May seem like a very obvious answer.....but is it ????

The ALK repositions the lower arm rear pivot. From what I can see in the pics it moves the pivot down and outward from C/L.

This will do a number of things -

1 - Increase castor angle due to pushing the strut bottom ball joint forwards (and keep it there under load) This will probably improve 'turn-in' assuming the car has less than optimum negative camber to start with.

2 - Lower the front roll centre. This will result in less weight transfer across the front tyres, increasing the front to rear grip ratio.

3 - The lower front R/C will increase the cars roll angle for the same G force.

4 - The increased angle of the front wishbone (on the longditudinal plane) will reduce the amount of Anti Dive in the suspension ie increase dive under braking.

5 - This is the one that gets me, Due to the increased angle it will actually increase the amount of front lift during power !

I have no doubt that the overall balance of the car is improved by this mod but would suggest that spring/damper and ARB rates may be a better method of achieving balance. The front roll centre, anti dive and anti lift would not be compromised.

Of course I may have my geometry calculations all wrong and stand to be corrected.

John-F..... I can usually depend on you ;)

Andy

Well I have to say that on the two cars I have driven with it (one being mine ;) ), the car really does seem to lift less at the front when powering out of corners, and helps reduce power-on understeer on the exit.

I made my purchasing decision about buying mine based on the test drive of the first....

Perhaps RiciB (Big Rich from Powerstation) could comment? Rich?

Notes from Rich's comment in threadMatt :)


[Edited by mutant_matt - 5/20/2002 5:29:06 PM]

CC,

Point 3 is interesting - I'm still waiting for my 'proper' suspension, but fitted the ALK 4-6 weeks ago to the current Eibach's/adjustable Koni set-up (too soft for hard use).

Checking my front tyres over the weekend shows a noticeable increase in wear on the outside edges...even after upping the negative camber to 1.5 degrees....I'm bumping up pressure until the KW kit arrives :)

Can't say I've noticed a reduction in lift, just improved steering feel (especially under load).

Richard

Andy,

I have just read your comments about the ALK, and here are my thoughts on your points:

As you correctly observe, the ALK re-positions the lower arm rear pivot point down and outwards, or at least that is what the Australian Whiteline one fitted to my car does. This does indeed give increased castor (about 0.5 Deg on my car), but more importantly, due to the stiffer bushing material in the ALK the castor angle will be better maintained during hard cornering. From my observations it is this "dynamic" castor increase which gives the greatest performance benefit. It's interesting to note that this could also have been achieved with stiffer bushes alone, and many people have commented that you do indeed get a similar improvement by doing this.

I too, have often wondered what causes the observed anti lift effect. I think the answer lies in the change to the pitch centre height produced by lowering the rear pivot points. Just like roll centre height, the pitch centre height influences how much the vehicle pitches up or down when braking or accelerating forces are applied through the suspension.

If my understanding of the geometry is correct the pitch centre height will be raised when the ALK is fitted, so the pitch angle will be lower for a given braking/accelerating force. It is important to note that this will not alter the weight transfer, only a centre of gravity height change or a wheelbase change will do that.

You are right that the anti-dive effect will be reduced by the lowering of the pivot points, but this must be more than compensated for by the change to the pitch centre height. These are two distinctly different effects (although not independently variable), and it is the sum total of the two that will produce a particular pitch angle for a given accel/decel force.

So I don't agree with your points 4 & 5 on two counts. One, the observed pitch up during acceleration is in fact lower, due to the reasons above. And two, the amount of front lift (ie. weight transfer) will not be effected anyway, only the pitch up angle.

In my opinion there is no denying the improvement in feel and cornering stability the ALK gives. Of all the initial mods I did to my car, (big anti roll bars, stiffer drop links, wheel alignment, ALK) fitting the ALK gave by far the greatest improvement in handling. I now have Eibachs and Konis fitted, but that's another story.

Graham.

solmob,

Which model do you have?

Matt :)

Solmob

Due to the fitment of the "anti lift kit" The pitch centre is lowered due to the reduction in height of the rear wishbone mount. Project the line back to the C of G for the moment arm length.

This longditudinal pitch centre is is directly linked to anti-dive in the same way that lateral roll is related to the height of the roll centre.

Lower centre = greater roll (or pitch) moment due to the increased distance from the C of G

Andy

I have an Australian MY00 5 door WRX with Whiteline ALK (1st version - I believe they went to different bushes later).

Graham.

Graham

Do your bushes raise or lower the rear mount ? or just move it outward ?

Andy

Andy,

My ALK lowers the rear pivots, and moves them outwards.

I am not ignoring your earlier post, I want to double check the effect on pitch centre height before responding, and I need to look something up in and old fashioned book to do this.

Graham.


-

No problem Graham

I'm off on 2 wks hol now so no rush !!

Andy