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MG MGF Technical - Rear wobble

Rear wobble
I am after some help before I take my 97 f in to the garage to see if I have something loose or broken
My problem is this when I get the car up to between 76 and 82 km I get what feels like a rear wobble it is defiantly not in the front as I have no wobble in my steering wheel
What I have had done so far is wheels off and balanced
Front wheel alignment 2 times I thought after the first it was in the front so I had it done at another shop still the same
It has had this wobble since I brought the car 4 years ago but I think it is getting worse
I have looked under the back and to me all looks ok
What’s funny is it only happens at that speed not over or under
Any ideas
Thanks Andrew
AR Cayzer

Nave you checked the outer end of the rear tie rods? The original rubber bushes are not very good at controlling the rear wheels even when new and get worse with age. The first symptom is "shimmying" from the rear when braking hard. A lot of folk fit compliance washers at £10 a set, but you can also get new PU bushes that are easy to fit.

Chris
Chris

As Chris says, the back end of the F does go soggy and is well worth the effort of fitting uprated bushes, for high speed confidence but mainly it improves the braking 'control', I did one track day in an early standard F and ordered the complete poly bush kit the next day...

As for the wobble, have the technicians doing the wheel balancing checked for wheelbearing slack? Bearings are not unknown to go through a stage of wear that only manifests itself to the driver above a given speed, but is usually accompanied by discernible free play. As you've had the problem for 4 years, I guess this is a long shot... Other possibilities are a slight buckle on one rim, balancing will mask this fairly well but at higher speeds it can become evident. Not always easy to see either, even on the balancing machine. Fitting the spare to each rear corner in turn would prove or disprove that. A driveshaft that is out of balance, or missing its anti-vibration weights could also be the cause, not an easy one to investigate further unless it's visibly warped - unusual, but can happen as a result of an engine mount failing. Usually munches CV joints quicker than usual, so if one driveshaft feels to have more free play in it than the other then that may be a clue. Good luck, I know how annoying those 'little' things can be ;o)
bandit

I will try putting the spare on as you said but if i have a buckled wheel wouldnt it wobble all the time?and not at that speed as far as i can see all the joints are ok
AR Cayzer

The spare is a space saver so it won't tell you much. I felt that my F had rear end wobble so I replaced all bushes, lowering knuckles and adjustable shocks, well one of them worked !!!!.
Andrew W Regens

Sounds like your rear wheel bearings need replacing. I had the same a few years back.
JD

I have recently bought my first MGF, Its a 75th anniversary edition and it too wobbles or snakes slightly at speed. Scared the you know what out of me!! I checked for front steering play at the time which was ok. I will have to check the other bits which Chris mentioned.
Thanks from myself for the good advice on here.
P Atkins

Forgot to mention above that my steering is fine when turning left but quite hard when turning right, any ideas? my local garage said its probably the p.a.s valve??
P Atkins

The MGF has electric PAS so to test whether or not there is a PAS fault you can disable the EPAS and see whether the steering feel is now equal. If it is still a problem then you are looking at a mechanical fault.
Nick Atkins

EPAS readjust see here: http://www.mgf.ultimatemg.com/group2/common_problems/epas_reset/index.htm

Also check tyre pressures, evidence of abnormal tyre wear that might suggest problems with the tracking, and ensure that the dampers are in reasonable condition.

Hope this helps - and do let us know what you find out...
Rob Bell

Many thanks Nick/Rob, i will let you know =]
P Atkins

Well.....I cleaned the contacts and nothing doing....so then I went to Maplins and they dont do that specific relay anymore and the kid there didnt have a clue what other one to buy....anyone no of another relay??
P Atkins

What relay do you need? If you are adjusting the EPAS using the instructions that Rob posted above you don't need a relay.
David Clelland

will try the reset on my next day off and will keep you informed on my progress!!
P Atkins

Had a silsilar trouble once which turned out to be flat spot in a rear tyre, frustrating as it was worse on cold tyres and evened out a little when the tyre warmed but persisted at certain speeds and on some sweeping corners. Only a thought but may help if no other probs emerge
RD MADGWICK

just updateing my wobble i have changed over front to back and still have the problem now i think i might all be in my mind maybe it was that way before i put new tyres on
Andrew
AR Cayzer

Hi I have just bought my first MGF it 10yrs old but in good condition and I also have a snaking effect at 60-70mph its like wrestling a ferret in a bag, it really squirms all over the place, and can be quite scary, im guessing bushes and a splitter for more stability, I have a limited budget but are there any other recomendations?
Jenny

correct tyre pressures and decent tyres are a good place to start
Will Munns

Correct tyre presures and brand new tyres (correct sizes) on board. (all checked prior to purchase). I have had the car slightly raised on the hydragas as it was way too low even by boy racer standards, small speed bumps would have presented a problem, I havent put it back to the full recommended heigh as I thought this was a bit excessive.
Jenny

Jenny,
go for the splitter first and see how it goes. Never replaced the bushes.
Cheers
Gareth
Dolgellau
Ddraig G

Jenny,

New tyres can be a little skittish until the bed in. Also, did you get your alignment done (needs to be 4 wheel laser type) after the car was pumped up?
David Clelland

Jenny,

I wouldn't go for a splitter yet - at 60-70mph a standard MGF should not be "like wrestling a ferret in a bag"! There's something else to fix first.

I would back up David Clelland suggestion - when I first got my F it was way too low - after the suspension was pumped up it handled very poorly until the 4 wheel alignment was done. If yours has had the tracking done with the suspension low, it will have been thrown out by having the ride height increased.

The other time I had poor handling was when a rear wheel bearing was failing. This has been fairly commonly reported by others on here.

Hope this helps,

Mark
Mark Roper

Hi Thanks for all the help, the tracking was done after the suspension was altered, so that should all be fine, maybe a ferret in a bag was a bit harsh but I get a definate sideways movement at these speeds it doesnt follow a pattern very intermitant and during acceleration and braking at this speed the problem is not evident usually happens when at constant speed or when lifting off the accelerator.
Jenny

The rear suspension is very sensitive to both set-up and bush condition. It's designed to give a degree of rear wheel steering according to the fore and aft loads on the suspension - driving or braking. If one side's different from the other you'll get uneven handling, and if the tie bar bushes where they join the lower suspension arm are too loose there'll be too much movement. I always felt mine turned more readily one way than the other, but now it's been rebuilt with the TF set-up that's meant to get get rid of the sensitivity it's very well balanced. Not that going for TF suspension is going to be your answer (unless you're as daft as I am!), so have a close look at the bushes as well as the wheel bearing - give each a good hefty pull and push in all directions, and you should see a slight fore and aft movement and not get any clonks.
Mike Cunningham

This thread was discussed between 09/06/2008 and 05/08/2008

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