tire hit

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jaspermaggie
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tire hit

#1 Post by jaspermaggie » Thu Mar 10, 2011 7:39 pm

I am driving a 55 3400lb chevy with 430 crank hp th350 3000 stall 3.70 255/60/15 (27") mt drag radial 17psi. I have strange in front qa1 in back both single adj with cal-trax. Do I wont a soft or hard hit. Also soft or hard on nitrous 150hp. runs 8.0 in 1/8 and 7.03 on the bottle.

I am startiong over with the traction isue. It is inconsistant at best. I think I am on the right track. It was spinning now it looses traction after about 2 feet. I finaly got some good info on the cal-trax (thanks John). I know how the holes work.
My car is not as fast as I think it is.

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John_Heard
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Re: tire hit

#2 Post by John_Heard » Thu Mar 10, 2011 8:24 pm

If it's spinning at 2 ft out, then look for things that are upsetting the car such as front end running out of travel (slow down the front shocks or add travel), running out of rear shock travel, something hitting somewhere or binding, running out of driveshaft yoke travel.

I'll let some of the other guys give advise on the radials as I've not messed with them. The general idea on those things is to dead hook it.

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ytnova
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Re: tire hit

#3 Post by ytnova » Fri Mar 11, 2011 4:14 pm

John is dead on with his recommendations. The faster and smoother you bring on the power, the better. The radial tire likes to stay loaded the entire time, if something upsets it, it will spin, and they do not recover like a slick. Do not underestimate how much rear shock extension you need with leaf springs/caltracs or how stiff the rear valving may have to be. Always go back and check everything, like available shock travel(lol), after you make adjustments, ie. move weight or add/subtract preload. 17 psi is probably a little low for your weight, I would video the tire at launch and see if the rim is pushing into the tire, or wadding up needing more air. If you had double adjustable rears, the compression should be pretty stiff to hold the tire down and the rebound(extension) should be controlling how hard/fast it hits the tire. Generally, if the weight is close front to rear, and there is no suspension binding and there are no other issues, bottle not purged, stumble in the carb, lack of shock travel, etc. this is kinda what I go by. If it spins at the hit, soften the rear rebound(extension), speed up the front extension or take out some power. If it rolls out and spins, your either overpowering the tire(nitrous/timing ramped to quick), the convertor is locking up and you need to add power, ie, it doesn't have enough power to maintain the load on the tire so the front end drops(if you can data log the engine rpm, you can see where the engine rpm drops when the convertor locks, add power there), your running out of front or rear shock travel(shock is topping out and upsetting chassis, adjust height of shocks and/or stiffen rebound/extension), or the front is coming up too quick(slow down front extension and/or use a stiffer front spring). Last, but not least, walk the starting line, look for bald spots or bumps, ask what traction compound they use, etc. Radials are not the most consistant tire out there and track conditions effect them more so than a slick. I am by no means a expert, and I am sure others will add some stuff I forgot, but I hope this helps and keep us posted.
I am not really sure what the question is, but I am pretty sure the answer is Big Block.

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