PorscheAddict

It's time to start thinking about track tires for the 18's that many of us will be getting this Fall. I got 18x9 front 18x10 rear, which their guide shows to be fine with 245/45/18 and 265/45/18 with -2 camber and 255/40/18 and 275/40/18 with -2.5.

I'm already running -2.5 and may increase it anyway. I had my eyes on 275/255, but the diameters seem hard to find close to stock since few make 275/40 (lots of 275/35). Any reason 275/35/18 and 255/35/18 would not work? That would be within 0.2 inch of stock rake and would lower the car 1.5" in front and 1.3" inches rear, while increasing tread width about half an inch rear and .8 inches front. RE71 is what I'm eyeing.

Thoughts?

Apex Wheels

Thanks for kicking off a thread in relation to tires. As you know, tire selection really comes down to how much experience the driver has on track, how they plan to use the car (double duty or track only) and seasonal budget (how many track days you would like to get out of said tire). There aren't are ton of options in the sizes needed for the 981, but there are two very good options (bolded) in the following configuration which has proven to work well on this chassis.

OEM 981 Tire Specifications
Front: 235/35-20 - 26.48" tall
Rear: 265/35-20 - 27.3" tall
--> 0.8" / 3% difference in diameter from front to rear

Aftermarket Comparison
Front: 245/40-18 - 25.72" tall (-2.9% shorter than OEM front tires)
Rear: 275/40-18 - 26.66" tall (-2.4% shorter than OEM rear tires)
--> 0.9" / 3.5% difference in diameter from front to rear

Extreme Summer Tires:
Hankook RS4
Nitto NT05

R-Compound:
Nitto NT01


The Bridgestone RE-71R is a very capable tire, but their longevity is not anywhere close to other extreme summer tires in the 200 TW category. They wear quicker than NT01's, therefore NT01's get my vote as a more predictable tire that is known to get better as they wear. In fact, NT01's rarely heat cycle out.

If an enthusiast is still building speed or wants the ability to use their tires on and off the track, the Hankook RS4 is one of the best extreme summer tires. Assuming the car is setup correctly, you can get a lot of street miles and several track days on these tires as apposed to the RE-71R.

- Ryan

PorscheAddict

Thanks for the reply. I was more interested just in fitment. I know RE71 are awesome (and am fine with the mileage penalty). Folks over at P9 are running 255/35 275/35 with similar offsets so I'm going to try that, I think. Going an inch less diameter should help gearing, too.

FWIW, a good friend of mine who instructs with me runs RE71 on his E46 M3 street/track and gets 8-10 days and a few thousand street miles out of RE71 with -3 camber in front. That's running to cording, obviously, so they're kinda heat cycled out toward the end.

Apex Wheels

Copy that. In regards to the 255 / 275 combo:

OEM 981 Tire Specifications
Front: 235/35-20 - 26.48" tall
Rear: 265/35-20 - 27.3" tall
--> 0.8" / 3% difference in diameter from front to rear

Aftermarket Comparison
Front: 255/35-18 - 25.03" tall (-5.8% or 1.5" shorter than OEM front tires)
Rear: 275/35-18 - 25.58" tall (-6.7% or -1.7" shorter than OEM rear tires)
--> 0.6" or 2.2% difference in diameter from front to rear

I do not have any seat time with this tire combo, but they are very short on paper. This could be beneficial in the gearing department, but I am interested to know how car reacts otherwise. PSM and all the nannies check out OK? I would also be concerned with ride height clearance assuming one has already lowered the car.

There are certainly a lot of great extreme summer tires to choose from, the top three are all available...

Extreme Summer Tires:
Bridgestone RE-71R
Hankook RS-4
Direzza ZIII

R-Compound:
Toyo R888-R (I much prefer the NT01 personally)

A good running thread on P9 - LINK

PorscheAddict

Thanks, your math looks better than mine. 1.5-1.7" is a LOT lower. That's more difference than going X73 or installing coils (usually). Hmm. We have a few weeks to ponder. I like NT01's too, but think they're old tech and much worse if it rains than RE71. Similar grip, I think.

Scooby921

I'm using different wheels, but I do find a 265 width tire to be too narrow on a 10" wide rear wheel. They fit, but they look to be a bit stretched. The sidewall isn't vertical and this changes load transfer through the tire and contact patch. When steering and loading the car into a corner there is less flex in the sidewall, so the time between steering input and steering response is shorter (yaw delay). It requires adjustment of driving style because you have less time before you reach maximum load at the contact patch. The car can be faster and more responsive, but it is also less forgiving. Moving to a 285 on a 10" wide wheel will increase maximum grip while also making the car a little easier to manipulate at the limit.

Apex Wheels

While there are a number of factors to consider like tire brand (not all are created equal), personal driving style/preference, and vehicle weight, we promote installing wheels on the widest end of the suggested spectrum for any given compound. This ensures proper sidewall support which leads to superior handling characteristic and less sidewall deflection as you mentioned. It really is a case by case basis due to the massive disparity in some compounds advertised size vs real world width. Many of you club racers out there know there are a few Hoosier R7's out there (245 or 255 IIRC) that run wider than some 275mm compounds.

If I were to make a general outline, it would look something like this:

265mm - 9.5" or 10" wheel
275mm - 10" or 10.5" wheel
285mm - 10.5" wheel
295mm - 11" wheel
305mm - 11" or 11.5" wheel
315mm - 11.5" or 12" wheel

As they say, there are many ways to skin a cat.

- Ryan

gman3280

PorscheAddict

Tire rack is showing 275/40/18 as sold out for the season in RS4 anyway, looks like. Has anyone ran 255/35 275/35 18's on a 981?