How low (BG)?

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Our car (STS ZX2) is set up so that the front control arms are parallel to the ground. We have a bunch of people say that the car looks like it could go lower...but I have heard that the handling suffers once the LCAs go past parallel. Is this somethiung that is a legitimate concern...or is it worth dropping maybe another 1/2"-3/4" or so?

 

[gavin_leslie]

Arms level is good. You could probably go a hair lower, but I wouldnt go much more than 2.5deg past level. I did the math for my car(91 MX6) a while back when I had the arms at about 5deg past level and the roll centers were about 3" below the ground. The lower you go, the faster roll centers drop in relation to CG and then the more you need to rely on heavier and heavier springs and swaybars to keep roll angle in check....and then that screws up other things down the line like mechanical grip, acceleration, etc.

Try 1/2" and see how the angle of the arms are and how the car drives. You may be able to get away with it. If the car gets oogy, you can always raise it back up a bit.

Gavin

 

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OK...thanks for the input. It's pretty stiffly sprung already--550s in front, and we're looking for more (700-750???), along with a smaller FSB (25 to 22).

 

[gavin_leslie]

Thats a pretty stout jump in spring rate. A long time ago I tried 600lb fronts when I was in STX and the cars front end tended to wash out/skate...granted, that was Kumho MX days and may not mean much.

Still though, In DSP trim with 275 hoosiers, 500lbs and the stock 24.2mm front bar seems to be keeping things in check while affording some suspension compliance to get mechanical grip.

http://www.teamunemployment.com/gavin/autocross/Marina UFO 3-9-08/marypozzi/DSC_0589.JPG (first ever run, concrete surface)

Im guessing your plan is to "not make the suspension work"(old joke about struts) and have the car rotate on the nose? Isnt thats a lot to ask from the tires? I know street tires have been pushing the limits of traction nowadays, but Id imagine part of the trick would be to maximize grip as much as you can.

Gavin

 

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The car still leans a fair bit as shown in photos--at least it's not as flat as the Hondas. I don't necessarily mind that, but I don't want to make it worse by softening the FSB, and not adding the appropriate spring back to compensate. If it's only 50 or 100 pounds than so be it...I was just throwing a wild guess out when I said 700+

The car is not skittish with 550s...we put those in in June, up from 450s...big improvement in feel.