Can I somehow tighten a crankset with a shim?

[swee'pea99]

Having managed to get my crankset 'cap' off, I've removed, cleaned and refitted the crankset, which still now has a distinct 'non-straightness' to it in use (so that it brushes, then doesn't, then brushes the front shifter cage as it rotates). I think I've identified the culprit: play between the crankset and the crank - the square hole doesn't engage snugly with the square crank, so even with the retaining bolt tightened, there's still some play. I was wondering whether I might be able to bodge a tightening by cutting a shim from a Coke can or something. Anyone tried anything like this? Did it work?

 

[Profpointy]

i had similar symptoms and was astonished to find the (solid steel) axle had bent

If it is the taper a bit.of coke can shim has to be worth a try, but I'd not be too optimistic.

 

[simon.r]

I wonder if a few wraps of PTFE tape on the spindle might work?

 

[swee'pea99]

I wonder if a few wraps of PTFE tape on the spindle might work?

Interesting idea, but I'm very sceptical - the forces at that join must be tremendous...way more than PTFE tape would be able to resist, I'd have thought. (I'm even doubtful whether (alu) coke can material could.)

 

[MichaelW2]

Is the sq taper crank compatible with sq taper spindle?
Check if they are ISO or JIS

 

[subaqua]

Try it but for £40 a new crankset n bottom bracket may be in order

 

[swee'pea99]

Looking at it again, I think I might be looking at it the wrong way.I think I may need a new BB.

The one that's on there now has a washer added, for no obvious reason, until you take it off, at which point the inner chainring rubs against the frame. It's quite a fat washer. And I suspect the reason for the wobble might be that the washer prevents the chainset siding far enough onto the axle. The bottom line being, I need to get a new BB that's a few mms wider, so's to be able to discard the washer. Does that make sense? (Here's a few pics which might help that be clearer...):

 

[fossyant]

New BB

 

[Yellow Saddle]

I can't say from that picture whether you need a new BB or not, but a simply twist on the spindle should reveal a smooth turn or rough bearings. Only that will give you the answer. However, you have to find the source of the wobble. If it is indeed from the square taper and tightening it doesn't fix it, your crank is ruined. No amount of shimming will fix it.

 

[MichaelW2]

Consider a BB drainage hole.

 

[Smurfy]

A lick of paint wouldn't hurt either!

 

[swee'pea99]

New BB

Oh I dunno...squirt of WD-40, she'll be right mate...

 

[Gravity Aided]

View: https://www.youtube.com/watch?v=lar7mIMmTRE

This fellow seems to know something about rebuilding BBs.

 

[mrandmrspoves]

I wonder of your crank set is mixed with your BB......
There are 2 common standards for square tapers JIS and ISO - I can't remember which is smaller (Japanese I think) - I wonder if the big washer was put there to stop the crank sliding too far onto the slightly smaller spindle.
Doesn't help any except to be aware that not all square tapers are the same...