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October 10, 2007
tire grip
I've made a spreadsheet to try a few different "what if" scenarios (adjusting corner weights, Center of gravity, downforce, and power), and it all hinges on getting a good ballpark coefficient of friction for the tire. I know it's impossible for me to get an accurate model due to all the variables that can change (i.e. I don't have $20k to have Calspan model my Kumhos!) but I'd like to get a ballpark curve so I can at least see what a change will do.
So far from Herb Adams book, he's got a table on page 2 with traction vs weight:
0:0
500:275 (coef of friction is 1.81)
700:500 (1.4)
1000:1000 (1)
1280:1500 (.85)
1500:1900(.79)
The polynomial I got from an excel trendline is:
-.00028*X^2+1.261*X+73
Milliken has a few charts on p78 and 79 of slip angle vs lateral force that has several curves based on vertical load for the 275 goodyear eagle ZR, a 27x14.5 Champ car rear tire, and a 25x9-13 F1 front tire. I'll get the numbers from that in a few nights when I have a chance.
The goal of all this is to figure out that 300 lbs of downforce will give me an extra 200 lbs of grip, which will let me corner at .2 more g's, which gives 4 mph faster exit speed, and saves 3 seconds per lap (purely made up numbers, but should be ballpark). Or see that ditching the 150 lbs of turbo gear on the nose and losing 250 hp will not slow me down.
Posted by Z28tt at October 10, 2007 10:31 AM