18" Hoosier (DOT) Sizing for 997.1 GT3
#1
18" Hoosier (DOT) Sizing for 997.1 GT3
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?
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?
#2
Rennlist Member
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!
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!
#3
Rennlist Member
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
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
#4
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.
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.
#5
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?
#6
Rennlist Member
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.
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.
#7
Former Vendor
Join Date: Feb 2008
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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
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
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/
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#8
Rennlist Member
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.
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.
#9
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?
#10
#12
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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.
__________________
PCA National Instructor
TPC Racing stats:
2023 Porsche Sprint Challenge 992 Cup Am Champion
2023 Porsche Sprint Challenge GT4 Pro-Am Team Champion
2022 Porsche Sprint Challenge 992 Cup & 991 Cup Champion
2020 IMSA GT3 Cup Challenge 2nd Championship
2018 IMSA GT3 Cup Challenge 2nd Championship
2016 IMSA GT3 Cup Challenge Champion
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PCA National Instructor
TPC Racing stats:
2023 Porsche Sprint Challenge 992 Cup Am Champion
2023 Porsche Sprint Challenge GT4 Pro-Am Team Champion
2022 Porsche Sprint Challenge 992 Cup & 991 Cup Champion
2020 IMSA GT3 Cup Challenge 2nd Championship
2018 IMSA GT3 Cup Challenge 2nd Championship
2016 IMSA GT3 Cup Challenge Champion
2013 IMSA GT3 Cup Challenge Champion
2006 Rolex-24 @ Daytona GT Champion
2004 Grand-Am SGS Class Champion
#13
Pro
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?
So....Back on to this thread topic....Hoosier. Has anyone tried the 19" Hoosiers on a 997.1? What sizes and feedback?
Last edited by MC 968CS; 02-14-2016 at 03:54 PM.
#14
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.
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!