Orthojoe's GT4 track thread and ramblings
05-15-2016, 12:50 AM
#392
Joe, I flipped my RE71Rs at Buttonwillow with 23 HCs on them to give me some more life. I too noticed that the RE71Rs run wider than their stated size (as you showed with your picture the 285s are few within 1-2mm of 295 Cup2s). No problem at all. 
05-15-2016, 12:52 AM
#393
Nordschleife Master
Thread Starter
Awesome. Looking forward to running these tires! Only 2 more weeks!
05-15-2016, 02:22 AM
#395
Nordschleife Master
Thread Starter
05-16-2016, 12:10 AM
#396
Drifting
Sorry for the brief threadjack here, but I figure the right people to answer this are tuned into this thread. Since this is my first set of Cup 2s, I could use some help interpreting what I'm looking at. Are these basically done? The outer sipes are partly gone all the way around, and the outboard side of the outermost wear bar is basically flush with the outboard rib, though the others still have some remaining tread depth. These tires have 5 track days on them (23 heat cycles), although one day was a partially wet and completely cold day at CotA and another was basically a half day because for 3 out of 4 sessions we spent about half the time in the hot pits due to on-track incidents. I'm also still learning this car, so I'm definitely not pushing it as hard as I expect to be in the future. Is there a decent chance these will last another track day or two, or should I just bite the bullet and replace them now? If the latter, I'll plan to replace all 4 for heat cycling reasons.
(Sorry this photo isn't uploading in the proper orientation; it displays correctly on my PC and I even tried rotating it all the way around and re-saving it, but it still uploaded the same way.)
(Sorry this photo isn't uploading in the proper orientation; it displays correctly on my PC and I even tried rotating it all the way around and re-saving it, but it still uploaded the same way.)
05-16-2016, 12:47 AM
#397
Nordschleife Master
Thread Starter
Sorry for the brief threadjack here, but I figure the right people to answer this are tuned into this thread. Since this is my first set of Cup 2s, I could use some help interpreting what I'm looking at. Are these basically done? The outer sipes are partly gone all the way around, and the outboard side of the outermost wear bar is basically flush with the outboard rib, though the others still have some remaining tread depth. These tires have 5 track days on them (23 heat cycles), although one day was a partially wet and completely cold day at CotA and another was basically a half day because for 3 out of 4 sessions we spent about half the time in the hot pits due to on-track incidents. I'm also still learning this car, so I'm definitely not pushing it as hard as I expect to be in the future. Is there a decent chance these will last another track day or two, or should I just bite the bullet and replace them now? If the latter, I'll plan to replace all 4 for heat cycling reasons.
(Sorry this photo isn't uploading in the proper orientation; it displays correctly on my PC and I even tried rotating it all the way around and re-saving it, but it still uploaded the same way.)
Attachment 1051353
(Sorry this photo isn't uploading in the proper orientation; it displays correctly on my PC and I even tried rotating it all the way around and re-saving it, but it still uploaded the same way.)
Attachment 1051353
https://rennlist.com/forums/gt4/9263...l#post13166366
Your tires look pretty close to what mine look like currently. That was 10 sessions/2 track days. My tires (and yours) are still ok to run.
05-16-2016, 01:07 AM
#398
Drifting
Go back to post #137:
https://rennlist.com/forums/gt4/9263...l#post13166366
Your tires look pretty close to what mine look like currently. That was 10 sessions/2 track days. My tires (and yours) are still ok to run.
https://rennlist.com/forums/gt4/9263...l#post13166366
Your tires look pretty close to what mine look like currently. That was 10 sessions/2 track days. My tires (and yours) are still ok to run.
05-16-2016, 01:08 AM
#399
Sorry for the brief threadjack here, but I figure the right people to answer this are tuned into this thread. Since this is my first set of Cup 2s, I could use some help interpreting what I'm looking at. Are these basically done? The outer sipes are partly gone all the way around, and the outboard side of the outermost wear bar is basically flush with the outboard rib, though the others still have some remaining tread depth. These tires have 5 track days on them (23 heat cycles), although one day was a partially wet and completely cold day at CotA and another was basically a half day because for 3 out of 4 sessions we spent about half the time in the hot pits due to on-track incidents. I'm also still learning this car, so I'm definitely not pushing it as hard as I expect to be in the future. Is there a decent chance these will last another track day or two, or should I just bite the bullet and replace them now? If the latter, I'll plan to replace all 4 for heat cycling reasons.
(Sorry this photo isn't uploading in the proper orientation; it displays correctly on my PC and I even tried rotating it all the way around and re-saving it, but it still uploaded the same way.)
Attachment 1051353
(Sorry this photo isn't uploading in the proper orientation; it displays correctly on my PC and I even tried rotating it all the way around and re-saving it, but it still uploaded the same way.)
Attachment 1051353
05-16-2016, 01:30 AM
#400
Nordschleife Master
Thread Starter
Originally Posted by jphughan
Thanks! I remembered seeing that photo and the resemblance to what I have on my own tires now, but I didn't know how much longer you ran them once they had reached that point. In that case I'll keep these for my next event at CotA. If they don't make it all the way, no worries. I live near CotA anyway.
05-17-2016, 02:27 AM
#401
Rennlist Member
With Joe's permission, I wanted to post some impressions from this past weekend at Buttonwillow. I had the chance to finally drive my car with the latest setup on a track I know very well. I also got a chance to drive another GT4 with some alternate tweaks.
My car's current setup:
-2.7 FR / -2.2 RR camber
+1mm toe OUT FR / 5mm toe IN rear
toe links FR/RR
both bars in middle
Endless ME20 pads, Endless fluid
stock rubber
Guard 50/50 LSD
Light weight flywheel.
Overall, the car is very neutral with the addition of the LSD with a hint of understeer mid corner. The car now enters and exits MUCH better and feels like it's trying to help you to the apex and help you to track out on throttle (LSD). I experimented with full soft bar on front to add steering but the front end felt far too soft for my taste. I typically try to setup a car with adjustable bars in the middle and use them as a tuning tool for some tracks. I feel I'm now very close to this goal.
Tire wear, a frequent subject on this thread, was very even both front and rear on the Cup2's. I don't consider myself particularly easy on tires either. I'm now very curious what is causing the exaggerated edge wear that Joe, usctrojanGT3 are experiencing. Will try to compare notes, line and braking points next time Joe and I are at the track together.
In the last session of the day Saturday, I had the pleasure of driving SP Motorsport's development GT4. The key setup difference to my car was no LSD but stiffer springs and 255 front Cup2's. I've theorized that the slightly larger tire size would help balance the car better. Based on driving experience, both changes are incredibly positive for the handling and balance of the car. Where I experienced mid corner understeer in my car, the SP car just grabbed and TURNED. In transitions like the esses and Cotton Corners, the added roll stiffness made the car react and recover much quicker and felt like it had even more grip. The car did require a re-calibration of steering input because you had much more initial steer that you could unsettle the rear with similar inputs. That adjustment came quickly and then you could just point the car where you wanted it to go and it would do exactly what you asked. If I had timing during that session, I am confident I would have been nearly as fast as in my own car (even after dialing it back). On corner exit, the car definitely felt easier to drive due to the less aggressive lock of the stock diff. I'm very curious on this front to see if the stock LSD will wear out as quickly as the GT3 LSD when tracked hard. If it does, the case for the Guard unit will be even stronger.
After driving both cars back to back, I really like the idea of wider front rubber to balance the grip of the car. I'm going to wait on the springs for the moment so I can drive on a set on the street since that's where my car spends 50/% of it's time. I would hate to ruin the balance of the utility of this car for maybe .5 in lap time. I don't think it will though.
With my increasing familiarity with the car and greater comfort in going fast, I have found the ME20 pads to be slightly less adequate. They are by far the best compromise pad I've ever driven but I miss the added bite and stopping power of a dedicated track pad. Once they wear out, I will probably move back to the PFC08 or maybe the Ferodo that may here like so much.
At the end of the weekend, I managed to set personal best lap time while still having more left in the car for next time. This car is really impressive and still has so much development ahead. With another 100hp, the 991 GT3 would be squarely in it's sights.
My car's current setup:
-2.7 FR / -2.2 RR camber
+1mm toe OUT FR / 5mm toe IN rear
toe links FR/RR
both bars in middle
Endless ME20 pads, Endless fluid
stock rubber
Guard 50/50 LSD
Light weight flywheel.
Overall, the car is very neutral with the addition of the LSD with a hint of understeer mid corner. The car now enters and exits MUCH better and feels like it's trying to help you to the apex and help you to track out on throttle (LSD). I experimented with full soft bar on front to add steering but the front end felt far too soft for my taste. I typically try to setup a car with adjustable bars in the middle and use them as a tuning tool for some tracks. I feel I'm now very close to this goal.
Tire wear, a frequent subject on this thread, was very even both front and rear on the Cup2's. I don't consider myself particularly easy on tires either. I'm now very curious what is causing the exaggerated edge wear that Joe, usctrojanGT3 are experiencing. Will try to compare notes, line and braking points next time Joe and I are at the track together.
In the last session of the day Saturday, I had the pleasure of driving SP Motorsport's development GT4. The key setup difference to my car was no LSD but stiffer springs and 255 front Cup2's. I've theorized that the slightly larger tire size would help balance the car better. Based on driving experience, both changes are incredibly positive for the handling and balance of the car. Where I experienced mid corner understeer in my car, the SP car just grabbed and TURNED. In transitions like the esses and Cotton Corners, the added roll stiffness made the car react and recover much quicker and felt like it had even more grip. The car did require a re-calibration of steering input because you had much more initial steer that you could unsettle the rear with similar inputs. That adjustment came quickly and then you could just point the car where you wanted it to go and it would do exactly what you asked. If I had timing during that session, I am confident I would have been nearly as fast as in my own car (even after dialing it back). On corner exit, the car definitely felt easier to drive due to the less aggressive lock of the stock diff. I'm very curious on this front to see if the stock LSD will wear out as quickly as the GT3 LSD when tracked hard. If it does, the case for the Guard unit will be even stronger.
After driving both cars back to back, I really like the idea of wider front rubber to balance the grip of the car. I'm going to wait on the springs for the moment so I can drive on a set on the street since that's where my car spends 50/% of it's time. I would hate to ruin the balance of the utility of this car for maybe .5 in lap time. I don't think it will though.
With my increasing familiarity with the car and greater comfort in going fast, I have found the ME20 pads to be slightly less adequate. They are by far the best compromise pad I've ever driven but I miss the added bite and stopping power of a dedicated track pad. Once they wear out, I will probably move back to the PFC08 or maybe the Ferodo that may here like so much.
At the end of the weekend, I managed to set personal best lap time while still having more left in the car for next time. This car is really impressive and still has so much development ahead. With another 100hp, the 991 GT3 would be squarely in it's sights.
05-17-2016, 07:36 AM
#402
any one pyro their tyres yet with all these geo going on !
or are people still guessing at PSI and settings with no real data to back up what people are doing !
or are people still guessing at PSI and settings with no real data to back up what people are doing !
05-17-2016, 10:28 AM
#403
Drifting
ChrisF, what should one consider when choosing the numbers for a Guard diff? 60/40 seems popular, but I've also seen 70/30 and now your 50/50 choice. I don't have a very deep understanding of diffs, and even trying to research it I haven't found much that's both informative and comprehensible.
05-17-2016, 10:29 AM
#404
I've been posting temps in my thread but my setup kept changing. I think I've locked in on my setup for now and I've added the AIM data logger so between that and temps + pressures we should be able to sort some real data driven decisions soon.
05-17-2016, 10:55 AM
#405
Nordschleife Master
Thread Starter
With Joe's permission, I wanted to post some impressions from this past weekend at Buttonwillow. I had the chance to finally drive my car with the latest setup on a track I know very well. I also got a chance to drive another GT4 with some alternate tweaks.
My car's current setup:
-2.7 FR / -2.2 RR camber
+1mm toe OUT FR / 5mm toe IN rear
toe links FR/RR
both bars in middle
Endless ME20 pads, Endless fluid
stock rubber
Guard 50/50 LSD
Light weight flywheel.
Overall, the car is very neutral with the addition of the LSD with a hint of understeer mid corner. The car now enters and exits MUCH better and feels like it's trying to help you to the apex and help you to track out on throttle (LSD). I experimented with full soft bar on front to add steering but the front end felt far too soft for my taste. I typically try to setup a car with adjustable bars in the middle and use them as a tuning tool for some tracks. I feel I'm now very close to this goal.
Tire wear, a frequent subject on this thread, was very even both front and rear on the Cup2's. I don't consider myself particularly easy on tires either. I'm now very curious what is causing the exaggerated edge wear that Joe, usctrojanGT3 are experiencing. Will try to compare notes, line and braking points next time Joe and I are at the track together.
In the last session of the day Saturday, I had the pleasure of driving SP Motorsport's development GT4. The key setup difference to my car was no LSD but stiffer springs and 255 front Cup2's. I've theorized that the slightly larger tire size would help balance the car better. Based on driving experience, both changes are incredibly positive for the handling and balance of the car. Where I experienced mid corner understeer in my car, the SP car just grabbed and TURNED. In transitions like the esses and Cotton Corners, the added roll stiffness made the car react and recover much quicker and felt like it had even more grip. The car did require a re-calibration of steering input because you had much more initial steer that you could unsettle the rear with similar inputs. That adjustment came quickly and then you could just point the car where you wanted it to go and it would do exactly what you asked. If I had timing during that session, I am confident I would have been nearly as fast as in my own car (even after dialing it back). On corner exit, the car definitely felt easier to drive due to the less aggressive lock of the stock diff. I'm very curious on this front to see if the stock LSD will wear out as quickly as the GT3 LSD when tracked hard. If it does, the case for the Guard unit will be even stronger.
After driving both cars back to back, I really like the idea of wider front rubber to balance the grip of the car. I'm going to wait on the springs for the moment so I can drive on a set on the street since that's where my car spends 50/% of it's time. I would hate to ruin the balance of the utility of this car for maybe .5 in lap time. I don't think it will though.
With my increasing familiarity with the car and greater comfort in going fast, I have found the ME20 pads to be slightly less adequate. They are by far the best compromise pad I've ever driven but I miss the added bite and stopping power of a dedicated track pad. Once they wear out, I will probably move back to the PFC08 or maybe the Ferodo that may here like so much.
At the end of the weekend, I managed to set personal best lap time while still having more left in the car for next time. This car is really impressive and still has so much development ahead. With another 100hp, the 991 GT3 would be squarely in it's sights.
My car's current setup:
-2.7 FR / -2.2 RR camber
+1mm toe OUT FR / 5mm toe IN rear
toe links FR/RR
both bars in middle
Endless ME20 pads, Endless fluid
stock rubber
Guard 50/50 LSD
Light weight flywheel.
Overall, the car is very neutral with the addition of the LSD with a hint of understeer mid corner. The car now enters and exits MUCH better and feels like it's trying to help you to the apex and help you to track out on throttle (LSD). I experimented with full soft bar on front to add steering but the front end felt far too soft for my taste. I typically try to setup a car with adjustable bars in the middle and use them as a tuning tool for some tracks. I feel I'm now very close to this goal.
Tire wear, a frequent subject on this thread, was very even both front and rear on the Cup2's. I don't consider myself particularly easy on tires either. I'm now very curious what is causing the exaggerated edge wear that Joe, usctrojanGT3 are experiencing. Will try to compare notes, line and braking points next time Joe and I are at the track together.
In the last session of the day Saturday, I had the pleasure of driving SP Motorsport's development GT4. The key setup difference to my car was no LSD but stiffer springs and 255 front Cup2's. I've theorized that the slightly larger tire size would help balance the car better. Based on driving experience, both changes are incredibly positive for the handling and balance of the car. Where I experienced mid corner understeer in my car, the SP car just grabbed and TURNED. In transitions like the esses and Cotton Corners, the added roll stiffness made the car react and recover much quicker and felt like it had even more grip. The car did require a re-calibration of steering input because you had much more initial steer that you could unsettle the rear with similar inputs. That adjustment came quickly and then you could just point the car where you wanted it to go and it would do exactly what you asked. If I had timing during that session, I am confident I would have been nearly as fast as in my own car (even after dialing it back). On corner exit, the car definitely felt easier to drive due to the less aggressive lock of the stock diff. I'm very curious on this front to see if the stock LSD will wear out as quickly as the GT3 LSD when tracked hard. If it does, the case for the Guard unit will be even stronger.
After driving both cars back to back, I really like the idea of wider front rubber to balance the grip of the car. I'm going to wait on the springs for the moment so I can drive on a set on the street since that's where my car spends 50/% of it's time. I would hate to ruin the balance of the utility of this car for maybe .5 in lap time. I don't think it will though.
With my increasing familiarity with the car and greater comfort in going fast, I have found the ME20 pads to be slightly less adequate. They are by far the best compromise pad I've ever driven but I miss the added bite and stopping power of a dedicated track pad. Once they wear out, I will probably move back to the PFC08 or maybe the Ferodo that may here like so much.
At the end of the weekend, I managed to set personal best lap time while still having more left in the car for next time. This car is really impressive and still has so much development ahead. With another 100hp, the 991 GT3 would be squarely in it's sights.
As far as tire wear goes, I'm betting you'll see outer edge wear on the RIGHT side once you take the car to thill. The wear on the left side has been fairly even.
I think added front grip will allow more power and earlier power on corner exit. The rear end of the car has never broken away from me on corner exit. Instead it understeers, so you have to lift on throttle to keep the car on track. Watch Pobst at T4 a laguna seca in the GT4. That is what happens.
I'm not a fan of PFC08, and I don't think it is even available in GT3/4 sizes. PFC11 is better. I like the DS1.11. I'm curious about the new DSUNO. I will be test the project mu CR at Laguna in less than 2 weeks.
Did the whole pyro thing on the GT3. Even tire temps across, but still had outer edge wear. It's a problem specific to the tires, I think. No problems with edge wear when I drove on TrofeoR. I'm guessing no problems with RE71R either since these tires are not dual compound like the cup2