vindaloo

I've been thinking about the ALK and something struck me the other night.

If I'm right and the ALK moves the front, rear suspension pickup down and outwards, more castor is created. To do this, the bottom of the strut must be moved forwards as the top is fixed and it's not touched by the ALK. The front wheels are moved forward by some amount. This would place the front wheels ahead of more of the mass of the engine. What then is the major benefit, increased static castor or reduced (minor) mass overhang on the front end?

Also, in moving only the rear mount, the geometry changes in compression to reduce castor! As the bottom arm moves slightly backwards under compression. It strikes me that this is not what is needed.

J.

911

Yes.
A bit (lot) of a compromise.
This is why i installed the MRT top mounts on my Sti v3 and doubled the caster and camber.
911

vindaloo

Hello 911,

I've been following your progress for the last year or two on SN.

I've looked at the top mounts recently too and I have a few concerns.
i) The 10-15mm "lift" in ride height that may occur.
ii) My car is a road car and I'd like to keep NVH out of the cabin as much as possible.
iii) Though it may be negligible, the wheel is moved back slightly by increasing castor at the topmount.

I do like the idea of moving the wheels forward by pushing the lower arm forward

J.

911

1
I have AVO coil overs, height adjustable, so the ride height was not an issue.
2
NVH is not worse with the mounts as other mods I did definitly detract from the ride quality, especially the poly bushes as you would expect.
3
Front wheel positioning is negligable IMO as I recon factory build tolerances are more than the changes discussed here. If you lower the car the wheel centre moves also.
When Porsche needed to correct the wayward handling of the early 911's they had to shift the rear wheels back a full 47mm, the govening factor there was the CV joints were at max misalignment, or they would have gone further still.

It is all a compromise. My car is quite extreem now, harsh and a bit tireing, but I have a Jaguar X type estate too, and that rumbles a lot! (18'' rims).

A balance of comfort, performance and , dare I say it, looks too.

Graham.

DuncanG

Argh, this old chestnut!

The ALK does increase the castor slightly but that's not the main effect. The real purpose is to elliminate the 'anti' geometry. Whiteline tell you all about it here: http://www.whiteline.com.au/articles...WL%20ALK_b.pdf.

vindaloo, you are right about the hub being rotated forward - thats the castor change. The change in weight distribution will be slight. The major effect is neither of the things you suggest, it is the elimination of the anti-lift/anti-dive geometry brought about by lowering the bush.

Duncan

vindaloo

Hi Duncan, I had read this a while ago....though I'm now reading it again....

Edit: OK, so I hadn't read the article. The one I read was where they acknowledged that ALK was probably a misleading name as it promoted dive/lift rather than reducing it. Thanks for pointing me at this one.

J.