Unitah

Hey guys,
I know this has been posted before, but for the life of me, I can not find the darn post on the boards. So, I apologize for the re-post.

I am about to purchase a new set of Michelin Pilot Sport Cups for the GT3. Currently I am running the stock sizes of 235/35ZR19 in front and 305/30ZR19 in the rear. The car is set up running -3.0° in the front and -2.43° in the rear. Stock OEM rims. What are the largest Sport Cups I can use without rolling the fenders? The next sizes up would be 245/35ZR19 and 325/30ZR19. Will they fit? Has anyone tried? Any advantage / disadvantage to going up one size if possible?

I spoke to Damon at Tirerack; he wasn't certain about fitment of the larger sizes. He also said that non-N-Spec tires in GT3 sizes are no longer available, so, we are all stuck with the harder compound N-Spec (N0) Sport Cups for the GT3.

I appreciate everyone's input,
Thanks!

sasportas

My opinion, and again, just my perception, I prefer other tires more than the 19" sport cups that are available for our car. Others my chime in, but the 19" sport cups for our car is more similar to a street tire than say a Hoosier or Toyo.

Consider Hoosier R6 235/35/19 x 315/30/19 or Toyo in 19"

Or 18" Hoosier 245/35/18 x 315/30/18 or BF Goodrich 265/35/18 x 335/30/18

Terry L

I just ordered replacement Hoosier 315/30/18s from Tire Rack and there is a warning that this tire won't support the rated load for the 997 GT3. This is a new one on me. Tire Rack gives the load rating but the number means nothing to me since I don't know what loads exist on the tire in action. The rated loads for the Hoosier 19s are higher but not dramatically. Anybody have any ideas?

NJ-GT

On the stock wheel, you can use the 265/30R19 (this is a full spec MPSC) and the 325/30R19 (this is the N-spec from the 997 GT2). This will help to defeat the excessive understeer that comes with the car. I also ran a 345 full spec MPSC, but it's a tight fit.

I had no rubbing problems with either 265 or 325 MPSC, on a lowered 997 GT3 RS running at -2.5 camber with the strut tops on the factory position and stock wheels.

Another option is the 265/305 R888, good street/track tire, and affordable. This is what I'm running now as street tires.

DRG13

Unitah,

just an fyi, you probably already know this, but, the Hoosier R6 is not a street tire...your post didn't specify street only or track/street...the R6 is track only..yes a few of us have driven them on the street to get to or from the track, but it's a bad idea...

TripleM

stock rims 8.5J n 12J .....245 n 325 are probably the max available

265 in the front is too squashed in and bear in mind that 265 of Cup tires are like 275 on street tires due to wider shoulder block

I m on 245 front and stock 305 rear..of course the 245 being non N-spec

Fits well n runs well but after trying both Corsa n MPSC, I prefer Corsa

NJ-GT

I ran the 265 MPSC on stock wheels at a heavy load high banking race track (California Speedway Roval). My lap times where under 1:50s. At the same track with my previous GT3 on Toyo RA-1 275/335 with 10"/12" x 18" wheels, my fastest lap time was 2.5 secs slower. Temperatures for both front and rear tires in the GT3 RS where in a 15 degrees Fahrenheit range, tire pressures at 32 psi front/ 34 psi rear hot (started at 26/28).

The 265 MPSC is a 265 wide tire, it is indeed narrower than other R-comp 265 tires. The 315 MPSC is much wider than the average 315 tire. The 345/19 and the 335/18 MPSC are also wider than average, with the 325/19 being narrower than the 315/18. This is information from tires measured side by side with measure tape.

A recent sample I took when testing fitments for the 997 GT3 RS and Cayman S, I found a 265 being narrower than a 235 from the same brand and model tire.

Most recently I ran the Pirelli Corsa system tires against Hoosier A6. Three different road courses, where I found the Pirelli being 5 to 6.5 seconds slower than the A6. At the same venue, I tested the MPSC multiple times against the A6 (same day, same car, same driver, same road course), and the difference per average 60 secs laps was in between 2.5 secs and 3.8 secs, when comparing the Hoosier A6 to the Michelin Pilot Sport Cups. The MPSC shows consistently faster lap times compared to the Pirelli Corsa.

The Pirelli Corsa tires are not remotely close to the MPSC & R888 lap times in my experience.

By the way, the 245/19 MPSC is not yet available as a full spec MPSC, it's not a N-spec either. It has an extra groove, and it is built as a BMW OEM optional tire in Europe. I have a set of 245/265x19 MPSC for my E92 M3 right here.

Some pics with the 265 MPSC on stock 8.5" wheels.

Unitah

DRG13,
Yes, I know the Hoosiers are track only, I appreciate you looking out. I am looking for a track / street tire at this point. Thanks

NJ-GT
So it seems like the 3 options I have would be
1. OEM sizes
2. 245/35R19, 325/30R19
3. 265/30R19, 325/30R19

Which setup to choose? Is there a real advantage in going 245/325 as opposed to the OEM 235/305?
Anyone do any direct comparisons?
Thank!

GlennMc

Have you tried the Corsa R yet over in the states ?

325 rear, overall grip isn't 'that' far of the Hoosiers IMO....


G.

Snowboarder54

NJ-GT, when you say the R888 is a good street/track tire for the GT3 how would you compare the two, with the MPSC being a 10? And when you say street, do you mean stoplight to stoplight or do you have twisties in NJ? Thanks.

NJ-GT

Los Angeles is not nearby New Jersey, and last time I was in NJ there were not that many turns or elevation changes.

Los Angeles Crest Highway (google it) is 8 miles from home.

IMO, MPSC is not a 10 it is a 6 on N-spec and a 8 on full spec, with a 10 being the R6, assuming the rating applies to DOT-R tires dry performance. The R888 is a 8 as well, but in the wet it works better than the MPSC. The Corsa is a 4, the PS2 a 4.

Unitah

NJ-GT,
We can no longer get Non-N-Spec tires for the GT3 though, can we? I was told they were discontinued.
I am still uncertain which MPSC sizes to go with...

Snowboarder54

Thanks, didn't realize you were in LA, I'm from Manhattan Beach so know AC Highway. So, your giving the R888 a higher grade then the MPSC, think I will try a set. Maybe I can get more then 3K miles out a set of rears!!

NJ-GT

Keep in mind that the R888 is the spec tire for the Speed World Challenge Touring and GT classes, and the Spec Boxsters, so a lot of development is happening with multiple car platforms.

The R888 is as fast as the MPSC full spec, the N-spec MPSC is about 1 second slower per 60 secs lap compared to the full spec, I doubt they use the same compound for both the N-Spec and the regular (full spec) MPSC.

The 245/R19 MPSC is a BMW-spec tire designed for my E92 M3, not a regular spec MPSC, I have a set here with no use because I was planning on taking the M3 to a few track days, but I gave up after a couple of autocrosses (needs 300% stiffer springs + new shocks to work decently, too much body roll).

Unitah, you can go 235/305, 235/325. 245/305, 245/325, 265/305 or 265/325 on the stock wheels. My choice is 265/325, because the full spec MPSC 265 gives me a lot of bite braking and turning, in fact the car gets a little loose, but that's fixed with sway bars, moving the front bar 2 holes to stiff, gaining on steering feedback, no losing grip during braking, and helping to put the power down on the rear axle much better.

I really doubt the N-Spec MPSC has been discontinued. The 2010 GT3 is being tested in Europe with N-spec MPSC on the same sizes as the 2007/2008 GT3/GT3 RS.

Unitah

NJ-GT,
It isn't the N-Spec that are discontinued, it is the better NON-N-Spec (softer compound) that are discontinued in GT3 sizes.
So you are pushing for the 265/325 combination for the 997 GT3. Few questions then before I order.
1. Do you see any negatives to running the softer Non-N-Spec 265 in the front with an N-Spec 325 in the rear?
2. Will this work with my current alignment, or should I make adjustments?

FRONT
Camber -3°00’ / -3°00’
Caster 9°50’ / 9°40’
Toe OUT -0°05’ (1/16”) / -0°05’ (1/16”)
Ride Height 93mm / 94mm

REAR
Camber -2°43’ / -2°43’
Toe IN 0°10’ (1/8”) / 0°10’ (1/8”)
Ride Height 118mm / 120mm

SWAY BAR FRONT: 2nd hole closest to elbow
SWAY BAR REAR: 1st hole closest to elbow (full stiff)

Thanks...