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Tire Size Question


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#1 Matty Kling

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Posted May 03 2011 - 9:28 AM

Got a question for you guys...

My stock tire size is 265/75 R15... these are turning out to be somewhat of a difficult size that most places don't stock.

Does anybody know if I can replace this tire with, say, a BF Goodrich 31 x 10.5 R15?

#2 99ways2die

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Posted May 03 2011 - 9:31 AM

This should answer your Q:
http://www.miata.net/garage/tirecalc DOT html
N = R*fp nefl fi fcL

#3 Disassembler

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Posted May 07 2011 - 11:47 AM

31x10.5r15 sould be fine. What kind of truck is it?
My 89 suburban came stock with 235x85r16 and i was able to get 33x12r16.5 on 10 inch wide rims with no problems.

#4 Backbeach Jake

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Posted May 15 2011 - 4:34 PM

31x10.5r15 sould be fine. What kind of truck is it?
My 89 suburban came stock with 235x85r16 and i was able to get 33x12r16.5 on 10 inch wide rims with no problems.


Did you change rims?
To answer the question : you can change the first number without major problems..BUT... if the number gets too big you may experienct some tire and fender, liner interference.

#5 Disassembler

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Posted May 15 2011 - 7:48 PM

Yes the rims where changed for the bigger tires. They didn't rub at all. It is a 3/4 ton suburban, so it has some height to it compare to a 1/2 ton.

#6 BassAsssassin

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Posted May 18 2011 - 7:17 PM

31 x 10.5 R15 <---- that is a 265 tire, the same size as what you have now I believe. or it may be a 265/70

I just replaced the tires on my jeep 255/70/16 PrimeWell PA 100. Buy 3 get 4th free. great A/T tire, and failry cheap

#7 Chief2

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Posted May 19 2011 - 8:33 AM

265/75/15 equals 30.6"x10.4", so converting to 31x10.5 would be zero issue.

To understand the numbers more:

a P-METRIC, read as xxx/xx/xx

the first 3 numbers are the WIDTH of the tire, in MM. 25.4mm per inch. so 265mm = 10.4"

The second 2 numbers are a percentage of the width, IN HEIGHT, from the rim to the end of the tread. So, 75% of 265 = 192mm in height. 192mm = 7.8" You have 7.8" on opposite sides of the rim, so you double it, to 15.6".

Then you add in the diameter of the rim to your tire height of 15.6", and you get 30.6" tire.

This will help you figure out what up-sizing you can do in the future.