Bill's Wheel alignment, step 1: find centerline of car Options

[Borderline]

I've been working on a system to do my own wheel alignment at home in the garage. I'm one csob and this is getting to be a lot of work, but I like to be able to do things myself. The general idea is to use a laser light that points in the same direction of the wheel and reflects back from a mirror in front of the car. If the mirror is square to the centerline of the car, you can see the toe angle in the light reflected from the mirror. Having the mirror several feet in front of the car will make measuring small angles easier. The real problem becomes setting the rear wheels as they must be symetric about the centerline of the car.

To find the centerline of the car I decided to use the wheel mounting surfaces with the car up on....jack stands where it belongs. I dropped a plumb bob from each corner and marked it on the garage floor.

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After locating all four points, I was able to measure between the two fronts and mark the centerline on the floor. I did the same measuring the centerline and marking the floor for the rear of the car.

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That photo didn't come out too good. What I ended up with is a piece of tape at each end of the car with a line on it representing the center of the car. I then took one of the laser levels and lined it up with the two marks on the floor. the light then scribed a line under the car down the centerline. I drilled a small pin hole at each end to be used later as reference.

The interesting thing is that the line of the laser went straight down the centerline of the engine case and through the two holes in the floor of the front trunk and the tow hook.

Am I crazy doing this?? Should I continue??

[Dr Evil]

Interesting...you should see how this plays out (IMG:style_emoticons/default/popcorn[1].gif)

[McMark]

I'm very interested as I've been thinking about the same thing. Keep it coming.

[Jeroen]

(IMG:style_emoticons/default/popcorn[1].gif)

[URY914]

Keep going. We're all csob's, thats why we all do our own work. Lasers have gotten so cheap that anyone can get one from Home Depot for a few $$.

Paul

[KenH]

This is a whole lot easier and repeatable.

Read this:

http://www.smartracingproducts.com/pdfdocs...ings_manual.pdf

Make this:

A 1/2 conduit with eye hooks and some fish line are all you need.

Clamp them to the front and rear bumper.

Ken

[john rogers]

You could pull my article off the Pelican site and not have to worry about lasers or things like that. It works on both front and rear wheels too. Remember, if you make an adjustment that the car has to be moved, rolled, bounced so the suspension takes the new setting. Also what ever you do, make sure to have you weight in the driver's seat so that it mimics your weight ready to race.

[Borderline]

Ken:

I've done the strings before and never thought that it was very accurate. Just something about trying to measure small angles with a scale or tape measure. Besides, I love playing with the laser lights in the dark. (IMG:style_emoticons/default/biggrin.gif)

[URY914]

I just printed that Smart Racing manual. There's a lot of good info in there no matter what system you're going to use.

[Demick]

Ken:

I've done the strings before and never thought that it was very accurate.

If you use a steel rule with 1/64" markings, and use thread instead of string or twine, it can be extremely accurate.

Demick

[914forme]

I use the string method also, now it is not 1/4 rope, I use fishing line, you can get it in bright colors etc. If you can tell a difference of 1/64th of an inch your butt is way more talented than mine.

BTW, camber is the next one I am playing with.

I picked up one of these Digital Level the 0.3% accuracy thing bugs me a little, but then I figured I was off by more than that on my old method of a level and tape measure. Anyway, I cram my drivers side in as far as I can, and the passenger side is set to match. Darn hand built cars, why could they not give me at least 3-4 degrees negative to play with. I am lucky on my drivers side to 1.75 degree. I would like a little more, looks like I need to get a camber plates, or shop for camber tolerant tires.

[Joe Ricard]

I've been using John's method for some time. I think it works good just have to be critical with measurements.

Also Bill, are those jack stands supporting the suspension or the car.

If the car then you will never get things lined up.

The suspension MUST be loaded and at at ride hieght.
Finding a method to attach the digital level to the wheel consistantly is a tough one.

[lapuwali]

0.3% accuracy sounds amazingly good to me. That's better than 0.01 degrees, which is far better than you're going to need. You have to remember than the tolerance on the car itself is over 1mm for each suspension point, and after 30 years, you'd be very lucky to have everything still with 2-3mm of where it was when it left Karmann. Fishing line and an 1/64th rule is roughly 0.5mm, so you're already doing better than the factory.

There really is a point beyond which a search for furthur accuracy is pointless.

[KenH]

I tried a laser but found the "beam'' was wider than the fishing line I was using.

With the fish line I can read to 1/32 or 0.033"

Ken

[Borderline]

Yeah you guys are probably right. I was always frustrated trying to measure to a "string" (always used monofilament ...fishing line). the idea was to shoot the laser beam a longer distance so that by the time it bonced back I would be measuring 5/8" instead of 1/16". Any way let me show you what I did.

I set up a straight piece of angle and attched 3 mirrors to it. The center mirror is to reflect the centerline laser.

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Next I rolled the car up in front of the mirrors and set up the centerline laser to shoot straight down the center of the car. The mirrors were adjusted to reflect the laser straight back.

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Wow, its hard to show photos of the laser light. Its either too dark or to light. To continue here is my carefully calibrated alignment gauge.

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And here is a shot of my checking the alignment of the right front wheel, which was toed in way too much. The rears ended up being dead nuts straight ahead.