Brompton - Why Only 3 Speed Hub?

[UpWrong]

it is OK but sadly the hub itself is not very reliable, not very long lived and not very efficient (except in bottom gear).

Having said that, if you are going to have this hub, it might be the best place for it.

cheers

well that probably explains why they dont sell Bromptons with the hub, only a kit. so thats one I will pass on, shame as the price would have been right.

I fitted one and was rather impressed by it apart from the weight. It improved with use.

[Brucey]

https://forum.cyclinguk.org/viewtopic.php?f=5&t=109103

contains more talk of relative SA 8s inefficiency. IIRC Bob posted pictures of his colleague's worn out 8s hub(s) in another thread. I think the worst wear was in the rightmost gear stage (which is used in four out of five of the top gears). The pinion bushing design in that is pretty hopeless, and is bound to be both draggy and wear fast. There is not just one weak spot; I have seen these hubs break in several different places. Small parts are mostly not available, so the only repair is usually a replacement centre.

As a long-time sturmey user it pains me to say it, but the SA 8s hub is near the bottom of my list of good IGH choices.

cheers

[Gattonero]

Why do Brompton only use a 3 speed hub?

They do make a 6 speed version, but that uses a derailleur system on a 3 speed hub. I would have thought that a multi (8?) speed hub would be a better option. Am I missing something or is there a technical reason?

Because is simple, reliable, and covers the vast majority of the use the bike is intended for: a means of transport for A to B when portability is paramount. You are not going to race on it (even if you could do that ) nor do heavy touring or go over big mountains (again, nothing stops you from doing that!) but you can add the 2x derailleur gears and playing with chainrings and sprocket you can actually have a nice spread of gears while keeping the bike simple as it was meant to be

[UpWrong]

https://forum.cyclinguk.org/viewtopic.php?f=5&t=109103

contains more talk of relative SA 8s inefficiency. IIRC Bob posted pictures of his colleague's worn out 8s hub(s) in another thread. I think the worst wear was in the rightmost gear stage (which is used in four out of five of the top gears). The pinion bushing design in that is pretty hopeless, and is bound to be both draggy and wear fast. There is not just one weak spot; I have seen these hubs break in several different places. Small parts are mostly not available, so the only repair is usually a replacement centre.

As a long-time sturmey user it pains me to say it, but the SA 8s hub is near the bottom of my list of good IGH choices.

cheers

I got the impression than reliability improved when they introduced the wide ratio (W) version. Paper bicycle use it as their standard hub.

[Brucey]

I got the impression than reliability improved when they introduced the wide ratio (W) version....

they used revised pawls (that take the load when each gear stage drives in 1:1) and there may have been other changes too. But the revised pawls do not solve the underlying problem (being that they don't necessarily all engage at the same time), they still break, and anyway it is only one of several problem areas. Better, maybe; good enough, probably not.

...Paper bicycle use it as their standard hub.

I have no idea why; if their SA8 hubs are like those I have seen in comparable (large wheel, utility) applications, they will break quite quickly. The other effect of using this hub is that, for a bike of this type, it has a stupidly high top gear and a bottom gear that isn't really low enough. There is very limited scope for changing this, too.

cheers