Board logo

Creaking suspension???
Sloan85 - 23/4/14 at 11:00 AM

My suspension has been creaking which thought was down to the crush tubes not being adequately lubed in the polybushes. Upon stripping down the front end it appears there is plenty of lube still in there. It does appear that the U shaped mounts on the chassis have been rubbing the outside of the polybushes - dont think I lubed the outsides.

I also thought I may have overtightened the bolts causing the brackets to bend but the crush tubes should stop this, shouldnt they? How tight should the bolts be, in case this is causing the creaking.

Cheers

40inches - 23/4/14 at 11:05 AM

The crush tubes should me longer than the bushes, I set mine around 1/2mm longer.
Bushes binding on the brackets can cause wishbone failure
A search will bring up a few horror stories.

ReMan - 23/4/14 at 11:12 AM

Annoying though it is , intollerances in all the parts mean that careful sellection is needed to get the best fit
As said aim at 0.5-1mm longer tube than bush to ensure that the bush pivots on the locked tube . YUou may need to make shims for this. and as plenty of grease

skov - 23/4/14 at 11:21 AM

I had the same problem and spent last weekend rebuilding my suspension.
As well as liberally greasing them I trimmed the outside edge of the polybushes by a mm or so to stop them rubbing against the suspension brackets.
I've got nice, smooth, creak-free, suspension travel now

nick205 - 23/4/14 at 11:55 AM

I spent a fair amount of time matching crush tubes, bushes and wishbones from my MK kit to get the best fit. Even then, I had to trim a few bushes to get a good rotating fit. Plenty of grease on assembly, including between the outer faces of the bushes and the inner faces of the U brackets.

jps - 23/4/14 at 01:37 PM

quote:
Originally posted by nick205
I spent a fair amount of time matching crush tubes, bushes and wishbones from my MK kit to get the best fit. Even then, I had to trim a few bushes to get a good rotating fit. Plenty of grease on assembly, including between the outer faces of the bushes and the inner faces of the U brackets.


What's the best way to trim the bushes - is it simply a case of using some abrasive paper (I call it all sandpaper but that might be the wrong term) or is it more complicated than that?

aka Keith - 23/4/14 at 02:50 PM

I too am interegsted on how to trim my poly bushes, if needed.

cheers
Craig

skov - 23/4/14 at 03:01 PM

I suspect the best way would be on a lathe or milling machine.

Not having those to hand, I resorted to using an angle grinder
I just held them against the face of the spinning angle grinder disc, then cleaned up afterwards with a scalpel and sandpaper.
Not sure I'd recommend that method though!

Slimy38 - 23/4/14 at 05:55 PM

quote:
Originally posted by Sloan85
I also thought I may have overtightened the bolts causing the brackets to bend but the crush tubes should stop this, shouldnt they? How tight should the bolts be, in case this is causing the creaking.

Cheers


I would expect the brackets to bend a little and clamp on the crush tubes to keep them fixed, then the bushes should rotate around the tubes.

I actually trimmed a little off the wishbone outer tubes, that had the same effect of moving the poly bushes away from the bracket. And it's a lot easier to mark and trim the tube than the bush!

I believe someone on here cut some thin washers out of teflon sheet to go between the bushes and brackets, seems like a good idea to me.

Sloan85 - 29/4/14 at 08:37 PM

what sort of gap should I have between the side of the bush and the bracket?

Having looked at all the wishbones more closely it is only one of each pair that is rubbing so I am thinking about removing and trimming the bush a bit to give a small gap.

The teflon sheet seems a decent idea also so may try that.

Sloan85 - 30/4/14 at 05:25 PM

Sorry for bumping this thread but can anyone tell me what sort of gap should I have between the side of the bush and the bracket?

Cheers

Slimy38 - 30/4/14 at 06:26 PM

How bizarre, I'm sure I wrote a reply! Mind you, I was using my phone and I'm lucky if it lets me make a phone call, let alone browse the interweb.

Anyway, I didn't leave any gap at all, at least not a visible gap. I just made sure that the bush lip didn't compress when I tightened the bolt.

[Edited on 30/4/14 by Slimy38]

ReMan - 30/4/14 at 06:50 PM

Again in reality I doubt you see much of a visiblea gap on any of them
Main thisnhg as said is that the tub is longer so it tightens on this not the bushes and plenty of grease inside and out.
I don't believe most of the creaking is from the sides personally more likely on the tube. ISTR the MK tubes on the outside pivot surface is not particularly polished either, some use stainless I believe for this reason

Sloan85 - 30/4/14 at 06:58 PM

With the fronts I stripped, re-greased and put back. Still one bush is badly creaking but this goes away if the bolt is loosened. This is one where the wishbone arm doesn't sit centrally in the chassis bracket, so I think it can only be the outside of the bush rubbing.

Looking at all 8 of the rear brackets, its the same where there is a gap on one side but tight on the other. I may just strip it all, sand 0.5mm off the affected bushes and reassemble.

Its not just the creaking thats bad. If I rock the car left and right, it won't return fully upright... It will stay slightly to the side I pushed it to. Thats how stiff they all are.

The crush tubes are fairly smooth and are still lubed up so I don't see how they can be the problem.

[Edited on 30/4/14 by Sloan85]

ReMan - 30/4/14 at 07:42 PM

still says your inner tubes are too short to me then, but either way if it helps trim the bushes then or grind back the eye of the wishbone that carriers the bush

MikeRJ - 30/4/14 at 09:11 PM

quote:
Originally posted by Sloan85
With the fronts I stripped, re-greased and put back. Still one bush is badly creaking but this goes away if the bolt is loosened. This is one where the wishbone arm doesn't sit centrally in the chassis bracket, so I think it can only be the outside of the bush rubbing.

Looking at all 8 of the rear brackets, its the same where there is a gap on one side but tight on the other. I may just strip it all, sand 0.5mm off the affected bushes and reassemble.

Its not just the creaking thats bad. If I rock the car left and right, it won't return fully upright... It will stay slightly to the side I pushed it to. Thats how stiff they all are.


You definitely need to fix that, as it can cause fatigue failure where the main wishbones tubes are welded to the bush tubes (mild steel crush tubes can also cause this by rusting and seizing up within the bush). As others have said, you don't want any significant end clearance as you need to prevent the wishbone moving forward/back. It's ok for the brackets to lightly touch the bushes, provided the movement is free.

[Edited on 30/4/14 by MikeRJ]

Sloan85 - 30/4/14 at 09:29 PM

I measured a crush tube at 44.5mm, not sure how that compares to other people? A quick search shows Haynes Roadster crush tubes at 44mm... Cant see anything about MK.

Had a quick test sanding a spare bush tonight, seems to work ok. Plan is to check which bushes are tight as its only half of them and sand 1mm off. Then re-grease and reinstall with a 0.25mm PTFE washer that I will cut from an A4 sheet I bought on eBay.

Hopefully I can get this all done on Saturday and then off to Stoneleigh on Sunday!

Thanks for the advice.



Photo of the issue




[Edited on 30/4/14 by Sloan85]