[chongo]

My truck came with the stock 265x70x17 Michelins and the next day I put 305x70x17 Maxxis Bighorns on - I filled in a little chart on line that calculated the revolutions per mile etc. With the stock tires I was getting 638.10 revolutions per mile - now with the 305's I am getting 596.50 revolutions per mile - my question is since I have not reprogrammed the comp. for the bigger tires - my odometer/speedo. are going to be reading less miles traveled and a slower mph than what I have actually traveled correct? How much of a difference is there in miles traveled with my comp. thinking it's still running the stock 265's and actually running the 305's. It comes down to a difference of 41.6 revolutions per mile. I have 170 miles at a half tank - would it be more like 175 miles or 180 miles instead?

Thanks for the help.

 

[RB24]

i would get the speedo recalibrated since it is a new truck...

265/65R17
305/70R17

Section Width: 10.43 in 265 mm
Section Width: 12.00 in 305 mm

Rim Diameter: 17 in 431.8 mm
Rim Diameter: 17 in 431.8 mm

Rim Width Range: 7.5 - 9 in
Rim Width Range: 8 - 9.5 in

Overall Diameter: 30.56 in 776.22 mm
Overall Diameter: 33.81 in 858.77 mm

Sidewall Height: 6.78 in 172.21 mm
Sidewall Height: 8.40 in 213.36 mm

Radius: 15.28 in 388.11 mm
Radius: 16.90 in 429.26 mm

Circumference: 96.00 in 2438.4 mm
Circumference: 106.2 in 2697.4 mm

Revs per Mile: 680.6
Revs per Mile: 615.2

Actual Speed: 60 mph 100 km/h
Speedometer1: 54.2 mph 90.3 km/h

Speedometer Difference: - Speedometer Difference: 10.63% too slow
Diameter Difference: - Diameter Difference: 9.62%

 

[chongo]

I am getting it recalibrated tomorrow morning - I am just trying to figure out what the difference is in regards to miles traveled.

Anyone know how to do that?

 

[RB24]

yeah its 9%...lets say you go 100 physical miles, your odometer will register 90 of those

 

[duso02]

Sure, that's easy math. Go here in and punch the sizes in. (I'm lazy like that)

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

 

[RB24]

Sure, that's easy math. Go here in and punch the sizes in. (I'm lazy like that)

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

wow that is sweet :rck:

 

[chongo]

okay so the 170 miles it's showing now is actually 185.3 or so?

 

[RB24]

actually 170 equals closer to 189 according to my math

 

[chongo]

Thanks for the help rb - I never was much for math anyways.

 

[RB24]

no problemo brotha