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MG Midget and Sprite Technical - Strange noise from rear (the cars, not mine)

I've been driving my 1500 midget in a rather "sporting" fashion lately, certainly harder than I did when it was new to me last year and I have been getting more confident with it. The roads round here are very twisty and up and down all the time which makes for very fun driving. I have found that when I am cornering hard, or bottoming out of a dip hard, there is a brief sort of rummble/knocking noise from somewhere around the rear wheels. It happens on both sides, depending which wheel is under load.

Has anybody experienced the same thing, or got any ideas what it could be?

I have checked the wheel bearings and they seem good. Nothing appears to be loose or have moved in the rear axle mountings. The springs look ok. The tyres are not foulding. The mud flaps are well off the deck so I don't think is them dragging on the road. The only thing I can think off is that when the suspension is fully compressed, the bump stops are pressing against the body and transmitting vibration direct in to the body shell.

The car is in for its MOT tomorrow, so I will ask the tester to investigate as well, but I thought there is likely more midget experise on this forum than in my local garage.

Any help gratefully received.
Ben.
Ben Whiteley

Ben, it's easy to check the bump stops and see if they are coming into contact with the axle, just dab some chalk or white shoe polish on the end of the stop and go for a drive then check if there is any transfer to the axle. One other area you might check is the prop shaft which may be coming into contact with the body when the suspension is fully compressed.
Bill Young

Bill,
Thanks for your reply. The bump stops are deffinately contacting the body, because I can see where they have marked the underseal. I just wondered if this would also cause the noise I can hear?

I didn't think to check the prop shaft so I will look for signs there as well. I would expect if this was the case the sound would be much more metallic or mechanical sounding.

If I manage to find out what it is, I will post an update.

Thanks again,
Ben.
Ben

Ben:

Another area to check (if you haven't yet) is the leaf spring front bushings. I had a similr sound eminating from over my shoulder and it turned out the bushings were toast. Try getting a large screwdriver or prybar up between the spring and the body and see if you can get the front of the spring to move around at all. Any signifigant movement there may mean the bushings are bad.
Matthew
M Moment

If everything else checks out, my guess would be the drive shaft is banging into the top of the tunnel....if thats the case you might need a pan hard rod....Now that and a heavier sway bar on the front will make your butt cheeks pucker up and say kiss me.

prop
Prop

And notwithstanding the other suggestions

my money (not a lot of that either) is on the shock absorber body mounting bolts on the body allowing a fractional amount of movement under load

I had the noise you describe, sounded as if the back of the car was falling off in lumps. Knocking and banging like a good 'un.

I found that the shocker attachment nuts and bolts had a miniscule amount of "tighten-up-a-bit-more" in them

Hyke them up even tighter and off to visit Uncle Bob.
Bill

OH ...Good one Bill,

I hadnt thought about that, thats a definte possabliity...

prop
Prop

Ben,

I have the same problem with noise, it took me ages to work out what I think it is. The car is not used much in the winter and I am sure its rust between the rear spring leaves. As if I go for a long run the noise has almost gone by the time I get back also if its raining it goes off a lot quicker. I have even taken the rear shocks off, still noisy, put new pads between the axle and spring had the front of the spring out to check the bush but the noise is still there. I have now borrowed a special tool to put grease between the spring leaves, next weekends job.

Mike
M J Pearson

My 2 cents. Children's plasticine clay, not potter's clay, positioned in suspect areas will show movement by the deformation of the clay. Put some on the bump stops and the top of the tunnel, drive around the corner and check the clay. It will tell you something is hitting, then you have to determine what is worn.
J Bubela

This thread was discussed between 14/04/2008 and 15/04/2008

MG Midget and Sprite Technical index

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