Anyone have their Mk2 rear control arm bushing "fall" out?

[GTIspirit]

Has anyone experienced this on their Mk2?!?!?

Over the winter I installed new Audi TT rear control arm bushings in new Mk2 front control arms, along with new front bushing and new balljoints. After three autocrosses (no comments please as it is built to IT spec) and maybe 200miles on the road this joint "fell" out.

I can't think of how this would happen as there are virtually no vertical loads on the A-arm at this location. Of course I need to fix it, but I'd first like to understand how it happened and how to prevent it, short of tack welding the bushing into the A-arm.....

 

[Knestis]

Mine are tack-welded (MkIII and aftermarket spherical bearings)...

K

 

[Flyinglizard]

Those are not round. Point the longer sides to the tire contact patch. Next use some red loctite to keep them in. Stake the edges with a sharp chisel. If you weld them in you cant reuse them after the wreck...MM

 

[GTIspirit]

Those are not round. Point the longer sides to the tire contact patch.

Yes, the stock bushings are not round and have some voids in them that must be oriented in a specific direction. The nub must point outwards.

Here is a picture of the Audi TT bushings I was using, since an Audi TT is a Golf after all.

These are round and so will limit the compliance of the stock bushings that is designed to cause understeer that is desirable in production vehicles.

Bushings are cheap enough that I wouldn't worry about trying to re-use them after a crash bends the front control arm.

Maybe I should first stake the bushing in place before tack welding it to the control arm?

 

[Flyinglizard]

The OD of the bushing is not round. Close to round, but not round. Turn the one that fell out, 90* in the arm, scuff with some sand paper very lightly, coat with red stuff, press it back in. Stake after, if you want to. I do.
The TT/R32 bush is the only one that I use and sell now.
The hole is bigger, leave out the sleeve, pry the control arm foreward, tighten. You can gain a little bit of castor here. HTH, MM

 

[GTIspirit]

I fixed up the A-arm and control arm bushing and made a few notes.

1. The Audi TT control arm bushing is round, as best as I can tell. It measured 59.40mm in two directions which were 90deg to each other.

2. Control arm bushing hole measured 59.30mm in the middle, slightly more where the bushing is started to press in, slightly less where the bushing comes to rest.

3. I think the source of the problem is basically the design of the new/replacement A-arm.

What you can't exactly tell from the picture is that the mounting hole for the rear bushing is stamped/extruded from one side. In this case, looking at the picture, the press would come from the underside and push the material up. So the bottom of the mounting hole is a rounded edge and slightly larger diameter. The top of the mounting hole is squared off and tilted in slightly.

Because these replacement A-arms are asymetrical the right side one has the squared off/smaller edge pointing up so the A-arm couldn't slip down. On the left side it's the other way around. So maybe on that side I didn't have the new bushing quite pressed all the way in to really grab hold.

So I think it's all fixed up now with some red loctite and some tack welds, belt and suspenders approach. It was pretty tough to tack weld that joint so I am looking for a better long term solution, maybe sphericals.

The original A-arm has a little bit different design. This rear bushing mounting point is a round tube cut and squared off at both ends. Passes through the A-arm and is welded on both sides of the two metal sheets that form the A-arm. So the diameter is a lot more constant and the same from both directions, top or bottom.

I think the old design is better and I'll be cleaning these up and getting new bushings ready to go, maybe see if I can make my own sphericals because the Shine and Bildon ones are way expensive considering the cost of the materials that go into them.

 

[Flyinglizard]

I measure a bunch today. Your right, the solid bushings are almost round. I have three sources, all are a different size.
"FEQ" brand is the roundest and largest@ 2.372- 2.377
Meyle is the smallest,2.364, 2.368
VW in the middle. round +- 008thou, 2.374- 2.378
The size range is about 012. I will post the actual sizes wed. I thought I had my notebook tonight but left it@ work.
I think that you have what is called a tolerance stack. IE the bushing is small and the hole is big. Still inside the size allotment, but both at the ends of tolerance. HTH. MM
I have not had any failures with any of the solid bushes. They are my new standard racing bushes. Better than poly, solid enough to match the solid metal ball setup,but the cost is way better.