Would this be a problem? 255 supercar tire and 245 RSA tire, both on the rear?

[SSpray]

I am getting a spare SRT8 wheel with a 245 RSA tire on it. I have the 245/255 supercar tires on my car. If I were to get a rear flat and put the 245 RSA spare tire on, would this cause problems? Is the diameter different? Would the problems be long term or would they go away once I put the same size diameter tires on the rear as they are supposed to be?

Thanks!

[EricG]

Ah the spare tire dilemma continues...

I guess it depends on whether or not our open differential can take different-sized tires attached to it. I want to say it can but I'm not sure, assuming of course that it's only for a short period of time. Hopefully some of our wiser members know.

After I work this first set of tires over, I'm definitely going to ditch the staggered tire size set up and go 255s all the way around and then just get a 255 spare on a stock rim. Then it comes down to putting it in the trunk and sacrifice the room, or just keep it in the garage and hope the fix-a-flat can will bail me out until I put it on.

What would be great is if we could get a manufacturer to design some special 18-inch donut that clears the front and rear brakes. Anyone know some high-up tire company people?

Eric

[1fastsedan]

I thought the 245/255 numbers referred to width, not side-wall height. It is my understanding that the 255s shouldn't be rotated to the front due to rubbing, not any problem with 245s coming to the rear. The heat generated in the differential from uneven wheels comes from different heights. If you run an 18 inch wheel on one side and a 20 on the other, then you will heat up the rear end very quickly. That is why donut spares have a 50 mph/45 min rating on them. I would think that if the side-wall numbers are the same, than you would be fine to use a different width spare.

[SSpray]

I was using 255 and 245 for short hand for the rest of the #'s.
I am asking if the two diameters are different...

[srt8danno]

This is good question as I’m in the same boat. I plan on doing what Eric mentions in his post. In fact it won’t be too much longer and the change will take place.
So do we have an answer to your question yet?

BTW…I’ve seen way too many idiots driving like crazy people with a doughnut tire on!

[SSpray]

Originally Posted by srt8danno

This is good question as I’m in the same boat. I plan on doing what Eric mentions in his post. In fact it won’t be too much longer and the change will take place.
So do we have an answer to your question yet?

No answer yet...

[Kruzinhi]

Yea the 245/45/20 and the 255/45/20 is the same overal diameter the only differencew is the width see the 245 stands for the width the 45 is side wall and the 20 is the size of the ID of the tire (rime) so no it will not cause any long term problem the only thing is one side of the car will be thighter than the other cause one tire is wider than the other.

[HEMI_MAN]

I would'nt do it, no if's and's or but's about it!

[Mungo404]

According to Goodyear's website the 245/45/20 has a height of 28.7" and the 255/45/20 has a height of 29.1". I don't know if 4/10ths of an inch will have a damaging effect on the rear end. I guess that's a question for the SRT engineers section.

[SSpray]

Originally Posted by Mungo404

According to Goodyear's website the 245/45/20 has a height of 28.7" and the 255/45/20 has a height of 29.1". I don't know if 4/10ths of an inch will have a damaging effect on the rear end. I guess that's a question for the SRT engineers section.

I guess that difference could be achieved under normal circumstances anyway. If one tire was low on air?

If that is the case, I would not think it would cause big issues, especially if just used for a short period of time?