steve-in-kville 

I am gathering all I need to set up the ol' Kilo as full-time fixed. I want to have a cog on both sides of my hub, as I know many here that do distance events roll that way. I am currently running a 46T ring up front, which I plan to keep. I've been using a 18T cog which brings me to 68.3". This is about right right for me considering the terrain I commute on, plus my current fitness level. It can get a bit "spinny" if I have a tail wind on the flats, but that is super rare.

So, moving forward... if I were to gear down a bit for my other cog, how low is practical? I don't have the longest drop out in the world to be sliding the rear wheel all over the place, but even dropping to a 19T cog would cut me to 64.6". Is this a noticeable change? Should I go even lower to a 20T?

I would love to hear from those that run a double-fixed hub. Thanks.

fietsbob

Riv Bike; Quick Beam gearing had a double chainring so when you flipped the rear wheel over ,
bigger rear cog & smaller chain ring and smaller cog bigger chain ring had about the same total tooth count
so required chain length was about the same ..


you decide what gear is right for you, I use internal geared hubs that freewheel, myself.

Bandera

You will be limited by both chain length and the length of your track ends as to how many teeth difference you can run.
Consider what your requirements are first and that your hub is most likely not set-up track style w/ a lockring on both sides for FG so the "flip" side will be FW.
If it is track style on both, good to go FG/FG. Cogs are inexpensive as such things go, get a 19T and a 20T and experiment on the types of terrain you will encounter.

-Bandera

steve-in-kville 

The wheels I am getting are FG/FG both sides (from Retro). So I'm okay there. And you're right.... cogs are like $20 at the most.

79pmooney

I took the Riv Bike a step further. I wanted to convert an old road bike with standard horizontal Campy road dropouts to ba able to ride serious, long paved mountain climbs as well as having my preferred flat ground gear and a good dwnhill gear. So I set the bike up with three chainrings and a flip-flop (both fix gtear) hub and a Surley style "dingle" screwed on one side. Cranked a touch of dish into the wheel. Now I had near perfect chainlines for (say) a 44-17 and 38-21 on the dingle and flipping the wheel, 46-13.

This is a really cool setup. The gear changes are easy and fast. Bike works very well in all three combinations. But (there's always a but"), this wasn't either cheap or easy. The dingle was custom fabricated as were the chainring bolts and I needed a Phil Wood bottom bracket to dial in the chainline.

You can do a simpler version like what fietsbob describes. Move a spacer from one side of the axle to the other to create dish. Now you can have each cog lined up with its respective chainring. For gears, any combo that add up to roughly the same number of teeth will work. (Going from a 46-18 to a 42-22 won't move the hub location on the dropout at all.)

Ben

ThermionicScott 

If it were my bike, and the 68.3" felt a little "spinny" at times... I would bump it up to a 46/17 and put a 20T on the other side. That's only a 3/8" difference in axle position, should be doable.

steve-in-kville 

That's exactly the info I was after. My fitness suffered a bit over the fall & winter due to some broken ribs. I gained some weight but I think dropping a tooth in the back isn't gonna be a deal breaker.

Jmclay

I had mine set up with a 45 x 20/18. I never tried to get a 3t difference in the rear but from looking at it at the time I don't think I've succeeded, and my axle slots are fairly long. Pic, for reference, here:
https://www.flickr.com/photos/216244...7629417200546/

I don't know if half links are available for 3/32" chains but they are for 1/8", which is what I now use (ring & cogs too). If the slot throw is adequate, but not positioned fore/aft such that the axle stays in the slot with the chain length necessary and the cog difference you're using, then a half link might line it up such that it does.

steve-in-kville 

I have another wheelset on the way and I ordered another 18T for now. I will re-approach this further down the road to see what my needs are. My fitness level can certainly be a lot better, too!

ThermionicScott 

That's a sweet bike, @Jmclay. Fixed-gear and fat tires make such a nice combination. Did you make the cable stop yourself?

Jmclay

Thank you! I was back from a few months away for work and needed to make something so I built a simple frame.

FG + Fat Tires = Wonderful. I've ridden that bike everywhere; pavement, crushed rock roads, dirt roads, single track, turf. Only deep sand and mud are a problem. You obviously already know this but tires (from merely "very good" like the CdlV to "best") in the 30 to 40ish mm range really are superbe. Riding, handling, comfort and general bicycle capabilities are much better. And they look better to me now! At this point even a 32 looks borderline emaciated to me.

The cable stop, the one on the fixed? No, that's just something from a parts box. Here is how I do it now, and I need to get off my duff and do it on the fixed stem: https://www.flickr.com/photos/216244...7690862863394/