Suspension for AWD drag racing Options

[KOU In3]

I've been meaning to post this for some time but keep forgetting. I've done a lot of searching on DSMtalk and others but have been finding mainly info on FWD or autocross set-ups.

What the consensus on the best suspension settings for drag racing. Obviously maximizing contact patch as far as camber, etc. But what about stiffness? As stiff as possible all the way around? Or some slack up front to minimize rebound after the initial backwards weight transfer shifts forwards again?

I know the general comment is, "it's awd, it doesn't matter." But I'm not so sure there isn't a healthy amount of time to be shaved off from proper suspension work. It seems to pay dividends with the FWD and RWD guys, why not us?

[natedogg]

Its a good question, Travis. I experimented a little with my suspension on Sunday. Setting the rear to full stiff seems to work well at keeping the front tires on the ground, but according to some people in the audience I was lifting the driver side front tire off the ground about an inch. I attributed this to the fact that I had the front suspension set full stiff which causes the shock to take longer to expand when weight is taken off of it. But at the same time, keep in mind I had my best 60' time off this setup. I tried loosening the front suspension and was pulling slightly lower 60' times, but I actually attribute that to me launching the car at too high an RPM for this setup. I was used to launching it around 6500-7000 with everything at full stiff. I think with the the looser front I can launch her at a lower RPM. This is good because its easier on the drivetrain and helps 1st gear last a little longer.

I'd definitely like to do some more experimenting, because I haven't come to any conclusions yet. The data right now says I get my best 60' times at full stiff, but that may not be the best set up.

[KOU In3]

I hope to use your info as a starting point to go from when I finally get running and get a chance to play with the suspension. Different brand, but with all the adjustability it'd be nice to have some reference points.

I'm surprised that cage doesn't give you the rigidity to keep that last wheel on the ground though.

[akamiami]

darryl uses JIC-FLTA2's. sweet.

[awd4kicks]

If you watch an AWD with a stock center diff. launch in slow motion you will see that the front tires spin more than the rears due to weight transfer. With this in mind I would try to keep the weight from transfering to the rear as much as possible, because that's just lost power.

With a welded center diff. or a spool, all four wheels will turn the same number of revolutions no matter what. The rears will still not gain traction as fast if you don't have all four wheels on the ground, but it wouldn't be as severe as the viscous coupling center diff. Even though the the locked center diff. is not a suspension component it will keep you from loosing un-necesarry HP through free moving, unloaded front tires.

BTW - The fastest AWD racers I've seen to date show very little weight transfer while they seem to spin all four tires through the entire first 60 ft. Pretty wicked!

On a side note, my koni's are only adjustable on the compression stroke. I'm not sure about AGX's or other brands but I thought adjusting the rebound was an expensive additional option to the adjustable struts/shocks. What I'm saying is that adjusting the compression of my front struts would not do much for me besides control any spring bounce after weight transfer evened out towards the front again.

[KOU In3]

Some good points there Marcus. When I've reseached I've found a lot of AutoX stuff but even the little we've gone over here has been more specific info than I found in a few hours of reading back DSMtalk threads and sifting through cornering set-ups. Not that it's not good info on that forum, just not quite what I was looking for.

I've got a couple of Quaiffes in the new set-up so I'm not worried about losing power through the fronts spinning and not the rears. But I suppose I with the autocross and suspension tuning experience of some you guys I should just ask for suggestions on initial settings for the ShockTek suspension (with drag racing instead of autoX in mind though).

I've considered making it all as stiff as possible (when making a run) to minimize any weight transfer and gain maximum traction. Could use some basic advice for a starting point and things to look for when adjusting though. It's a couple weeks out still but I've been doing some research so I thought I'd come here for a little advice too though.

*Braces himself for flames on bastardizing an autoX set-up for drag use*

[natedogg]

I've read in a few places that the AGX's are rebound/compression adjustable with the same knob/screw. Haven't actually heard this from KYB though, so I don't know how true it is. But even if the shocks are only compression adjustable, from what I understand, it still takes the shock longer to expand when a load is taken off of it, if the shock is set at full stiff compression. This is my reasoning why the left front wheel was coming off the ground at the full stiff setting and not at the fool loose setting in the front. But there are other factors to consider as well, such as maybe I didn't launch it quite as hard or maybe the angles of the sun and the moon caused the gravity in the vicinity of my rear end to preload the rear suspension making weight transfer an impossibility...maybe not.

A spool or locked diff definitely has its launching advantages and I'm still considering one for my set up, but I just don't know if I want to put all 4 CV joints through that kind of punishment around slow turns. Guess I'll wait til my weak 2-spider blows up to decide.

[KOU In3]

Been doing a little reading. What I came up with is that on some/most of the shocks out there the compression and rebound damping are essentially both adjustable. But what IS fixed on a lot/most shocks is the ratio between the two.

Meaning that on most shocks you can't for instance make the compression damping looser and the rebound stiffer. Looking up some of the Shock-teck stuff I found that part of what they do is take a Bilstein shock and fix the ratio of compression to rebound stiffness for a specific application. So when one is stiffened, so is the other in the same ratio.

On the center dif, I should hav a couple of stock diffs around. If anyone wants one to weld on just let me know.

[awdnot2]

As Kris said the orange car is setup with JIC's. He acutally knows more about them than I do. Marcus said the fastest AWD's show little weight transfer. This is what the orange car does. The rear is very stiff to prevent squatting.
The front is also stiff with limited travel. When you raise the front more than about 2 inches with jack the fronts wheels live the ground. Overall as mentioned earlier this setup helps the front tires bite harder which reduces stress on the rear axles, driveshaft, and transfer case.

Darryl