Auto Racing: mustang 1/3 mile handling, sports car racing, dot tires

Question
Hi we have a 86 mustang on an 1/3 mile oval track. Spring rates 600RF 550LF 150RR 175LR and a 1 3/8 sway bar thats set at and inch of pre load. My problem has been since the track put a new rule on tires before every one was running 50s( now a 60 series), the car was really fast before. Now it doesnt connect to the track. Loose in and under gas but pushes a bit. We tried spring rubbers, adding major preload on the sway bar,tire pressures, raising the height of the LF corner a bit, and even tring hot lap. We've tried 3 different kinds of tires, so I dont think it 100% tires, and no luck. Any help please. And do you know of any good DOT 300 above TreadW 195/60/15 tires for us to try. Thanks

Answer
Hi Steve:

Complex problem there !  I'll start with the tires.  For sports car racing in SCCA Hoosier makes some excellent DOT tires that have a hint of tread but are largley a cheater street tire.  I have used them extensively and have a couple of season championships to show for it.  Beyond that, I've never used reas street tires on a race car.

From the other changes you describe, it looks as if you have done a lot of stiffening.  Your tire rule is requireing a tire with less grip, for that reason I would suggest you try softening the rear a bit. Keep your pre-load on the anti roll bar, but go to a softer spring. If you have adjustable shocks, go for a little less bump in the rears.

Take some tire temperatures and see which ones are hottest, then take weight off that corner- - -just a little though. It's important that you change only one thing at a time though, and take  LOT of notes.  Also make sure you are using the right amount of air pressure.

If you don't have it already, get the book "How To Make Your Car Handle" by Fred Puhn.  It's available at book stores for about $16.00. If you can't find it locally, you can order it from Summit Racing or most any of your catalog vendors. REad it several times !!

That's all I can think of at the moment, but try these things and write back with results.  We'll get it right eventually !

Good Luck

Dan Liddy
Sarasota, Florida