who runs R7 on GT4
04-28-2016, 08:42 AM
#91
Burning Brakes
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.
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.
The guy that owns CCW is quirky. But he's not a bad guy. He guards the specifications of his wheels closely. He's not eager to share offsets and other details for others to copy. I wouldn't hesitate to buy a set of 9"F and 11"R wheels from him for $4K. But the OZ wheels at half the cost are very tempting. The choice really depends on your goals.
Will marginally wider tires on marginally wider wheels be faster? Yes. But if you're running narrower Hoosier R7's with the narrower wheels you're still going to have a fantastic setup. It's not going to be a dramatic difference. You'd have to be driving at a pace that exceeds the grip of the tire before you could appreciate the difference a wider tire will make.
04-28-2016, 09:30 AM
#92
One other potential advantage of the narrower front as others have pointed out is running with a lower aspect ratio (lower profile) front and rear. This has two potential benefits. Reducing sidewall flex and every so slightly reducing rolling diameter, thus slightly improving gearing. I probably could feel the sharper steering inputs, not sure I could feel the gearing difference.
I also wonder a bit if the 265 is more likely to overwhelm the stock springs and could paradoxically cause less grip if the tire rolls to the outside (now I am really throwing something out there I can't back up!). Obviously if you ran the wider 265 and stiffer springs, the combination would be mega.
I also wonder a bit if the 265 is more likely to overwhelm the stock springs and could paradoxically cause less grip if the tire rolls to the outside (now I am really throwing something out there I can't back up!). Obviously if you ran the wider 265 and stiffer springs, the combination would be mega.
04-28-2016, 10:16 AM
#94
Rennlist Member
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.
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.
Did you have any issues with ABS or other gizmos (if you had them on)? I ask since the diameter of the 235 is listed at 25.6" and the 295 is 26.1".
04-28-2016, 10:32 AM
#95
Thank you for the report! The ho hos in 235/295 is my next step if I don't like the RE71Rs I have on my OZs currently.
Did you have any issues with ABS or other gizmos (if you had them on)? I ask since the diameter of the 235 is listed at 25.6" and the 295 is 26.1".
Did you have any issues with ABS or other gizmos (if you had them on)? I ask since the diameter of the 235 is listed at 25.6" and the 295 is 26.1".
04-28-2016, 11:21 AM
#96
Rennlist Member
What hot pressures did you settle on? I have heard from others around 32 hot as they get greasy over 34-35 psi.
Last edited by electron mike; 04-28-2016 at 01:18 PM.
04-28-2016, 04:15 PM
#97
One other potential advantage of the narrower front as others have pointed out is running with a lower aspect ratio (lower profile) front and rear. This has two potential benefits. Reducing sidewall flex and every so slightly reducing rolling diameter, thus slightly improving gearing. I probably could feel the sharper steering inputs, not sure I could feel the gearing difference.
I also wonder a bit if the 265 is more likely to overwhelm the stock springs and could paradoxically cause less grip if the tire rolls to the outside (now I am really throwing something out there I can't back up!). Obviously if you ran the wider 265 and stiffer springs, the combination would be mega.
I also wonder a bit if the 265 is more likely to overwhelm the stock springs and could paradoxically cause less grip if the tire rolls to the outside (now I am really throwing something out there I can't back up!). Obviously if you ran the wider 265 and stiffer springs, the combination would be mega.
The change in rake is most likely to dominate most people's feeling of the setup, not the delta in rubber width between a 235/265.
Wear-wise, I can see the argument that a 235 might wear better than a 265 given that there is smaller sidewall, and less deflection. If I didn't have to re-corner balance my car, I might try the setup.
04-28-2016, 07:10 PM
#98
The 235 vs 265 is interesting. From hoosier's mounted specs (both on a 9" rim), the tire section is close to being the same 10.1" vs 10.4" (what matters for fitment...this measurement is not the effective tread width).....but the height is about 0.75" less. The height is where you are going to find some extra clearance - but you will need to compensate the rake of the car by about 5mm (raise front by 5mm, or lower rear). Leaving the rake alone (5mm down in front vs rear) might actually help a bit with mid-corner understeer.
The change in rake is most likely to dominate most people's feeling of the setup, not the delta in rubber width between a 235/265.
Wear-wise, I can see the argument that a 235 might wear better than a 265 given that there is smaller sidewall, and less deflection. If I didn't have to re-corner balance my car, I might try the setup.
The change in rake is most likely to dominate most people's feeling of the setup, not the delta in rubber width between a 235/265.
Wear-wise, I can see the argument that a 235 might wear better than a 265 given that there is smaller sidewall, and less deflection. If I didn't have to re-corner balance my car, I might try the setup.
As for any problems, I would say no. No obvious ABS issues (though the car is pretty unstable under heavy braking but others have mentioned this as well so I don't think it's ABS). I generally shut off the traction and stability control so can't speak to it interfering with them though I did one run with them on at the beginning of the day and all seemed fine.
04-28-2016, 07:50 PM
#99
Do you have to adjust for rake if you are running the lower aspect 295 in the rear (295/30/19)?
As for any problems, I would say no. No obvious ABS issues (though the car is pretty unstable under heavy braking but others have mentioned this as well so I don't think it's ABS). I generally shut off the traction and stability control so can't speak to it interfering with them though I did one run with them on at the beginning of the day and all seemed fine.
As for any problems, I would say no. No obvious ABS issues (though the car is pretty unstable under heavy braking but others have mentioned this as well so I don't think it's ABS). I generally shut off the traction and stability control so can't speak to it interfering with them though I did one run with them on at the beginning of the day and all seemed fine.
See rake adjustments in this spreadsheet for a list of tire's a available size combos I've been compiling.
https://docs.google.com/spreadsheets...it?usp=sharing
04-28-2016, 08:08 PM
#100
Thanks for all of the good info on this thread. I purchased the OZ wheels with RE71Rs. I'll use these to get a feel for the car and setup. I'll run @ NJMP and WGI. I have many years driving a well setup 987 with data for these two tracks. I plan to run the R7 235/295 combo next. If running the 265 front, I would have started by dropping the front ride height about 10 mm.
05-06-2016, 01:27 PM
#101
More updates. Finally got around to taking the tires off the car to check things out. With 295/30/19 in rear and about -2.25 camber, there is rubbing on the inside back wheelwell. I couldn't see anything on the tires so it's not a dangerous rub but I am pretty surprised as there seemed like there was a lot of clearance.
05-06-2016, 01:30 PM
#102
Furthermore, there is significant lack of clearance between the caliper and the wheel barrel where a lot of crud including stones got wedged in there. The end result is scoring of the wheel barrel and chipping of the caliper paint. Not the end of the world but a pain to clean up. For those with 19" Forgelines, are you getting this too?
05-06-2016, 02:32 PM
#103
It looks like you could use thrust arm bushings in the rear. The geometry of the rear is the same as the front, just reversed. So as you add shims, the wheel moves towards the rear of the car. The bushing will help you bring it back towards the center, and should help with that rubbing - which is not bad...but if you're paranoid.
I didn't realize the barrel diameter on the OZs was so small. That's a good reason not to run them. I made the mistake on my prior car to run a formula43 18" wheel that really was not cut out for the task, and they ended up gouging up my calipers from rocks getting trapped in the gap. This does not happen with forgelines, there is plenty of clearance - with one exception. The barrel narrows right as the spokes start. One time my shop tried to put wheel weights on the smaller diameter part of the wheel, which interfered with the caliper.
I didn't realize the barrel diameter on the OZs was so small. That's a good reason not to run them. I made the mistake on my prior car to run a formula43 18" wheel that really was not cut out for the task, and they ended up gouging up my calipers from rocks getting trapped in the gap. This does not happen with forgelines, there is plenty of clearance - with one exception. The barrel narrows right as the spokes start. One time my shop tried to put wheel weights on the smaller diameter part of the wheel, which interfered with the caliper.
05-06-2016, 03:58 PM
#104
Rennlist Member
Good feedback. The OZ wheels are a fantastic value. Like Bill Lehman, I've run two sets of 18" OZ's on my 987 track car for years with no issues. As long as you can live with having only a 8.5" wheel in front and a 10" wheel in back you won't find another set of wheels that come close in price and offer the same weight and reliability.
05-07-2016, 12:49 AM
#105
Rennlist Member
I wouldn't run OZ with Hoosiers. The wheels are strong but are not forged. The last thing you want is a crack in the wheel or a broken wheel at speed and higher G forces. In my opinion, a forged wheel is the way to go on the track.