Folding Bikes - Have any of you opened up a Downtube suspension pivot?

I've had an email from a bike mechanic regarding an IXFS (not bought from me). It's about 2-3 years old, and the rear suspension pivot has developed a lot of play, causing chain derailment. I've never heard of such a thing, and neither has Yan, but I'd like to be helpful to him. Thing is, I don't know what's inside one of those? Is it a simple bushing, or does it have bearings? What can he expect to see when he opens it?

Sammy: Can't help you out, as it's not a procedure I've undertaken. But have you tried asking Yan?

I've taken mine apart, and I seem to recall that jur did his as well. Mine had developed some slop that couldn't be tightened out of it, and I had to figure out for myself how to fix it. I only did this once, so the fix must have been successful... but it was over a year, perhaps two years ago.

What exactly I did... as I recall... and whether I can describe it adequately... well, you be the judge:
The pivot bolt is two pieces of steel that screw together until they bottom out at, theoretically, exactly the right level of tightness. Once it is all the way tight, you cannot tighten it further; so if it isn't tight enough, you need to put a washer of some sort in there. But what? I wove a ring of thin (22 gauge?) insulated copper wire; that is, I took a piece, maybe 4 or 5 cm long, and formed it into a circle of the correct diameter --I'm guessing here, maybe about 12 mm diameter??--, pulling the end of the wire through the hole in the circle repeatedly until I had a fairly loosely woven circular 'washer.' I coated this with some lubricant --I think I used a wax bike chain lube-- and put this over the female end of the pivot bolt and reassembled the whole thing. When I tightened the two parts of the bolt until they bottomed out against one another the copper and plastic of the wire were thin enough and flexible enough to deform into a thin washer that took up the side-to-side slop between the two pieces of the frame.

I hope that makes some sense. Good luck!

See Mini linky in my sig - I understand all Downtubes use the same mech.

Chain derailment? Unlikely I would think.

If I'm understanding RHM's response correctly I carried out a similar fix when I noticed excessive flex of the swing arm under higher pedal loadings.

I cut rings (one for each side) that had the same radial dimensions as the platic bushings that sit inside the pivot point on the frame - same process as RHM but a different choice of materials.

It's a very simple (but effective) design. I find it a bit strange that a bike mechanic would have difficulty in understanding it, my full suspension Specialised MTB has a similar set up and their must be other variations out there?

R

See Mini linky in my sig - I understand all Downtubes use the same mech.

Chain derailment? Unlikely I would think.

I disagree, I think this problem does (or can) contribute to chain derailment. But it's probably not the only factor; the chain is probably worn as well. I've gone through a half dozen chains on my Mini, maybe more.