calibration, where you hit a button at the beginning and end of 10 miles using highway markers (no dic or gps for me). i also think they should add a heartrate transmitter ;)

thanks.

Use the mile markers.
Start with the Attitude adjusted for your calcs.
Straight line and flat road works best.
3600 divided by time equals mph
3600 divided by 60 seconds equals 60 mph.
change cm in attitude till ya get it.
SC

2742

2742wow. that's a big difference. how'd you come up with that? is the chalk on the driveway just an inaccurate method? why do you suppose?

thanks.

formula i use tread x 2 x sidewall divide by 25.4 plus rim,
315 x 2 x .7 / 25.4 + 17 = 34.36. tire mfr sometimes list on website, have seen 1/2 in diff for same tire size by different mfr. hope this helps

formula i use tread x 2 x sidewall divide by 25.4 plus rim,
315 x 2 x .7 / 25.4 + 17 = 34.36. tire mfr sometimes list on website, have seen 1/2 in diff for same tire size by different mfr. hope this helps
need circumference in cm... 34.6 * pi * 25.4 = 2759.6

it's not too far off from the chalk, but i guess the right thing to do is a highway mileage test every once in awhile as the tires shrink :eek: (they calc off the rears?).

or, with a load on for a trip, the different psi and weight can change things up.

Scott,

I used this calculator, http://www.1010tires.com/tiresizecalculator.asp, I got 2740.6.


Tom

TheBac...that's sweet!!! I had the calculation for my Attitude totally wrong! I'll have to reset it after I get my Juice module back from Edge!