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My Fixed/free 1-speed/2-speed/3-speed Mountain Bikes

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by Sheldon Brown
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If you like strange bikes, you would like my Fixed/free 1-speed/2-speed/3-speed mountain bikes. They have a truly weird drive train!

These bikes are equipped with "flip-flop" (reversible) hubs, which are threaded for a freewheel on one side, and a fixed sprocket on the other.

This, in itself is not that unusual; many fixed-gear fans keep a slightly larger single-speed freewheel on the opposite side. This provides a freewheeling gear slightly lower than their fixed gear. If they find themselves getting overtired, or if they just want to go on a longer ride than they feel comfortable with on the fixed, this gives them a gear that is a bit easier to climb with, and that also allows them to coast down hills.

Hercules

My Hercules has a 165 mm Shimano 105 crankset, with 52/42 Biopace chainrings. It has a 52/18 fixed gear, which is what I use most of the time. If I flip the rear wheel around, I have a 52/20 freewheel gear, good for longer or hillier road rides.

Spoke Divider

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The most unusual feature of this bike, however is that it has a 2-speed freewheel, with a 30 tooth sprocket as well as the 20. The crankset has a 42 as well as the 52, and I can change gears manually, much as the speeds are changed on a drill press. The 42/30 gear is the off-road combination, and makes a pretty good general purpose gear for the local singletrack.

FrontRearGain
Ratio
InchesMeters
Fixed52185.46756.01
Freewheel52204.92685.41
Freewheel42302.14362.91

This system is very light, very efficient mechanically, and very reliable. I highly recommend it to fixed-gear fans who may have an older mtb frame gathering dust. Ideally, you need a bike with horizontal dropouts, so you can adjust the chain tension when you change from one combination to another. Some bikes that have semi-vertical dropouts can be used, but you may have to have the same road gear on both sides.

The freewheel is an old discarded Sun Tour "Perfect" 5 speed unit, with 3 of the sprockets removed and replaced with spare spacers.

image

My first experiments along this line were on a 50 or 60 year old Hercules three-speed frame. It had been crudely re-painted by the previous owner, so I covered the frame (and Zéfal pump) with wood-grain contact paper. It looks like a wooden bike, makes a great conversation piece...

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Hercules front brake

This bike has been through a lot of changes. Before I converted to the drive-train described above, the Hercules was my first derailer-geared off-road bike. In the late 1970s I adapted it into an early mountain bike. It started out as a 12 speed, then an 18 speed after I bought my first triple crankset, then a 21 speed. The 21-speed configuration featured a 52/47/34 triple, with a 7-speed 12-38 freewheel (that freewheel was a whole story in itself...)

Since the frame was originally made for 590 mm (26 x 1 3/8) wheels, I had to do some violence to it to fit fat 559 mm (26 x 1.95) knobbies.

At that time, I didn't have the facilities to install cantilever brake bosses, so I made home-made "drop bolts" out of aluminum stock. (See: Home Made Drop Bolts for details on this.)

The frame has relaxed geometry, 68 degree angles and a long wheelbase. It is quite comfortable, and in some ways I prefer it to modern mountain bikes. It has a low (by mtb standards) bottom bracket, which means I have to pay attention to where my cranks are in tight off-road situations, but the low bb also makes it less scary to attempt to ride marginal sections, since I am low enough down to be able to get a foot down if I can't make it.

Bianchi Osprey

Hercules

The Hercules turned out to be so much fun to ride that I am searched for something a bit more up-to-date, eventually coming up with an early '90's Bianchi Osprey, which I have given a similar treatment to.

This bike has truly vertical dropouts, but I wanted to set it up with a flip-flop hub: fixed gear on one side, two-speed freewheel on the other. The vertical dropouts don't allow chain tension adjustment because the axle is a snug fit in the slot. I solved this by cutting the axle off short, so that it does not extend past the cone locknuts. Only the quick-release skewer goes through the dropouts. Since the skewer is thinner than the axle, this allows some front-to-back adjustment. So far, I've had no problems with this unorthodox rig, but I carry a spare skewer, just in case.

The Osprey has 42/34 chainwheels, a 14 tooth fixed sprocket and a 15/23 freewheel. I may add a third freewheel gear, since the cranks are set up for a triple...

FrontRearGain
Ratio
InchesMeters
Fixed42145.65756.01
Freewheel42155.28685.41
Freewheel34232.79362.91

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