I decided to have a go at checking my wheel alignment after messing about with my castor angle and it ocurred to me that there must be a way to use today's cheap technology to make it very easy but accurate.

I went into my local B&Q and found a pair of laser levels for under £4 each......

[Edited on 10-10-07 by RazMan]
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and picked up a couple of tape measures for £1 each.

I then made up two ally struts with pads which rest on the rim, adding a couple of steel strips to hold the magnetic laser levels.

Total cost - a tenner!

[Edited on 10-10-07 by RazMan]
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Then I lashed the complete assemblies to the rims with masking tape, placing a tape measure and laser 'target' in front of the wheel...

[Edited on 10-10-07 by RazMan]
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I then chose a convenient place to use as a reference on the tape - in this case the 200mm mark

[Edited on 10-10-07 by RazMan]
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... and then took a reading from the other end - 2071mm


[Edited on 10-10-07 by RazMan]
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and then ... ?

I then rolled the car forward so that the lasers pointed backwards at roughly the same angle and took another measurement.

Taking the two measurements along with the distance between the two targets and using a bit of schoolboy Trig, I came up with 2mm (divided by two of course) over a 900mm distance which I think equates to a 0.5 degree toe in which was what I was hoping for.

You can in fact get extremely accurate using this method by extending the distance between the targets - the laser shines up to 160 feet so if you want to work in millionths of degrees you can !

The beauty of using this method is that you are using your wheel bearings as the reference point and it doesn't depend on accuracy of the laser - you are comparing measurements rather than taking measurements (if you see what I mean)


[Edited on 10-10-07 by RazMan]

I like that a lot. Makes my technique with bits of string through the chassis before the body and engine were on look pretty archaic!

Dom.

good effort Raz!

Could you check the camber by using one strapped to the rim and one set vertically a short distance away and measuring the difference?

Easier to check the camber with spirit level -- particularly an electronic one from Lidl

quote:

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Originally posted by nick205
good effort Raz!

Could you check the camber by using one strapped to the rim and one set vertically a short distance away and measuring the difference?

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Nice idea. Not much point using longer distances to get more accuracy though as these things aren't built that precisely. I think they are usually specified with an error of something like 2mm per metre so the lasers are probably aligned in the body with an accuracy of about 0.1 degree. Which is plenty accurate enough for our purposes. I may be unfairly maligning them though!

Amusing that on the website they think specifying the wavelength of the laser is more useful than the accuracy of the device

For the camber it is a lot easier just to place a spirit level against the rim at the bottom, hold it vertically and measure the distance to the rim at the top. Or obviously use a digital spirit level if you've got one


[Edited on 10/10/07 by matt_claydon]

As long as the laser beam isn't deflected somehow it must be straight - it doesn't even matter if it is mounted a little wonky because its only being used as a reference. As long as the strut doesn't move on the rim the measurement will be totally accurate (unless your wheel bearing has some slack I suppose)

In theory you could have targets placed 320 feet apart and get things so accurate it would be ridiculous

Actually, thinking about it, a target distance of about 5 metres (2.5m each way) would be a realistic distance and would be as close to horizontal as possible, therefore accurately portraying the alignment. A difference of 25mm over 5m is easier to measure and calculate too.

You could also check front / rear alignment too, although the accuracy of the laser does then enter the equation so should only be used as a guide - it shouldn't be that far out though.


[Edited on 10-10-07 by RazMan]

Sorry, hadn't thought about it enough! You are of course right, the accuracy of the laser is irrelevant because any error is cancelled out by the fact you are taking two measurements fore and aft of the wheel.

If you were to just a shine the lasers straight ahead and measure the distance between them at two points in front of the vehicle then the error I described would be a problem. Your method cleverly gets rid of it though

altho pointing it at the floor isnt totally measuring toe , a mixture of both camber and toe .

as long as you make changes with the laser pointing at the same angle that would be fine .

you should really seperate the two measurements .

I did the same, although just used one level and a board 20ft infront of the car.

Way to go..... why pay silly ,money.

quote:

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Originally posted by Volvorsport
altho pointing it at the floor isnt totally measuring toe , a mixture of both camber and toe .

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can you still get these? i tried looking on the website and in store but could not find them.

can you still get these? i tried looking on the website and in store but could not find them.

Nice write up, so do i roll car back and forth or lift and turn wheel and drop again or do i move the level and laser around?

or does it not matter, just my garage is the flattest place and my car will only roll back and forth a foot, 2 foot at most.

[Edited on 28/3/11 by Krismc]

You'd have to ensure the lasers were pointing for and aft, not for and aft and down at the same time (i.e. get your targets at hub height. Easy to do with a little wooden frame. Not so easy with a tin-top unless your lasers are spaced out well.

Only problem that leaves is how to sort out full 4 wheel alignment next...