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MG Midget and Sprite Technical - Front damper failure leading to other damage?

While out for a drive today the steering went all sloppy (scary) and I discovered the (front left) damper arm pivot pin was sliding out of the damper housing. I've ordered an uprated pair of dampers from Peter Caldwell as they were already on my Christmas list.

My question is: should I expect to find any damage/alteration to the geometry of the suspension and what might I be looking for? I can measure toe-in, but beyond that I haven't a clue. I'm guessing the pivot arm being worked forward introduced some negative caster into the suspension equation, should I be expect that to be transient, and will I be good to go with the new dampers?


Richard Reeves

if that was loose for very long, then I would suspect that there might now be wear in your lower pivot (there the kingpin is attached to the A-Arm (wishbone). Those joints are not real hearty to start with, and I wonder how well they would hold up to the whole kingpin being able to move fore/aft at the top because of that failed damper pivot.


Having the suspension apart is always a good time to confirm that there isn't any freeplay in your kingpin, top trunion, lower pivot, steering end ball joints, and that the a-arm/wishbone rotates fully up/down smoothly (check this stroke when the spring is removed, of course).
Norm Kerr

>>there isn't any freeplay in your kingpin, lower pivot,...

There's bound to be some play in these items, even small. Does anyone have either with *no* play, however carefully reamed/assembled?

Agree no play in balljoints.

A
Anthony Cutler

"I wonder how well they would hold up to the whole kingpin being able to move fore/aft at the top"

Not well. Mine did someting similar, the arm went loose on the damper. It ate the cotter pin and turned the hole in the kingpin into a double arch sort of shape rather than a parallell hole - like )( but through 90 degrees. also wore the thread bearing in the wishbone out as well, but not as much.

I'd definately check all of that lower joint carefully, I had to put a new kingpin and cotter pin in when mine went.

I think that the little movement in the lever arm whenever you brake is what wears the whole thing out at the bottom - the frontline kit sorts this - my solution means I still have no bottom end play after about 4K of hard driving.

http://robsmidget.co.uk/modifications/mechanical/front-suspension

I'd agree with the scaryness! bet you're pleased it didn't come all the way out!
Rob Armstrong

I also would expect you to find some wear in the lower trunions to allow the top of the upright to move that far forward. As for the damper, that type of failure isn't that uncommon, especially if a heavier weight oil has been used before. The only thing that keeps the shaft in place is that it is peened to the rocker arm. Heavy oil or a possible over rotation can casue the rocker to break free and rotate on the shaft and the shaft to work out. Your new dampers will fix all that. If the lower trunion wear isn't excessive then I'd think you'd have no problems once you install the new dampers.
B Young

Richard,

I ordered a pair of rebuilt front shocks from Peter C. last summer and one of them did just that. Peter graciously and promptly sent me a replacement and said that those arms are just pushed on the splines inside. I thought that big nut held it on.

I don't think it should cause a problem, but it is easy enough to check everything once the shock and spring are removed. There should be hardly any play anywhere.

Lee
Lee Fox

Upgraded shocks (plus fresh upper bushes) installed today, feels like a whole new car, makes me wonder how long the old shock had been bad. I installed the old shocks myself ~6 years ~20k miles ago, you'd think stuff would last longer...

After removal, the failed damper arm spun freely in the housing, absolutely no damping whatsoever. Swivel axle on the failed side could be moved 3/8"-7/16 front to rear with damper removed. Non-failed side had a solid 1/4" front to rear play.


These swivel axle assemblies were installed by me when I bought the car (part of a complete front suspension rebuild, same ~6 yrs. ~20k ago). wish I had paid attention then to whatever free play that might have been there after the install.

So, does 1/4" inch front-to-rear slop sound pretty average after ~20k miles? Anyway, thanks everyone for your comments.

Drive Fast, Swerve A Lot! (my wife's old barstool Adieu)
Richard Reeves

that sounds like something was wrong with the unit, they ought to last for many, many years.

One thing that could cause premature failure would be putting in oil that was too thick.


The best source for information about these dampers is Peter at World Wide Imports, he rebuilds them better than new, and probably has forgotten more about them than most of us will ever know:

http://www.nosimport.com/



Norm
Norm Kerr

This thread was discussed between 03/02/2011 and 13/02/2011

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