SGT/SC#0471 Posted April 15, 2008 Report Share Posted April 15, 2008 So I have the stock tires and wheels on my car and I am wondering what everyone else is finding to be the optimal air pressure in these cars for an autocross track. And additionally, do you alter this setting for the ProSolo course due to the drag launch? I am totally stoked for this weekends 2 day SCCA event in Packwood!!! :happy feet: And could use any advice I can get I am new to this.. thanks! Link to comment Share on other sites More sharing options...
LuLu Posted April 15, 2008 Report Share Posted April 15, 2008 Tire PSI for autocrossing is not something anyone here can advise you of, and have that 411 hold any value for you. There is too much 411 missing, stuff you can't know until race day, and after a test lap. I suggest you memorize the high and low pressure ratings of your tires as they sit on your SGT, as guidelines. Know when your TPMS will alarm, or set off a traction control issue. Somewhere in-between those PSI numbers, is your ideal PSI. And, I mean to say ideal just on that day and on that track. The next day, or, another track, will require PSI adjustments to get back to your ideal PSI for this event. Watch a NASCAR race? Listen for how many PSI changes drivers call for, and change tires to accomplish. It's this sensitive, and no one here can call this shot for you. Best wishes, and happy motoring. Link to comment Share on other sites More sharing options...
Son of GT Posted April 16, 2008 Report Share Posted April 16, 2008 Buy yourself one of those laser aimed pyrometers. Go around the track a few times and then check the tempature of the front tires. Aim the laser on the tire tread about an inch from the inside sidewall and note the tempature. Next, aim the laser dead center of the tire tread and note the tempature. Repeat the same procedure for the outside sidewall that you just did for the inside sidewall and note the tempature. Do that on all of the tires. If the inside sidewall and the outside sidewall tread areas read hotter than the center area of the tire tread, it means that your tires are under inflated and the tires are rolling over during hard cornering. If the center of the tire is hotter than both sides, then your tires are over inflated and the tire is crowning. When the tire tempature is uniform across the face of the tire, then you have optimum pressure for the course and the current track tempature during that event. You should check your tire's tempature(s) throughout the day because the track tempature will change as the day progresses and that will change how the tire's compound reacts to the the track surface. Following this proceedure should help you determine the optimum air pressure for your tires. You should also consider running Nitrogen in your tires. Nitrogen does not have tempature fluctation like air does, and it keeps the tires cooler too. I believe that Costco will replace the air in your tires with Nitrogen for about $20.00 a tire. Good luck! Link to comment Share on other sites More sharing options...
JeffIsHereToo Posted April 16, 2008 Report Share Posted April 16, 2008 So I have the stock tires and wheels on my car and I am wondering what everyone else is finding to be the optimal air pressure in these cars for an autocross track. And additionally, do you alter this setting for the ProSolo course due to the drag launch? I am totally stoked for this weekends 2 day SCCA event in Packwood!!! :happy feet: And could use any advice I can get I am new to this.. thanks! Won't this change depending on the ambient temperature, track and tire temperature, etc? Link to comment Share on other sites More sharing options...
JeffIsHereToo Posted April 16, 2008 Report Share Posted April 16, 2008 Buy yourself one of those laser aimed pyrometers. I believe that Costco will replace the air in your tires with Nitrogen for about $20.00 a tire. Good luck! "Buy a what?" "Fill the tires with what?" This is getting to be one expensive "hobby"! :happy feet: Link to comment Share on other sites More sharing options...
SGT/SC#0471 Posted April 16, 2008 Author Report Share Posted April 16, 2008 Thanks guys forgot how dumb of a question that was relating to atmoshpheric differences... Son of Gt: Sweet, I have one and found it to be of great use to measure the temps of various components in marine cooling systems. Stuff gets clogged up with corrosion, gotta love salt water, haha. Nice tool, would not have ever thought to use it on treads. Thanks! I really dig this forum. Link to comment Share on other sites More sharing options...
LuLu Posted April 16, 2008 Report Share Posted April 16, 2008 Thanks guys forgot how dumb of a question that was relating to atmoshpheric differences... I really dig this forum. Your question wasn't dumb. Just not easy to answer due to variables on race day. It's been my experience with forums like this, that most folks like "the easy button" answer. They prefer off the shelf tuning and easy to install mods that don't require much forethought. And, once they buy something, it's automatically the greatest product since canned beer and they'll never admit it could have been done better, maybe cheaper, if more time had been spent in research. Forums like this are very helpful, but can't replace checking out the facts with a professional. Happy motoring! Link to comment Share on other sites More sharing options...
SGT/SC#0471 Posted April 16, 2008 Author Report Share Posted April 16, 2008 Your question wasn't dumb. Just not easy to answer due to variables on race day. It's been my experience with forums like this, that most folks like "the easy button" answer. They prefer off the shelf tuning and easy to install mods that don't require much forethought. And, once they buy something, it's automatically the greatest product since canned beer and they'll never admit it could have been done better, maybe cheaper, if more time had been spent in research. Forums like this are very helpful, but can't replace checking out the facts with a professional. Happy motoring! Well thanks LULU, my question was based on the fact that some Autocross beginner info I got listed that you should start at 10lbs over recommended psi and another said try 2-3 lbs less than recommended psi. I think I will be bringing some chalk for the sidewalls. I have seen the same "easy fix" with throwing money at a project on the latest greatest parts with HD stuff, and then watch the look on the guys face when they have trouble keeping up with an old shovelhead. But dang I thought you guys were pros...haha! Maybe a moot point for this weekend now as its looking like mixed rain and SNOW!!!!! I am hoping the forecast changes this is not good... Link to comment Share on other sites More sharing options...
07SGT0086 Posted April 18, 2008 Report Share Posted April 18, 2008 As a data point, my dry event Autocross tire pressures are 48 PSI Front / 43 PSI Rear with Hoosier DOT AutoX tires. Given that you are running street tires, you will need to adjust your pressures up/down from there... which direction and how much depends on too way many variables to discuss here. When experimenting with tire pressures, I usually apply a few dots of white shoe polish (touch-up polish in a bottle) on the heel of the tire and then adjust tire pressures to obtain optimum tire roll-over. Please note that this shoe polish method is too messy in wet weather, chalk might work. I have seen some folks use a paint pen/silver Sharpie for marking tires during inclement weather. Given the rain/snow forecast for Packwood this weekend, I'll likely be a "no-show"... be safe if you decide to go. Hope to catch you at a local AutoX event in the near future. -Rick Link to comment Share on other sites More sharing options...
WP64 Posted April 18, 2008 Report Share Posted April 18, 2008 It's been my experience with forums like this, that most folks like "the easy button" answer. They prefer off the shelf tuning and easy to install mods that don't require much forethought. And, once they buy something, it's automatically the greatest product since canned beer and they'll never admit it could have been done better, maybe cheaper, if more time had been spent in research. Forums like this are very helpful, but can't replace checking out the facts with a professional. Well said SGT4729. I will be honest about the Canton coolant catch can for the S-197, it's not as good as Moroso's coolant catch can that I am now using; same goes for the Powerhouse 4" aluminum drive shaft, it's not as good as the Drive Shaft Shop's 3.5" alum. drive shaft that I am now using... I'll admit and pay for my own mistakes and correct them, I'm certainly not going to live with them. Have a great time at your event McCoy, I'll be at Thundrehill next weekend doing some open track racing myself on Saturday and I'll have my laser temp. reader with me. Link to comment Share on other sites More sharing options...
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