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The laptime difference on a stock GT4 vs GT4 CS when same sport auto driver lap same day is ca. 3 sec on this short 2.6km track. My thinking Is if some One accually find 3 seconds in hosier vs cup2 on a stock gt4, them tire would be sticky like glu? And will for sure put some stress on car as a whole. For sure the whole houer/wear instruktion that Porsche print for stock gt4 is out the Windows and One would need an whole new attention on mantainance i guess.
The laptime difference on a stock GT4 vs GT4 CS when same sport auto driver lap same day is ca. 3 sec on this short 2.6km track. My thinking Is if some One accually find 3 seconds in hosier vs cup2 on a stock gt4, them tire would be sticky like glu? And will for sure put some stress on car as a whole. For sure the whole houer/wear instruktion that Porsche print for stock gt4 is out the Windows and One would need an whole new attention on mantainance i guess.
2,6km flat wide track
Although I've heard people say 3 seconds for hoosier, I don't think that's accurate, especially on a short course. From the data I've seen, it's about 2 seconds on a 2 minute course vs. Cup 2s, NT01. So, for your comparison, on a short course, it would only be a little over a second faster. Also, from what I've read, hoosiers will be slower after 10 HCs.
In any case, it's enough to see your friends leave you on the track, but not enough to really drastically change the g-forces in a corner.
Although I've heard people say 3 seconds for hoosier, I don't think that's accurate, especially on a short course. From the data I've seen, it's about 2 seconds on a 2 minute course vs. Cup 2s, NT01. So, for your comparison, on a short course, it would only be a little over a second faster. Also, from what I've read, hoosiers will be slower after 10 HCs.
In any case, it's enough to see your friends leave you on the track, but not enough to really drastically change the g-forces in a corner.
I respectfully disagree about 3 seconds not being accurate.
My actual experience in comparing Cup 2 to Hoosier R7 is just under 3 seconds on a 2 minute lap - not to split hairs. VIR it was 2.9 seconds 2:06.0 to 2:03.1
No other changes made to the car.
On a short course it would obviously be less.
I respectfully disagree about 3 seconds not being accurate.
My actual experience in comparing Cup 2 to Hoosier R7 is just under 3 seconds on a 2 minute lap - not to split hairs. VIR it was 2.9 seconds 2:06.0 to 2:03.1
No other changes made to the car.
On a short course it would obviously be less.
Thanks for the data point. I was mostly responding to the comment of 3 seconds on a short course.
Also, here's some other good data on a variety of tires
Actual laptimes on my 997.2 GT3RS using new tires as baseline. In most cases I've gone through 2+ sets of each:
Pirelli DH Slicks: 1:47-48 (add 1 sec after ~4HCs, HC out by 10-12th)
Hoosier R6: 1:49-1:50 (add 1 sec after ~10HCs, another 1 sec after ~20HCs, HC out by 25-30th)
Pirelli Trofeo (original not newer R's): 1:50-1:52 (add 1 sec after ~10HC, cord by 10-15th HC)
Mich Pilot Sports Cup+: 1:51-52 (these were my OEM rubber and street-driven, hence no accurate HC count; but they were HC'd out by my 10th track HC)
Toyo R888: not available in 997.2 sizes but in my 997.1 the times were similar as MPSC+'s, except they heat cycle out even sooner
Same day, back to back sessions. Cup2 fronts were new, rears original. R7s new. About 5 seconds at COTA. You can see where the time came from in the plot below. There is still a lot of time on the table, probably at least 2 seconds on each tire in better hands. If you look closely, you can see the difference in gearing between the 19" and 20" wheels.
My GT4 finally arrived and I'll have to make a tire decision soon. I considered the 18" wheel option but decided to go with 19" and am looking at the R7 235/35 and 295/30 on OZ wheels as suggested by johnr265 in post #18. Has anyone run this setup?
My GT4 finally arrived and I'll have to make a tire decision soon. I considered the 18" wheel option but decided to go with 19" and am looking at the R7 235/35 and 295/30 on OZ wheels as suggested by johnr265 in post #18. Has anyone run this setup?
Iam also very insterested in this setup.
Has anyone run this setup ?
My GT4 finally arrived and I'll have to make a tire decision soon. I considered the 18" wheel option but decided to go with 19" and am looking at the R7 235/35 and 295/30 on OZ wheels as suggested by johnr265 in post #18. Has anyone run this setup?
Bill, I have not yet pulled the trigger on a set of wheels for the track. Those OZ's are definitely the best value for our cars. Can't go wrong with them. They're reasonably light and have an excellent track record to withstand abuse without failing. They will be fine with those R7's. But, if you wanted to raise your budget you might want to consider the CCW option. Custom made for the GT4. 9"F and 11"R. Roughly $4K for the set. Excellent quality.
Beantown Kman, I ran the OZ wheels for several years on a 987 and was very satisfied with them. I've been in contact with CCW, for some reason they won't give me the offset dimensions. I think a 9" front would be important if running the R7 @ 265 wide. Not sure if +.2" tread width is required.
My GT4 finally arrived and I'll have to make a tire decision soon. I considered the 18" wheel option but decided to go with 19" and am looking at the R7 235/35 and 295/30 on OZ wheels as suggested by johnr265 in post #18. Has anyone run this setup?
Ok, finally got to run this setup. I thought it worked out pretty nicely. I haven't done a careful postmortem of wear and looking for rubbing but car balance was very similar to when I had the Sport Maxx on just with lots more grip. That is, I had a touch of understeer that was easily adjusted with some trail braking and weight modulation and overall, gave just enough security to really let me push the car hard. For me on that day, I dropped 1.2 seconds on a short (1.9 mile) track.
Alignment was -2.75F/-2.25 rear, zero toe in front, 1.5-2 mm toe in per side in the rear. Front bar full soft, rear bar middle. Also, I do not have a thrust arm bushing in the front but I don't think I had any rubbing up front. I do have the rear toe links and the front tie rods.
I was able to pass more than half of the GT3's in the Red run group so I figure this is a fairly quick setup. I was even able to keep a well driven 996 Cup car in sight for a whole session though not pass it. I can imagine that a 265 up front would be nice but I don't think mandatory. The relatively marginal benefit may not be worth the extra $ (between 2-4,000 more per set of rims) but kind of early for me to make this statement. Would be interested to hear from anyone who has tried the CCW option.
04-11-2016, 09:11 PM
