Tight track

[ojh]

We got embarrased late last fall at not being able to qualify at an event. We typically get a low 1.0X 60' time and run 4.40's. Late in the fall the temp was very cool and the starting line tight, we went into tire shake at the hit of the throttle, the 2nd attempt we went up 2lbs on tire pressure and backed the nitrous off and it did the same thing.
We tested the following weekend but conditions were different and were unable to determine anything.
What do you guys reccommend we should have done. Thanks, oj

[John_Heard]

Maybe you should have only went up in air and left the power alone?

[ojh]

Throwing hp at a tight track and going up in tire pressure is what we've heard too. Any idea why? Thanks, oj

[John_Heard]

I assume the deal was your tire speed was dropping and the tire was trying to deadhook, making it go out of round causing the shake. Do you have a logger? Can you compare your drive shaft RPM between the two different track conditions?

[ojh]

1st pass rattled the tire so that it shut power off, the data is there but i haven't looked at it. The 2nd pass i'd have to have another looksee and overlay it against what it should run but i'm thinking it was so quick and violent that the data won't be relevant. The car didn't even get off the wheelie bars when it went sour.
The week after we could get out there a ways and the driver would drive thru it, i recall the car moving a bit to the left and rattling but not as severe. Thanks, oj

[Craig W.]

I ran into some tire shake issues last fall myself. I tried more air and adding power to try to slip the tire. Both helped but I really made improvements when I start slowing the extension of the rear shocks.

[ojh]

Slowing the rear shock extension? Can that be done with penskies, we have them stiff at launch and they soften up but that would be on compression i think? Do i need to read the book again?
I have yet to take advantage of the ignition, would it be a good idea to do a launch retard pulling another 10deg out and ramp it back to normal retard out to the 60'?
We've looked at a progressive controller for the N2O but the layers of electronic complexity stack up and we'd like to master the tuning of what we've got before adding another layer.
Back on the tire pressure, we run the big hoosier, what pressure would you reccommend? We normally run under 7psi, i am thinking we should go up a lb or two anyway, thoughts on this?