Upgraded suspension equals worse launch????

[Roger Stattel]

So I just got done putting on pedders xa coilovers and bmr trailing arms, toe rods, all bushings and sub frame and differential bushings and pedders sway bars. Got it alligned and took it out for a spin and first and second are sloppy as hell now. I'm running 11" with 305 35 20 Goodyear f1 in rear. Any advice? Camber is set at pedders aggressive street specs. I need to get the power down. Only at 465 rwhp right now.

[BMR Sales]

What exactly do you mean by "sloppy"? Sounds like possibly something was not reassembled and/or tightened up correctly. Should be a very nice set-up!!!

[durbojones]

I would double check that everything is tight. I went from consistently running 8.7s in the 1/8th to consistently running 8.2s on the stock Pirellis.

[Roger Stattel]

Well I've gone through everything myself along with the alignment shop also going through all the bolts to re time them. Sloppy meaning, on hard acceleration the rear end gets more fishy than before. Some friends of mine who are into drag racing say that it is due to the fact that it can't squat due to how stiff the coils are.

[Mean Green Z28]

Well in that case yes. You're not going to transfer as much weight to the rear with the stiffer springs. That's the reason we used to use the V6 springs on the rears of the 4th Gen V8 cars due to being softer and allowing more squat for weight transfer.

[BMR Sales]

Originally Posted by Roger Stattel

Well I've gone through everything myself along with the alignment shop also going through all the bolts to re time them. Sloppy meaning, on hard acceleration the rear end gets more fishy than before. Some friends of mine who are into drag racing say that it is due to the fact that it can't squat due to how stiff the coils are.

That could certainly be part of the problem, maybe try reducing your compression setting to allow easier compression of the rear coilovers. Also, I'm not sure what the camber settings are on Pedder's aggressive street alignment specs, but extreme negative camber settings will have a negative effect on your ability to launch hard in a straight line. It's great for the "twisties", but for maximum straight line performance and traction, the typical negative camber settings found in most "aggressive" alignment specs are NOT to your benefit. This is why most drag racers try to have as close to "0" degrees rear camber, which puts the largest tire patch possible in contact with the pavement!!! If you're looking for hard launch capability, maybe try to find a happy medium in your rear camber settings.

[Str8_W8]

Was everything tightened down with the suspension loaded?

[Roger Stattel]

Originally Posted by Str8_W8

Was everything tightened down with the suspension loaded?

Yes I made sure to specify that at the alignment shop. I'm pretty positive it's between the camber and the stiffer coils which allow virtually no squat.

[sting808]

Originally Posted by Roger Stattel

Yes I made sure to specify that at the alignment shop. I'm pretty positive it's between the camber and the stiffer coils which allow virtually no squat.

If there's movement in the cradle or the Toe is off, it will get squirrelly on hard acceleration. Rear would get unstable and move side to side. I have XAs, all bushing replacements on rear, and trailing/toe arms. I've run 0* to -1* rear camber and various toe. Only time it got squirrely was the eccentric was stripped and alignment would drift due to movement. One side toe was really off. Rears are 20x11.5 running 295/35 to 315/35 sizes.

Took it back to shop and had to replace eccentric. Only problem with my auto-x setup is weight transfer is dampened with the stiffer springs. Front doesn't nose dive and rear doesn't squat like stock spring rates. I have a KB and never could hook 20" street tires, just spins. Not a good setup for drag. You may be able to find 6kg springs for the rear if you drag. I believe XA stock is 8kg fr, 10 kg, rear.

I would get the back timed and alignment checked by a reputable shop if the rear is unstable on hard acceleration.

[BronxxBombers213]

sounds like toe to me !