Just wondering about fitting a BB-mount chain-device type thing (the sort that replaces a spacer) to a bike which presently has square-taper cranks on it.

Need to check the measurements, but say it has 68mm shell. Is there any reason not to fit a BB with 73mm shell, a 2.5mm BB spacer on the non-drive side, and a BB-mount chain device on the drive-side?

it’ll push the chainline out by 2.5mm.

that’s the point of putting the spacer on the non-drive side too and using the 5mm longer shell.

I fitted a std 73mm BB to my Soul with a BB mounted chain guide.

I did look for a BB with a fairly decent cup insertion just to be sure though.

No issues with running it though.

I found it mad no noticeable difference to shifting.

Grated it mush have been “out” by 2.5mm ish but I didn’t have any problems.

letmetalktomark – perfect. Thanks.

Just have to hope I can fit a longer shell to my old Cindercone…

Just have to hope I can fit a longer shell to my old Cindercone…

eh?

I meant deeper cups on the BB.

Think I went with an UN91

that’s the point of putting the spacer on the non-drive side too and using the 5mm longer shell.

sorry, I thought the point was to fit the BB mounted guide – the chainline change is a side effect of that which you hadn’t acknowledged in your post so I thought I’d mention it as a response to ‘Is there any reason not to’.

wwaswas – no it wont as he is theoretically spacing everything to keep the axle central, so chainline will be unaffected.

The non-drive side cup doesn’t butt-up against the frame, it butts up against the bb shell, so you don’t need to bother with a spacer on the nds – the cup will just thread further into the frame.

wwaswas, I see…

I’ve got hold of a WI double freewheel, so thought something like a Yess ETR-B would work to allow my to manually switch gears.

cp – good point. So I might just need a longer axle, to compensate for changing the q-factor.