Fatbloke

This question is totally unimportant as I'll get my geo readjusted as soon as I'm happy with the ride height, it just came to mind while I was mucking around with my coilovers; when you alter the height adjustment, what effect does it have on the geo, i.e. increases/decreases camber etc? Presumably, double wishbone suspension is designed to minimise the change in camber as the wheel moves up and down over bumps, but would toe be affected more owing to the nature of the components and mounting points?

Like I say, it's not important, this kind of stuff just fascinates me (wanted to be an engineer but apparently you need something called 'qualifications' for that gig)...........

jayok

Well,it depends on the design/setup of the suspension. But generally, if you lower the car, the camber will become more negative and the suspension will toe-in. Why? Consider if you were not lowered, but just had extra force on the wheel as you went around a bend, you'd want more grip so increasing the camber, takes the pressure of the side-wall of the tyre. Also, by toeing-in, the car will "push" back in the direction opposite to the bend (i.e. turn you out of it)

All of this of course occurs in tandem with multiple other factors, but generally that's what happens.

Fatbloke

All makes sense. Presumably the camber change is more pronounced on ordinary suspension because the single wishbone is creating an arc, whereas double wishbone, if the inboard and outboard ends are equidistant (no idea if they are BTW) would maintain the same camber as the suspension is compressed?

noodels

Be more worried about Toe in/out.
the only car to not have camber issues with cornering /lowering is Morgan cars with a sliding pillar 1950s design
http://www.talkmorgan.com/ubbthreads...spension_for_t

chrispayze

You could design it to be parallel, yes, and this is part of the benefit of double wishbones, but in reality, it's designed to give a slightly more 'custom' response than that, depending on a number of factors, like stiffness of springs, damping, roll centre etc.

Dembo

If by "ordinary" you mean a McPherson Strut then actually the hub is clamped (by two bolts) to the damper and the wishbone pivots (at least I think that's how it works). What that means is you don't get any camber change under bump/lowering. The toe will still go out though.

If it was fixed to the single wishbone the arc would be far too small and the change far too great. Double wishbones allow the centre point of the arc to be outside the car on the other side and for the engineer to decide how much camber change they want.

The other interesting thing is that the change in angle of the wishbones lowers the roll centre (i.e. the point the car rolls around). The amount of roll is determined by the distance between the centre of gravity and the roll centre, so although lowering lowers the CofG it lowers the roll centre more and so counter-intuitively lowering increases the amount of roll.

Fatbloke

Is that an absolute increase or as a percentage relative to ride height?