2 speed BB

1 in RBR classifieds (cyclecross)

I just saw one in the classifieds at RBR.

http://marketplace.consumerreview.c...sults_format=long&db_id=45624&query=retrieval

Seems pretty cool

here is a link to Sheldon Brown disscussion of them.

http://sheldonbrown.com/harris/schlumpf.html

Would be cool to go super over kill and mate this with a Rohlf speed hub.

I've had a speed-drive for a few years now, originally bought it to convert a SS into a 2-speed. I wanted a ~2:1 ratio or general riding, and a lower gear for climbs, skinnies, stunts, technical sections, etc... Schumpf make them in either a 2.5:1 step-up or step down, or a 1.65:1 step-up. Ideally I would have liked to get a 2:1 step-down gear.

The unit is nicely made, heavy but sturdy. The smallest regular chainring is 34t, but you can get a special 27t.

I ran it on my trail bike (converted SS!) for a few years, and it worked fine. However, there is some play in the clutch which is built-in to allow it to shift properly, and it makes ratchetting more difficult - alot of play before the wheel engages. Shifting is easier with the old non-low profile strait arm cranks, it's harder to hit the button with your heel on low profile crankes. Strait crank arms are only available in 170, unless you can score some old RF Turbine strait crank arms with the removable spider. Sometimes you accidentally push the button when you are manuvering the bike in technical sections. Depending on the unit, you have to modify the BB (45 deg chamfer) so that it can transfer torque to the frame. You hit your ankle on the crankarms alot more with non-low profile cranks. There's a slight but definite energy loss feel when you are in the step-up gear.

Schumpf said NO to fixie use with my unit. I think the play in the clutch would be a pain.

In the end, I moved the cranks over the the road bike, and returned the trail bike to SS. It works and feels much more natural on the road than on trails.

PS: Rohloff does not need this, the gear range is wide enough - unless you are on a recumbent...

Cheers,

Tom

Yeah I run the Sclumph bracket drives. I run a mtn. drive in conjunction with a 7spd (sorry for the sacriledge) on one bike pictured here,



and have a speed drive on another bike with a 9spd. I didn't like them as a 2 spd, but a few others here have them and like them just fine.

They have proven to be pretty bombproof. There are a few special tools needed to get them setup and apart also. I will probably keep using them for my needs for some time to come.

I built the bike in that ad and sold it last year....Fixed gear use is not an option according to Florian, also use at temperatures below 0 degrees F can be a problem.

Cloxxki, I ran my 2-speed as a trail bike, 34:26, so I had a 2.16:1 high gear and a 1.3:1 low. Because you have 2 gears, you should 'bracket' what you are using now, since the SS gear is a comprimise between spinning out on flats and stalling on hills. Most smooth trails could be run with the higher gear, and when the slope got too steep (or long) then I'd drop into the lower gears. The low gear was good for the rock gardens too. I thought a 1.65:1 step in gears was pretty good for trails, but I would have prefered the high gear to be direct drive, as there is a small but noticable loss though the gear train. IMHO - my uninstrumented experience, my Rohloff hub gears "feels" more efficient than the speeddrive.

45°-milling cutter: not a big issue in reality, standard BB's can still be used after you have chamfered the BB shell, and most BB shells on aluminium bikes have a small chamfer already. The chamfer just needs to be big enough for the torque transfer ring to bite into.

Cranks: takes standard square taper cranks, but you need to find a spiderless driveside. However, you can use 2 left cranckarms, and swap the axle in the right pedal. However, the BB is designed for non-low-profile crankarms, which are not the easiest to get. Low-profile arms will work, but the pedal stance gets pretty wide. I found some old 175mm RaceFace Tubines (pre-LP versions) with a removable spider in an lbs junk bin that worked fine.

3-speed hubs: I've tried several 3-speed hubs (Shimano/Sachs/SRAM), most didnot hold up to mtb'ing. I currently still have a SRAM Dual-Drive 3-speed disc hub that is working, but Bob (RedHaze) broke his last year, and I'm expecting to do the same eventually. The Speed Drive appears to be mtb-able. The Rohloff is the only one that is really designed for mtb-ing.

Dotek (Taiwanese) was advertising a 2-speed crank, and I was trying to get one in to try out (much cheeper than Schumpf) but it never made it into this country (Canada). Probably a good thing, I would have broken those too...

Cheers,

Tom