Cycling UK Forum

Currently I've got a bike set up with the above hub. To enable luggage carrying and use on Peak District hills the range is set up at roughly 36-48-64, but I've recently come across the efneo crank product which could potentially increase the range significantly.
I'd be looking to set up with a low gear of about 25" and can't see anything in the pdf from Sturmey Archer about a recommended lower limit on the crank / sprocket ratio, but gather they formerly stated no lower than 2:1. So, if it's not advisable I'll knock the idea on the head straight off. The frame is otherwise suitable and would be used as a tourer / commuter / moderate load lugger.
Any views from the mechanically inclined would be appreciated.

I think the hub is strong enough to withstand a much lower gear ratio than that. Obviously it will benefit from improved lubrication in hard use.

However.... the consequences of a problem will almost certainly be worse, if you have one; under high torque conditions a slippage of any kind will be much more likely to break stuff. In an SRF 3 hub the low gear pawls will likely be the first things to fail; these parts can be bought for about £5, and the shrapnel arising won't get into the other parts of the workings (and cause collateral damage) if the repair is carried out promptly.

cheers

Thanks Brucey, helpful as ever.

Mmm, but how low would you dare to go? How low have you ever gone? I think I'm running only just over 2:1 which I suspect isn't anywhere near the limit.

it has been reported elsewhere that in high torque tests the chain broke in a (mostly similar internally) CS-RF3 hub before the internals gave up. I believe it too.

However this is presumably with both low gear pawls already engaged; if only one engages (as happens occasionally), there will usually be a small slippage and the hub will sort itself out. If such a slippage occurs under high load, it is likely that the pawls may break; they are not intended to withstand shock loads of this sort.

Seasoned users of IGHs often 'light pedal' for a few turns after any gear shift, to make sure that the gear is properly and fully engaged, before mashing on the pedals. It is not a bad policy.

cheers

Brucey wrote:it has been reported elsewhere that in high torque tests the chain broke in a (mostly similar internally) CS-RF3 hub before the internals gave up. I believe it too.

Brucey wrote:Seasoned users of IGHs often 'light pedal' for a few turns after any gear shift, to make sure that the gear is properly and fully engaged, before mashing on the pedals. It is not a bad policy.

I do it on all bikes, as I'm not a big fan of causing a huge clunk by slamming freewheel/freehub pawls into their slots on derailleur bikes either.