Larry Herman

Seeing as how Kibort got everyone torqued out of shape on the HP thread, I figured it was my turn to start up a suspension squabble.

The basic premise is simple - Do stiffer springs offer more grip, less grip, or both, depending on the circumstances?

My feeling is that on smoother surfaces, stiffer springs offer more grip because the car leans less and the tire contact patch stays at a more optimal shape. On a rougher track, grip suffers because the stiffer springs load and unload more quickly, causing a larger variation in grip than with softer springs that track better. All this assumes that your shock settings are optimized for the conditions.

Your well-thought out opinions and experiences are appreciated. Knee-jerk reactions and regurgitation of dogma will be dealt with Rennlist style.

stownsen914

In general, I think you can say the smoother the track, the more good a stiff suspension will do you. Here is the Northeast, where smooth tracks are few and far between, you'll get lots of opinions on whether stiff is better or worse. I can think of several quite successful SCCA and PCA racers who liked very light springs on their (fast) 914 racers. Like 300 lb/inch or less. Their cars are of course comparatively light. Some people prefer much stiffer, even on bumpy tracks. Personally I tend toward the lighter end of the spectrum with 500 lb/in on the front of my 914 race car and 350 on the rear. You can of course run stiffer sway bars to avoid lean in turns even with a lighter sprung suspension.

Scott

wanna911

Perfect timing, I was going to start a thread like this one myself.

My common sense, which may not be applicable, tells me that stiffer springs should allow a larger opportunity for using less damping (bump). If they can control the body roll some, you can go some clicks softer which on a 2-way adjustable suspension should be very helpful since you don't have high and low speed bump controls. Using more spring to keep the car stable and planted, but less bump to handle bumps and curbs.

THIS IS A GUESS.

Rassel

In general yes.
Nordschleife - Soft
Normal Short Track - Medium
Major GP Track - Hard

+ another zillion of parameters.

Professor Helmüt Tester

Just about everything on this board is a guess.

Veloce Raptor

I agree with this totally. More suppleness is better on rougher surfaces.

Larry Herman

Yep, except for some of the stuff Chris Walrod & Geoffrey come up with. But some guesses have a lot of experience and testing behind them, and some are just pure speculation disguised as "opinion".


Are we a little testy today?

tomburdge

Scott,

Holly cow! 500# springs on a 914.

I run 350# front and 200# rear in my 1.8 ltr (4cyl) and turn 1:01's @ Lime Rock prior to recent re-pave.Doug Arneo put this package together for me years ago and I think it works pretty good.Also run front and rear sways but not real big ones.To me the car feels like its on rails with no white knuckle sensations.

You must be running a big six cyl.

Tom B.

Animus

I don't have the seat time in to notice the difference, but every suspension book I've read says, most people have a misconception about springs. They think that the car's reaction (bounce) is based on what the contact patch surface of the tires are and the spring's stiffness. However the car is typically heavier, and therefore the wheel's reaction (bounce) is based on the car's weight and the stiffness of the spring. That is basically the Car is usually the heavier object and therefore pushes the wheels down back to the road faster or slower based on your spring rates. This also leaves the argument of which feels better open due to your ratio of sprung (weight supported by springs) and unsprung wieght (weight not supported by the springs), which affects the feel of the spring rate....

DaveM993

My thought has always been

smooth roads - stiff springs, weak sways
bumpy roads - light springs, strong sways

Streak

Anything more than a 22/30 T-bar with weltmeister sways on a pre-89 911 is cheating

RedlineMan

Depends;

It's like tire pressures. The graph is a pyramid, the peak being optimal. If you are undersrprung for the weight of the car and the grip of the tires, then obviously stiffer springs will increase grip (and braking performance too) by "pushing back against the chassis" and planting the tires into the pavement harder. If you are already at the limit of weight:spring rate: tire grip, then stiffer springs will decrease grip.

Then of course there is track surface. Smooth tracks will handle more rate, while rough tracks reward a more resilient ride.

Then there is aero. More aero squats a car more, and may require increased rates to simply keep the chassis from bottoming and reducing grip. INDY cars don't need 1500lb springs based on a weight of about the same, but they do because of the aero effect they generate. It is the downforce that makes the cars "heavy."

All of this is open to revision based on actual circumstances.

Larry Herman

Is this an obtuse way of saying "of course, I could be wrong"?

multi21

Definitely Maybe.

TheOtherEric

This question is identical to: "is more air pressure better in tires?" The answer is the same: "yes, to a point. After that point, no." For a given situation, there's generally an optimum.

Larry, with all due respect, I think you should have asked: "How do I determine if I need stiffer springs?" People could squabble forever over the practical meaning of "grip".