If I can jump in here really quick.

First off, most race cars don't have pre-load whatsoever. It's ok to have the spring loose when extended. That's not a problem. People think that when you go around a corner with the inside wheels off the ground like in Touring Car, the springs will come loose. That's not the case. The sway bar has enough pressure to keep the un-loaded spring from coming loose.
So if that is the case, why would anybody want to have preload on their springs?

 

Not that I have much (or any) experience setting up professional race cars, but I believe you're wrong here. Most race cars when jacked off the ground do not let the wheels sag almost at all. I've seen in nascar they use a chain attached between the chassis and the suspension to limit travel and keep the wheels up high when the car is jacked up, but I think with most road racing cars this seems to happen because they're preloading the crap out of the springs. You and I are running 12 kg/mm springs all around and no one really runs more than about double that on a car like ours, even for track-only use... and I've never seen a road race car drop a wheel even half as low as my car does when I jack it up.

 

[QUOTE]Originally posted by gernby
[B]

 

[QUOTE]Originally posted by slick rick
[B]If I can jump in here really quick.

First off, most race cars don't have pre-load whatsoever.

 

Yes, that method is used in late model modifieds, etc. That's mostly on oval course. That's totally different. They do that mostly because it takes less time to jack up the car since they have to use regular jacks. It's still different than having pre load on your spring.
When I raced Formula Ford and Continental (FF2000), we did not pre load our springs.

Pre loading could well have some advantages that I don't know about. I'm relaying information based on my experience and know how.

I personally don't like pre load on my springs.