Setting rear camber & toe with eccentric rtabs

#1

Is this do-able as a DIY? Fred Switzer, Al K, and I have a camber gauge but rear toe intimidates me. I’m thinking that it might be a helova lot of trial and error adjusting my rear camber and not screwing up toe. Especially since any toe plates I buy will just give me relative toe, not absolute toe. Getting absolute toe sounds like a nightmare.

I already have eccentric rtabs in, so I’m not talking about installing them. One of my rear wheels has somehow lost a degree of camber so I can either take it to an alignment shop, or buy a set of toe plates and fix it myself.

#2

Definitely DIYable. Of course, with our trailing arms any time you adjust either toe or camber you affect the other - so there is a lot of back-and-forth. My personal opinion is that getting toe “right” is more important for speed/handling, getting camber “right” is more important for tire wear.

With toe plates, you can measure total toe then eyeball from the rear of the car and see if you are way off. A quick and dirty method to check relative toe (assuming un-bent parts) is to take a straight edge forward from the toe plate and measure perpendicular from the straight edge to the center of the subframe stud. That is quicker than doing the whole string box thing and is probably close enough for government work.

The toughest part is getting a flat enough place at RA to do it. And getting enough weight in the driver’s seat so your setup is right. I’d recommend using Robinson for that, but hauling cinder blocks to the track may be easier (less b!tching).:laugh:

#3

I’d be doing it at home, not RA. I don’t know that I’ll be able to spot 1/16" worth of absolute toe problem. So you think DIY can get that kind of accuracy?

How hard is it to adjust the position of the eccentric rtabs? And turning which rtab in which direction does what?

#4

With Longacre toe plates you can measure 1/16" toe in or out. For me, that amount is within the acceptable range +/-.

The bolts are a pain to get to. As I discovered again at NJMP as I was putting a nut back on mine (Thanks Andrew Z) after I lost one on track and got some wacky ‘dynamic toe.’

Here’s my understanding: You get max camber with the inner bolt at the bottom of the eccentric and the outer bolt at the top of the eccentric. Then check toe. If OK, then check camber. If OK, go buy lottery tickets. Your luck will never be better.

I replaced the nut, checked toe and had 5/16" out. I rotated the outer bolts to the rear of the car a bit, measured again and magically had zero toe. And sand in my shorts, forearm burns from hot rotors, grease on my face…

I still need to go back and check absolute toe but I was happy to get zero relative toe at the track.

#5

PS - A 3/4" flare nut wrench helped me get to the original 19mm nuts but IIRC the Ireland kit uses 18mm nuts? Another hint is to buy a cheap 18 and/or 19mm 12 point wrench and hack the open end off (1 1/2 or 2" ). Then you will have a long enough wrench to get the bolt tight but it won’t get hung up in the spring (like an unmolested wrench will).

#6

I just bought some toe plates. I’ll give it a try. If it kick’s my ass the alignment shop isn’t far away.

#7

Ranger wrote:

4 pages of good info…

http://www.e30m3project.com/e30m3performance/tech_articles/susp-tech/ecc_bush/ecc_bush.htm

I haven’t actually tried to adjust mine yet, but hopefully this’ll help.

Matt

#8

After having lived with a Miata and double wishbone suspension and completely adjustable suspension for the last 19 years, all this hokey crappy alignment adjustments, (camber plates, weld on adjustable plates, eccentric bushings etc.) is driving me a little batty.

That being said, I would strongly recommend getting the Ireland Engineering kits from Jeff. I live near the shop and visit it on occasion and have seen the kits… Once I have the 2x$85 for both the toe and camber kits I’ll be getting them.

The front end of the E30 is kinda perfect, it’s easy enough to adjust for racing and works well enough… The rear is a crazy, crazy mess and demands way more attention from us to make work.

#9

Good find, thx. I think I understand what the charts are trying to tell me but I may have to play with it to be sure.

#10

Forget toe plates, except for their bearings. Use strings to set toe front and rear.

I set the wheels on blocks about 12" high and then set up a string (fishing like works great) on each side referenced off the center of the hub. Toe measurements are then absolute and independent.

#11

jlevie wrote:

I got a buddy that’s been saying I need to learn how to use smart strings for a long time now. After paying $150 for an alignment, I think it may be time to learn. When I was at Grand Am/VIR in April I saw some smart string setups using Zebco 33’s.

Like you guys, I’ve always referred to ’ 1/16" toe '. But thinking more in terms of doing it myself, 1/16" with respect to what? 1/16" toe on a 14" wheel would result in more toe than the same 1/16" on say a 15" wheel.

Where would the reference point be measured at?

#12

Not necessarily different for a 14 and 15 inch wheel. If you are referring to the front or rear wheels, the toe is in reference to the oposing wheel. The variance is measured from the front of the plate to the rear and is either + or -. We have used the Longacre toe plates (http://www.longacreracing.com/catalog/item.asp?id=152&catid=5) with good success for several years in getting basic setup adjustments at the track. A full chassis string setup will help with 4 wheel setup and front to back variances, especially if the chassis has been tweaked.
Ed

#13

jlevie wrote:

[quote]Forget toe plates, except for their bearings. Use strings to set toe front and rear.[/quote] I think you might mean turn plates? Toe plates and bearings?

[quote]I set the wheels on blocks about 12" high and then set up a string (fishing like works great) on each side referenced off the center of the hub. Toe measurements are then absolute and independent.[/quote]Putting the car up with blocks under the wheels prevents you from being able to roll back and forth while bouncing the car to eliminate any suspension binding and get a true reading.

#14

Steve D wrote:

[quote]jlevie wrote:

[quote]Forget toe plates, except for their bearings. Use strings to set toe front and rear.[/quote] I think you might mean turn plates? Toe plates and bearings?

Yes I meant turn plates.

While you can’t move the car with it on blocks, that does allow you to reach the adjustments. What would be nice would be to have a pair of plates to go under the wheels that allow both rotation and translation during adjustment. Placing a magazine under each wheel works tolerably well.

#15

jlevie wrote:

I’ve heard some guys use a trash bag with grease between the two layers.

The ideal setup would be something like this:
http://classifieds.specmiata.com/detail.php?id=2944
but with longer ‘roll-on/roll-off’ pads.

PS - If anyone decides to make these, you will want to add a little stop on either end and provide roll-off room on either side of the scale pad, like this: ^-----______-----^

Dropping your car off the end of these can’t be good for setup.

#16

A cheap way to make some turn plates is to use two pieces 12" x 12" linoleum face to face with some grease in between. Just don’t put too much grease as it gets a little messy.

#17

edavidson wrote:

That’s relative toe. The trick is to get absolute toe.

My toe plates should arrive tomorrow. I thought I’d get Jones linoleum plates today and take a look those laser leveling gizmos, like you see at home depot. I bet that there’s a way one could be fastened to the toe plate such that by shining the dot on the wall in front or rear of the garage, getting 1/16" accuracy at the wheel would become really easy. I bet that it would allow you to eyeball absolute toe also.

Imagine if your relative toe was zero but both rear wheels were pointed 1/16th inch to the right. If you put the laser on one of the toe plates and the dot was on a wall in front of the car 14" away, the dot would be ~3/4" of an inch to the right. From the rear of the car you should be able to see that the laser is not parallel to the side of the car.

#18

The combo of Longacre toe plates and a harbor freight laser level turned out to be an easy win to get plenty of accuracy with both relative and absolute toe. The plates tell you relative toe, obviously, but then you just lay the laser level on top of the toe plate, and check how far the laser is going from the other wheel.

The front is fine but the rear is all messed up.

Example. Lay the Longacre toe plate against a rear wheel and put the laser on top lasing forward. Laser axis to rear wheel was 2". Now put a tape measure on the front wheel and see where the laser strikes the tape measure. Mine hit at 2 3/4" and 3". Call it 18mm and 24mm.

The math works out such that you divide the problem by 6. 18/6 and 24/6 works out to roughly 3mm and 4mm of rear toe out. Call it ~1/8 and 3/16th toe out.

Cost of the Ranger Toe measuring system, used toe plates and a Harbor Freight laser level, $45.

Those eccentric rtabs are just torture. It took me 45min to loosen the passenger outboard side. At that point it was pushing 1AM and I decided that was enough.

Between loosening all 4 rtabs, a bunch of trial and error with settings, and then tightening them back up again, I can easily see how this would consume a 1/2 day.

#19

Ranger wrote:

Just to double check, when you use the Longacre plates does that show a 5/16ths difference? That’s a lotta toe out.

In my experience, you don’t want/need to loosen them any more than it takes to rotate them (sometimes not at all). And relatively small changes in eccentric position yield surprisingly big changes in toe.

#20

Re. 5/16ths. Yes. The first thing I did with the toe plates was get relative toe. After doing about 10X I decided that I had slightly more then 1/4" of relative (total) toe out. That’s when I shifted fire and started working on the laser to see if I could figure out where the 1/4" was, which is to say, absolute toe.

Somewhat to my surprise, I’d have to say that I can’t really see the toe out. The RR is toed out 3/16th" and my eyeball doesn’t spot it. It’s good to know that a person can’t trust their eyeball in this. We usually assume that we can spot gross alignment problems. What this tells me is that I have to check toe more often. My car has no more then a couple dozen hours on it since it’s last alignment.

Re. It doesn’t take much change in the bushings. Thanks for the info. The bushing charts are in degrees, not inches. So this morning I converted the inches to degrees and spent some more time trying to understand the bushing charts. Your comment tells me I’m on the right track because that was along the lines of what I was thinking. It’s a comfort to be on the right track. For a change.

It was frankly somewhat of a surprise that my laser level idea worked so well. Usually I don’t get anything to work until the 5th or 6th idea.