I'm not sure how many of you drag race your Z but I thought I would ask anyway. I'm considering new springs and I have always heard a stiff suspension is best for drag racing.

It would also be nice if I could find something that would lower .6" or less and eleminate the bounce.

The research I have found suggests that Hotchkiss would give me the perfect height and would eliminate the bounce. However the gains for drag racing would be poor if any.

Your thoughts?

 

**bump**

 

KONI shocks have helped me on weight transfer! I loosen them all the way on the fronts and firm them all the way on the rears. It worked so well I broke the half axles coming off the line on the very first run. I have gone to a little more air pressure and that seems to work.

 

So you have a Koni/Eibach setup? It sounds like softer in the back/firmer in the front AKA Hotchkis might not be a good idea for drag racing? Thats is the opposite of your set up. I have heard mixed reviews? Maybe I am missing something?

 

Yes to the Koni/Eibach setup. I've tried it both ways and softer in the front raises the front higher than the rear when leaving the line thereby causing the weight shift. I'm going back to the track on the 22nd after 2 months off and will try to get a short video coming off the line.

 

You want to allow more "squat" in the rear when dragging.

 

I certainly don't proclaim to know bug squat about drag racing setups, but. So that everyone understands, when we talk about a better drag setup being a softer rear. That's what the above is.

Koni shocks do not adjust for firmness, they do not have compression dampning adjustability. What they do have is rebound adjustability, which is how quickly the shock allow's a compressed spring to return to it's normal length. Adjusting the rebound down in the front and higher in the rear would promote the front end to rise on take off and the higher rebound in the rear would tend to keep it squated down.

Thing you have to watch out for is dialing in to much or too little rebound control. Too little and that spring is allowed to do things that are unproductive to the car as in poor shock control. Too much and the suspension will not be returning from being compressed quick enough to be productive for the car.

 

Knowing the spring rates for the Eibachs, the initial softer rates and the higher final rates, the oem rates and the Hotchkis rates, I thought I'd have a look.

At launch front Eibachs springs being progressive mean your slightly softer then oem up front -6% softer. In the rear, things are more complicated your a little softer then oem -8% for a certain amount of suspension travel. Yet as soon as the rear suspension compresses, sooner or later the higher progressive spring rate is going to take over and when it does the spring stiffness will suddenly change as the progressive coils bind, your rear rate suddenly changes to be +23% higher then oem from being -8%. Thing I'd like to see is a picture rear Eibach springs installed with the weight of the car resting on them. What we just don't know is how much suspension travel has to occur for the rear spring rate to suddenly change higher.

Let's look at the *Hotchkiss springs, during launch (really at any time) the front springs are +8% stiffer then oem and the rear springs are -3% softer then oem.

So, Eibach Front: -6% Rear: -8% compressing to +23%
*Hotchkis Front: +8% Rear -3% never changing

*What Hotchis says are oem rates and what I say are oem rates differ ever so slightly. If we use their data this would be the result. Front:+10% Rear:-6%

 

and remove the front sway bar as well