Single speed freewheel thread compatibility

[SimonCelsa]

Hi,

I put together a single speed bike for the 15 year old daughter late last year using a 44 tooth stronglight chainring & 16 tooth shimano freewheel. The freewheel screwed onto the rear hub (King Kong 219R) without problem. I believe the shimano freewheel is a standard 1.37" x 24 TPI fit.

Recently while out on a ride she complained that it was too hard to pedal (slightly undulating) so I said I'd put a bigger freewheel on. After a bit of experimenting on another bike (geared) she reckoned a 19 tooth freewheel would be preferable. The Shimano freewheel seems to be only available in 16, 17 or 18 teeth flavours & thus I purchased a Sturmey Archer 19 tooth instead form Derek's cysles (E-Bay).

That arrived this morning so I thought I'd fit it quickly & try it out. However, it doesn't 'feel' quite the right thread when attempting to screw it on. It's a bit of a stiff fit with a little 'swarf' emanating from the hub after a couple of turns (then I stopped)- I'm pretty sure it was screwing on square. No damage done (yet) but does anyone know whether all these 'off the shelf' freewheels have the same thread....?? It would be nice to keep the daughter happy as she is at that age of angst when 'the dark side' beckons & the cycling may act as a conduit to normality.

Or does anyone know if Shimano do a 19 tooth single speed freewheel?

Thanks, Simon

[Brucey]

it could be that you have a duff freewheel there. Unfortunately they are made for pennies (literally) and problems are not uncommon. Most good quality single freewheels are made in smaller sizes for BMX racing, so larger ones are not common at all.

If you want to check the thread is OK without wrecking a hub, take an old BB cup (RH threaded as fitted to the left side) and fit that to the freewheel..

If it is tight, you can turn a BB cup into a kind of thread chaser by grinding some grooves across the threads using a cutting disc in an angle grinder.

Chasing these threads is difficult because the freewheel centre is usually made in very hard material. I wouldn't use a conventional BB tap on one, even though it is the right size; there is too much risk of damage.

cheers

[SimonCelsa]

Yes, you were right there Brucey, it seems the threads were a little duff & with a bit more force it went on OK.

Luckily it came off again fairly easily & now both Shimano & Sturmey freewheel turn up nice & easy. I must admit it does sound pretty cheap (not a nice regular clicking of pawls) compared with the Shimano one (which isn't really that much better).

thanks, Simon