Running a small sprocket

[Beardy]

A question to the engineers here abouts regarding running a small sprocket full time.

My limited understanding of metal mangling and the like leads me believe that there could be stress and wear issues, though it could be so minor that I'm getting my knickers in a twist over nothing

To be specific, I've currently got a 16 cog sprocket on a rholoff hub and was wondering if going to a 13 cog sprocket would be an issue.

Ta

[tonycollinet]

There will be more wear and loss into the chain/sprocket interface - probably not significant. There will also be more torque applied to the hub.

Check the rholoff maximum allowed ratio between front and rear ring/sprocket combinations.

[rogerzilla]

13T is noticeably less efficient than a larger sprocket and also more likely to fracture.  Best avoided.

There isn't more torque; that is only determined by the wheel size (hubs on Bromptons have an easy life).  There is, however, more chain tension.

[tonycollinet]

Dammit

I was talking about max torque applied (eg stationary standing on pedals) but got it 180 wrong - there is of couse less static torque on the hub with the smaller sprocket.

[LittleWheelsandBig]

13t Rohloff cogs don't fracture. The larger Rohloff cogs are reversible, doubling service life but the 13t is not and is offset, requiring the chainring to be mounted further outboard.