New To Auto Crossing
03-08-2015, 07:00 PM
#1
Le Mans Master
Thread Starter
New To Auto Crossing
Yesterday I attended my second auto cross. Although my times were no where near the top, they were not the slowest either and each run I improved. My first run was a 52. 571 and my final run of the day was a 47.154.
My question is, I am running Michelin Pilot SS 245/40/18 in the front and 325/30/19 in the rear. What tire pressure should I run for these events. I have not messed with the pressures at either event. Or should I concentrate on on my driving and car control before I start to adjust tire pressure.
Cold they are 32 psi on all four corners. I have never checked to see what they are after runs, although in that short of time I am not sure they would build up much.
My question is, I am running Michelin Pilot SS 245/40/18 in the front and 325/30/19 in the rear. What tire pressure should I run for these events. I have not messed with the pressures at either event. Or should I concentrate on on my driving and car control before I start to adjust tire pressure.
Cold they are 32 psi on all four corners. I have never checked to see what they are after runs, although in that short of time I am not sure they would build up much.
03-08-2015, 11:42 PM
#3
Max G’s
I wouldn't be concerned with the pressure after the tires warm up. What you want to watch is how far the tire rolls over on the shoulder. There should be a mark on the tire where the tread and sidewall meet. This is where you want the tire to roll over to; as long as you are driving the car hard. It may take some seat time to get to that point. So for now, run your 32psi and note how far the tires roll over to the sidewall. You also want to listen for the the tires to let you know when they are at their at the limit. When they start to squelch, they are reaching the limit.
03-09-2015, 12:36 AM
#4
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Start with a cold pressure that has the rears about 2 lbs less than the fronts. Make one run and see what the warm pressures are after you make the run. Then balance the pressures by adding or removing air so the tires are close to equal in pressure. Then see what happens on the next run and repeat the sequence if they didn't come out very close to equal. When the pressures are equal that is an indication all of the tires are contributing grip to getting the car around the course.
Once the event is over get the car home without changing any of the tire pressures and let it sit over night before checking the cold pressures. Record those cold pressures so you have them for the next event. When you leave for the event set the pressures at the recorded cold pressures and your warm pressures at the event will come in close to what they were before. If the course is the same setup (I autocrossed on a lot of Go Kart tracks) you will be almost exactly what you had the previous event. If the course is different (like parking lot courses change) you will be close enough to start the event.
Bill
Once the event is over get the car home without changing any of the tire pressures and let it sit over night before checking the cold pressures. Record those cold pressures so you have them for the next event. When you leave for the event set the pressures at the recorded cold pressures and your warm pressures at the event will come in close to what they were before. If the course is the same setup (I autocrossed on a lot of Go Kart tracks) you will be almost exactly what you had the previous event. If the course is different (like parking lot courses change) you will be close enough to start the event.
Bill
03-09-2015, 04:17 AM
#5
Here's a link to a tire manual that offers general tire tuning principals:
http://social.bfgoodrichtires.com/14...28FINAL%29.pdf
.
http://social.bfgoodrichtires.com/14...28FINAL%29.pdf
.
Last edited by B Stead; 03-09-2015 at 04:31 AM.
03-11-2015, 08:26 AM
#7
Drifting
For AutoX, raise your tire pressure about 4-5#'s over your "normal" and work from there.
When i first started on street tires, I ran about 36-38#'s on my PSS's
When i first started on street tires, I ran about 36-38#'s on my PSS's
03-19-2015, 11:44 PM
#8
Sorry for the late reply...
I've found it depends greatly on many factors, including, but not limited to, your alignment, temperatures, course design (site size limits this sometimes - tight course vs large open course) and the type of surface you're running on (grippy concrete, fresh asphalt, rough asphalt with loose aggregate, sealed asphalt).
Best thing to do, is make some chalk marks where the tread meets the sidewall. Keep lowering the pressures until you start to see wear just above where the tread ends..
On my 2008 C6 Z51, I'm seeing that at the sites we use the most, either 34 all around or between 34 front 32 rear and 32 Front 30 rear, makes the car happiest w/ the PSS ZPs..
(As noted in other posts you'll want to monitor your pressures before every run and lower as they warm up to maintain the pressure(s) you find your car/tire/etc work best)
But, as noted above, YMMV depending on many factors.
Trial and error, mostly error, is what it took to get those numbers ;-)
I've found it depends greatly on many factors, including, but not limited to, your alignment, temperatures, course design (site size limits this sometimes - tight course vs large open course) and the type of surface you're running on (grippy concrete, fresh asphalt, rough asphalt with loose aggregate, sealed asphalt).
Best thing to do, is make some chalk marks where the tread meets the sidewall. Keep lowering the pressures until you start to see wear just above where the tread ends..
On my 2008 C6 Z51, I'm seeing that at the sites we use the most, either 34 all around or between 34 front 32 rear and 32 Front 30 rear, makes the car happiest w/ the PSS ZPs..
(As noted in other posts you'll want to monitor your pressures before every run and lower as they warm up to maintain the pressure(s) you find your car/tire/etc work best)
But, as noted above, YMMV depending on many factors.
Trial and error, mostly error, is what it took to get those numbers ;-)
03-21-2015, 09:24 PM
#9
Burning Brakes
Start with a cold pressure that has the rears about 2 lbs less than the fronts. Make one run and see what the warm pressures are after you make the run. Then balance the pressures by adding or removing air so the tires are close to equal in pressure. Then see what happens on the next run and repeat the sequence if they didn't come out very close to equal. When the pressures are equal that is an indication all of the tires are contributing grip to getting the car around the course.
Once the event is over get the car home without changing any of the tire pressures and let it sit over night before checking the cold pressures. Record those cold pressures so you have them for the next event. When you leave for the event set the pressures at the recorded cold pressures and your warm pressures at the event will come in close to what they were before. If the course is the same setup (I autocrossed on a lot of Go Kart tracks) you will be almost exactly what you had the previous event. If the course is different (like parking lot courses change) you will be close enough to start the event.
Bill
Once the event is over get the car home without changing any of the tire pressures and let it sit over night before checking the cold pressures. Record those cold pressures so you have them for the next event. When you leave for the event set the pressures at the recorded cold pressures and your warm pressures at the event will come in close to what they were before. If the course is the same setup (I autocrossed on a lot of Go Kart tracks) you will be almost exactly what you had the previous event. If the course is different (like parking lot courses change) you will be close enough to start the event.
Bill
good advice