Camber and height equation

[hsk8te2006]

At my current ride height (roughly stock), I'm actually experiencing too positive (I think) camber. Acording to my alignment specs, the tops of my tires are farther from the body of the car than they should be. I'm not looking to purchase a camber adjustment kit, because I have no intention of lowering the vehicle (at least not very much) at this point.

I know enough about alignments to know that if I lower my ride height, it will bring the tops of the tires closer to the car and reduce or eliminate the current camber problem. The question is does anyone know of an equation I can use to predict the camber change resulting from a measured ride height adjustment for the rear end of a FWD 2g dsm?

Thanks for your help!

 

[timmy]

If you have the stock suspension, i am not sure why it would have pos camber. Is the alignment machine correct?

 

[hsk8te2006]

I am not running a stock suspension. I am running Koni Sport (Yellows) with Ground Control adjustable Coilovers. I am running at somewhere near stock ride height (not sure... forgot to measure stock ride height before taking stock parts off the car), and the machine is showing too positive (-1.0 degree) a camber for the driver side rear.

 

[DGajre777]

Drop the rear until you see zero camber, you probably aren't on stock height.

 

[timmy]

I am not running a stock suspension. I am running Koni Sport (Yellows) with Ground Control adjustable Coilovers. I am running at somewhere near stock ride height (not sure... forgot to measure stock ride height before taking stock parts off the car), and the machine is showing positive camber for both rears.

I would assume it will be difficult to use any sort of mathematics seeing how they are coil overs that probably vary slightly during manufacturing. With that said, see if you can adjust the coil overs while it is on the alignment machine and adjust till it is in spec.

 

[hsk8te2006]

I'm not an expert, but as far as I know, which shock is installed shouldn't have any impact on the bump camber curves ( a.k.a. ratio of camber to ride height). I think [on our cars] it's a function strictly of the control arms, knuckles, and toe adjusters. Can anyone confirm whether my assumption here is correct or not?

If I'm right, then does anyone know how many inches (or fractions of inches) of ride height change equals 1 degree of camber change?

Sorry to effectively ask a second time, but I would have to make my height adjustments at home between alignments, and that would get expensive to just experiment until I eventually get it right.

Thanks again everyone!

 

[PieEyedPiper]

I'm not an expert, but as far as I know, which shock is installed shouldn't have any impact on the bump camber curves ( a.k.a. ratio of camber to ride height). I think [on our cars] it's a function strictly of the control arms, knuckles, and toe adjusters. Can anyone confirm whether my assumption here is correct or not?
Thanks again everyone!

You'd be correct.

Variations in manufacturing would be a negligible variance. There surely is an equation that describes the ratio of suspension travel:camber curve, but I just as surely couldn't tell you what it is. All things quantifiable can be described by mathematics, and as nice as it would be I think you're barking up the wrong tree. There will be some guess and check involved, sadly. But word on the street is that 3/4" of washers will be a nice place to start for a mild drop.

From the factory our cars come with a lot of negative camber in the rear. If you're truly at stock ride height than something is wrong. Either you have a camber kit installed back there already or something has been misinstalled, if that's even a word. My car, with like a 3-4 finger gap in the rear can easily have -2.xx* camber if I didn't use a kit. Maybe even more. These are not atypical results.

Can you post some pictures of the rear goodies for us? I'd do a careful inspection of all mounts/bushings.

 

[hsk8te2006]

I might be able to get some pictures tomorrow...

I'm the first person to ever modify the car, and the only changes to the rear suspension are the shocks and springs. No camber kit whatsoever, and all other parts are the originals from the factory.

Currently, I'm running about -1.5 degrees negative camber in the rear on the passenger side, and -1.0 degree on the driver side. I'm looking to correct the -1.0, NOT by a using a camber kit, but by lowering that corner of the car until the camber is back to about -1.5 degrees. I'm just trying to figure out how much to lower it to go from -1.0 degrees, to -1.5 degrees.

 

[DGajre777]

If I'm right, then does anyone know how many inches (or fractions of inches) of ride height change equals 1 degree of camber change?

Sorry to effectively ask a second time, but I would have to make my height adjustments at home between alignments, and that would get expensive to just experiment until I eventually get it right.

Thanks again everyone!

Yes, you are correct. Generally speaking a 1" drop will result in 1 degree negative camber. Assuming that none of your bushings are shot and that you don't have any bent parts, I'd say that you are not at stock height in the rear which is why you have positive camber. If you drop it to stock height, your camber should be in spec.

As for experimenting every time, I believe Firestone offers a lifetime alignment. It was $140 last time I checked. You pay once and they align the car as often as you want, as long as you own the car.

Stock height on a 2G -

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[PieEyedPiper]

I might be able to get some pictures tomorrow...

I'm the first person to ever modify the car, and the only changes to the rear suspension are the shocks and springs. No camber kit whatsoever, and all other parts are the originals from the factory.

Currently, I'm running about -1.5 degrees negative camber in the rear on the passenger side, and -1.0 degree on the driver side. I'm looking to correct the -1.0, NOT by a using a camber kit, but by lowering that corner of the car until the camber is back to about -1.5 degrees. I'm just trying to figure out how much to lower it to go from -1.0 degrees, to -1.5 degrees.

Camber will likely not be identical just because ride height is. That's just the way it goes, so you may not really want to lower your car on a specific side if the ride height already matches, left to right. You might end up giving the car a weird stance that may or may not be acceptable.

Camber kits are both easy and cheap, don't rule it out. I bounced around figuring this stuff out for myself, guessing on how many washers, living with that alignment for 6mo. and then fine tuning. And thanks to shitty equipment at a shop, I've now fine tuned my rear left camber to -1.9* and rear right to -.02*. Sweet, right?

So I finally got smart and went for the lifetime alignment at Firestone for $150. It ranges from $150-180 depending on your area. And then, I got even smarter, instead of essentially starting from scratch with my homemade washers and bolt kit, I just went ahead and eBay'd the ingalls rear camber kit that not only includes better washers and an appropriate bolt, but it comes with new mounts equipped with an eccentric mechanism for a 3* swing in adjustment. That way I only have to ballpark the number of washers and I can let Firestone dick around with getting it right. I paid something like $70 shipped. Not bad to end all this hassle once and for all.

On another note, what kind of driving are you doing? You might consider bringing that rear right from -1.5* down to -1* to match the other corner, instead of vice versa. -1.5* camber will work just fine, but it's more than necessary and it is desirable to have half the camber in the rear that you do in the front. But that's for a DD type setup, for all I know you're running -3* up front and you're looking to really attack the track by increasing your rear camber to match.

Clearly define your goals/purpose then you can more easily be sure about what kind of specs you want on your alignment.

I don't know what it is but I love suspension discussions.

 

[Oldsid]

I'm not an expert, but as far as I know, which shock is installed shouldn't have any impact on the bump camber curves ( a.k.a. ratio of camber to ride height). I think [on our cars] it's a function strictly of the control arms, knuckles, and toe adjusters. Can anyone confirm whether my assumption here is correct or not?

If I'm right, then does anyone know how many inches (or fractions of inches) of ride height change equals 1 degree of camber change?

Sorry to effectively ask a second time, but I would have to make my height adjustments at home between alignments, and that would get expensive to just experiment until I eventually get it right.

Thanks again everyone!

There is a way to know by measuring the gap as shown in the sketch below. You need to put your car on a level gound and lift it slowly with bot wheels moving up so that the measurement will be correct. The angle is the inverse tangent of the gap divided by 14" in the sketch. If you use a different length square, just divide the gap by the length of the square and find the inverse tangent (angle).
The hard part is to put the staight edge parallel to the ground.
The sketch comes from an old book, "how to make your car handle" by Fred Puhn and published by HP books. It is a great read and it can be found in some public libraries. I do not know if it is still in print because the first edition appeared in 1976!

 

[hsk8te2006]

To answer your question about my goals, this car is my daily driver, and has never seen track use. Someday, I may convert the car to an autocross machine, but for now it's my daily driver. I tend to drive in a spirited fashion semi-regularly (not all the time) around town, but I do about 75% or more of my driving on the highway.

My primary concern is reducing tire wear without impacting the handling too much.

Incidentally, my camber up front is currently -0.8 driver, and -1.2 passenger. I'd be willing to drop the front a little if you folks think more negative camber up front would be appropriate for my goals. What do you think my camber goals should be?

 

[PieEyedPiper]

Dropping the front a little bit is a good idea because it improves your rear roll center and can get you a bit more of that camber. An average of -1.5* to -1.75*(since the sides won't perfectly match) is a nice place to be in the front for a spirited DD. It is suggested that to maximize both tire wear and performance one should shoot for around half the negative camber for the rear.

-1* on both rear sides would be dandy too, don't stress too much over exactness.

 

[hsk8te2006]

Dropping the front by 1 inch would be nice. that was my plan and the reason wy I got ride height adjustable coilovers anyway.

But, alas the spherical bearing shock mounts RRE used to sell are unavailable now, and I've heard that dropping even an inch without them puts the shocks at risk...

 

[hsk8te2006]

Has anybody dropped a 2g by an inch using stock upper strut mounts and NOT killed their expensive shocks?

 

[eltoshan]

I've been waiting for my spherical bearing upper mounts, so I've been using the stock upper mounts for a while now. Konis are still alive.

 

[hsk8te2006]

May I ask:
1)How much you've dropped the car?
and
2)How long have you been running at that height with koni's and stock mounts?

Thanks!

 

[PieEyedPiper]

I've not killed anything. I'd imagine almost no one does. It's under certain circumstances that that risk plays a factor. I will look it up and get back to you. I will also get back to you with some new information I've come across about how much drop vs. how many washers etc.

 

[hsk8te2006]

New info... I just had to temporarily mount a stock strut to my passenger side front corner, and it appears I've already been running about a half an inch below stock height.

So has anyone been running lowered with Koni's and stock upper mounts? If so, how low and for how long?

Piper... I'd love to have those equations you've come up with...

 

[PieEyedPiper]

So has anyone been running lowered with Koni's and stock upper mounts? If so, how low and for how long?

As I've mentioned, MANY people do. And for long periods of time. The thing is is that you need some flex (ala OEM mount) or pivoting action such as the RRE plates or the DG plates. This link explains much much more Autocross to Win (DGs Autocross Secrets) - Suspension but the jist of it is GC uses old tech that doesn't take into consideration the weird things that can happen to the sides of the springs being compressed at different rates and that is caused by the fixed mount - no pivot, no flex = bent shock shaft/weird suspension behavior and eventually failure. There are a number of posts talking about this, pay special attention to anything DG or Jtoby says. Search around for further details.

I'm going to go out on a limb here and just go ahead and say you're perfectly fine on stock mounts. Especially for a DD. The fancy plates are for serious athletes. I have friends who run konis (not different than illuminas really, just way better) and have done so over the long term.

I'll get back to you on the camber info tomorrow.