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MG Midget and Sprite Technical - Caster angle and Damper position on Heritage shell

Had an interesting but frustrating weekend in the garage. I'm putting the front suspension on at the moment and got the RHS kingpin on the bottom arm and it turned really good as shown in the image attached. I should say I have put the MGB damper mod on at the front in case you think it looks strange.

Rob

MG Moneypit

Quite happy until I did the LHS and got this.

MG Moneypit

Bug**r. or words to that effect.

At this stage I had no idea what was happening but the angle of the kingpin on this side looked slightly out. So I set about measuring the kingpin angle, using a spirit level and ruler, on both sides.

Had to look up a bit of trig on google. It's 50 years since I did that in math lesson.

There was a 1 degree difference between the two kingpins but 1 degree only accounted for about 4mm movement at the top of the kingpin and I was looking for something like 15mm so even though the kingpins were out slightly there must be something else.

Looked through the archive and several threads mentioned early Heritage shells were affected by similar maladies. (my shell is Heritage from 1998).

I measured from the bottom of each kingpin to the firewall and it was within 3 mm this time so the bottoms were in about the correct position. Some threads suggested the A arm could be out or more likely the mounting points in the brackets so I had a good mooch around but everything look ok to me.

So, I loosened the damper on the LHS which was mounted on an adapter plate to convert from Sprite mounting to MGB mounting pattern.
I moved the damper by putting the arms in the correct position in relation to the kingpin and measured from the inner face of one arm to the firewall, on both sides and the measurements were within 5 mm again.

So, I rebolted the damper to put it back into its original (wrong) position and the measurement on the LHS went 20mm out.

So the damper mounting position on the LHS is wrong!!!!

Rob
MG Moneypit

Do you think that the damper plinth itself is too far back? Or maybe it is "pitched" wrongly in which case maybe you could pack at the rear margin between the plinth and your adapter plate?
GuyW

At one point I thought the chassis on the LHS might not kick up enough to give the correct caster angle on that side but checking with a spirit level across the chassis rails at various points and when set level (the shell is on a rotisserie) its level at every point. I also checked by using a level across the welch plug in the top of MGB shocks and both sides were identical. Identical in that I had to put a 2mm thick washer under the rear end of the level to get the bubble in the middle. It was identical on both sides.

I'm pretty sure the problem is the holes for the 3 mountpoints on the LHS are out slightly.

Luckily, because there is a mounting adapter I can correct it on the adapter rather than having to hack the damper mounting points.

Rob


MG Moneypit

And the other side.

MG Moneypit

Mine was probably one of the ones you found in the archives. Right hand had positive camber which I had to adjust and I do believe one side also had a similar issue to yours. It wasn't out a lot but I think I had to force the king pin back to get it past the trunnion. It would have been a mid 90's shell I think.
John Payne

When I fitted my mgb dampers mine had a very slight difference. But it was only one or two of the shim washers that you get in the kit. Mine say so all washers are aft of the trunnion (I guess this gives me more castor angle).

Not sure if that's how it should be, but with about 1.5 deg of camber, I am absolutely amazed at how it drives now. Very very stable and It will not understated. Very pleased.
Karl Bielby

Ah, the pleasures and simplicity of a heritage shell rebuild. Just take it all off one and fit it to another. Simples. Not.
However Rob - you will get there in the end!
John Hutton

hi all
I did the mamba/mgb conversion recently. My observation was that the king pins were not central in the levers of the shocks. As both sides were the same
I carried on and all is well. About 2 deg neg camber and castor as it is...no unusual tyre wear so i assume all is well
rgds tony
tony boyle

This thread was discussed between 06/08/2017 and 11/08/2017

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