Pa Different Size Rims on Front and Back

Mondalmi Stance · Sunday, December 19, 2021

12-11-201406:40 PM #1

Veteran Member Three Rings

Different size tires in the front and back??? Cause issues??

My tires are different in front and rear. I had a flat went to big O tires and talked with the guy about some options since the rear ones are wearing out. He said he has to put on matching tire size because with awd cars it messes up the transmission. He had trouble with a subaru in the past. I understand his point of view he doesnt want to be liable for anything. Would this cause issues??? Tire size in rear 255/40/r18 in front i believe 235/35/r18. I thought it would if side to side is different because the differential would be doing extra work dealing with the offset size's however front to back seems like it wouldnt be such a problem. Anyone??
12-11-201406:49 PM #2

Veteran Member Four Rings

If the rolling diameter difference between the two front to back is less than 2%, you'll be fine. If it's greater than 2%, you'll damage the center diff over time.

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12-11-201406:52 PM #3

Veteran Member Three Rings

Two percent in diameter huh. Well Looks like i will get the same size tire's in front and back then. Good to know.
12-11-201408:09 PM #4

Veteran Member Three Rings

What about side to side?? Can there be any side to side or is 1.13% ok? I got a spare on atm get me home (still 800 Miles).

My front to rear is only .245% So im looking okay there.

EDIT***I will let some pressure out until they are very close in diameter. I essentially only have to make up .72 diameters. Also the larger side is very bald so it might even be close already.*********

Last edited by kingkhalilz; 12-11-2014 at 08:51 PM.
12-11-201410:26 PM #5

Veteran Member Four Rings

You can also run into stability control issues if the computers see different amounts of wheel rolling. My ABS blinked on occasion until I put the same tires all around.
12-12-201407:15 AM #6

Veteran Member Four Rings

I don't think it was 2%, it was actually something to the tune of 5/32 difference in diameter max which means 0.6% or so.

http://www.alloywheels.com/Tyre_Calculator

Hit "Show / Hide specific tyre size to compare against" just under the first tire size drop down boxes to compare to other size tire.

Input both tire sizes and it shows 6% difference between the two tire size listed in first post.
12-12-201408:22 AM #7

Veteran Member Three Rings

I did that when i blew my rear tire. now i have moaning noises coming from the rear, car is jerking i think my rear diff is on its way out
12-12-201408:53 AM #8

Veteran Member Four Rings

Originally Posted by Pizdets-b5

I did that when i blew my rear tire. now i have moaning noises coming from the rear, car is jerking i think my rear diff is on its way out

Replacing rear diff is easy so you got lucky it was rear tire. If you did the same with a front tire or did what OP wants to do, that would kill front axle diff (in your case) or middle diff (in case of mimatched sizes between front and rear) and that's a major problem as tranny would have to be partially disassembled to replace either...
12-12-201410:03 AM #9

Veteran Member Three Rings

Torsen type awd systems don't like variety in rolling diameters. Did the same research when I wanted to run a staggered setup. I will be running 18x8.5 and 18x9 with 235/40 all around
12-12-201410:48 AM #10

Veteran Member Three Rings

correction to first post the sizes are. 255/35/r18 and 225/40/r18. Its smaller than six. My worry know is my spare is different size. 1.3 percent. On the rear

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