Rusty911
A2OC Donor
Well, I said this was going to be a good one, and I'm not completely disappointed. Now, I have to say I've not driven it yet, so this might not be 'the' problem, but it most certainly 'a' problem.
Forgive some missing pictures, I'll do my best to explain.
The leading wishbone bushes have an internal metal element. This has an internal diameter of 15mm. A bolt passes through this with a nominal diameter of 12mm. I say nominal, the thread is 12mm, but the shank is smaller, the thread having been rolled on (I guess) rather than cut.
As you can see, achieving any sort of alignment between a 12mm(ish) bolt and a 15mm hole isn't going to work. To overcome this, washers with a sintered spigot temporarily align the bush until the bolt can be tightened and the bush clamped into place between the pressed steel sub-frame and the cast aluminium console. (Bolt is from my scrap bin and not an A2 item btw).
From what I can see, this clamping is what the design relies on for all working strength and alignment. Imagine what would happen if you couldn't pull the bush up tight, say, if there was a gap.
Like this:
To the left is the black cast wishbone, then the end of the rubber (outer) portion of the bush, then that sintered, spigot washer. To the right is the area of the console that takes the bolt's thread. And in the middle ... well there's a great big gap. When the bolt was tight, this was pretty much invisible, but I had noticed it was possible to rotate the washer a fraction before. At that point though I hadn't received my new bushes so hadn't understood the design.
The net result is that the bush has clearly been able to move due to the complete lack of clamping force. This meant those lightweight alignment spigots in the washers had (for a while) taken the entire load of the bush until the front one had worn away, the arm moved forward a bit and started to move everywhere. As the forces are mainly in and out, when I levered the bush around I didn't see much movement as was levering up and down as that was the only place I could get a bar into. That explains why all seemed pretty much O.K. despite this issue.
I think there's actually a misalignment between steel subframe and aluminium console. I did attempt to undo all the bolts, but stopped early on as couldn't really see anything would move to that extent, the bolts were bonkers tight and I'd already established that externally (wheel in arch etc) everything looked O.K.
I elected to take a two pronged approach. The first was to turn up a 15mm OD, 12mm ID steel sleeve to go up inside the bush, just to provide initial alignment and an insurance should the bush try to move again in the future. It's not a tight fit due to the thread formation of the bolt, but it reduces a total potential play from 3mm to 1mm max.
The other was rather than trying to shift the whole subframe / console relationship, I simply turned up a 3.5mm aluminium spacer and slid it into the 'hole'.
Immediately I could feel the bolt clamping the bush as soon as any torque went on it.
The whole area just feels absolutely rock solid. The bushes themselves (front / rear on both sides) look and feel perfect so I'll keep the set I bought back for PYXi the FSi project.
As I say, not driven it yet, but am pretty confident that at the very least, it won't have done any harm. Out of interest, I put the tracking gauges on just as I was leaving the workshop: gone from parallel to 30' toe in, so something's moved!
Will track it up tomorrow (I think I'll start with deal parallel) and run it up the road.
Looked at the rear beam bushes last night, they are complete toast, so ended up cancelling today's MOT and have some poly ones ordered. I would have preferred O.E. style ones, but they are the 69mm versions which seem impossible to find (including genuine): everyone does 72mm.
Forgive some missing pictures, I'll do my best to explain.
The leading wishbone bushes have an internal metal element. This has an internal diameter of 15mm. A bolt passes through this with a nominal diameter of 12mm. I say nominal, the thread is 12mm, but the shank is smaller, the thread having been rolled on (I guess) rather than cut.
As you can see, achieving any sort of alignment between a 12mm(ish) bolt and a 15mm hole isn't going to work. To overcome this, washers with a sintered spigot temporarily align the bush until the bolt can be tightened and the bush clamped into place between the pressed steel sub-frame and the cast aluminium console. (Bolt is from my scrap bin and not an A2 item btw).
From what I can see, this clamping is what the design relies on for all working strength and alignment. Imagine what would happen if you couldn't pull the bush up tight, say, if there was a gap.
Like this:
To the left is the black cast wishbone, then the end of the rubber (outer) portion of the bush, then that sintered, spigot washer. To the right is the area of the console that takes the bolt's thread. And in the middle ... well there's a great big gap. When the bolt was tight, this was pretty much invisible, but I had noticed it was possible to rotate the washer a fraction before. At that point though I hadn't received my new bushes so hadn't understood the design.
The net result is that the bush has clearly been able to move due to the complete lack of clamping force. This meant those lightweight alignment spigots in the washers had (for a while) taken the entire load of the bush until the front one had worn away, the arm moved forward a bit and started to move everywhere. As the forces are mainly in and out, when I levered the bush around I didn't see much movement as was levering up and down as that was the only place I could get a bar into. That explains why all seemed pretty much O.K. despite this issue.
I think there's actually a misalignment between steel subframe and aluminium console. I did attempt to undo all the bolts, but stopped early on as couldn't really see anything would move to that extent, the bolts were bonkers tight and I'd already established that externally (wheel in arch etc) everything looked O.K.
I elected to take a two pronged approach. The first was to turn up a 15mm OD, 12mm ID steel sleeve to go up inside the bush, just to provide initial alignment and an insurance should the bush try to move again in the future. It's not a tight fit due to the thread formation of the bolt, but it reduces a total potential play from 3mm to 1mm max.
The other was rather than trying to shift the whole subframe / console relationship, I simply turned up a 3.5mm aluminium spacer and slid it into the 'hole'.
Immediately I could feel the bolt clamping the bush as soon as any torque went on it.
The whole area just feels absolutely rock solid. The bushes themselves (front / rear on both sides) look and feel perfect so I'll keep the set I bought back for PYXi the FSi project.
As I say, not driven it yet, but am pretty confident that at the very least, it won't have done any harm. Out of interest, I put the tracking gauges on just as I was leaving the workshop: gone from parallel to 30' toe in, so something's moved!
Will track it up tomorrow (I think I'll start with deal parallel) and run it up the road.
Looked at the rear beam bushes last night, they are complete toast, so ended up cancelling today's MOT and have some poly ones ordered. I would have preferred O.E. style ones, but they are the 69mm versions which seem impossible to find (including genuine): everyone does 72mm.