Michelin PS2 275/40ZR18 on the rear

2923 Views 31 Replies 14 Participants Last post by thebigjimsho, Jun 12, 2007

CrashCadillac

Discussion Starter · Jun 8, 2007

Does anyone know what actually happens when you stuff a wider tire in a rim than it was designed for?
Michelin gave this response: “We do not recommend putting the 275/40ZR18 Michelin Pilot Sport PS2 in a wheel with a rim width less than 9 inches wide. A smaller rim size can cause irregular wear, poor handling, cracking, and other issues. We do offer the Michelin Pilot Sport PS2 in a 245/45ZR18.”

Others have already done this – so it can be done. But what actually happens? Can anyone offer a more technical answer?

1 - 20 of 32 Posts

thebigjimsho

· #2 · Jun 8, 2007

Nope, that's about it. Physically, you can mount that tire on a stock rim. But it's not worth it. There is no benefit except for what some people call a cool factor. They think the tire bulging over the rim is cool. I think it looks liks crap. And your handling is not going to be any better. Extra rubber does not help if the wheel width has not changed.

Plenty have done 245/45 fronts and 275/40 rears on stock wheels. Just don't waste your money on PS2s to do it.

rand49er

· #3 · Jun 8, 2007

Okay, going from 245 to 275 is of no benefit.

But, what about going to 255 or 265? (Not sure if PS2s come in these sizes, but guess I'm just wondering about this in general.

)

The Tony Show

· #4 · Jun 8, 2007

You'll actually have more sidewall flex by stuffing a wider tire on a narrow rim, which will result in a poor contact patch on your outside rear tire under hard cornering. The possibility also exists for the rim to stress the sidewall and cause a belt seperation inside the tire.

Most guys who have gone to staggered setups are the drag racing sort -If you widen the rear wheels and put a staggered setup on it can be good for that. As far as road racing though, I think staggered is a poor choice as it promotes understeer (greater contact patch = higher lateral grip), and we don't need any more understeer than we already have.

Reactions: 1

GMBOUND

· #5 · Jun 8, 2007

Tony how bout you do a Forza simulation for him?

Luna.

· #6 · Jun 8, 2007

Agree with BigJim and Tony's comments.

While you will get more rubber on the road with a 275 vs. a 245 (on an 8.5" rim), there are other considerations that, in my mind, make it not worth it. The tire really has to fight to not rollover the rim, resulting in extra sidewall stress, you aren't getting the full benefit (rubber on the road) of the 275 tire, as it's squeezed on a smaller rim, etc.

I applaud Tony for mentioning understeer with wider tires in the rear. I believe this to be true. It's probably best to run the same width tire all the way around for roadracing; I think Mallet runs 275s all the way around for that matter. For a car as heavy as the V, which already understeers more than it oversteers, that isn't necessarily a good thing.

thebigjimsho

· #7 · Jun 8, 2007

Luna. said:
Agree with BigJim and Tony's comments.

While you will get more rubber on the road with a 275 vs. a 245 (on an 8.5" rim), there are other considerations that, in my mind, make it not worth it. The tire really has to fight to not rollover the rim, resulting in extra sidewall stress, you aren't getting the full benefit (rubber on the road) of the 275 tire, as it's squeezed on a smaller rim, etc.

I applaud Tony for mentioning understeer with wider tires in the rear. I believe this to be true. It's probably best to run the same width tire all the way around for roadracing; I think Mallet runs 275s all the way around for that matter. For a car as heavy as the V, which already understeers more than it oversteers, that isn't necessarily a good thing.

Which is why while I'm running 275/40 18 PS2s on widened stock rims, I'm still tracking the V on 245/40 Hoosiers all the way around...

V-Love

· #8 · Jun 8, 2007

The Tony Show said:
As far as road racing though, I think staggered is a poor choice as it promotes understeer (greater contact patch = higher lateral grip), and we don't need any more understeer than we already have.

Man, I'm going to be so much faster now that I know that. Plus, I'm ordering tires today. Thanks.

thebigjimsho

· #9 · Jun 8, 2007

Although, I do see you can get Hoosier R6 rubber in a 255/40 18 size. You don't see that size too often on a race tire...

LV_V

· #10 · Jun 8, 2007

In addition to all of the above, throwing a 275 on the rear stock rim will also add unnecessary rotating mass to your rear wheels (weight of 275 > 245). And its on the outside of the wheel, even worse.

lawfive

· #11 · Jun 8, 2007

i run staggered but got my rear rims widened 3/4" for 275's more expensive more unsprung weight more understeer looks cool though so i get laid a lot full stop

LV_V

· #12 · Jun 8, 2007

Well as long as it gets you laid more then I think everyone should do it! If I didn't care about getting laid I would be driving a Prius...

thebigjimsho

· #13 · Jun 8, 2007

lawfive said:
i run staggered but got my rear rims widened 3/4" for 275's more expensive more unsprung weight more understeer looks cool though so i get laid a lot full stop

I'm guessing you're posting remotely...:alchi:

Dreamin

· #14 · Jun 8, 2007

...interesting how the people who haven't tried 275's on stock rims are the most opinionated about them...

CTSV_Rob

· #15 · Jun 8, 2007

Dreamin said:
...interesting how the people who haven't tried 275's on stock rims are the most opinionated about them...

They are just trying to justify why they didn't do it. :stirpot:

thebigjimsho

· #16 · Jun 8, 2007

CTSV_Rob said:
They are just trying to justify why they didn't do it. :stirpot:

Because I'm not stupid.

Look, I used to own a '92 SHO which had 215/60 16 tires on 6" wide wheels...stock! I've driven SHOs which had 235 rubber on 6" wide wheels. And I know the difference from 1 to the other. If you want to go tooling around on stock rims with 275 rubber, that's cool. But I'll be faster...

CTSV_Rob

· #17 · Jun 9, 2007 (Edited)

thebigjimsho said:
Because I'm not stupid.

Look, I used to own a '92 SHO which had 215/60 16 tires on 6" wide wheels...stock! I've driven SHOs which had 235 rubber on 6" wide wheels. And I know the difference from 1 to the other. If you want to go tooling around on stock rims with 275 rubber, that's cool. But I'll be faster...

I'm 245's still, just wanted to see if I could get a rise out of someone.

BTW, I don't think running 275's on a 8.5" rim will determine if your stupid. There are many things that could like driving a Ford possibly... :bouncy:

thebigjimsho

· #18 · Jun 9, 2007

CTSV_Rob said:
I'm 245's still, just wanted to see if I could get a rise out of someone.

BTW, I don't think running 275's on a 8.5" rim will determine if your stupid. There are many things that could like driving a Ford possibly... :bouncy:

Easy to say now. But Ford had a Yamaha engine that could not be touched by another V6 until about 7 years after SHO production started...

CTSV_Rob

· #19 · Jun 9, 2007

thebigjimsho said:
Easy to say now. But Ford had a Yamaha engine that could not be touched by another V6 until about 7 years after SHO production started...

I was just yanking your chain, awesome car in it's day.

thebigjimsho said:
...But I'll be faster...

I'd still race you even though your V may be quicker!

thebigjimsho

· #20 · Jun 9, 2007

CTSV_Rob said:
I was just yanking your chain, awesome car in it's day.

I'd still race you even though your V may be quicker!

HAHAHA Bring it!

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