RWHEELS

I currently have a 2011 brembo gt with the stock 19x9 wheels, 255/40/19 tires. I am wanting to get an aftermarket 18x10 prob sve drift wheel and get a 275 tire on all four to get more rubber on the road and a little less weight. Plus I can get 275 18 inch tires at the same price as 255 19 in tires which is important to me since my tires only last 10-12 months. Are there any issues with either getting a wider tire or a smaller diameter wheel that I haven't thought of? I know the overall diameter of a 275/35/18 tire is 25.5 in and my current 255/40/19 is 27in, how noticeable will that be? I have a tuner so I can adjust speedo, etc.

Simon1

If you are looking for more traction the wider tires won't help as much as you think. You would get better bang for the buck by getting a better compound, something designed for competition.

Remember that a wider tire will have more lateral contract, but a taller tire also gives a longer contact patch. I wouldn't be surprised if the contact patch your looking for doesn't change at all or just gets slightly bigger.

Secondly, what's the weight difference? Not only overall weight, but the change in centrifugal mass? Something to think about.

Norm Peterson

It's about the same as moving up to the next numerically higher axle gear ratio - think in terms of swapping 3.55's out for 3.73's (or 3.73's for 3.90's, or 3.31's for 3.55's).

My track day tires are 285/35-18 (25.9"), and there is definitely a little more 'sparkle' to the throttle response.

The weight issue, and even the matter of rotating weight are not significant (and the rotating "weight" of your proposed 18" setup could very well be the smaller amount. Just to be a little pickier, mass moment of inertia is a function of weight times radius(squared), meaning that the smaller radius of the wheel barrel and tire OD are both working in favor of the 18's even if the wheel and tire weights were the same. There's a bit more to this, but that's the general gist.

A wider tire may tramline or rut-wander more, but this isn't strictly a function of tire or tread width. Some tires are just worse about this than others even in the same sizes.

Are your tires wearing out evenly? If not, your alignment and/or inflation pressure settings might need a little tweaking to better suit your driving. Factory preferred alignment settings and door sticker inflation numbers are good enough as average settings for average people and average use, but can't be guaranteed to fit everybody's driving equally well.


Norm

RWHEELS

thanks guys, definitely some good points to consider. Overall my reason for new wheels is about half aesthetics and half handling improvement. I do autocross, track days and mtn roads , no drag racing. I am trying to minimize the effective gearing change with the overall wheel/tire height as the 3.73's are already a bit too much for autocross and everyday driving so I'm trying to figure out how close I can get and how much an inch or 1/2 inch decrease in height will make.

DPE

A 275/40/18 is closer to your OEM Brembo setup, though you're still going to lower your overall gearing a bit. One reason I got the Brembo package but stayed with the 3.31 rear diff. 275/40/18 all around on the 18x10 Drifts should work well, and those Drifts are about 6lbs lighter than OEM Brembo wheels; you'll notice that, I believe (not sure about tire weight between those sizes). I run GT500 18x9.5" wheels on mine (2 different sets) with 275/40/18, and the car seems to work well with that setup; no rubbing or the like even being lowered about an inch. And despite the smaller diameter, I think it looks better with wider rubber, fwiw.

I have not noticed excessive tramlining or in fact any ill effects. And I too have a tuner and adjusted accordingly to dial in the speedo. Definitely sounds like a good way to go IMO.

RWHEELS

thanks! Yes the 275/40/18 is only .3 in shorter so that would be the closest, but unfortunately my favorite tires, sumitomo htr z3 don't come in that size, I'm open to another tire, but in terms of price/performance I havent found anything that comes close.

Norm Peterson

In 2500 or so street miles (not all mildly driven miles, either) and six track days with the tires talking in more of the corners than not I managed to wear almost 3/32" off my set of Michelin PSS. While the up-front cost looks high, their durability at least on the S197 chassis does seem to be there. I am running about -2° camber, though.

The PSS comes in 275/40-18 . . . and as of a few minutes ago TR was still showing a few still in stock, with an estimated late November restock date.


Norm

DPE

Ah the sweet Sumi HTR Z3; not a great tire at anything, but a good tire at everything. And so very cheap. And then they killed it off in that size!

A better tire for not a lot more money is the Cooper RS-3. Definitely comes in 275/40/18 as it was developed with Roush for the Roush Mustangs (in that specific size). No idea if it would hold up for track use, but on the road I liked it better than the HTR Z3 (a bit more grip, a bit more direct feeling) and the price is right over at Discount Tire Direct. Given the large outer blocks, there's at least a decent chance they'd survive some casual track days.

One day I'll step up to good stuff like the Michelin PSS, but it's just so hard to stomach that up front cost. Sounds like it's worth it though, if they are holding up that well. Norm, do you have another tire you've run in the past on track that you can compare the wear rates too? Any others you like or didn't like?

Norm Peterson

I did my first half dozen track days on Goodyear Asymmetrics (the original ones, not the 2's) in 255/45-18, mounted on 18x9.5 FRPP/GT500 wheels. Got somewhere above 20,000 street miles on them as well. As it happened, all four were finally down at or under 3/32 and there were some sub-2/32 grooves out near the outboard shoulder. Not good enough for non-freezing weather even if they weren't little round rocks, so they've been scrapped (I pick up the second pair from my tire guy this morning).

They weren't quite as fast as the PSS - not unexpectedly. But I think they'd have held their own against the Cooper-shod Roush Mustang that I did share a few sessions with after getting the PSS. Admittedly, the Roush driver was running with an instructor (while I was solo'ed), but I was lapping him well inside a 20 minute session every time, I'd be on his bumper within about 7 or 8 laps.



Norm

RWHEELS

I checked out the cooper rs3 and at $176 they look pretty good, I might give them a try. Someday I will try the pilot sports just to see if there as good as everyone says, but the price would hurt! LOL