jfmckenna

I used to ride a borrowed Panasonic track bike many years ago. The bike was my roomates who was a messenger in NYC. What a beautiful ride. Never had breaks on it! and lite as a feather. Anyway after looking at all the pics and posts in this forum I am now setting my sites on building one. I saw a really cool one in town yesterday and here is what I think I saw? It looked like the rear wheel had two sprokets on it. one on each side of the hub. So is it possible that this guy has it set up so that he can 'change gears' by flipping the wheel around? Has anyone sceen this befor. I basically live in the mountains now but the town is sort of on a high plain. So for commuting a fixie would be great except for some of the bigger hills and I was wondering if this is what this guy has set this up for???

fixedgearhead

The hub in question you saw is called a fixed/ fixed Flip/Flop and it is used for the purpose that you imagined. Some people run a freewheel on the off side so that they can coast when they are tired from all that peddling. You, of course, would need to run brakes on the bike in that event. I have 2 bikes set up in such a manner fixed/fixed and aside from trying out the concept once I have never in fact used the off side because I couldn't get up any hills I was trying to. The concept is valid in the abstract, but I am not sure it is really necessary unless you are cycling over the Rocky Mountains or other such extended long uphill challenge.

fixedgearhead

...jeff

from sheldonbrown.com:

Flip-Flop Hubs
any fixed-gear bikes are equipped with "flip-flop" hubs, designed to accept sprockets on either side. These permit a choice of two different gears by removing the rear wheel and turning it around.

The most common use for a flip-flop hub is to have a fixed sprocket on one side, and a single-speed freewheel on the other side. Usually the freewheel will be 1 or 2 teeth larger than the fixed sprocket.

The idea is that, most of the time you would ride the fixed gear, but if you found your self far from home and getting tired, or were in unusually hilly terrain, you would turn the wheel around and use the freewheel. This helps two ways:

The lower gear will make it easier to climb the hills.
The freewheel will let you rest (coast) on the descents (which could be painful with the lower gear if it were fixed.)
Note that for each tooth difference, the axle position in the fork end will change by 1/8" (3 mm.)
Also, note that you should have two brakes if you will be using a freewheel.

You can also use two different sized fixed sprockets on a flip-flop hub. Generally I would recommend only one tooth difference in this case. I run 14 & 15 with a 42 front myself on a couple of my own bikes.

Most flip-flop hubs are only threaded for a lockring on one side, but the sprocket/freewheel thread is the same, so you can screw a fixed sprocket onto the freewheel side. I'd put the smaller sprocket on the side without the lock ring, because it's less likely to come unscrewed.

There are double-fixed flip-flop hubs, and, to me, this is the most desirable configuration. This arrangement is the most versatile, because you can set it up either with 1 or 2 fixed sprockets, or 1 or 2 freewheels.

Any standard track hub can also be used with a single-speed freewheel just by leaving the lockring off. The thread is the same. Sometimes people worry because the hub thread isn't as deep as a freewheel specific hub, but this is never a problem with a single-speed freewheel.