• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

if my calculations are correct????

kdub41

NAXJA Forum User
Location
hemet
Specification Sidewall Radius Diameter Circumference Revs/Mile Difference235/75-15 6.9in 14.4in 28.9in 90.7in 698 0.0%31/75-15 0.9in 8.4in 16.8in 52.9in 1198 -41.7%

so if i go 150 miles i have actually gone around 200. Am i correct?
 
What exactly are you trying to figure out? By looking at the second set of calculations it shows a sidewall of .9" radius of 8.4" and diameter of 16.8". Even the smallest low profile lowrider tire is bigger than that.
 
What number is this supposed to be? Should 31/75-15 be 315/75-15? If so you are comparing the following:
235/75-15 is 28.9 inches in diam
315/75-15 is 33.6 inches in diam
33.6/28.9 = 1.16

If your speedo is geared for the 235 tires and you put on the 315 tires you will have gone 116 miles for every 100 miles your odometer shows. You will also be going 16% faster than the speedo shows.
 
the wierd thing is, is that when i am going 52 mph im actually going 40. I have 31in tires with 4.56 gearing. so with that said what would be the difference every 200 miles on a non calibrated odometer
 
52MPH indicated / 40MPH actual is a speedo error of +30%. So when your ODO reads 260 miles, you will really have gone 200 miles.
 
Last edited:
Back
Top