Front suspension geometry

[gnutz2]

I'm in the process of redesigning the front macpherson strut suspension on the S2 golf and would appreciate people's input. To make things easier I'm going to scrap the subframe and mount all the lower parts on to the car and there's no inner wings so I really can place anything where I like.

Currently my setup is standard geometry apart from the struts leaning backwards to produce 5 degrees of caster, the car is lowered by a good amount also which puts the wishbones horizontal with the ground.

My plans so far are to make the inner wishbone mounting points adjustable so they point downward again which would allow me to adjust the roll centre up and down and I'm adding camber plates to the top mounts to adjust camber quicker.

Is there anything else I need to consider like correcting any bump steer which I'll likely be checking when it's bolted together.

Any point in changing the steering axis?

I know it's a massive subject but my plan was to make the setup as adjustable as possible to allow for fine tuning on the track.

Cheers.

Baz.

[Error404]

If you can, move the rack so it's in the same plane as the wishbone pivot points. This will eliminate most of the bump steer. Alternatively, make sure you can adjust the bump steer. I would go for more caster, I think from memory around 8 degrees pretty much dials out the +ve camber gain on compression.
Best bet really Baz would be double wishbone if you have space

[gnutz2]

If you can, move the rack so it's in the same plane as the wishbone pivot points. This will eliminate most of the bump steer. Alternatively, make sure you can adjust the bump steer. I would go for more caster, I think from memory around 8 degrees pretty much dials out the +ve camber gain on compression.
Best bet really Baz would be double wishbone if you have space

I think our gearbox gets in the way if you try go lower with the rack so I'll see if I can make some spacers to move the steering arms.

Didn't realise people ran that much caster.

Double wishbone did cross my mind, the only tight bit would be the turbo downpipe.

[Error404]

If you look at the modern VAG McStrut cars like the Golf R and RS3 they are running around 7,30' caster these days

[gnutz2]

If you look at the modern VAG McStrut cars like the Golf R and RS3 they are running around 7,30' caster these days

Thanks that's good to know.

One other thing that bothers me about caster is the bottom arm pivot angle and it's relationship between the caster angle.

For example if you set the bottom arm pivots at 90 degree to the caster angle (like an upside down T) or horizontal to the ground, one setup would keep a consistent caster throughout the suspension travel and the other would have caster gain.

Which would make the better setup?

[Error404]

The wishbone pivot axis angle affects dive / squat, I'll be honest I don't know enough about it to offer much advice, but my gut feel is doing what you've suggested will result in massive dive under braking due to the way the angle affects the reaction to the torque. I would keep the wishbone pivot axis parallel with the ground, with the option to slightly adjust either end independently, that way you can tune it somewhat.
I believe small changes here will make quite a difference