JarheadGT3

Esteemed GT3 forum, long-time listener, first-time caller...in the middle of prepping a 997.1 GT3 for track season this year and am trying to get some tire sizing info together on DOT Hoosiers (I guess that would be R7's now).

I currently run Nitto NT01's at 245/40 up front, and 305/35 in the rear. Did a quick search on Tire Rack and didn't get anything back for those rears. Seems I could only get Hoosier Wets with a 305/30 rear, or R7's with a 315/30 rear. Is this is an in-stock issue, or do they just not come in those sizes?

Protocav

The R7 size lineup is a little spotty for the GT3, in terms of keeping similar rolling diameters (if that's important to you). A good setup is the 255/30-18 and 335-30/18 sizing that is available for the R7. I have put this 335 on the back of my narrow body GT3 with no issues, and my fenders are not rolled. I run a pretty low ride height as well.

The 255 front will fit on a 9" or 9.5" wide wheel, and will require some camber (which you need for R comps anyways).

both sizes have a smaller diameter than the NT-01's that you run (my standard setup as well) so you get a little bit of fender clearance, which is nice because the tires are so wide.

The 245/40-18 R7 is an option as well, but would be large compared to the rear, if paired with the 335. it is actually a wide tire though, and should be run on a 9.5. I put it next to my 245/40 NT-01's, and they were over 1/2" wider!

P.J.S.

Safe fitment
245/35/18
315/30/18

also works
255/35/18
335/35/18

buy here: http://competitionmotorsport.com/18-Rim-Size_c43.htm

best deal in the country that I could find
no affiliation, just happy customer

JarheadGT3

Excellent info, thanks guys. I'll definitely check out that link - I always default to just the big two (DTD and Tire Rack) when I go tire hunting.

Protocav, you bring up a good variable that I should put more thought into. I think I'm on 8.5" wheels up front, may have a set of 9" but need to verify. I'm also running Cup LCA with a healthy dose of camber so I should be able to absorb some more width up front.

JarheadGT3

Another dumb question...are the GT3's as susceptible to diameter differences like the TT? In other words, if you're not within a few percentage points of even F/R ratio, will it throw some errors?

TAI2

I run 245/35/18 and 315/30/18 and Competition Motorsports is a great source.

You want to keep the % difference in diameter F/R around 2-3% as I find this helps reduce ice-mode with our cars. Ice-mode is well covered in the GT3 forum.

philstireservice

Not so.....Phil's Tire Service also offers FREE SHIPPING on Hoosiers $1399 and over. But we can heat cycle them if you like for ONLY $12 per tire. That is the best deal in country on Hoosiers !!

So BUY HERE ....https://philstireservice.com/

Protocav

Phil, thanks for the heads up!!

And yes, ice mode sucks. Once it happens to you, your braking habits will change immediately. If the braking zone is bumpy, it's inevitable.

JarheadGT3

Great, thanks...the Turbo has the same concern, just wasn't sure if it was an AWD thing or not. What size rim (width) are you running up front?

JarheadGT3

Ditto Phil, I'll definitely give you guys a look. I'm a fan of having the heat cycle option.

MC 968CS

Has anyone tried the 19" Hoosiers on a 997.1? What sizes and feedback?

Tom@TPC Racing

Sorry to be off topic from the thread but this is something we have been developing for couple years to help prevent this. We have been reducing(sometimes even eliminating) ice mode in bumpy brake zones using our DSC dynamic suspension module and software to add rebound to the rear shocks during braking to keep the nose of the car from diving while keeping the front shocks supple. With the front end being more compliant the front tires have more grip braking over bumps which reduces the triggering of ABS and ABS related activities when braking at the same rate. This suspension management strategy allows for deeper braking over smoother brake zones without ABS intervention.

MC 968CS

Thanks Tom, that product looks great! I also find squeezing the brake pedal hard but not thumping it makes a phenomenal difference in ice mode not activating when threshold braking in a 997 GT3

So....Back on to this thread topic....Hoosier. Has anyone tried the 19" Hoosiers on a 997.1? What sizes and feedback?

JarheadGT3

Tom already knows how I feel about the DSC, but for anyone else considering it...if I had three hands, I'd give the DSC module three thumbs up. Single biggest improvement I made on the TT last year was swapping OEM PASM for the DSC. Changed the car completely.

As such, it was one of the first changes I made to the GT3. Only this time around, I took it up a notch and paired it with the Tractive DDA coilovers to get maximum benefit from the wider and more responsive dampening range. Felt phenomenal at Sebring earlier this month...especially when watching the other cars bounce and hop around!

MC 968CS

So....Back on to this thread topic....Hoosier. Has anyone tried the 19" Hoosiers on a 997.1? What sizes and feedback?