Caster Adjustment

[fridayman Senior Member Find all posts View Profile Close fridayman]

I've been thinking about caster again too, specifically how do those big alignment machines know what the caster is? Especially on vehicles with lifts and different offset wheels (where the stock numbers programmed into the machine no longer apply). The post above shows how it can be calculated, but I don't recall the alignment staff turning the steering once they start making adjustments (usually the steering wheel is locked in the centre position). All they seem to have are those "reflectors" that they bolt onto each wheel. If I have changed:
1) the wheel offset (and the distance between opposite wheels), and
2) more importantly lifted the vehicle (my brain gets hot trying to figure out what impact this has on geometry, but I think it would reduce the distance between front and rear wheels assuming I had positive caster to start with),
how does it know what the caster is? Distance between front and rear wheels? Can anyone enlighten me please?

[glen_ep Addicted PP Member Find all posts View Profile Close glen_ep]

I've sometimes wondered the same thing, but never dug around to find the answer.

Offset rims definitely mess with the steering geometry, and probably caster as it turns, but there's no solution other than reverting to original rims.

Since both my front and rear suspensions are all adjustable, my wheel base would be quite different from standard, so I'll probably need someone very specialised to do it properly. Now that I think about it, what is "properly"? I think if we alter the geometry from standard than there is no going back to standard settings, and it is now a matter of tweaking the alignment for what works well for our particular vehicle / terrain / driving style...?

[fridayman Senior Member Find all posts View Profile Close fridayman]

Since both my front and rear suspensions are all adjustable, my wheel base would be quite different from standard, so I'll probably need someone very specialised to do it properly. Now that I think about it, what is "properly"? I think if we alter the geometry from standard than there is no going back to standard settings, and it is now a matter of tweaking the alignment for what works well for our particular vehicle / terrain / driving style...?

It would be great to have someone knowledgeable nearby that could set up the suspension, and then I could go back to them 2 or 3 times to tweak it, or just to see what impact certain changes have. A bit like a pit crew

[brissy Member Find all posts View Profile Close brissy]

After using the info from my previous post to set caster,camber and toe the alignment is great , will prob have to check it again once i find time to fit the upper control arm bushes