On 04/06/2021 21:01, Murmansk wrote:
I have a Witter bike rack that attaches to the towbar.

You put it on and at first its all loose and of course will lift off, then you tighten a big bolt which at first is really easy as it goes round for quite a few turns without much resistance, then as it grips the towball you give it a couple of really firm turns with the spanner to make it fully grip the ball.

Removing the rack is the reverse of the above where you apply big force for a couple of turns to loosen it, then lots of relatively easy turns to make it loose enough to actually come off the towball.

The problem is that once Ive loosened it enough to make the rack sag but not actually come off, the bolt starts to feel really tight again €“ almost as tight as it normally does at the last stage of attaching it €“ so much so that I feel as though I need to apply so much force as to damage the thing.

Im now left with the bike rack attached and sagging but cant remove it and Im wondering if anyone has any experience of this?

Could be damaged threads or contamination. A grain of sand or small grit
can do this. Would it be possible to get some light oil into it? Maybe
apply oil then tighten and untighten a few times to work it along the
thread. Then untighten as far as you can before the resistance starts,
then go just a bit further, then back off, then go again, try to go a
bit further still, and so on. I've had exactly the same problem with
other things and this has usually worked, but it needs patience.

Bill