phil T5
|
| posted on 23/7/08 at 10:03 AM |
|
|
MK suspension rear
Hello
Taken my mk xe out on trackday and its quick in straight line but behaves strangely on limit in bends
I think whats happening is that the springs are reaching max compression and bottoming out.
The feeling is like loading up the rear end under weight transfer then a further compressin due to bump a metal grind/connection sound and it will
spin you if you're not quick enough.
I get the same noise but only for an instant when i have passenger in car and go over bump, although this has been minimised by setting damper
harder.
I guess it sounds like its happening in corners as the damper is not reacting to fast bump as its in roll situation and spring is fully compressed.
Does this sound right?
The car is MK with live axle, with vauxhall xe engine. It weighs roughly 150 KG for each corner. I weight about 100KG in helmet and all gear etc.
What spring rate should i expect ot have on the rear.
I havent checked whats on now yet?
|
|
|
|
|
phil T5
|
| posted on 23/7/08 at 10:37 AM |
|
|
oh yes
see
http://www.locostbuilders.co.uk/viewthread.php?tid=93811
for it doing a standing 1/4
it does seem to sit quite low?
|
|
|
mr henderson
|
| posted on 23/7/08 at 12:22 PM |
|
|
quote:
Originally posted by phil T5
I havent checked whats on now yet?
Well, there's the problem. You need to get those springs off, check the unfitted length and the poundage.
It may be that the poundage is ok but the unfitted length is too short, thus giving you a low ride height (I'm assuming you don't have
adjustable spring seats?
On the other hand it may be that the poundage is too low if you are happy with the ride height but find that the suspension is compressing too
easily
Info on what others have is interesting but not really helpful unless their situation is EXACTLY the same as yours. Once you've analysed what
you've got you will be in a good position to start sorting it out
John
|
|
|
procomp
|
| posted on 23/7/08 at 03:07 PM |
|
|
Hi there are various problems with the MK live axle rear end.
1. The springs if running with 1.9 id springs can end up coil bound. This obviously gives the sudden change in spring rate as hitting the bump stop
but more visious.
2. The max spring poundage you want is 160lb and no lower that 120lb for road use.
3. the main problem is that they never modded the rear cross member that crosses the rear bulkhead and hits the top of the diff unit in compression
and roll. All other manufacturers have raised the crosmember to give clearance but NOT MK. Means you have to run a much higher ride height. This can
be exadgerated if running 15" rims and trying to achieve a 4" ride height for example.
5. some times the axle will not be centered in the chassis and when cornering the diff casing will catch the chassis on the inside of the tunnel. It
can be centered if it has an adjustable panhard rod but i do not recall MK's having an adjustable one fitted.
6. as others have said make sure you have the correct length dampers and springs fitted. Get someone to check how close you are to the bump stops
visually when seated in the car. And also check how much droop is available by lifting the chassis on one side and measure how far the chassis can
raise before lifting the wheel/tyre from the ground. Ideally you want close too 1 1/2" travel in compression and droop available.
Cheers matt
|
|
|
phil T5
|
| posted on 23/7/08 at 03:21 PM |
|
|
Thanks for advice
is there a way of finding out spring pound ratinwithout removing?
are they marked in a standard way somewhere?
|
|
|
procomp
|
| posted on 23/7/08 at 03:46 PM |
|
|
Hi if you can see the end of the spring where is has been croped ans flatend some have the poundage marked there. Other wise it have to go into a
tester. But if you post up the open lenght of the spring and wire dia. it will be possible to estimate with in a few pounds.
Cheers matt
|
|
|
phil T5
|
| posted on 23/7/08 at 04:02 PM |
|
|
Thanks
its sounds to me like axle is hitting cross member /frame, will check other things too though
Im thinking this cos of the sound it makes under load cornering but could be wrong
Ive got avo shocks on so first thing is presumably
Check for marks where it may be hitting
Jump up and down on back with a couple of people to see it it connects with cross member
The wind up the ride height so if if it helps
After this check springs
|
|
|
phil T5
|
| posted on 23/7/08 at 04:10 PM |
|
|
The other thing I could check I guess is marks on the actual coil to see if the coils are contacting each other i.e coil binding is happening
|
|
|
procomp
|
| posted on 23/7/08 at 04:35 PM |
|
|
Hi sounds like you have a plan of action. 
cheers matt
|
|
|
DIY Si
|
| posted on 23/7/08 at 09:23 PM |
|
|
Having just watched your 1/4 mile vid, it might be worth raising just your driver's side ride height. It looks as if the car has been set level
with no weight in it, but then drops when you get in it. Mine does similar, as I too weight about 100 kgs all up. It might look a bit silly and wonky
when sat still, but will sit flat when you're driving.
|
|
|
phil T5
|
| posted on 23/7/08 at 09:27 PM |
|
|
thanks
thats my first step i think
|
|
|
DIY Si
|
| posted on 23/7/08 at 09:29 PM |
|
|
quote:
Originally posted by phil T5
thanks
thats my first step i think
Just don't blame me if it doesn't work!
|
|
|
