Will I be ok with one 245/40/18 tire and the rest 255/40/18?

JMorton6

Senior member
Jan 25, 2009
406
1
71
One of my tires popped, I don't have a spare and the only replacement I could find is a 245/40. It's a RWD car and the tire is going on the front. I need it to last 3 months til the winter, at which point I'll put new winters on and garbage this whole set. Will I be ok?

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Vette73

Lifer
Jul 5, 2000
21,503
9
0
1: Wrong section

2: Dont; do it. Just order some new tires from treaddepot.com, tirerack.com, or tires.com
 

PricklyPete

Lifer
Sep 17, 2002
14,582
162
106
What'll happen if I do this?

The car won't ride correctly at all. One tire will be a different diameter than the other three. One tire will also have a different sized foot-print than the other three causing a very odd balance in grip.

Just don't do it. You have 18 inch wheels...and you're trying to cheap out on one tire. fail.
 

IcePickFreak

Platinum Member
Jul 12, 2007
2,428
9
81
The 255-40 is 26in. diameter, the 245-40 is 25.7in. diameter.


Close enough that I wouldn't worry about using it as a spare in an emergency, but 3 months? Unless it's the same brand/model tire, the composition is going to be different, the load rating, tread pattern, plus the contact patch is going to be smaller obviously, so it could definitely cause some weird steering behavior. I wouldn't advise it.

That said, since the diameters are so close, it's only about 9 revs per mile difference so it shouldn't throw any abs/tcs codes.
 

Vette73

Lifer
Jul 5, 2000
21,503
9
0
I went from a 225/55 to a 225/50 on my car. My Car freaked out and put me in limp mode because one set of tires was faster/slower to each other.

Might happen here as well as ABS/Traction control might freak out.
 

PricklyPete

Lifer
Sep 17, 2002
14,582
162
106
I went from a 225/55 to a 225/50 on my car. My Car freaked out and put me in limp mode because one set of tires was faster/slower to each other.

Might happen here as well as ABS/Traction control might freak out.

Don't forget he's talking about just one tire...not changing the whole set or 2 fronts.
 

holden j caufield

Diamond Member
Dec 30, 1999
6,324
10
81
depends on the car but car spares/donuts are obviously a different size and most run them fine if you aren't going too fast. Isn't 245/45/18 closer to diameter of the other 3? I would never do it again but my first year in college I only had like $40 to my name, had to get a used tire that was different from the other 3. Ran that for a really long time. I think 3 were 205/60/15 and the odd one was 205/55/15.
 

Rifter

Lifer
Oct 9, 1999
11,522
751
126
its not ideal, and the right thing to do would be not to do it. That said its only for 3 months just dont push the car for that time, the uneven traction will probably make it less predictable.
 

jlee

Lifer
Sep 12, 2001
48,518
223
106
One of my tires popped, I don't have a spare and the only replacement I could find is a 245/40. It's a RWD car and the tire is going on the front. I need it to last 3 months til the winter, at which point I'll put new winters on and garbage this whole set. Will I be ok?

Moved to the Garage
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There are 54 tires in 255/40-18 on Tirerack...
 

thescreensavers

Diamond Member
Aug 3, 2005
9,916
2
81
yea dont do it, just buy some used tire in the right size, that's from a good brand that wasn't manufactured more then 5 years ago. I know some people running different tires in the rear its fine but I am not sure about steering?
 

Paperlantern

Platinum Member
Apr 26, 2003
2,239
6
81
fucked up traction and speed because that wheel will be getting less traction, but also spinning faster because its smaller diameter

just get two or get the right size

This.

As someone said, this would be fine in an emergency situation, or even, i would think, for a week or two tops while you get another tire, but for 3 months? You're talking about putting roughly 1000 - 3000 miles depending on your driving, on a tire thats not matched to your set. This can wreak havoc on not just the tires, but other parts of the car too. I wouldn't recommend it for that long either.