They all do caster, camber and toe.
All the laser does is to magnify the same effects that you would find with tracking discs, except that because they use teh width of the kart, you are effectively using discs as wide as your kart.
A useless bit of info, a error of 1 degree, will show as an offset of one unit at 60 units. eg. If you are 1 degree off, at 60 mm from the measuring point, at 600mm it will be 10mm off and so on.
Lets assume your kart is 900mm wide at the front.
if the stubs are set up absolutely zero (no caster, no camber no toe) the laser dots will point directly at each other. If you turn the wheel, the laser will sweep along the zero line forward and back. (Note, as most karts wont allow you to set zero caster, this is just theory, you cannot do it on your kart.).
you return the kart to the centre point of steering (and lock the steering). If you now alter the length of one tracking rod, then the laser will move along the horizontal axis.
Now for a bit of maths. A front wheel has a 10 inch wheel, so that is 5 inch radius which is 127mm as near as matter 120mm which is 2 * 60.
so if you want 1 mm toe in, by the 1 in 60 rule that is 0.5 of a degree movement of the axle.
if the width of the kart is 900mm, then that same 1 in 60 rule means that the dot will move 0.5* 900/60 mm= 7.5 mm.
Now, if we add camber, (moving the top of the wheel in or out by tilting the stub axle) then
clearly the laser will move up or down the target plate on the other side. Again if you want 1% of camber, then the top of the tyre moves 2 mm, or if you want 1 mm of camber then you move the stub 0.5 of a degree. Camber is just toe in or out in the vertical plane. (so 0.5 degree (1 mm) of camber offsets the laser 7.5 mm above or below the centre of the target plate. (Positive camber= top of the wheel further out than bottom=laser above centre line)
And again, assuming you had zero camber, if you turn the steering, the lasers will move along a level line so that the same height above or below the centre line when fully left or fully right.
Caster tilts the kingpin so the top is no longer vertically above the bottom of the king pin. Is the top is moved in front of the bottom, the wheel will fall going forward and rise going back. The laser will move on not horizontal, straight line, but a line equal to the angle of caster.
If you don't have any camber on the wheel, then that line will pass through the centre of the target plate, if you do have camber (say 0.5% positive) then the line will be offset 7.5 mm above the centre point.
Caster can be confusing because you have to measure the angle, and most of the target plates only hav teh protractor set up around the centre line. The easy way is to set a piece of paper to the angle of the laser, then slide it up or down till it goes through the centre and read it off.
But, if your laser unit is 60mm wide, then you know that for every degree of caster angle, the dot on the front edge will be 1 mm higher than the dot on the back edge, (1 in 60 rule again) so if you measure them directly and the difference is 15mm, the you know you have 15 of caster angle.
Simple, no?
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Best value kart lasers for Caster/Camber/Toe by 'kelvyn' (12 Aug 2009 @ 15:35)
