Dynamic changes to rear toe & camber


#1

Hey guys,

Trying to decide if I want to run a set of posi-lock IE rear toe and camber adjustment plates on my street car ('87 325is) which sees spirited driving. (Possibly a track day or two in the future)

I’m running a mild H&R Sport setup now, but I may possibly go to something more aggressive in the future. M52B28 turbo setup is also in the cards, so traction will be a big issue.

Anyways, the reason I’m posting this on the spec30 forums, is that I am hoping you guys may know how the toe and camber changes when the suspension is loaded. (Dynamic camber and toe).

Also, how much does moving the trailing arm pivot points (with adjustment plates) change the dynamic curves?

Since I obviously can only set static settings with an adjustment kit, I’m trying to decide if it will be worth it.


#2

Rear toe doesn’t change within the reasonable range of our trailing arm movement. There are folks that will disagree with me on this, but I measured it and I couldn’t detect change. I was using a laser and measuring it 6’ away so any change in toe would have been amplified a bunch. It it’s changing, it’s not much.

Rear will gain camber on compression. There’s some curves around that show this, but the curves show such a large range of wheel movement, that they are hard to interpret for the prob +/- 3" of movement we get with HR Race springs. I would estimate that we get about a full deg of neg camber at full compression (~1.5")

If I had to do my subframe all over again, I’d put in camber adjusters at the inboard swing arm pivot points, but leave the outboard unmolested. I’d set the camber to what I wanted, and if my toe was off, I’d take the car to a frame shop and have them bend it to my spec.

The reason for this is that the outside adjusters can be the very devil to get to and adjust. Maybe IE has a new solution that makes it easier to get to those adjusters, I don’t know. The last thing I heard is that they were experimenting with deleted the outboard nut and instead putting threads in the serrated plate. The thread would then strip soon after. If they are still doing that, then weld a nut on the outside of the serrated plate so the bolt will have more to hang on to. Use a 10.9 nut.

The adjustable pivot points have trouble hanging on to their toe setting. That’s the other reason why I like the idea of having a non-adjustable rear toe. I had to weld on a gizmo that prevented my toe adjuster from moving. The SOB wouldn’t stay put more than a couple laps. I have an old design adjustable pivot points tho, so my experience won’t necessarily be yours.


#3

Hi Ranger,

Thanks for the quick reply.

In other words, static toe settings are comparable to the dynamic toe.

What kind of rear static camber do Spec E30 guys run? Or in other words, what dynamic camber under load do you guys shoot for?

Really? You’d rather them bend the subframe to your spec then have adjustment?
I guess that speaks to how bad the older style toe adjustment plates hold their alignment.

[quote=“Ranger” post=82640]
The reason for this is that the outside adjusters can be the very devil to get to and adjust.

The adjustable pivot points have trouble hanging on to their toe setting.[/quote]

Are the new Posi-lock style plates that IE offers Spec E30 legal? I’m hoping someone who has used them can chime in here as to how well they hold adjustment.

I’m the type of person who will set something up properly, and then not want to have to adjust it for years.

In that vein, I wouldn’t mind finding a race shop who will take the time to set the rear alignment to my specs, as long as it will hold adjustment and not need a re-alignment every year.


#4

Those #'s, 1.5" and 3", are at the spring, not at the wheel.

I think that most folks have 2-2.5 neg rear camber.

Re. static and dynamic toe. Yes, imo toe is toe and it doesn’t change. Just be advised that I’m considered by many to be a lunatic so you’ll want to get other opinions. But ask them “did you actually measure this, or did you just read it somewhere?”

Our cars losing their toe settings with adjustable subframe kits were driving us bonkers for a couple years. I don’t know that it ever got solved. Lots of theories as to the cause. My favorite theory was that when our cars bottom out (fully compression our HR Race springs) it puts lots of force on the swing arm pivot point and they move. Our springs are darn near bound up when the car sits stationary so it doesn’t take much. There was another theory that strapping the car down by it’s wheels could cause the car to lose toe. I never really bought into the 2nd theory, I just don’t strap my car down that tight and banging over gators is a lot more force then the gentle rocking of the trailer.

Recall that I mentioned that I’d welded in a lock mechanism to help the toe eccentric stay in place. A lot of people struggled with this so there were a variety of DIY solutions employed.

A couple years ago I quit using the rear wheels to strap down the car. I’ve a sneaking suspicion that helped the problem. But if I admitted to that, I’d have to buy into the idea that my trailer straps were (or were part of) the problem and I was totally wrong.

The reason I’d be good with having to bend things to fix toe, is that I’ve had to fix toe problems unexpectedly prob a dozen times. Each goddamned time I had to fight to get to the outboard adjuster. I have a set of cut down thin wrenches special for the task. Each can handle the nut at a different point. My subframe bushings even have a slice taken out of them in order to make it easier to get to that damned adjuster. Having the bastard bent to set toe would be very nice.

Keep in mind tho that I have the old subframe adjusters, not the new ones that I think have no nut you have to get to next to the rear subframe bushing. This is because that serrated plate is threaded. So you will dodge some of my problems. Just weld a nut on that puppy so the plate doesn’t strip.

Yes, the subframe adjuster kit from IE is legal.

Any decent alignment shop can set your alignment to your specs. It will be a little outside the box for them, but it’s not rocket science.

I would encourage you to figure out how to do your own alignments. For toe, I use a laser level. I first align the front wheels by getting them centered and shooting a beam back past the rear wheel. Then, leaving the front centered, I use the laser level to shoot a beam from the rear wheels forward.

You can do everything with toe plates except for set rear “absolute” tow, which is important. So rear toe plates can be darn useful, but they don’t get you all the way home.

You can set camber by getting a digital angle gauge. Then use thin sheets of wood or something to create for yourself a flat surface for the 4 wheels.

Learning how to do your own alignments gives you control. You’ll never have to worry if you banged on something at the last event and might have thrown something out of whack. You can just go to your garage and check. Also, with a bit of care, you can end up with a much more precise alignment. You can’t assume that the local tire shop has had their equipment calibrated anytime in the past decade.