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MG MGF Technical - Suspension shudder/scuttle


Can you upgrade a 1996 MGF suspension to help reduce the shudder/scuttle that occurs when ever you hit a pot hole or is it poor design. I understand the TF suspension was modified to reduce the problem. Any suggestions would be appreciated, starting with the cheapest....

Darren
Darren

Hi Darren,

If your car has covered a fair few miles then the rubber bushes in the suspension are probably showing their age. Replacing these with poly items will tighten everything up and give the shock absorbers chance to work properly, and most people report improved steering feel & handling. Involves a fair amount of labour but the costs aren't excessive.

Being an open 2 seater the MGF will never quite have the rigidity of a saloon car.

Mike Hankin

Not sure where the idea of TF suspension causing less scuttle shake came from. The TF suspension has harder spring rates and firmer dampers - overall noise, bumps, shake can only be worse.

A 96 car almost certainly needs a suspension work over by now. Starting with the cheapest - live with it! But take a test drive in a newer F or even a TF to get a feel for how bad (or good) yours really is.
JohnP

Scuttle shake, as Mike says, is an inevitable consequence of an open top design. I guess the question is whether your car is more susceptable than other cars.

A hard, stiff suspension will exacerbate the problem - as will a soft, lowered suspension (low hydragas pressure).

The first thing I'd check on your car Darren, is the ride height. If the hydragas is at the right pressure, the ride height is about 368mm at the front wheel (measure left and right) ± 10mm. If may be a little lower at the moment thanks to the current cold weather spell (remove 0.4mm for every degree C below 17C).

If the car is, say, 340mm, then the chances are the suspension is bottoming out on the bump stops has you go over pot holes etc. These shocks will be transferred directly into the cabin of the car. You should then consider getting the hydragas pumped up, and the tracking reset.

If the car is riding at the correct height, then there isn't much else you can do to the suspension to reduce scuttle shake. What you need is a stiffer chassis. Interestingly, fitting roll hoops to my car made quite a difference to the feel of the car - so while this doesn't completely solve the issue, you may appreciate the difference, plus they look good!

HTH
Rob Bell

My TF has a lot less scuttle shake than my 2001 F, does the new lower sill manufacture help as I seem to remember some figures about increased torsional stiffness?
Tony

A usefull upgrade that reduces some of the perceived scuttle shake is to fit the Brake server brace bracket that was available from Brown and Gammons. This stops the pedals jumping around when you hit a pot hole.
Dave

Another good upgrade is to fit the Front subframe bushes from a 2000 model year car - these are identified by being green painted - they are a stiffer rubber to the 96 bushes, and improve the steering precision. Or you could go the whole hog and fit the solid mounts from a TF, but I don't know how this effects the NVH ( Noise Vibration and Harshness).
Dave

The solid alloy bushes aren't bad Dave. You certainly feel more coming from the road - but it is a long way from being uncomfortable :o)

The pleasing things are what you'd expect - far better steering precision and feel through the steering (even with the EPAS switched on).

Part of the impression may be comparing old worn rubber bushes with new solid alloy ones, but the car certainly feels a good deal tigher with the alloy bushes, so I'd certainly recommend them. Not sure how they compare with the PU alternatives though?

As for the bushes helping with scuttle shake - they're probably not a great deal of help for this, as the subframes themselves have a degree of flex...

Tony is right: the TF has a torsionally stiffer body than the F - but many of these upgrades are in the sill structure and A-post and aren't really retro-fittable to the F...

No idea whether it is worth fitting the TF strengthening bars found in the engine bay and front subframe... But if MGR fitted them, then they are there for a purpose!
Rob Bell

< But take a test drive in a newer F or even a TF to get a feel for how bad (or good) yours really is.
>

And this is exactly what I'm doing tomorrow morning... taking an '04 TF for a test drive from the dealers just to compare it handling and bumpy-ness wise to my 5yr old VVC because thats clattering about like it actually has no suspension or damping :-)

At my last service, MG pumped my suspension up but I don't think they did an alignment check afterwards and certainly didn't suggest I had it done... so I'm thinking that maybe linked to my shakey-rattley ride and needs sorting...

I look forward to the results after tomorrows drive :-)

Just out of interest, if I take photos of all the suspension and tie bar bushes in place right now would someone be able to tell me if they're knackered just by looking at the photos?

Chris.
Chris Tromans

That shouldn't be a problem Chris. Actually, you should be able to spot the difference as well - failing bushes often look badly cracked from the outside - and also look to see if the bush is mis-shapen or if there is any gaps evident between the bush insert and rubber, or rubber and mounting eye.
Rob Bell

This thread was discussed between 24/02/2005 and 25/02/2005

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