mountainbiker2

Why not just put on stiff springs to control body roll? I thought swaybars take away grip to a certain point. Plus I have 4 wheel independent suspension. Why tie it all together with bars? Since were rear wheel drive, why would I put on a swaybar in the rear? Just spring it stiffer. Educate me.

thanks,
Steve A.

ipuig

Take the sway bars off and go for drive, you'll find out.

rfn026

In an ideal world you run the softest springs possible and huge sway bars. You control body roll with sway bars - not springs.

There is no ideal world though. You can't find huge sway bars for the C4 Corvette. Z51 and Corvette Challenge bars are as good as it gets. That's why C4 folks need Corvette Challenge springs.

Basically I'm now using both sway bars and springs to control body roll. The car is just wonderful.

Richard Newton

gkmccready

Your car is not the same width as it is long...

dfinke23

Not a suspension expert, and just learning this stuff, but I would think enough spring to keep the car flat would severely compromise tire grip. That, or eat tires like a fat kid eats cake.

95jersey

We'll, for example, GM designed the T1 kit with stiffer springs AND MUCH larger sway bars. The T1 front bar is very large. I would say the T1 sways are a more dramatic of an increase to the OEM suspension, than the additional spring rate in the leafs. This is much debated on this forum and I don't think we ever got a clear answer, just a bunch of opinions.

fej

Generally I think there are 2 schools of thought on this, big bars, softer springs with some assistance from stiffer shock valving; and the stiff spring, stiff shocks, stock front bar, stock or no rear bar theory. Depending upon the driving style, both can work pretty well from what I have seen.

I do have to say that good friends of mine, one of which builds/designs his own suspensions, were very much in the stiff spring/shock theory for years, they are now moving towards less spring and shock "stiffness" or rate, and more overall system control via the shocks, with body roll being controlled more by the bars and less by the spring/shock rates.

Ankeney has set up a ton of autocross cars that have won many events and championships with very high spring/shock rates, effectively having the shock shove the tire down with very high compression valving. It can be done and work well for the right driver / style.

I am leaning towards a little more spring for my car than the factory z06 rates, and a T1/stock bar combo.

Fej

aggie_corvette

There are different schools of thought about this.

One thing to note though is you would not put stiffer springs on to control body roll. Springs are there to hold up the sprung weight. To control body motions either bump, rebound, or roll, you would put on different dampers (shocks).

So your comparison should be about roll-bars vs dampers.
Google that comparison and have fun reading...

Remember their is no perfect solution. Everything is a compromise.


Will

ltborg

Overall you just want to achieve your desired wheel rate. You can use ARBs or springs to do this in roll. At a minimum, you need a certain amount of spring to control the pitch of the car. Stiffer springs will help prevent a lot of dive or squat (outside of changing the suspension points). This also helps control roll. The trade off is that the springs do not absorb bumps or curbs as well. On a super smooth track, this may be the way to go.

On a car with set suspension points on a track that is pretty rough or in a parking lot for an autocross, you need softer springs to keep the sprung weight (car body) settled and keep the tires in constant contract with the ground. A larger ARB/softer spring helps here because the bumps do not unsettle the car as much, but you can still keep the tires at a desired orientation (camber angle) by preventing body roll with the ARBs.

Generally, the softer spring will also help you put power down assuming there is enough spring rate to keep the suspension in an acceptable operating range. If they are too soft and you end up hitting bump stops or getting undesirable amount of camber or toe, you have to add some rate, change the suspension points, or drive around it.

Class rules obviously dictate what you end up going with, which may not be the preferred solution.

John Shiels

http://auto.howstuffworks.com/question432.htm

Kubs

The springs are used to absorb bumps, the anti-roll bars and shocks control the body roll. If you use stiff springs the car will bounce over bumps and make it very un-settled in cornering conditions. Softer springs and big bars are the only way to go.

gkmccready

How much force do you generate accelerating (squat) and decelerating (dive)? How much force do you generate cornering?

When you rotate your cG around your roll center the force you're controlling looking front/rear is different than the force you're controlling from side-to-side. Swaybars make up the difference in wheel rate required to control those forces. If you jack up the spring rates to control the side-to-side motions you're likely to be oversprung for the front/rear motions. (You can do things like dual-rate springs so you get "just enough" roll at a lesser rate...)

Autocross has a lot of transitions where you want to control/limit the roll because it's likely you're about to head back the other direction (ie. slalom). Road racing typically doesn't have as harsh transitions so you can afford the body roll in an attempt to keep more contact patch without upsetting the weight transfer... meaning on a road course you usually have more time between left/right transitions than on the autocross.

Remember, shock valving doesn't limit roll, all it does is control how fast it occurs...

I'm no suspension engineer but start thinking about the cars weight and where that weight gets applied as you do certain maneuvers and what it will take to control the forces generated.

froggy47

lurk

40YRW8

Good analysis. Remember that on the weight transfer in the left/right transitions, there is another reason to control the roll. In the transition, the roll has inertia as well. The inertia causes the car to over roll and then recover. Less roll, less inertia and less roll, ect. That is why you need to turn the wheel as slow as possible when making the transition. Slow wheel also means less inertia. For the guys looking for philosophy, don't forget that most good road racers bounce their cars over the curbs to cut down the turn radius and save some time. The stiffer the spring, the more roll energy and inertia gets imparted into to the chassis. Once you truly understand the philosophy, it will seem pretty easy. The hard part is plugging in hundreds of variables for each corner and each track and coming up with the best overall compromise to give you your best lap times. One of my favorite things about road racing was to feel how the car reacts, make notes, take the car home and, between races, sit down and try to come up with solutions that would make the car a little faster. Seeing your lap times at a certain track slowly go down, for me, was very rewarding.
Gary

mountainbiker2

Thanks guys for all the comments. I only autocross my car. Every time I've tried a bigger front bar (35mm) it just understeers more. My favorite setup has been Hotchkis 32mm front and 25mm rear, set at the softest setting. This last autocross I tried no rear bar and a 28.5 front. I went from .2 behind the competition with the Hotchkis bars to .6 ahead with my no rear bar, little front. Seems like the consensus here is to go back to big bars.

Steve A.

c4cruiser

Can you further define "huge sway bars" for the C4?

My 87 Z52 coupe has stock 30mm front and 20mm rear bars (both solid). Looks like both VB&P and Vansteel have 32mm front and 26mm rear bars. Is that the biggest bar sizes currently available for the 85-87?

Guess the issue I have is for the front bar for the early C4. Even the Z51 front bar for 87 is the same size as it is for my Z52 suspension. And the Challenge bar is for the 88 and later C4.

trapp

Then why does the Z06 have stiffer leaf springs then a Z51........and a Z51 stiffer then a Base .....

John Shiels

control roll, squat, and dive/

RX7 KLR

And yet the clock does not agree. Forget what the consensus is, only the results matter.

In many cases big bars are a popular band-aid for classes/cars that cant use, or lack the proper springs.

Don't forget the diet you put your car on will have changed you wheel rates.

froggy47

The "philosophy" of the stiffening has to do IMO with the purpose of the car. Base car drive to golf course (hit potholes) comfy ride required, z51 car, not going on the track but maybe wanna carve canyons will put up with "some" loss of ride quality (but I rode in my buddies z06 once and didn't like it) , z06 hit the (smooth) track.

The stiffness is all relative, my 04z has soft springs compared to T1 springs or other aftermarket springs. If I autox'd with T1 springs I'd imagine due to parking lot traction issues & patched asphalt & drain ditches, that I'd be flying off the course more than I already do. If I ONLY tracked the car I'd have T1 springs or (maybe) coil over.

The suspension "package" has to fit the use.