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Ranger wrote:
Word. With the plates you can measure total toe and eyeball relative toe easily enough it should be done each track day. Depending on the tracks you run, maybe more. Roebling? Every other weekend. Use T14 curbing at CMP? Every other session. Really like to launch T3 and get all over T5 at Road Atlanta? Once a day…
A couple dozen track hours is a long time. What is that, like three engines worth? 
Steve D wrote:
[quote]
A couple dozen track hours is a long time. What is that, like three engines worth? ;)[/quote]
As a matter of fact, I think that’s exactly right. But I might still be on the same set of brake pads. There’s always a silver lining.
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.
Ranger - understand the above, however, curious what the distance is between where the laser line is read for the absolute toe? Doesn’t that factor in to the absolute toe reading? Is there a correction factor based on distance from the point read?
thanks,
Ed
edavidson wrote:
[quote]
Ranger - understand the above, however, curious what the distance is between where the laser line is read for the absolute toe? Doesn’t that factor in to the absolute toe reading? Is there a correction factor based on distance from the point read?
thanks,
Ed[/quote]
Yes. I put the laser against the rear tire and shot it forward past the front tire. The laser axis was 2" outboard of the rear wheel so if toe was perfect the laser should miss the front wheel by 2". My correction factor was 6. So 6mm of problem measured at the front wheel was actually 1mm of toe problem.
I just finished the whole effort. Took about 5hrs all told. I did the whole thing up in the air. This was the process.
Figure out how much toe and camber you want to change. Say for example, add 1/4" toe-in and add -0.5 camber. Then lift the car up and with wheel hanging down, measure camber and shoot a laser line against the far wall. That gives you a hanging wheel baseline.
Then loosen the rtabs, figure out the geometry of the eccentric rtab axis and the trailing arms and start playing with the rtabs. I drew pictures of how the bushings looked before I started screwing with them. Then I visualized where the axis of each eccentric ws and where I wanted it to be. Then play with the adjusting nut, check the camber and toe, play, check, play, check.
Critically, I did not have to drop the car the whole time. I was able to keep it up in the air because I’d created a “hanging wheel baseline”.
That being said, I actually dropped car car down many times because I wasn’t sure if I could really trust this “hanging wheel” wheel business and I wanted to confirm how the alignment was changing. It wasn’t until the end of the whole process that I decided that it could have been done with the car in the air the whole time.
Outboard rtabs were harder to adjust because the wheel had to come off to access them. But then the wheel had to go back on each time to check alignment.
A 1" thin wrench fit the adj nut best. I had to cut it down smaller so it would do better in the confined space.
The toe ended up almost perfect. I was aiming for neutral rear toe and ended up with slightly more then 1/64th of toe out which is more accuracy then an alignment shop will do.
My right rear ended up with a little too much neg camber tho. I’ll decide later if I want to screw with it again.
Later edit. I talked to DeVinney and he said that if I left too much RR camber I’d regret it so I went back and fixed it.
It looks like I’m going to get to have a similar fun time with my ecc. rtabs but before I start…
After getting pushed off of turn 6 at NJMP Lighting two weeks ago by a dive bombing GTS-4 car that decided he owned the apex from 50 feet back and slamming the curbing hard enough to bend my right front wheel - I decided it would probably be a good idea to check alignment.
Lacking toe plates, but having plenty of string I decided to give that a try.
I set strings up at the centerline of the wheels on both sides of the car and measured out from the center of the wheels so that the string measured an equal distance out from the wheel front to back. Theoretically (assuming the track width is equal front to back on the E30) this would give me parallel strings on each side of the car.
First issue: the strings measured 75 13/16” between them at the front and 75” between them at the rear. So – not parallel even though a double check of the dimension from string to wheel center confirmed the distance was equal front to back.
Second issue: Rear toe appears to be really out of whack. RR measured 7/32” toe out and LR measured .25” toe out for a total relative toe out of 15/32”
Third issue: FR measured 1/16” toe in and FL measured 3/16” toe out for a relative toe out of 1/8”
Assuming normal competence in being able to use a tape measure – can I trust these measurements or did I make a fundamental mistake here?
I don’t know. My geometry is as good as the next high school graduate but I’ve not done strings before so I don’t have a feel for where a person can go wrong. My suggestion is to do what I did. By putting a laser level on the tire and shining it forward (or backwards) toe problems get multiplied by 6. That makes it really easy to see small toe differences. I don’t think that the string method exaggerates problems like that.
It’s important to understand the difference between relative toe and absolute toe. Toe plates alone won’t give you absolute toe.
rsott wrote:
[quote]…First issue: the strings measured 75 13/16” between them at the front and 75” between them at the rear. [/quote] Trick cheater subframe.
That would be damn near undrivable. I hope the measurements are wrong.
[quote]Third issue: FR measured 1/16” toe in and FL measured 3/16” toe out for a relative toe out of 1/8” [/quote]Absolute toe on the front is all that really matters unless you have to have your steering wheel absolutely centered.
I’m not sure. When using a string system, have the strings attached to a set of bars that attach to specific, non-bendable parts under the hood and trunk (in other words, not hanging from the radiator support or other parts that will eventually get tweaked). That way you can jack up, let down, bounce to settle, roll to unbind, etc. Take a look at the Iron Canyon stuff for ideas.
http://www.ironcanyonmotorsports.com/product_info.php?products_id=41
They have really slick wheel plates that can give you close-enough camber measurements.
Bent wheels can play hell with measurements.
If your front track is 13/16" more than your rear, measuring toe over a 15" wheel (+/-102" wheelbase) will account for 15% of your perceived toe out on the rear (13/16" / 102" x 15" = 1/8" ).
If it is a cheater sub-frame - it’s not working. That is clearly evidenced by mylaps. 
Thanks for the input. I think I’ll borrow some toe plates at Hyperfest this weekend and check with those before I start adjusting.