| Re: Autocross rant ...... |
Subject: Re: Autocross rant ...... by BillH on 2010/6/14 13:42:58 Kudos for working the grid. Waiting for someone to pull off the grid because they were wetting tires is BS and letting them run in the next group shouldn't even happen. It takes one minute to adjust pressure in 4 tires and get back in the car. Anything else (soaking) should be done by someone besides the driver, crew, friend other driver. If they ain't ready, they don't go. In road racing, if you aren't on pre-grid when the 5 minute sign goes up, you loose your qualifying position and have to start in the back. Input for tire temps.- You can get a baseline from the Mfg's but the variables (chassis setup, track surface temp,etc) make a difference. The only good way to know the best temps is from experience and data. I have temp/pressure sheets that I made. I have them for different tracks and keep them in a logbook for reference (you can't go out at Laguna on a cold morning and remember what pressure you started at last year). Drag racing's a different deal, the tires are at ambient and need heat put in them to get to the optimum starting temp for grip (varies wildly depending on the specific tire). Time in between runs is way longer than in an autox and the tires return to ambient temp. Cooling the tires - depends on temps. Tires are severely abused in one run and the temps go up fast. It's really the temps and press that should determine if they need cooled or a press adjustment. I would imagine that your champs are doing their adjustments by the way the tires felt on the last run and by their experience from 1,000's of runs. The best way is to take tire temps looking for even temps across the tire (taking into account camber heatup of one edge of the tire). IR guns are better than nothing, probe temp gages are much better since the tire surface cools very fast. Cold tire starting press is iffy unless you use nitrogen. You can't be sure of the moisture content in compressed air. And moisture content is determines the pressure build up. Also, is you're sitting with one side of the car in the sun, the temp difference right to left can be a lot. Many guys use tire covers. |
