Evil handling - update
JeffHs - 22/11/08 at 03:53 PM
Many thanks for all of your replies to my previous post.
I can report some progress. I've just got back from a blast round the local lanes and it's much improved, but there's still some way to
go. On smooth roads the car is wonderful with perfect balance and easy to hold rear drift when booting it round bends, but it's still fairly
terrifying at speed on bumpy surfaces. So the back lanes at entertaining speeds are still a bit of a trial rather than a delight.
I've softened all 4 dampers to minimum.
I've lifted the rear as far as it will go (any further and it extends the dampers to maximum travel on rebound with horrible sounding noises).
This has improved the rear end a lot - I was too low before and hitting the rubber bumpstops. To fix this properly I need longer dampers , or the
locost way, I will move the bottom damper mount up by 1 inch which will put the suspension travel in the right range with a sensible ride height.
I'm working towards the D Jenkins height recommendations but I'm still a bit low at the back and a bit high at the front. The damper mount
mod above will fix the back, but I need to lift the engine a bit to lower the front any more. I wince every time I see how close to the ground my ali
sump is!
My rack is not dead level. I knew I had to re-engineer the rack mounts due to a previous cock up, so I should be able to almost eliminate the little
bump steer I have.
Castor is as recommended on here - top wishbones moved back 1 inch.
I think the front springs are probably ok, but the backs are too hard, something like 120 to 140 would be better.
For those who missed the previous post
car is
original book chassis
pinto engine
live axle
185/70 Yoko on 13 inch RS alloys
300 lb front
180 lb rear, Gaz shocks
mookaloid - 22/11/08 at 04:25 PM
minimum damping setting on bumpy roads doesn't sound right to me.
That's exactly when you do need damping!
Minimum damping setting on my indy made it nearly undriveable - it certainly felt dangerous on a bumpy road.
Try driving long the same bumpy road several times with different settings each time to see which is best.
Cheers
Mark
GeoffT - 22/11/08 at 04:48 PM
Don't know if this was mentioned in the previous thread, but one thing I quickly found out when I first put my car on the road is that they are
very sensitive to tracking errors.
Mine was much like yours, ok on the smooth stuff, but darting about all over the place on uneven surfaces. The transformation after I adjusted out,
what didn't seem that large an error, was very noticeable, turning it into a much more stable machine.
My theory about this is that being a very light car, the steering input tends to switch from wheel to wheel on rough surfaces, and unless they are
both pointing in exactly the same direction, you get varying inputs.
It's just something that may be worth checking - if you want to get it right forget Kwik fick, clamp a couple of metre or so long pieces of
straight steel to the brake discs, and measure and adjust till they're parallel, or maybe just a trace of toe-in
David Jenkins - 23/11/08 at 09:33 AM
quote:
Originally posted by mookaloid
minimum damping setting on bumpy roads doesn't sound right to me.
That's exactly when you do need damping!
Minimum damping setting on my indy made it nearly undriveable - it certainly felt dangerous on a bumpy road.
Try driving long the same bumpy road several times with different settings each time to see which is best.
Cheers
Mark
That's what I suggested - start off at minimum and work up a click at a time. I was always told to use the minimum damping that worked, no
more.
In my case, the front dampers were general-purpose adjustable Avo ones, and were probably set up by the factory for a heavier car. For me, minimum
settings gave the right amount of damping.
When I replaced the rear ones I bought them directly from Avo, who were more than happy to set them up for a light car with 140/150 lb springs. As a
result they are now set about 3 or 4 clicks off minimum, and work very nicely. When I get round to replacing the front shocks I'll do the same
thing again.
This is a subject that Procomp mentions now and again - the off-the-shelf shocks aren't set up ideally for very light cars like ours.
HTH,
David
mad-butcher - 24/12/08 at 07:45 PM
If the front is darting all over the place it might be worth while checking the bump steer, I was amazed when I checked mine the way initialy it went
from 1mm toe out to 2mm toe in on full bump
Tony
Marcus - 23/1/09 at 12:39 PM
Hi Jeff, I remember seeing a bare chassis and MKll Mexico in you garage about 7 years ago when I collected my donor from you Pleased to see
you're mobile now..
Anyhooo, are you running poly bushes or rubber ones? I ask because even slight movement of rubber bushes, especially over rough ground, will make for
interesting handling traits at higher speeds.
Just a thought.....
Good luck
greggors84 - 2/2/09 at 08:42 PM
When you talk about 'Minimum damping' do you mean full soft or full stiff? Full wound in or fully wound out?
David Jenkins - 2/2/09 at 10:09 PM
quote:
Originally posted by greggors84
When you talk about 'Minimum damping' do you mean full soft or full stiff? Full wound in or fully wound out?
Fully soft - but don't expect to stay at that setting (before anyone complains 
) - I don't know what you mean by "wound in" or
"wound out" - my shocks have a knob at the base, with "minimum" when it's wound fully anti-clockwise.