Car side a-arm mounting points (laterally)

[second]

Sorry, I'm having hard time trying to come up with better topic name.

Anyways I've noticed that some cars have the a-arm mounting points on the car side not mounted at equal distance from the tire but the front mounting point for example is laterally less far away from the tire than the rearward (or vice versa). I think this geometry is result of packing reasons but how does it affect the suspension characteristics?

In the image you can see what I mean. The image shows an a-arm and tire from above:

[rjsa]

It will induce toe in under load.

[second]

It will induce toe in under load.

Yeah that I thought as well. But it is just bumpsteer which can be tuned (out) with the steering arms I think?

What I'm kinda having hard time understanding how does that angle influence the anti features of the suspension for example? I have milliken's race car design book and at least the book I have doesn't talk about this anywhere in the book.

I'd guess most simple example of this could be mcpherson front suspension. Could there be any advantages to having the lateral mounting points at different distances from the tire (on the lower a-arm)?

[Tim.Wright]

Depends on the suspension type - but for a typical double wishbone this arrangement won't unconditionally impose a toe movement in bump.

The bumpsteer can be regulated more or less how you want it using the toe link.

This arrangement imposes an extra longitudinal component to the upright movement as the wheel moves in bump and rebound. This has then 2 main knock on effects:
1. For a front axle it can change the kingpin geometry (caster angle, trail, scrub and KPI) and therefore the steering feedback.
2. For any axle it changes the consistency of the anti-pitch characteristics with wheel travel. You can make the anti-pitch (which is just the jacking force) either constant or varying with bump travel by moving the wishbone attachment points laterally.

[Greg Locock]

I strongly recommend laying out the enormous sum of zero dollars on a copy of wishbone.bas, or its later versions, so you can see the kinematic effect of these changes. http://www.locostusa.com/forums/viewtop ... 8&start=90

The compliance effect will be slight, unless you go all the way to an L arm type configuration, where one arm is a pure lateral and the other is a leading link.

[second]

I strongly recommend laying out the enormous sum of zero dollars on a copy of wishbone.bas, or its later versions, so you can see the kinematic effect of these changes. http://www.locostusa.com/forums/viewtop ... 8&start=90

The compliance effect will be slight, unless you go all the way to an L arm type configuration, where one arm is a pure lateral and the other is a leading link.

Thanks for the link. It does look like the program doesn't run in windows 8.1 though.

[graham.reeds]

I strongly recommend laying out the enormous sum of zero dollars on a copy of wishbone.bas, or its later versions, so you can see the kinematic effect of these changes. http://www.locostusa.com/forums/viewtop ... 8&start=90

The compliance effect will be slight, unless you go all the way to an L arm type configuration, where one arm is a pure lateral and the other is a leading link.

Thanks for the link. It does look like the program doesn't run in windows 8.1 though.

That thread does mention that. You could run a VM with Win98 or XP running it. Or fix the issues - you have the source now.