Kappstein 2-speed bottom bracket

It's not cheap, but not ridiculous price either. Certainly looks interesting. Hopefully the price drops a bit and they offer shorter crank lengths soon

Am I reading it right that it is the wrong way round for what I want for MTB which is direct drive for the majority of singlespeed-esq riding, then a geared down granny gear so I can get up crazy steep stuff? I.e. it is like a Schlumpf high speed drive rather than MTN drive.

Hopefully the price drops a bit and they offer shorter crank lengths soon

Just look like square taper cranks, no? Stick any ones you want on it?

DrP

I’m reading that to mean the lower ratio would be direct, and the high ratio would be 1.57 times higher.
Interesting system though, especially since it can be retrofitted into a standard bsa bb.

the hammerschmidt is reborn! I would steer well clear of anything with a square taper bb - there's a reason they were abandoned in the early naughties for all mountain biking. Fine on a town bike though

I’m reading that to mean the lower ratio would be direct, and the high ratio would be 1.57 times higher.
Interesting system though, especially since it can be retrofitted into a standard bsa bb.

yes, from a bit further down it seems to imply that the higher gear is the geared option and the lower gear the direct drive.

Single-speed - Doppio
It is also possible to use the Doppio as a single-speed version. This option uses only the heavier gear with a ratio of 1.57. With a mounted 32t chainring this corresponds to a number of about 50 teeth. The switching device, shift cables and shifter are not necessary in this case and are eliminated.

ST BBs are fine, longevity is unmatched.

I would steer well clear of anything with a square taper bb – there’s a reason they were abandoned in the early naughties for all mountain biking. Fine on a town bike though

Actual reasons or marketing reasons?

I always thought they were a casualty of the bike industry's 00s obsession with 'laterally stiff but vertically compliant'.

Actual reasons or marketing reasons?

Alloy crank squeezed onto a steel bb, not the best engineering solution. I managed to warp more than one crank at the interface, and that was waaay back when I was a 60kg whippet riding tame trails

Actual reasons or marketing reasons?

I'm not a habitual destroyer of kit and I was tootling around the bucolic Chilterns when square taper were all you could buy and even I broke them (snapped axles). they came loose with boring regularity. awful bearing life (even worse than now) the removal tool was a PITA, and you had you play a game of "guess the axle width" or it's alternative "hunt the axle width" in your LBS or on line. HT2 was a game changer. Although; developed and marketed by Big Axle obviously, so you can hate it irrationally as is your idiom if you want.

Although; developed and marketed by Big Axle obviously, so you can hate it irrationally as is your idiom if you want.

Ooh, you found a new marketing brochure.

Your knowledge of engineering has once again multiplied.

Alloy crank squeezed onto a steel bb, not the best engineering solution. I managed to warp more than one crank at the interface, and that was waaay back when I was a 60kg whippet riding tame trails

I've generally found cheap kit is crap regardless of the design (with some notable exceptions).

I've had external BB cranks that have been bombproof and others that have been made of cheese.  Same with square taper cranks.

The actual square taper BBs themselves have always been fine but I've never looked much beyond UN52s.

Nice but rather a classified hub.

They make some great chainrings. but in this case it's cable-operated and overdrive not lower drive. The Schlumpf was neither of those things. Could be interesting in a fixed wheel bike, but I always want lower infrequently, and don't want a cable. Not bothered about square taper. In fact UN52 solved that problem and I've never had an issue with them.

Yea, I'd much rather have something with a lower-drive than overdrive. That's the main reason I'm unlikley to buy one of these -- although I'm not particularly keen on square taper either.

I also thought lower-drive was generally more efficient? But I'm basing that on anecdote only -- Rohloff uses a lower drive to get the lower 7 gears; Schlumpf Mountain Drive are apparently more efficient than their Speed Drive; Hammerschmidt was apparently horribly draggy and was also overdrive.

The cable shifter isn't terrible though, surely. That'd certainly be better than the Schlumpf button for proper mtb riding.

A Classified hub would be better still, but they'd have to more than half the price to get close to this.

Is stepping down vs stepping up inherently more or less efficient?

I guess it comes to what you need it for.
do you want a tall geared single speed with the occasional use of a low climb gear.
or do you want a climbing gear with the occasional overdrive for fast sections.
I guess it depends on the anticipated trails.

personally I think I’d rather lose efficiency in the high gear. I’d be using it for road sections where I’m not really trying anyway; and for short bursts of power on trails, where I’d not be too concerned by small efficiency loss.
pedalling uphill on the other hand takes up about 2/3 of a ride, even in flattish/rolling terrain.

Yeah, square taper cranks were a pain.
Agree with Nickc.
There’d either creak, come loose for no good reason or be on forever. Essentially meaning If you needed to replace the BB, you’d need to budget for new cranks as sometimes the puller carefully pulled the threads out and the crank stayed put.

As a concept, I’d like it on a singlespeed but I don’t think I could face square taper again.