My Bird doesn't make enough low end grunt to pull itself out of the hole, and the 60ft times are killing the car. Anyone ever air down the rear tire's in hope's of inducing a slight wheelspin to get the rpm's up and the motor into a more favorable rpm range?
Tom, A coupla years ago, when I was getting the good 60 footers, I balanced off my rear air bags to make the car sit level and it let the car spin a little more. Used to run 25 in the RH and 5 in the left. Now run 20 in each. Doesn't bite as hard. That combined with harder launches (3500 at Stanton, 4500 at Norwalk) got good numbers. Tire pressure was a disaster when I let them down.
I'm going to experiment I'm going to drop from whatever they're at now down about 10psi and see what happens. :TU:
I run 30 psi in the Polyglas on the street. Looks like only the outer 3/4 inch is doing anything according to the tracks. 10 psi? I wouldn't make a full pass. That thing will be all over the rack at higher speed.
Tom; Let me know at the track if that works out for you. I too am running 40psi. Thought about trying 30psi at martin, but did'nt have a compressor to go back up if it did'nt work out. Martin was the first time out on the wide ovals on the lemans. Was getting 2.1s and 2.2s all the time. o No: See you guys at the comfort inn. Don :3gears:
Each combo is different so I would start high and air down 3 psi at a time and watch the 60 ft's, mph and et's. Just make sure you have access to air to air back up when you find the right psi for your combo. This takes some time but is the best way to find the optimum psi for your combo.
Tom I went down a total of 5 psi on the Challenger T/A and loosened the extra spring clamps a bit. It worked. The car was bogging before this change and having to climb up the cam on the start. I marked the tire with shoe polish and had my friend watch for spin. We were getting a 1/4 to 1/2 turn and that gave me my best short times. Any more than 1/2 turn and it would spin the tires. It worked consistant and well when I found the combo. Mark
This is enlightening. My car will NOT launch with the current setup. It either bogs big time (even with the secondaries locked out and sliding the clutch as much as it'll let me) or I have to let it spin almost all the way through 1st gear. The first way gets me 60 footers in the 2.20-2.30 range and the second (spinning) does same. (This car was consistently in the 1.90-1.95 range the last few years). Big difference, though in the MPH. 98 with the bog (secondaries back on) and 102+ with the spinning. So the upper horsepower is there. et's for both are in the 14.20-14.40 range which is almost embarassing for this car. It ran that with radials and a 30 year old untouched motor. I've always run it (which came from when Rob was driving and gary was tuning it.) with 45 psi in both rears as it always gave the best tire patch in the burnout tests. Maybe that's not the best plan for this car with this combo. It needs to spin a little to avoid that dreaded bog. It's almost impossible to slide the Centerforce clutch (much easier with the factory Scheiffer setup). Certainly something to try, nothing else has worked. Thanks! :TU:
Now see, I've never run 45 psi instead for me it's been 38. The tire is rated for 32. That's why I wondered the starting point when Mark said he dropped 5psi. 32, 40, 45?
Not enough grunt??? What is the best 60ft time? What does it weigh and what gear do you have in it now?
Yeah, Miller! Spill your guts! :spank: :spank: :spank: :blast: :blast: :blast: :laugh: :laugh: :laugh: :laugh: :laugh: :laugh: :bglasses: :bglasses: :bglasses: :bglasses:
Weymouth and Miller aren't talkin' eh? See, this is how secret societies start! They call themselves "PSI." There'll be chapters in New York, Miami... Stanton. :grin:
Sorry guys I had not checked in since that post. On the Challenger T/A w/ G60 x 15's I started at 42 cold. I moved down to 37 psi warm and maintianed 37 to 38 psi warm the rest of the weekend. It got more traction at 40 and 42 psi warm. I run the Judge's G70 x 14's at 42 psi warm. I do the same for my cars with F70 x 14's. The F60 x 15's on the HO works great at 40 to 42 psi warm. I come to the race with the tires at 45 psi and adjust down from there after I make a couple passes. Anyone have a good base setup for E70 x 14 's? If I can finish up the SC/360 that is what is on that girl. Mark
