trinydex

something not mentioned yet is droop tuning. some suspensions have helper/droop springs that allow the wheel to droop under reduced load, however even that can only do so much.

three wheeling happens under acceleration and braking. any one car can do both if the loads are right.

Bob Rouleau

triny - I'd like to know more. My experience with helper springs is to provide a sort fo step function variable rate - allows the springs to be softer for small imperfections and stiffen up a lot under heavier load.

My experience is that I three wheel only when cornering and then with sticky tires.

How could I three wheel under braking?

Rgds,

chris walrod

How about lifting more than one wheel

chris walrod

this one?

Steve Weiner-Rennsport Systems

Bob:

You're correct: adding tender (not helper) springs to the main springs gives a "dual-rate" effect and makes a stiff setup more compliant over small bumps and road imperfections. Altering the ratio of tender & main spring dimensions alters the point in suspension travel where the rate changes.

These spring packages can be tailored very nicely for street, track or competition applications.

Lifting the inside front tire on these cars is a function of front & rear roll stiffness as well as front roll center height.

They all do it a little bit, but its all a question of degree. If the "liftoff" is just momentary, there is no harm in that but if you see one's inside front tire being carried off the ground for part or most of the corner, then combinations of additional rear stiffness, shock valving adjustments, or front roll center relocation is needed.

Steve Weiner-Rennsport Systems

FWIW, droop travel is determined by the shocks, not the springs,...

In some cases, the shock internals can be reconfigured for additional droop travel but there are tradeoffs.

Helper springs just serve to keep the springs tight in their perches at full droop and always coil-bound unless the wheels are off the ground. Tender springs, OTOH are part of the active suspension package and play a working role in suspension performance.

Larry Herman

Chris, how would you adjust your swaybars to correct that condition?

cgomez

I guess a 911 would be the most common car to lift inside front wheel. Not only from cornering grip and stiff suspension, but even in stock form, rear traction is so good that the car just wants to do a "wheelie" powering through the apex:

chris walrod

Stiff, very stiff

CG height, of course, plays a role, but so does X axis CG. With the 911's general -very- aft CG, the front is at the mercy of rear roll stiffness and that wonderful sounding counterweight in the back. More weight aft = higher rear spring rate = higher roll stiffness and increased leverage on the front.

95m3racer

If you are inquiring about the Jacking Effect, look it up in any suspension book.

It can get fairly complicated. The answer of why it happens and how to cure it is fairly long, and involves determiing what kind of jacking is occuring.

Droop is ciritical in motorsport suspension design.

Stiffer is not always better, and can bring up bigger problems.