Camber plates or sway bars?

[Jb325is]

Yep with GC or Vorshlag you get lower stack height, more travel and ultimately more adjustment. I have 3.5° on mine. I prefer GC since I have bought so much stuff from them over the years and they have always been great to deal with. Both are high quality though

[Northern]

I like the dual bearing setup on the GC's. I've never had to replace the spherical bearing on them, and the used set that came on my M3 roller are still tight as well.

[Jaxx_]

Except, of course, on cars with McPherson front struts. In which case the exact opposite is true (up to a point).

Assuming that the individual spring rates were adequate for the car, is this really true? Please explain.

[dmmai]

I like the dual bearing setup on the GC's. I've never had to replace the spherical bearing on them, ...

The set-up on my E30 is fairly substantial with H&R Cup kit, I.E. adjustable swaybars and GC camber plates. This allows me a neutral car on track and yet with good rotation for autocross.
Which to do first ... ?
What is your current camber?
If straight up or especially if it's tending toward positive, the plates will save you some serious tire wear. Probably get them first.
Castor can come into play too.
If you really want a flat cornering car, the swaybars are something you won't want to delay for long. You'll like them. But, that's a choice.
Have fun.
.

[Emre]

Assuming that the individual spring rates were adequate for the car, is this really true? Please explain.

All the "rules" about adjusting understeer and oversteer via spring rates and anti-roll bars (as we've all read in Carroll Smith books, etc.) assume an "ideal" suspension. That means a formula car with stiff chassis, double-wishbones, springs in-line with dampers (like coilovers), linear spring rates, etc.

A sedan with McPherson struts in the front and semi-trailing arms in the rear behaves very differently from a car with "ideal" suspension. Here's the short version:

• With McPhersons in front, there's not much dynamic camber gain with compression (nowhere near as much as double-wishbones can have), plus the strut towers themselves flex to some degree.
• With rear semi-trailing arms, there's plenty of negative camber to begin with...and you only get more as the suspension compresses.
• On top of that, the 4 wheels don't remain square. The E30 (and E36) chassis twists significantly when cornering under power such that there's more roll over the front of the chassis compared to the rear.
• Paradoxically, using wider wheels, decreasing offset of the wheels (i.e., pushing them further out), and/or using stickier rubber compounds can actually make the problem worse as they induce more body lean in the corners.

All that adds up to insufficient negative camber at the front (both in absolute terms and relative to the rear) under hard cornering.

How do you manage that? You have a number of options, of course, such as stiffening the chassis, adding more static negative camber to the front, but the general idea is to minimize roll over the front axles.

Carrol Smith tells us an ideal car will have more grip over one axle if you make it softer. Stiffen the front (with higher spring rates, stiffer damper settings, and/or bigger anti-roll bars) and the front will grip less, so you'll have more understeer. Unlike an "ideal" car, an E30 with McPherson fronts will absolutely have more front grip if you stiffen up the front axles. Whether you do that with springs, dampers, or sways is a finer point. But you need the front to stay flat.

[TobyB]

Unlike an "ideal" car, an E30 with McPherson fronts will absolutely have more front grip if you stiffen up the front axles.

This is true- but only up to a certain point. After that, the loss in grip due to suspension non- compliance
(skipping over bumps) starts to cost you again. All else being the same (or compensated for)
as the front ROLL rate goes up, the car will corner faster. But as the front WHEEL rate
goes up, grip will increase- and then plateau, as the tire becomes the softest element
in the suspension.

In other words, yes, you can overdo it. But we're talking about #1000+ springs at that
point.

t

[Emre]

This is true- but only up to a certain point.

Agree 100%. As I said in my first post in this thread...

remember, bigger front = more understeer.

Except, of course, on cars with McPherson front struts. In which case the exact opposite is true (up to a point).

[MX339]

Carrol Smith tells us an ideal car will have more grip over one axle if you make it softer. Stiffen the front (with higher spring rates, stiffer damper settings, and/or bigger anti-roll bars) and the front will grip less, so you'll have more understeer. Unlike an "ideal" car, an E30 with McPherson fronts will absolutely have more front grip if you stiffen up the front axles. Whether you do that with springs, dampers, or sways is a finer point. But you need the front to stay flat.

I do have a question here. Is there a point at which you find that giving the front end more roll resistance through spring rate, dampers, or ARB's, is no longer productive due to the chassis flexing? I would think that as you get more aggressive in trying to counter roll through the suspension components, the more stress (flex) you're putting on the chassis.

Just to be clear, I'm not alluding to what Toby mentioned. I'm more so trying to figure out if, say with factory E30 torsional rigidity, you have less suspension compliance and transfer those roll forces into the shell, will there be a point where reducing suspension compliance will no longer have a positive effect on overall grip due to the chassis flexing to a point where the roll resistance generated by the suspension is actually overcome by the amount of twist in the chassis? I'm not sure if I've been entirely clear here.

By the way, do you happen to have any sources where I could read up on the long version of your McPherson theories? I recently acquired a few Carroll Smith books and have been slowly getting through some of them, but I'd love to read up on some suspension theory that's more relevant to what I'm actually going to be working with.

[Emre]

I do have a question here. Is there a point at which you find that giving the front end more roll resistance through spring rate, dampers, or ARB's, is no longer productive due to the chassis flexing?

Sure. You can make the springs/dampers stiff enough that the car starts bouncing around over even small bumps. That's going to decrease traction and make the car handle unpredictably.

Even if you don't go that far, you can make the suspension so stiff that the tires become the most compliant part of the system. That can be fast, but it also wears out your tires very quickly...so quickly that it might not be practical even on a race car.

Just to be clear, I'm not alluding to what Toby mentioned. I'm more so trying to figure out if, say with factory E30 torsional rigidity, you have less suspension compliance and transfer those roll forces into the shell, will there be a point where reducing suspension compliance will no longer have a positive effect on overall grip due to the chassis flexing to a point where the roll resistance generated by the suspension is actually overcome by the amount of twist in the chassis? I'm not sure if I've been entirely clear here.

I see what you mean. I can see that happening with really old cars, like vintage racers with ladder-frames. I don't think you could ever get to that point with a (fairly) modern unibody chassis. But I don't have any evidence to back that up; just a feeling.

By the way, do you happen to have any sources where I could read up on the long version of your McPherson theories?

I can't think of anything specific. But there's a ton of knowledge out there.

Remember that winning touring cars by Porsche, BMW, Mercedes, Audi, etc. all use MacPherson struts. So do pretty much all rally cars, like the Evo, STI, Peugeot, Citroen, Lancia, Ford, etc. etc. So, there's lots of accumulated knowledge out there in terms of how to set up and tune a car with MacPhersons +/- coilover conversion.

I recently acquired a few Carroll Smith books and have been slowly getting through some of them, but I'd love to read up on some suspension theory that's more relevant to what I'm actually going to be working with.

Those books are great for the fundamentals, but don't treat them like a bible. Look at what FIA Group A touring cars (e.g., DTM, BTCC, French Supertouring), German Klasse I cars, WRC cars, Porsche GT3 Cup cars, etc. are doing. You can learn a lot from guys with winning C-Mod cars, for example.

[Larro]

I dont post much here however, I have a little real world info on this subject. My last racecar was an e30 for chumpcar. Saved a shell from the scrap heap and built an in between race car, race car for cheap seat time. Rubber bushings, tokicos stock swaybar, etc. I bought fixed camber plates (which are good and cheap for daily use) but ehh for a track car. Picked up cabby front sway bar and ix rear sway bar which were the largest stock sway bars. We gained more per lap with sway bars than camer plates. Camber plates helped save tires but didnt do much for handling.

The sway bars obviously kept the car from rolling over itself but made much better use of the tires and the lsd. Keeping the inside wheels on the ground with some weight over them helped tremendously.

Imo buy quality sway bars. Keep that car flat on the ground. The rest of the car will appreciate it.


Again the fixed camber plates were good for daily use but not everyday track use.

The swars bars obviously kept the car from rolling over itself which made better use of th