Tire pressure help.
07-16-2009, 03:50 PM
#2
Melting Slicks
As I recall, we're around 21 or so in front and about a 4 pound split to the rear (around 17). We try to get the hot pressures in front to about 32-34 and the rear to about 26-28...
I think those numbers are pretty close. You'll obviously have to adjust depending on the weather though. Good luck.
I think those numbers are pretty close. You'll obviously have to adjust depending on the weather though. Good luck.
07-16-2009, 05:25 PM
#4
Race Director
Take a look at this Hoosier site - scroll down and you'll see their recommendations for alignment setup, initial heat cycling, tire pressures, etc.:
https://www.hoosiertire.com/rrtire.htm
You'll see that they recommend a much higher pressure than wtknght1 recommends. Keep in mind that Chris is doing full-out w2w racing and trying to qualify fast and pass everybody on the race course - and he wants every possible ounce of grip. He probably also runs A6's on road courses because they're stickier. Racers pretty much aren't concerned at all about trying to get max length of life out of a set of tires.
If you're just having fun doing HPDE's and want your investment in tires to last a little longer you might try Hoosier's recommendation. But the real track hounds here probably know more from their practical experience than Hoosier does about how to get the absolute most grip and lowest lap times out of the tires, but probably with less length of life from them.
I'm a track rookie doing HPDE's and just finished off my first set of R6's on my C6Z. I used Hoosier's pressures (about 33 front/31 rear cold, and got about 7 to 9 psi more when hot). Being they were my first set, I'm still learning to drive on R-compound tires, but using those pressures I got 21 sessions/heat cycles out of the tires. I'm sure I would have gotten a lot more grip at a lower pressure, but I'm sure I also wouldn't have gotten 21 sessions. At lower pressures I'll bet the tires are done after 8 or 10 sessions. Plus, more heat cycles than that and the grip drops off and the racers will get rid of them whether they're corded or not.
I run camber of about -2.5 degrees up front and -1.5 rear. The treads wore perfectly smoothly across the entire tread, and the only tire to show cord was a front tire on the last session I ran at VIR - and it actually corded on the inside edge. I can tell the other tires would be showing cord after another session or so.
So....if you want every last ounce of grip, run lower pressures, but I bet you'll be cording the outside edges after 10 sessions. If you aren't racing and just doing HPDE's and you want a little more life out of the tire and don't mind running the tire beyond 10 heat cycles, run Hoosier's recommendations.
YMMV!!
Bob
https://www.hoosiertire.com/rrtire.htm
You'll see that they recommend a much higher pressure than wtknght1 recommends. Keep in mind that Chris is doing full-out w2w racing and trying to qualify fast and pass everybody on the race course - and he wants every possible ounce of grip. He probably also runs A6's on road courses because they're stickier. Racers pretty much aren't concerned at all about trying to get max length of life out of a set of tires.
If you're just having fun doing HPDE's and want your investment in tires to last a little longer you might try Hoosier's recommendation. But the real track hounds here probably know more from their practical experience than Hoosier does about how to get the absolute most grip and lowest lap times out of the tires, but probably with less length of life from them.
I'm a track rookie doing HPDE's and just finished off my first set of R6's on my C6Z. I used Hoosier's pressures (about 33 front/31 rear cold, and got about 7 to 9 psi more when hot). Being they were my first set, I'm still learning to drive on R-compound tires, but using those pressures I got 21 sessions/heat cycles out of the tires. I'm sure I would have gotten a lot more grip at a lower pressure, but I'm sure I also wouldn't have gotten 21 sessions. At lower pressures I'll bet the tires are done after 8 or 10 sessions. Plus, more heat cycles than that and the grip drops off and the racers will get rid of them whether they're corded or not.
I run camber of about -2.5 degrees up front and -1.5 rear. The treads wore perfectly smoothly across the entire tread, and the only tire to show cord was a front tire on the last session I ran at VIR - and it actually corded on the inside edge. I can tell the other tires would be showing cord after another session or so.
So....if you want every last ounce of grip, run lower pressures, but I bet you'll be cording the outside edges after 10 sessions. If you aren't racing and just doing HPDE's and you want a little more life out of the tire and don't mind running the tire beyond 10 heat cycles, run Hoosier's recommendations.
YMMV!!
Bob
07-16-2009, 06:05 PM
#5
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I agree with Chris about pressures. Not really sure what pressures will give you the most heat cycles but there is no question that the grip in the Hoosiers are best with hot pressures in the 27-30 psi range The cold pressure will depend on track temp/using air or nitrogen etc I haven't noticed any increase in wear going from 32 psi to 28-30, but I have noticed a huge improvement in grip. Agree with the comments on camber .
07-16-2009, 06:43 PM
#6
Melting Slicks
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As I recall, we're around 21 or so in front and about a 4 pound split to the rear (around 17). We try to get the hot pressures in front to about 32-34 and the rear to about 26-28...
I think those numbers are pretty close. You'll obviously have to adjust depending on the weather though. Good luck.
I think those numbers are pretty close. You'll obviously have to adjust depending on the weather though. Good luck.
I usually recommend 28F and 26R cold, which puts them at around 32F and 29R hot.
Saw your car at Phoenix, beginning to look good.
Frank Gonzalez
07-16-2009, 06:45 PM
#7
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I have been struggling with the tire pressures on the Hoosiers as well. I have the R6s and they do not impress me as far as real traction. So far I have tried the higher and lower pressures and really didn't get that much improvement. After running a couple of track days with -1.3 camber in front I went to -2.2/3 to keep from cording the outside edge. So far I have 7 track days on them and 6 autocrosses. I flipped them after doing the 7 track days and 4 autocrosses. Hopefully, they will last me the rest of the season (about 8 more track days and 9 or 10 more autocrosses).
Some of my handling problems were due to a slippage in the rear control arm settings after I had the alignment changed which caused a massive toe in on the drivers side and toe out on the passenger side.
At my last autocross I ran 34 front and 32 rear cold and they heated up to 36/34 where I left them. The car seemed to perform better but I realize they won't be as good as A6s or 710s. Next track day I will probably start with cold pressures around 32 front and 30 rear to get hot pressures around 39 and 37 which are right in the range Hoosier recommends.
When I replace these tires I will go back to the 710s which I can run with less camber and so can run one alignment setting for street and track and I pretty much know what it takes to get them to perform and last long. Until last year I had been buying used 710s from Chris and others and I can safely say at the end of last year when I used up all the used tires the worn out 710s were outperforming the new R6s this year.
Bill
Some of my handling problems were due to a slippage in the rear control arm settings after I had the alignment changed which caused a massive toe in on the drivers side and toe out on the passenger side.
At my last autocross I ran 34 front and 32 rear cold and they heated up to 36/34 where I left them. The car seemed to perform better but I realize they won't be as good as A6s or 710s. Next track day I will probably start with cold pressures around 32 front and 30 rear to get hot pressures around 39 and 37 which are right in the range Hoosier recommends.
When I replace these tires I will go back to the 710s which I can run with less camber and so can run one alignment setting for street and track and I pretty much know what it takes to get them to perform and last long. Until last year I had been buying used 710s from Chris and others and I can safely say at the end of last year when I used up all the used tires the worn out 710s were outperforming the new R6s this year.
Bill
Last edited by Bill Dearborn; 07-16-2009 at 06:48 PM.
07-16-2009, 08:51 PM
#8
Melting Slicks
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I have been struggling with the tire pressures on the Hoosiers as well. I have the R6s and they do not impress me as far as real traction. So far I have tried the higher and lower pressures and really didn't get that much improvement. After running a couple of track days with -1.3 camber in front I went to -2.2/3 to keep from cording the outside edge. So far I have 7 track days on them and 6 autocrosses. I flipped them after doing the 7 track days and 4 autocrosses. Hopefully, they will last me the rest of the season (about 8 more track days and 9 or 10 more autocrosses).
Some of my handling problems were due to a slippage in the rear control arm settings after I had the alignment changed which caused a massive toe in on the drivers side and toe out on the passenger side.
At my last autocross I ran 34 front and 32 rear cold and they heated up to 36/34 where I left them. The car seemed to perform better but I realize they won't be as good as A6s or 710s. Next track day I will probably start with cold pressures around 32 front and 30 rear to get hot pressures around 39 and 37 which are right in the range Hoosier recommends.
When I replace these tires I will go back to the 710s which I can run with less camber and so can run one alignment setting for street and track and I pretty much know what it takes to get them to perform and last long. Until last year I had been buying used 710s from Chris and others and I can safely say at the end of last year when I used up all the used tires the worn out 710s were outperforming the new R6s this year.
Bill
Some of my handling problems were due to a slippage in the rear control arm settings after I had the alignment changed which caused a massive toe in on the drivers side and toe out on the passenger side.
At my last autocross I ran 34 front and 32 rear cold and they heated up to 36/34 where I left them. The car seemed to perform better but I realize they won't be as good as A6s or 710s. Next track day I will probably start with cold pressures around 32 front and 30 rear to get hot pressures around 39 and 37 which are right in the range Hoosier recommends.
When I replace these tires I will go back to the 710s which I can run with less camber and so can run one alignment setting for street and track and I pretty much know what it takes to get them to perform and last long. Until last year I had been buying used 710s from Chris and others and I can safely say at the end of last year when I used up all the used tires the worn out 710s were outperforming the new R6s this year.
Bill
Frank Gonzalez
07-16-2009, 08:56 PM
#9
We have both run Hoosier A6 and R6 in HPDE's for the past few years and they have been great. I couldn't be happier with them.
To each his own. Just my personal experience.
Maybe if we're on track together we can do some testing to see the level of grip.
Steve
07-16-2009, 09:56 PM
#10
Drifting
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According to Hoosier , they recommend cold pressures for vechicles 3000 + lbs between 27-33lbs. Temperatures down here in FLA. are in the 90 + . I have set my pressures at 28 all around.
07-16-2009, 10:11 PM
#11
07-16-2009, 10:59 PM
#12
Former Vendor
Vettes like a 1-4 lower rear pressure. Make sure if you are turning one way alot, to run even a lower pressure in the "hard" working tires.
Randy
07-17-2009, 07:06 AM
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I think Hoosiers air pressure charts have not been updated in years. Especially when you start talking to guys who are winning races, and their starting pressures are much lower.
07-17-2009, 08:58 AM
#15
Melting Slicks
Chris, your hot pressures are right on the money (of course), but most of these guys don't get the tires hot enough to use your cold pressures.
I usually recommend 28F and 26R cold, which puts them at around 32F and 29R hot.
Saw your car at Phoenix, beginning to look good.
Frank Gonzalez
I usually recommend 28F and 26R cold, which puts them at around 32F and 29R hot.
Saw your car at Phoenix, beginning to look good.
Frank Gonzalez
And yep, running that low will burn the edges up quicker...but you can always flip the tires if needed.
Thanks for the info on the car. I'm still sick about the VIR thing and my car getting trashed. But, that incident combined with the CRB's decision not to lower the weight of the LS3 to something reasonable gave me the perfect time to sink my "saved" cash into a dry sump, new engine, etc. I'll really be surprised if any LS3 shows up at the runoffs...and if they do, I doubt any of them will get within 2 seconds of the leader. I hate not going, but because of that fact, the SCCA is not getting my money this year. Sad.
Hopefully I'll get everything back together and come have some fun at the ARRC with you guys...running around 3300. Maybe with new stuff, I can get closer to the lead lap times!
Sorry to hijack the thread. Now back to your regularly scheduled Hoosier debate.
07-17-2009, 09:17 AM
#16
Race Director
Yeah, that is probably true...which is why I listed the "hot pressure range." That info came straight from Bruce Foss (Hoosier Czar) and seems to work pretty well.
And yep, running that low will burn the edges up quicker...but you can always flip the tires if needed.....
And yep, running that low will burn the edges up quicker...but you can always flip the tires if needed.....
For having fun at HPDEs I felt the higher pressures on the Hoosier site worked pretty well for my first set of R-compounds (R6s). Hot pressures of around 40 psi gave a very consistent temp across the tread (usually about 185 across). Compared to my OE tires they were sticking great - even in my last session at VIR (21st session on the tires).
I knew they were about heat-cycled out after 14 sessions, but they looked good so I planned to use them at VIR. At first I was going to flip them prior to VIR to finish them off at the event, but the tread wear from the higher pressures was even all the way across so I didn't bother. As mentioned earlier, during my last session at VIR I finally corded the INSIDE edge of a front tire.
I've got a new set for the NJMP event next week and I think I'm going to try the lower pressures you experienced guys are recommending.
Hope to see many of you at NJMP!!!
Bob
