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MG Midget and Sprite Technical - Front suspension alignment/fitting problems

Hi, this is my first post on the forum.
I have been restoring an 1976 MG midget since last May.

Some of you may think its taken a while to get to this stage but my excuse is the restoration was interupted by the restoration of a 1980 Midget in much better condition! This car was excelent over the summer, Possibly the most fun car Ive ever driven. The best encoragement I could have had for getting back to finnishing the first one.

However the easy task of fitting the front suspension soon turned into a nightmare, what should have taken about an hour or two has basicly brought a temporary halt to the project.

The problem is this:




A Fairbairn

This side is the worst affected but neither line up I cannot get the bottom of the kingpin into the wishbone.

I have been very lucky to have had Mike from the Caladoian MG club have a look at my car.

We have now been able to confirm that my wishbones are not bent and that Im assembling the components the correct way.

We have also done some measurements of the king pin position relitive to the bulk head.

Using Mike's car as a refference

From the top of the kinkpin centre to the bulkhead
341
From the Bottom of the kingpin centre to the bulkhead
362

On My car the Passenger side is
Top: 338
Bottom: 346

Drivers side
Top: 344
Bottom: 347

So I think something on the shell is out, although it might be a shock absorber.
The problem is with so many varables Im not sure what needs to be moved and how to move it? Welder? Hydraulics?

Im trying to keep an open mind and I'd love to hear from someone who's had a similar problem and fixed it.
A Fairbairn

Have you fitted replacement / exchange shock absorbers? I understand that some currently available are faulty such that the pivot pin that the lever arm fits to isn't properly located, so that there is a gap between the lever arm and the body of the shock. This would move the lever arm and therefore the kingpin forwards as in your photo.

The arm should be fairly close up against the forward face of the shock body, with just enough clearance for movement.
Guy W

I'd be most concerned about the lower measurement, but since you have two the same, I suspect the reference car! Lower inner pivots can be a problem, especially if the brackets have been previously damaged.

You put the bottom on first, and the lower wishbone will flex enough to deal with a few MM either way when installing the upper pin, though the top measurements <should> be the same. You are well within observed variation there.

FRM
FR Millmore

I hope im the only one to.ask... But what are we looking at in tye photo...

I see the wishbone and i see the fulcrum pin....and i see the bottom side of the kign pin... But how and why is it attached to the spindle ???

Prop
Prop and the Blackhole Midget

I know this is an even more stupid question, but do you have the shocks on the correct side of the car... Im not sure if its possiable to have them reversed

Any chance your running 2
Differant wish bone bushings... Or maybe A new and an old used

Prop
Prop and the Blackhole Midget

I agree with FRM. it is usual and easier to build from the bottom up, attaching the king pin to the fulcrum pin first. Then add the swivel hub and lastly fit the top trunnion to the lever arm. There will then be enough movement in the fulcrum pin to allow the top to align properly.

But do still check the shock spindle and arm are not coming put of the shock absorber body as there are some bad ones about.
Guy W

Don't know if this will help with your problem but lots of good reference pictures non the least

http://mikeamick.com/76midget/page%201.htm
Alexander Sorby Wigstrom

Alex, sorry, that link doesn't work.

I went to see Adam's car on Monday and it is a strange problem. The bodyshell is all stripped down and has been properly repaired. It looks straight, and some basic measurements seem to indicate that it is not suffering from the effects of a front end crash. The chassis rails are straight and have no visible kinks or creases in them.

On the LH side of the car the swivel hub assembly simply cannot line up with the wishbone. Adam fitted the damper, then attached the trunnion to the arm, and then as his photo shows, the bottom of the king pin is about 3/4" too far to the rear to enter the gap in the wishbone.

On the RH side it is possible to assemble the components with a bit of a struggle but it is then quite tight and the load on the fulcrum pin is obviously at an angle. Once the damper arm is attached it becomes impossible to unscrew the fulcrum pin.

I measured my car and these are the first set of measurements Adam gives. I measured horizontally from the vertical rear of the wheel arch forward to the top and bottom of the centre of the king pin. (Suspension was at full droop). As my car has a new Heritage shell I am assuming it is as good as they get. The measurements were identical on both sides of my car, 341mm for the top and 362mm for the bottom. This higher bottom measurement reflects the built in caster angle of the king pin.

I suggested Adam might try the same measurements on his car and this he has done, but really the figures haven't helped solve which bit is faulty - the damper or the shell. It can't be the wishbones because I took with me a new set of that I had and there was no difference using those.

I'm at a loss as to how to proceed. Here is a young guy who really wants to build up his little car but is stuck with this problem. What can we do to solve the puzzle? What measurements might help prove if the shell is indeed straight?
Mike Howlett

Mike,
Did you check the shock arms as I suggested? Where the the lever arm is fitted to the shock absorber spindle it should be close up against the body of the damper unit, with no visible length of the spindle showing. Some are badly assembled, moving the lever arm too far forward.

Another thing worth trying is to slacken the 3 damper mounting bolts by a few turns which may give it sufficient slack to align the other components. Then re-tighten.
Guy W

I agree with Guy, and FR.

You don't usually build it that way. The last connection is at the top, not the bottom. The top trunnion has rubber bushes, that will allow movement enough to accomodate the apparent out of alignment in the photo. And as Guy says, loosen the shock bolts and that will allow a degree of movement at the end of the shock arm, enough to centre the trunnion.

When I take mine apart, if I did the build in the same way as you have, I would have the same problem.

As regards not being able to turn the lower fulcrum when it's assembled, again, you don't try to remove this with the shock arm connected. You disassemble it first.

Mine hasn't lined up exactly in all the time I've had it and that's 35+ years -- and it hasn't caused any particular problem.

Bolt it up, the inner w/bone and top trunion rubbers will eventually shape themselves to suit the alignment.

But check the point Guy mentioned about bad shocks first.
Lawrence Slater

I had a similar problem although I had worked from the bottom up. Top trunion would not lign up with the damper arm. Because I used nylatron bushes, there was no flexibility in the assembly and I did not want to pre-load the upright massively. I loosened the 3 damper bolts which allowed assembly of the top trunion then tightened the damper bolts until contact was made between the lower surface of the damper and the chassis. At this point there was a small gap under one of the fixings. I used a thin washer under that fixing. I then undid the top trunion and confirmed that it now lined up perfectly. Worked for me. Good luck.
s baker

Recently replaced my front shocks with units from Peter May. Needed to keep the bolts loose in order to line up the trunnions/pinch bolts/trunnion bolt . Don't forget to check the tracking afterwards.
David Cox

I had the same problem putting my car back together and it was a bent deamper arm. I'd driven it for a few years like it and never knew because it drove fine.


Greg H

Here's how to check it. The kingpin end of the arm should be in line with the front of the damper. Like the LHS not the RHS.


Greg H

+1 on a bent damper, they bend surprisingly easily in small head on shunts as there is no real structure in front of the wheel.
Have you taken any measurements from the damper body to the end of the arm?
BH Harvey

I started a thread a few months ago on this, after carefull assembly with new / upgraded components I couldn't get the whole arrangement to line up, I was searching for utopia and eventualy gave up, applying a large spanner and some brute force, in the end it all seemed to work ok. Whilst its entirely possible that you have got it wrong, or something is bent, its just possible that because you are essentially dealing with 1950's tech, not F1, it might need a bit of gentle persuasion. I'm not advocating that you force it in to position, but all the different tolerances can add up.
S G Macfarlane

Just measured my 2 new moss shockers, not installed yet, and they are OK, matching Greg H's RHS picture.
so probably a bent arm as BH suggests.
This is a really good argument for fitting AM telescopic kits, which, apart from providing superior damping, are stronger and don't allow the top of the suspension to deform under braking thereby changing the caster angle.
R W Bowers

"This is a really good argument for fitting AM telescopic kits, which, apart from providing superior damping, are stronger and don't allow the top of the suspension to deform under braking thereby changing the caster angle."

Really? Stability under braking is very good, but having detachable bits that take the damage without deforming the main structure might be better. And while I am not familiar with the kits available, if they attach the dampers like the one in Rob's nearby thread, read my comments.

Further, if there really is a problem with the car structure. the much stiffer arrangement will be impossible to assemble and quickly destroyed.

FRM
FR Millmore

FRM Yes Really, the caster angle will change when the original top arm attached to the shock deforms. Remember that we are all running higher spec pads which increase braking force beyond the original design limits. I am only fitting original to get my car past our equivalent of the MOT. Once registered I shall fabricate and fit my version of a "frontline" conversion, and it won't be welded on. Why DIY? because the frontline kits do not address all the issues (still only single sided arm) and are expensive.
FYI the AM kits bolt on not welded on, which I suspect may be part of the problem.
Cheers Rod
R W Bowers

This thread was discussed between 05/09/2012 and 09/09/2012

MG Midget and Sprite Technical index

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