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MG MGB Technical - Installing Superflex bushes

I recently installed superflex suspension bushes to my front A arms. The bushes consist of a stainless steel inner tube and the blue bush itself in two halves. At first I thought that the fulcrum nut should be tightened sufficiently to clamp the stainless tube to prevent it moving. But I found that the suspension arm became solid and would not move at all, so I slackened off the nuts enough to allow movement. After a couple of thousand miles I have stripped one side down to find that the Stainless tube, washer and nut are moving with the suspension arm. The split pin in the castlated nut has worn considerably with the movement.

To my mind the tube should be fixed and the bush move on the tube. At the moment the stainless tube is moving on the fulcrum pin (metal on metal).

Anyone else had this happen?.
I can see 2 ways to fix the problem, either get slightly longer tubes made or reduce the thickness of the A arm tube that the bush fits into.

The car is very high performance and need to get this sorted.
http://www.youtube.com/watch?v=lWa4n7iVCm8

Cheers
Mark
M Rawlins

there should be a very large washer between the nut and the bush.I lightly greased the washer on my car to stop squeaking.
http://www.moss-europe.co.uk/Shop/ViewProducts.aspx?PlateIndexID=451

#41
P.N. Sherman

Yes of course I have the washers fitted.
Everything greased up well with copper grease.
If I tighten the nut to clamp the inner tube the suspension becomes rigid, thats the problem.
Thanks
Mark
M Rawlins

That's how the originals are supposed to be, both 4-cylinder and V8. The 4-cylinder bushes slide on the clamped-up distance-tube, but because the V8 bushes are one-piece the nuts should only be fully tightened when the normal load is on the suspension otherwise the rubber can get ripped as with these all movement is supposed to take place withing the rubber. Surely the purpose of these after-market bushes *is* to make things even stiffer, but something will eventually give - either the bush will flex internally or the A-arm will slide on the bush under normal road loads.
Paul Hunt

I have the same bushes on my car and I have had a long discussion about them with John Hoyle of Hoyle Engineering who supplied them for me. The stainless tube MUST be clamped up tight by the big washers to prevent premature wear, and the bushes should be fixed in the wishbone arm, even if it means gluing them in place. Then the only movement that is possible is the bush round the stainless tube. This means that the bush must also be able to slip against the face of the large washers which are clamping the inner tube.

On my car they were so stiff that the suspension was effectively locked up. This was partly due to the powder coating on the eyes of my arms, which was so thick it was holding the bushes out by a fraction and stopping them from moving. But mostly I cured it by making sure that the stainless tube and the big flat washers were shiny clean and smooth and well lubricated with the special lubricant.

John was going to contact the manufacturer of the bushes to see if there had been any slippage in the manufacturing tolerances for the bushes or tubes, because he has seen this problem before. I haven't heard if he got anywhere. It seemed to me that the inner stainless tube could have been fractionally too short for the assembly.
Mike Howlett

Paul
So am I right in thinking that the V8 rubber bushes are bonded to the distance tubes and it is the flex in the rubber that gives movement,
And with the superflex the bush atcually moves on the distance tube. Things are stiffened up through the superflex material being harder than the rubber v8 ones,

Mike
Im glad its not just me that has had this problem.
Ive done some measuring and there is no way the bush can move freely as the sides are being clamped so tight. The distance tube really needs to be 3 or 4mm longer.

If I take 3mm off the housing end on the wishbone arm it would have the same effect, think Ill try that first.

Thanks
Mark
M Rawlins

Just watched your videos. That is a quick car, but you obviously have to keep on your toes to keep it pointing in the right direction. Very well driven.
Mike Howlett

Thanks Mike
Yes there is a tendency to oversteer, great fun to drive and can out accelerate most things on track.
Seriously considering a 5.0L upgrade but worried about trivetrain coping with the extra torque.
Cheers
Mark
M Rawlins

I have posted detailed analyses of this matter re the various shoulders etc. in recent months, on this and/or the MGA/TD boards. Don't modify the arms, cut the bushes, as that's the problematic part. Fit of the poly bushes on the sleeve should be like any other bearing - free but not sloppy, and lubricated. The sleeves should be fitted as the V8 type bush is.
FRM

Here's some of it:
The secret is that they MUST be assembled correctly. There is a small shoulder on the fulcrum shaft, just past the threaded bit. The big washer MUST go on this shoulder when tightened. Takes some finesse! Today's aftermarket washers supplied in front end OH kits have a hole that is too small to fit on the shoulder. I use the OE ones or machine the new ones to fit. If the washer is not ON the shoulder, the preload on the rubber is too low, and rapidly failure is the result. If the hole is too big and goes OVER & PAST the shoulder, the preload is too great and the bushes fail. OE bushes used to last 10 years minimum, if not oil soaked.
***
Werner-
The fulcrum shaft has three diameters: the largest dia & smooth bit the bush sits on, the somewhat smaller dia shoulder the washer goes on - only about 3/32 long, and the threaded part. The now supplied washers don't fit ON the intermediate shoulder, but rest against it. This prevents the correct compression from being applied to the bushes, which as you say is required also for correct axial location. The correct compression is designed into the length of the large diameter of the shaft.
Getting the washer up on the shoulder is a little tricky whilst compressing the rubber, and more so when installing the V8 Metalastic bush. With the V8 bush, if the washer is not on the shoulder, then the rubber is not compressed enough to locate the bush in the control arm, AND, the steel inner tube moves on the shaft, giving the situation described by Rich B way back at the top. Some "V8" bushes are not made correctly - the inner sleeve should be just a bit longer than the largest diameter part of the shaft, so that the tube is clamped axially on the shaft, but not so long that the washer does not fit on the shoulder. It helps a lot to assemble the washer and nut on the shaft first, measure the amount of threaded part sticking out of the nut and the relative position of the split pin hole, and be sure that measurement is duplicated on final assembly. If the nut gets tight when about 3/16 from that measurement, you need to tap radially on the washer until it locates on the shoulder, then final tighten.

FR Millmore

I had worked out the shoulder problem some time ago.
To make it easier to fit the washers I assembles the washer and nut onto the shaft without bush, nipped it up tight and spot welded the nut to the washer.
Now it acts like a large flanged nut with the washer always centred. This is not the problem at all.
I have now machined 3mm off the wishbone arm tube and it all fits together much better. Moves more easily but firm. Just need to do the other 7 now!

Mark
M Rawlins

This thread was discussed on 22/11/2009

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