Fixing bolt in place?

[aclivity]

Hello all

I have a Brompton for riding to and from work - now I have moved it is only 6 to 8 miles per day total.

I keep on having problems with one of my cranks; never had an issue on any other bike like this. The bolt comes out every time I use it, usually it will stay in for a week or so but I tested tightening it each day and it has come out by about 20 to 40 degrees per day.

What is the best bet for fixing bolt threads in place? In the past I would have used superglue - is this still ok for steel bolts? Alternatively I could try plumbers PTFE tape, not sure if that would work? Any suggestions worth trying?

[sunbeam alpine]

Loctite make quite a good thread lock glue - we use it a lot in agriculture.

[egomeister]

aclivity said:

Hello all

I have a Brompton for riding to and from work - now I have moved it is only 6 to 8 miles per day total.

I keep on having problems with one of my cranks; never had an issue on any other bike like this. The bolt comes out every time I use it, usually it will stay in for a week or so but I tested tightening it each day and it has come out by about 20 to 40 degrees per day.

What is the best bet for fixing bolt threads in place? In the past I would have used superglue - is this still ok for steel bolts? Alternatively I could try plumbers PTFE tape, not sure if that would work? Any suggestions worth trying?

Is it definitely being torqued up to the correct level?

Assuming it is, you could try a thread lock as suggested above, something like Loctite 243 perhaps: http://www.loctite.co.uk/loctite-4087.htm?nodeid=8...

[gazza285]

Has the crank been loose at any point? If the square taper is worn at all, then you need to replace the crank, as it is the movement of the crank on the axle that is the problem. Non drive side I presume?