Tire size equivalent
 

I currently have 31x10.5x15 BFG Long Trails on my Bronco. I was told that 235/75/15 is the equivalent size. Something is telling me that is the stock size. Anybody know?? From what I've heard, 31x10.5x15 is a hard size to find?? Is that true??

Joe

Closest size to a 31 10.5x15 is a 265 75r15
31 10.5's are a VERY common size!!!

That's what I thought!!! Do you think there is any price difference between the 31's and the 265/75/15's??

And 265/75R15 is a very rare size. I don't think there should be much, if any difference in price for equivalent tires, except you have a lot more choice with 31x10.50.

Frankly the price diff will be more in style, and brand. Hard to say.

long trails are good tires. i ran a set of 30x9.5 on my bronco for like 6 years, then i got another year on them on my f150.

ive heard that 15" tires are going to start coming up in price but i dont believe it. honestly once you go over 235/75x15 the price difference is probably pretty small. I think i got some 235s for like $50 a piece for my truck. I got some bfgs 30" for $70 a piece on a deal. if you look at tire prices your looking at $110 atleast if your getting anything larger then 30".


just so you know with tire sizes, 235 is the width of the tread, 75 is the aspect ratio of sidewall to width of tire and then 15 is obviously the rim size. so 235mm wide, 75% of the width for the sidewall is 176.25mm so 6.9" sidewall. 15" rim plus 6.9" plus 6.9" is roughly 28.8" tire.
When you get 31x10.50x15 its 31" tall tire, 10.5" wide tread 15" rim. now a 31" tire isnt exactly 31", a bfg 31" tire might measure 31.5" and a mastercraft 31" tire might measure 30.5".

30x9.50s are about the biggest you can run on stock rims without rubbing the radius arms. 31x10.50s rub the radius arms on stock rims. 32x11.50s clear with offset rims with no rubbing issues. 33x12.50s fit okay on pre 87. dont know about87+ yet as i havent tried them on my truck.

31x10:50x15
 

I think the OEM on my 93 was a 265---will have to look at the spare, it is a goodyear RTS. I have run 31's and now have 32X1150X15's on stock rims. If they do rub, it isnt much. Guess I need to looksee if I have polished radius arms. Very satisfied with the 32's (was also with the 31's).

I did a post (somewhere!) where I measured "rollout" of the 32's with PSI'S from 50 to 10 PSI and can say that my figures show very little difference in rollout (= circumference), maybe ~2-3 %. Also been my experience that a 31 and 32 may be a full inch short on actual height as computed by circumference. To be clear, thats MY tires (bridgestone APT) on stock rims on my bronco. I am not saying all tires do the same :)

i know with my 89 anything over 9.5" wide rubbed the radius arm with full turn to the stops, im sure rim options were different though

The main difference between a 265 75R15 and a 31x10.5 15 is the intention of what it's for.

265 75R15 mathematically is a 30.65"x10.45" 15 tire, almost exactly the same. However, tires that are measured in the 265 75R15 method are designed for road use, pavement, and highway. As a general rule, only tires measured in the 31x10.5 method are truck tires and have tread patterns designed more for off-roading, dirt, gravel, and other trucky things of that nature.

There's almost no difference in size between the two, except that the 31x10.5 method has a lot less lenient rules on it and sometimes they are much smaller. For example, when I take a tape measure to my 30 x 9.5" tires, they measure out to 28x8.5" tires. My speedometer is off as well as other things. Next time I go get truck tires, I'm bringing a tape measure with me. I'd recommend everyone else do the same.

225x60x16
 

Abandonedbronco--
I have been looking at the difference between quoted and actual sizes for years now and have no real good explanation as to why the difference. Even on spec'd rims, there still is a difference. My "guess" is that mfg's target the size they want to build then hit slightly undersize. Not that it really matters a whole lot, as long as the Consumer is aware. Most of the time (on tires I have purchased) even the mfg's rev/per/mile figures are off---which directly relates to the circumference.

Car spec'd tires seem to be the same, maybe not as far off. My 03 Gran Marq, oem 225X60X16 Michelin to 235X60X16 BFG traction TA's back to 225X60X16 michelin's were all off by approx 1" on height. Again, not a problem as long as the buyer beware!

Try walmart, they have 4 differnt 265's 2 of them are at $100.00 ea. PeP boys as well has both the 31's and 265's Any one knowing where i can get my hands on a Futura Adventuer H/T 265 75 R15 please let me know, I have 4 new ones but need a spair and PeP boys said that tire is discontinued. Thanks!
Keep Em' Twistin'! Bob B.

Bronco Stables: 89 thru 96 / XLT / Eddie B / BR II
http://www.supermotors.net/vehicles/registry/15608<WBR><WBR><WBR>

For the standard sizing, what differentiates is actually the P vs. LT. Ps usually have 4 treads while C rated LTs and floatation sizes have 5 or 6 treads.

if you buy tires from walmart be very weary of them mounting them. i havent heard good things about their service dept. I bought a set of tires for my truck there and mounted them by hand with tire irons and used a bubble balancer rather then let them touch my truck. I know first hand of someone who had their oil changed there and within a mile all the oil had drained out and the engine locked up.

tires are cheap though:)

Sorry wasn't thinkin about that, I own my own tire machine, Coats 1010. Once mounted I take em to goodyear for spin balancing.
Keep Em' Twistin'! Bob B.

Bronco Stables: 89 thru 96 / XLT / Eddie B / BR II
http://www.supermot<WBR>ors.net/vehicles<WBR>/registry/<WBR>15608