89 Reynard Sway bar question

[oh2winindy]

VERY ROOKIE question guys...

My rear swaybar (cockpit adjustable) on my Reynard is for all intensive purposes shaped like a squared off U.

One side has the blade, and the other side (left) is solid and attached to the bar itself.

My question is this. When I adjust the sway bar from soft to hard or the opposite, is this only changing the stiffness of the right rear? I looked at this from all angles, and still cannot figure this out.

Thanks in advance for any replies.

[Steve Demeter]

Jamie,

The car reacts to the total stiffness of the "system", meaning how much force it takes to twist the bar "X" degrees, because the bar rotates freely where it is attached to the chassis.

Rotating the blade changes the stiffness of that system.

If the bar could not rotate in it's mounts, it would simply act like an additional spring, increasing the total spring rate, and then yes the side that is simply round would react differently than the side of the car with the blade. This would be true except when the blade happened to be in the exact position where it's stiffness in bending, in the axial directionof the links connecting the bar ends to the suspension, was equal to that of the round side.

[Steve Demeter]

PS: I had one heck of a time understanding why an anti roll bar worked at all the first time I read about them.

[Mark H]

When the blade is flat the ARB is softer ( able to flex ) when it is straight up it is hard.

As the outside wheel pushs up in a corner it pushs the inside wheel down to help traction. That is the easy way to look at it. Changing blades and bar thickness is a real trick to get right.

[MartinRacing98]

As the outside wheel pushs up in a corner it pushs the inside wheel down to help traction.

Everything I ever read says adding a stiffer sway bar removes traction from the end the bar is on. Does anyone know the theory behind this?

[Purple Frog]

Yes.


Ed. note: The Frog is being a smart donkey today. Maybe Richard Pare or DaveW will jump in and explain ARBs accurately. If not, there are numerous posts in archives explaining the theory. Also very helpful is DaweW's NEOHIO course handout, also posted in archives. It has been strongly advised by many forum members to a. read Smith's books (multiple times)., b. Study up on Mitchell's program., c. Attend an ICP seminar., d. read Apexspeed archives for 38 consectitive evenings. e. all of the above.

[RacePro]

MartinRacing98,

The idea that a stiffer stabilizer at front or rear "loses traction" at that end, while somewhat true, is overly simplistic. If that were completely true, we would all remove stabilizers from the front AND the rear of our cars and our lap times would tumble.

To understand the mechanics, one needs to ask, "Lose traction in what way?" Obviously, we lose mechanical grip thru lockup under braking, wheel spin under acceleration. If springs are too stiff or our shocks are valved incorrectly, wheel oscilation (bouncing up and down) can occur. And then there is sliding . . .

Less obvious is UNloading weight from the inside tires under cornering, and perhaps OVERloading the outside tires. (Both conditions lose grip!) Without getting into roll centers and polar moments, this UNloading and OVERloading is very detrimental. Naturally, the stabilizers work to minimize this "tipping" of the weight to the outside. Stabilizers help to keep the downward pressure more equal on the inside and outside tires. In doing so, they ultimately transfer some of that "tipping" energy to "sliding" energy.

Now, if one starts with a fairly neutral handling car (understeer vs. oversteer), and then adds more stiffness in, say, the rear, (turning the BLADE to a more vertical position on the Reynard), one will induce oversteer. One has transferred some "tipping" to some "sliding" in the rear. Is this bad? Not if one can now induce some relative understeer by stiffening the front.

Many pro teams set up new chassis exactly this way, until the stopwatch tells them they have gone too "stiff".

Ed LoPresti

[GT1Vette]

As the outside wheel pushs up in a corner it pushs the inside wheel down to help traction.

That statement is inaccurate (you into the adult beverages at 10:30 AM Mark?).

As the outside wheel pushes up in a corner the sway bar (also known as an anti-roll bar, or ARB) also pushes the inside wheel UP. As others have stated, this keeps that end of the car "flatter" (reduces body roll).

What Mark describes above is what we called a "camber compensator" used on performance swing-arm VW Beetles (now ain't that an oxymoron) up until 1969 when the 4-joint rear end came out.

And as I tell the Frog often, "stiffer is better right up to the point where it throws you off the track"...

[R. Pare]

Sway bars have ZERO effect on the amount of weight transferred off of the inside wheels for any given cornering load - that is strictly a function of track width, CG height, and lateral load level. What they DO do, besides help reduce body roll, is to help determine just WHERE that weight is distributed on the outside wheels - taking load off of an over-loaded tire or adding load to an underutilized tire.

[GTmule]

Sway bars have ZERO effect on the amount of weight transferred off of the inside wheels for any given cornering load - that is strictly a function of track width, CG height, and lateral load level. What they DO do, besides help reduce body roll, is to help determine just WHERE that weight is distributed on the outside wheels - taking load off of an over-loaded tire or adding load to an underutilized tire.

Exactly! They also help reduce body roll (duh) and the negative (well...positive.....nevermind...detrimental) effects it has on camber.

[RoadHazard]

I'll see your rookie question and raise you one...

If the antiroll bar is set stiffer on one side than the other, will the car roll more in one direction than the other? Or does the stiffness of the entire "system" mean the roll will always be the same left-to-right?

[Purple Frog]

Same left to right.

If you really want to scratch your head look at my Tatuus rear ARB sometime. There are two blades, both adjustable.

[R. Pare]

I'll see your rookie question and raise you one...

If the antiroll bar is set stiffer on one side than the other, will the car roll more in one direction than the other? Or does the stiffness of the entire "system" mean the roll will always be the same left-to-right?

The stiffness is the same both directions.

We've used double blades for 20 years - nothing new or different there.

[RoadHazard]

So then there's no point in exactly measuring and matching the pickup points on the two ends of the ARB, right? The stiffness is determined by the product (or is it sum...) of the two ends of the bar, not the individual settings. I could adjust one end or the other, or both, as the whim strikes me. That makes life easier. I think.