What Size PSS for OEM 19" Wheels?

[Padfan9]

Originally Posted by CanAutM3

Ideally, you would want a rear tire that has a diameter ~2.3% larger than the front. The 255/35 - 305/30 is the better of the two options you mention with the rear 1.1% larger, but it is still not ideal.

If the rear wheel rolling radius (tire diameter) is smaller than supposed to, it needs to spin faster to travel the same distance. The DSC system will be under the impression that the rear tire is slipping more than it actually is and will therefore make interventions way before traction is actually lost. This can be quite annoying. I run a square setup (same diameters front and rear) for winter and do get a lot of useless DSC intervention.

Recommended wheel width for a 305/30R19 tires are between 10.5" and 11.5" with 11" being the ideal width.

So you're saying go with a 305/30/19? And in the front keep stock? I thought 265/35 goes with 305/30?

9.5 inch wheel would stick out on the 255 right? I definitely don't want wheel spin.

[CanAutM3]

Originally Posted by Padfan9

So you're saying go with a 305/30/19? And in the front keep stock? I thought 265/35 goes with 305/30?

9.5 inch wheel would stick out on the 255 right?

Go on http://www.tirerack.com and check tire diameters. Find a front-rear match that has the rear diameter as close as you can to 2.3% bigger than the fronts and you'll be good .

I am not saying that other sizes won't work on the car, just that it will upset the DSC calibration.

Originally Posted by Padfan9

I definitely don't want wheel spin.

You won't get wheel spin, DSC will only THINK it sees wheel spin and cut power .

[Padfan9]

Originally Posted by CanAutM3

Go on http://www.tirerack.com and check tire diameters. Find a front-rear match that has the rear diameter as close as you can to 2.3% bigger than the fronts and you'll be good .

You won't get wheel spin, DSC will only THINK it sees wheel spin and cut power .

That's even worse! I did check tire rack and it said 265/35 with 305. Can you verify that ? You seem to know a lot!

[CanAutM3]

Originally Posted by Padfan9

That's even worse! I did check tire rack and it said 265/35 with 305. Can you verify that ? You seem to know a lot!

According to Tire Rack, the 265/35R19 PSS and 305/30R19 PSS both have a diameter of 26.3".

That is the equivalent of running a square setup. My track setup is also square and I cannot really use MDM with it because it keeps kicking in all the time. If you don't push the car too hard, it will not matter. But if you do get on it, I believe you will get frustrated.

Have you considered 275/30R19 in front with 295 or 305/30R19 in the rear? That would work.

[Neil McRae]

Very useful thread chaps!

[gthal]

Originally Posted by Padfan9

That's even worse! I did check tire rack and it said 265/35 with 305. Can you verify that ? You seem to know a lot!

Originally Posted by CanAutM3

According to Tire Rack, the 265/35R19 PSS and 305/30R19 PSS both have a diameter of 26.3".

That is the equivalent of running a square setup. My track setup is also square and I cannot really use MDM with it because it keeps kicking in all the time. If you don't push the car too hard, it will not matter. But if you do get on it, I believe you will get frustrated.

Have you considered 275/30R19 in front with 295 or 305/30R19 in the rear? That would work.

This is what I would use with Padfan9's wheels... 275/30 and 305/30.

[W///]

Originally Posted by gthal

I hope to wear out mine soon and replace them with Potenza RE-11 in a 255/285 size.

Any particular reason why you'd go RE-11 over say PSS?

Originally Posted by gthal

This is what I would use with Padfan9's wheels... 275/30 and 305/30.

Just a friendly FYI, 275/30 is in backorder and has been for a while. I was told by Tirerack that it could be another 2-3 months. I think I'm OK with waiting, but push comes to shove, I might just have to go with another brand completely.

[gthal]

Originally Posted by W///

Any particular reason why you'd go RE-11 over say PSS?

Better grip, better responsiveness and hold up WAY better at the track to heat. They are a better performance tire than the PSS. However, the sacrifice is a slightly (and I mean slight) increase in noise and harshness. They also weigh more than PSS.

For a street only tire, I would stick with PSS as you get a great blend of performance and comfort. For a street tire with moderate track use, the RE-11 or AD-08R is notably better than the PSS which, IMO only, are not suited for track time after you get past a beginner level.

[Padfan9]

Originally Posted by CanAutM3

According to Tire Rack, the 265/35R19 PSS and 305/30R19 PSS both have a diameter of 26.3".

That is the equivalent of running a square setup. My track setup is also square and I cannot really use MDM with it because it keeps kicking in all the time. If you don't push the car too hard, it will not matter. But if you do get on it, I believe you will get frustrated.

Have you considered 275/30R19 in front with 295 or 305/30R19 in the rear? That would work.

Wouldn't 275 bubble over my 9.5 front wheels? I really want a flush look and don't want the car tricked into unnecessary slippage. I was told by two shops 255/35 and 295/30 or 265/35 and 305/30 but I wanted 265:35 and 295/30 but I have been told on here none of those combos would work!

[Mark's M]

Originally Posted by Padfan9

Wouldn't 275 bubble over my 9.5 front wheels? I really want a flush look and don't want the car tricked into unnecessary slippage. I was told by two shops 255/35 and 295/30 or 265/35 and 305/30 but I wanted 265:35 and 295/30 but I have been told on here none of those combos would work!

IMO, if you are any kind of a driver and will be pushing the car at times, your quest to achieve a 40mm difference in width between front and back will get you into trouble. Even 30 mm is pushing it.....no pun intended.

[Padfan9]

Originally Posted by Mark's M

IMO, if you are any kind of a driver and will be pushing the car at times, your quest to achieve a 40mm difference in width between front and back will get you into trouble. Even 30 mm is pushing it.....no pun intended.

So you are saying 275 and 295 is best? 265 and 295 wouldn't work? If you look at the different in height, 255 goes with 295 and 265 with 305. 275 is pretty ridiculous for the front tires..

[CanAutM3]

Just found out about a non-negligible drawback to the 275-295/35R19 setup: aquaplaning .

I just drove back home from work in a heavy downpour, and the car aquaplaned much more than it used to on the stock 255-275/35R19 setup. I expected a little more floating, but not that much. The car now gets skittish running through relatively mild puddles. The car is still plenty drivable, it is not dangerous or anything. It is just not as good as it used to when driving through standing water.

[gthal]

Originally Posted by CanAutM3

Just found out about a non-negligible drawback to the 275-295/35R19 setup: aquaplaning .

I just drove back home from work in a heavy downpour, and the car aquaplaned much more than it used to on the stock 255-275/35R19 setup. I expected a little more floating, but not that much. The car now gets skittish running through very mild puddles.

I hadn't thought of that but that is a great point! Something to think about for sure.

[CanAutM3]

Originally Posted by gthal

I hadn't thought of that but that is a great point! Something to think about for sure.

It is a rather big drawback for me, because my street MPSS are also my wet track setup .

[TahoeM3]

Originally Posted by CanAutM3

Just found out about a non-negligible drawback to the 275-295/35R19 setup: aquaplaning .

I just drove back home from work in a heavy downpour, and the car aquaplaned much more than it used to on the stock 255-275/35R19 setup. I expected a little more floating, but not that much. The car now gets skittish running through very mild puddles.

That's strange, because I haven't had that problem at all, and I live in Florida where it rains heavily pretty much every day in the summer.

[Mark's M]

Originally Posted by Padfan9

So you are saying 275 and 295 is best? 265 and 295 wouldn't work? If you look at the different in height, 255 goes with 295 and 265 with 305. 275 is pretty ridiculous for the front tires..

What I'm saying is that you need to keep the stagger respectable. A 40mm difference between front/back will result in the rear tires overpowering the fronts during extreme driving, i.e. understeer that's fairly significant which you absolutely do not want. Personally a 30mm difference would raise my eyebrows but if you're worried about looks over performance, it'll work.

[Padfan9]

Originally Posted by Mark's M

What I'm saying is that you need to keep the stagger respectable. A 40mm difference between front/back will result in the rear tires overpowering the fronts during extreme driving, i.e. understeer that's fairly significant which you absolutely do not want. Personally a 30mm difference would raise my eyebrows but if you're worried about looks over performance, it'll work.

Well that leaves me with no good options!

255/35 275/35 sucks and won't work

265/35 and 295/30 I wanted but then the height is different and will cause DSC issues.

265/35 and 305/30 is too big of a staggered difference and will hurt performance

275/35 and 295/30 is way too big on the front and I don't even know if it would be flush with a 9.5 wheel.

Not sure what to do again...

[gthal]

Originally Posted by Padfan9

Well that leaves me with no good options!

255/35 275/35 sucks and won't work

265/35 and 295/30 I wanted but then the height is different and will cause DSC issues.

265/35 and 305/30 is too big of a staggered difference and will hurt performance

275/35 and 295/30 is way too big on the front and I don't even know if it would be flush with a 9.5 wheel.

Not sure what to do again...

Why don't you use a 295/35 rear with the 265/35 front? Part of your issue is trying to go 30 in the back with a 35 front. Or just go 265/305 even if the stagger is a bit too large. Likely won't really matter for the street.

This is the problem with modding wheels... often compromises need to be made in some way.

[Padfan9]

Originally Posted by gthal

Why don't you use a 295/35 rear with the 265/35 front? Part of your issue is trying to go 30 in the back with a 35 front. Or just go 265/305 even if the stagger is a bit too large. Likely won't really matter for the street.

This is the problem with modding wheels... often compromises need to be made in some way.

The 35 rear wouldn't look as good. I like having less tire because it makes the wheel look bigger and better but a 30 front would make the ride harsher.

You're saying 265/35 and 305/30? My only concern besides too much stag is if it would rub.

[gthal]

Originally Posted by Padfan9

The 35 rear wouldn't look as good. I like having less tire because it makes the wheel look bigger and better but a 30 front would make the ride harsher.

You're saying 265/35 and 305/30? My only concern besides too much stag is if it would rub.

That's what I mean when I say compromise... 30 looks better but 35 might function better

If the offsets of the wheels are right for a 305, it shouldn't rub.

Also, I really don't think the 305 rear makes that much of a difference relative to understeer outside of a track. If you are getting excess understeer because of 20mm extra front/rear stagger then you are going WAY, WAY, WAAAYYYY too fast on the street. I would bet you wouldn't even notice on a track unless you were a fairly advanced driver.

The biggest consideration, IMO, the height ratio front/rear relative to DSC. Therefore, given everything you are trying to balance, I would go 265/35 and 305/30.

[Padfan9]

Originally Posted by gthal

That's what I mean when I say compromise... 30 looks better but 35 might function better

If the offsets of the wheels are right for a 305, it shouldn't rub.

Also, I really don't think the 305 rear makes that much of a difference relative to understeer outside of a track. If you are getting excess understeer because of 20mm extra front/rear stagger then you are going WAY, WAY, WAAAYYYY too fast on the street. I would bet you wouldn't even notice on a track unless you were a fairly advanced driver.

The biggest consideration, IMO, the height ratio front/rear relative to DSC. Therefore, given everything you are trying to balance, I would go 265/35 and 305/30.

Yea that's what I was thinking! Do you think the 40Mm difference will hurt performance at all? I'm confused as to why the other guy said that?

[gthal]

Originally Posted by Padfan9

Yea that's what I was thinking! Do you think the 40Mm difference will hurt performance at all? I'm confused as to why the other guy said that?

Here is my take. The 40mm wider rear is 20mm wider stagger than OEM. This, in theory, keeps the rear more planted and allows the rear to go into a corner faster with more stability. This, in theory, would allow you to push a smaller front tire beyond its limit easier and cause understeer. IMO only, this is not something you would notice unless you were at the very limit on a track. Certainly not on the street. The rear will rotate less with a wider rear and more grip. That simply puts more stress on the front but, IMO, this car doesn't understeer much anyway so I don't personally think it will be an issue.

I'd love other (CanAutM3 ) views on this but that would be my view.