Increasing 'Rake'

[HustleRussell]

I want to fine tune the handling of my E34 and also fix the 'nose high' stance it currently has. I want to stiffen the suspension as little as possible.
What effect would lowering the front suspension but not the rear have on the handling?
I have experience with setting up geometry and corner weighting the Caterham but I doubt any of this is of any relevance to a 1600kg estate car!
My expectation is that lowering the front relative to the rear will move the weight distribution rearwards slightly.

[PaulKemp]

Lowering the front will move weight forward

[HustleRussell]

Trying to think about it from a 'corner weighting' background was a bit silly because I confused myself with static spring compression etc (I'm used to dealing with adjustable suspension platforms!). Okay, increasing rake moving the weight forwards makes perfect sense.
What I am trying to acheive is tuning the handling to my taste, I'd like to have the possibility of a little oversteer fun without having to resort to heavy-handed driving techniques. I think lowering the front 25mm or so, raising the back slightly and fitting a stiffer rear anti-roll bar will have the desired effect.
Thanks for your input, Paul.

[Huff]

First, be very sure it is actually 'nose' high'. If so - just replace the rear springs if they've settled, or any contributing knack'd bushes.

The E34's front and rear arches are not the same - the rear arch crown *is* flatter & lower. SO, for example, dropping the front enough to get equal gaps is both wrong-headed and takes a lot of castor out for a start, and almost certainly requires resetting the tracking. And it won't ever be right. (Thus the stance mob attempt to 'fix' what isnt broken, probably buggering-up the handling in the process)

IIRC Dims from wheel centres to arch are given in Bentley, I'll look it up in my copy in a bit...

[Huff]

Aha. Found it. HTH.
Also note that certain model variants deviate from this, e.g. cars with the M-tech suspension kit ride 25mm lower..:

Front:



Rear:

Edited by Huff on Thursday 27th June 20:48

[HustleRussell]

Brilliant data there Huff. I'll measure it out of interest to identify if my car actually has a problem.
I suspect it doesn't. I had it on a ramp a few weeks ago and had at it with a torch and a pry bar and I couldn't find anything dodgy.
Is it nose high? Not significantly- but it looks like it is and this bothers me, more so since I put new Bilstein shocks in the front. Rear suspension is self levelling.
As I say, this is fine tuning. I'm not 'slamming' it, I'm not going for 'stance'. I want it handle a little bit pointier and look less nose high.

P.S. I do the tracking myself, IIRC the car has about 7 deg of castor on the front and I doubt such a small change in ride height will upset this noticeably.

Edited by HustleRussell on Friday 28th June 00:45

[Huff]

Fair enough, my point is that by altering rake one is rotating the whole front geometry more 'upright' (say 50mm on 2500mm wheelbase - more than one degree)

I suspect the key to 'slightly pointier' would be a tad more -ve camber on the front but I've never got around to trying it. In passing - I did find rear beam bush replacement worthwhile in terms of body control and turn-in response, even though the originals appeared Ok they were 15yrs old of course. I have polys in the front end.

I'll be interested in what you find

Edited by Huff on Friday 28th June 09:12

[Mr2Mike]

Lowering only the front will effectively reduce the castor angle as well.