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255/35/20 front with the factory diameter
295/30/20 rear
+1, jpgunn knows what he's talking about. BTW, stock diameters for the GT4 are 26.8" for the 245/35-20 front and 27" for the 295/30-20 MPSC2. You want to keep the front and rear diameter ratio within 3-6% of stock in order to not confuse the onboard computers.
+1, jpgunn knows what he's talking about. BTW, stock diameters for the GT4 are 26.8" for the 245/35-20 front and 27" for the 295/30-20 MPSC2. You want to keep the front and rear diameter ratio within 3-6% of stock in order to not confuse the onboard computers.
I was looking to the SPORT AUTO super test GT4 to see if the car was corner balanced or not. In the same issue, they have tested R-comp tyres as well. Pirelli Trofeo R, Michelin Cup 2 and Dunlop Sport Maxx. The reference tyre was a regular Pirelli Pzero and car was Golf R.
The recommended tyres pressures were also written.
- For street use cold 2.6 bar
- For track use warm 2.3 bar
I think the Golf should be same pressure all corners. It is a bit heavier then GT4 and GT4 has mixed tyre sizes. But this shows that from cold the pressures should be 0.4-0.5 bar less, if you are not trying to push the car too much.
If we take the base pressure for GT4 and reduce 0.4bar cold, might be a good start. Actually i havent received the car yet. What was the regular pressure?
Please make 20 inch RE-71R tires to fit the last 4 years of Porsche cars.
255/35/20 with a 26.8" diameter would be perfect for the front of Cayman's and Bosters.
245/35/20 with a 26.8" diameter would be perfect for the front of 991s
295/30/20 with a 26.8" to 27" diameter would be perfect for the rear of 991s
305/30/20 with a 27" to 27.2" diameter for 991 GT3, Turbos, and 991.2s
Please make 20 inch RE-71R tires to fit the last 4 years of Porsche cars.
255/35/20 with a 26.8" diameter would be perfect for the front of Cayman's and Bosters. You want those shaved? Otherwise its 27".
245/35/20 with a 26.8" diameter would be perfect for the front of 991s and GT4s.
295/30/20 with a 26.8" to 27" diameter would be perfect for the rear of 991s and GT4s You want those shaved? Otherwise its 27".
305/30/20 with a 27" to 27.2" diameter for 991 GT3, Turbos, and 991.2s You want those shaved? Otherwise its 27.2".
Good on ya! Where did you get their ear? I'll vote too.
Contact link for Bridgestone is back on the last page in my post #58 (along with Nitto's). Here's the phone number for their customer service:
1 (866) 775-6480
Monday – Friday 8:00 am – 10:00 pm (Eastern Time)
Saturday – Sunday 8:00 am – 8:00 pm (Eastern Time)
Let's all blitz them with requests. I'm going to stir up the GT3 forum too.
I also emailed Jeff Speer from Hoosier to ask when the long-awaited 20" A7 & R7s were coming and it doesn't look like they will be out for Porsches until maybe the last half of 2016, after the Corvette folks get theirs. Here's what he said: "...we do have intentions on offering 20" - A7 and R7 tires for 2016. The Corvette sizes will come first and then Porsche later. Stay tuned to our website or write me next Spring for any news regarding this."
i´ll also start with the GT4 in spring some autocross/slalom/hillslalom/hillclimb competitions.
swaybar front in Soft - back in Medium or Hard.
max out chamber with shims.
if not enough possible with shims (i guess -2,3° will be maximum in the front with shims) --> i have to buy from Manthey-Racing a suspension kit (longer front part of the front control arm, longer tie rod (longer thread), longer "control diagonal arm". all those parts which i mean showed in red in the picture.
does anyone have already experience with upgrading the allignment for autocross?
tires i have to use MPSC2.
pressure i will play - but for sure something around front 24 rear 28 psi at 15°C outside and tire nearly cold as it has to be based on the rules (no pre-heating)
I was happy with 32F, 35R on stock MSPC2, and liked the way the wear looked. Factory alignment, front swaybar middle, rear stiff. Street tire FTD.
If I were trying to tune balance, I'd go down rather than up. This was also a fairly cold event (dry, 55F), and things might be different in a long 100F summer day. Surface was typical parking lot asphalt with some elevation changes and camber.
I had 32 front 35 rear hot and that got good feedback from my co driver who took ftd for street tire.
Originally Posted by Yomi
I was happy with 32F, 35R on stock MSPC2, and liked the way the wear looked. Factory alignment, front swaybar middle, rear stiff. Street tire FTD.
If I were trying to tune balance, I'd go down rather than up. This was also a fairly cold event (dry, 55F), and things might be different in a long 100F summer day. Surface was typical parking lot asphalt with some elevation changes and camber.
Okay great. I'm currently at 29F 33R cold so I will let a little air out for the rears and may need to add 1-2 psi for the fronts.
Two weeks ago was my first event with the car. I ran 30 psi front and rear, hot, on the dunlops. In the afternoon when hot psi rose to 34, it skated around more so I let air out to 30 again. I didn't try less - wear was right to the line at 30. I ran front sway at middle, rear at stiff. Front camber is -1.75, rear is -2.00. Got 2nd overall on Saturday, 4th on Sunday. Never had a perfect run and was hauling passengers - could have done better. Launches were tougher than I expected though. My clutch was not happy. I am happy enough with the setup to concentrate on better driving now.
12-11-2015, 06:01 PM
