This year my buggy got a fail on the mot. When they put it up on the ramps and did the vibrate test afterwards the upper offside trailing arm could be moved in and out of the end of the beam by a couple of inches.

Pushed back in and dropped onto its wheels couldn't move it. Had done quite a few miles with no steering or suspension issues noticeable.

Took it home and wouldn't budge when it was jacked up even using a crowbar.

Took the bolts that locate in the leaf springs out and the 2 top ones were worn into more of a point than the balk shape they're meant to be, bottom ones fine.

Changed all 4 and retested ok.

That's not something I would have ever thought of checking, they're the original bolts at least from build and have been in there 15+ years to my knowledge  so not an annual check but maybe every 5 or so years.

Anyone else seen this?

Does emphasise the benefits of an mot test

The same problem Dave had with his after market beam incorrect grub screw shape to torsion bar/rod location point. yours must have been slightly loose so moving and abrading the contact areas . You cannot apply the forces that the mot test plates do so it feels fine by hand.

Sort of knew you would have seen it before Keith

Duff parts again

I have not seen it before and thanks for sharing as its worth knowing these things and will add to my check list.

One problem I've found is that the lock nuts can rust onto the threads, people remove them with a spanner on the nut so the nut and grub screw come out as one but they replace them as one also again with just a spanner. Sometimes if the whole front end is stripped down screws can end up in different threads than they came out of.

This can leave the end of the grub screw not quite tight enough into the countersink.

As David say always free your nuts any tightness on threads can lead to an incorrectly secured item.

Mine were defined tightened screw first and held while nut tightened so I'm guessing poor quality bits

As Snoopy said, thats pretty much the problem I had from day one with my Arms not staying in place. The end of the grub screw was not the right shape to locate into what you would have as a torsion spring and the downside was that it moved under driving.

Never heard of a grub screw changing shape, but I guess if the torsion arms are being moved excessively up / down / in / out as a result of out potholed roads, then the weakest part is the shape of the end of that grub screw and it is being physically worn away.

As they are so easy to check, its something that we should all maybe check 

Good spot by the MOT tester

Good spot by the MOT tester

Not really, almost 2" of shiny greasy metal sticking out was fairly obvious