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Basically its just geometry, with the triangles (archive)

[ Follow Ups ] [ 5-series (E34) Message Board ] [ Msg. Board FAQ ]

Posted by MicahO on August 27, 2001 at 16:14:32:

In Reply to: Re: I don't think you are getting picky, especiall posted by Chris Rose on August 27, 2001 at 15:27:58:

drawn on your garage floor or driveway. This is what you did in measuring, the extra geometry is just used to determine the actual difference in toe that should exist, all e34's should have 3/10ths of a degree of total toe-in. Since you need to be able to turn the wheels freely while in a loaded state, some people suggest putting a bunch of grease between two plates of thin aluminum or steel so the wheels can turn and be adjusted freely. The link below has a few different methods described, but they all have the same basic premise - Geometry, worked out with a pencil, rather than on a computer driven rack.


I'm not sure if they adjusted the rear toe, or if it moved as a function of something else or perhaps the difference is within the measurement error of the instrument. Here's the numbers

Left Rear Toe
Final Before Spec Range
0.28 0.26 0.15 - 0.27

Right Rear Toe
Final Before Spec Range
0.25 0.26 0.15 - 0.27

The way I aligned the front in the garage after replacing the outer-tie rods, was as follows:
First I tried counting threads on the old ones but since they were not OEM tie-rods, that didn't work so well. I put them on and it was visibly out of align. You could see that the tires weren't parallel. So I thought that if I got them parallel then that'd be good enough to drive it. My tires (Michelin's) have grooves that go circumferentially around the tire. First I measured on the front side of the tires from the inside groove of the left tire to the inside groove of the right and then I got under the car and made the same measurement on the back side of the tires. I adjusted out 1/2 the difference of the back-side and front-side measurements. I then itererated this process a few times to try to average out measurement errors. This ensured that the tires were at least parallel to each other. In the end it came out pretty well I guess. I'd be interested in hearing of your mathematical methods. I didn't research any methods of doing it. This just seemed to be a sensible easy way to get it close enough to drive.

if they didn't even get the steering wheel right the first time. Since they did it wrong once, they should be trying very hard to get it right (right for me means as close to the center of the range as possible) the last time.

->How did they change the rear toe? I didn't think that was changeable.

->How did it go when you were aligning things by measure in the garage? I have read a few different do-the-math methods and contemplated going after it myself......

Micah O'C

Replaced outer tie-rods and idler arm so it was time for alignment. Went to NTB. When I checked out I asked for the computer print out. They acted suprised that I wanted it. I got the car back and returned it to them immediately. The steering wheel was cocked 5 deg to the right. They fixed that and then I drove back to work. But before I got out of the car I decided to see the report to see how close I was using the tape measure that I'd used to align with in the garage. It turns out that I had the left front tire closer to the spec range than they did after aligning it. What's more is that the left-rear toe was in spec before and now it's out. Also, the left-front caster, the left-rear camber and right-rear camber are all out of spec after the alignment. Also the parameters that are in spec are mostly "just-in" spec. They spent no time trying to put things in the center of the specified range.
I think I'll take it back a third time and insist that they put a different tech on it and that they get it right. Am I being to picky here?

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