HOW DO DETERMINE THE DIFFERENCE IN MILES TRAVELED VS WHAT IS REGISTERED ON THE ODOMETER WHEN CHANGING CHANGING FROM THE STANDARD 35"S TO 85 TIRES?

 

A little clarification:

Are you saying, your going from 35" tires to 85" tires?
Thats a 7' tall tire!
Thats almost 2.5 tims as large (2.43857) to be exact.

Either way, lets assume that your original post is correct and your going from 35" tires to 85" tires.
Then you divide 85/35 =2.4387 (or roughly 2.5 times as big)
This means that a 35" tire would rotate 2.5 times faster than an 85" tire.
Translate that to your odometer and it would tell you for every 10 miles traveled on 35" tires, you traveled rougly 4 miles on 85" tires.

So, assuming I didnt screw up my math, your odemeter would be slow by a little more than half.

Rich.

 

I thought he meant he went from 235s to 285 but I think his originals were 245s.

Herb, go to this site.
http://www.miata.net/garage/tirecalc.html

 

[quote author=Bearfoot2 link=board=4;threadid=24180;start=0#msg228328 date=1072216629]
I thought he meant he went from 235s to 285 but I think his originals were 245s.

Herb, go to this site.
http://www.miata.net/garage/tirecalc.html
[/quote]

Yeah, you are probably correct, but what threw me was the double quoute at the end of the 35 signifying inches ???

Rich

 

sorry. i did mean 245-16 changed to 285-16. according to the scale at the site you gave me to check at 60 mph i am actually doing 64.1.
wish i had paid more attention in math class, then i could have been able to convert this formula to actual miles traved at the end of a trip and actual fuel mileage.
i have a 16 year old grandson who will be able to calculate it for me if i can get him away from the girls long enough to help me!!
appreaciate the help guys
Herb

 

http://www.dakota-truck.net/TIRECALC/tirecalc.html

Go to this web site and foolow the instructions it will give the info that you need to calculate the difference.
The orig equipment on my truck was 265's the tire I choose was a 285/75/16 there was a 3.6% diff in my speedo. I did not correct this. If you find your difference is something you want to correct then you may want to look into the Truespeed product.

 

I went from 245's to 285's odometer/speedo is now out by 8%