Urban Velo

London Fixie Bike Cog


There is no doubt that from a pure engineering perspective, the traditional screw on fixed cog and reverse-thread lockring setup is not ideal in situations where there is back pressure applied. …Like a bicycle drivetrain. Bolt on cogs simply make sense, even if the traditional setup works well the vast majority of the time when installed correctly. London Fixie Bike out of the UK makes not only a very high quality cog, but spacers and custom rebuilt mountain hubs for street use.

The basic cog design comes from mountain biking, with an interface that matches the 6-bolt disc brake standard. Simple, and conveniently a mountain rear hub, flipped over with a cog such as above bolted on, provides a near perfect chainline. This provides a solid interface that simply can’t unscrew, and is better suited to the low gears (and high torque) of mountain biking. The bolts themselves are plenty strong, pro downhill racers have been known to ride with only three of the six bolts installed to save brake weight without any dire consequences, though I wouldn’t advise it. The London Fixie Bike cog is machined from a solid piece of chro-moly and then heat-treated before getting a shiny hand polish, yielding a fine piece of bicycle componentry. By the specs, these should last quite some time without showing much wear. Due to the interface, the minimum number of teeth is 16, available in one-tooth increments up to 19.

gal3.jpg London Fixie Bike has some other bases covered too, like 1 and 2mm thick aluminum 6-bolt spacers to tune in chainline, and extra long chro-moly bolts to tie it together. About those converted hubs mentioned earlier, and pictured at left – it’s a Shimano XT front mountain disc hub with a solid axle swapped in, respaced for 110-120mm track bike rear ends for street use and a 41mm chainline before spacers. ‘Cross or mountain bikes could just use a mountain rear disc hub, no need for the custom spacers and handiwork. Check their site for instructions on how to respace your own hub.

For a true test, this cog needs a few offroad miles logged. While at one point I was logging some fixed trail miles, I pretty well retired after Team Mondo Guano a few years back. I’ll occasionally dip into the woods fixed, but not anywhere near as much as Mondo teammate Joe Whitehair of Single Speed Outlaw. So the cog is off, with updates to come as miles are logged.


  1. Chip HaynesApril 10, 2008 at 6:19 am

    Yeah, that makes sense and all, but I’ve never had a problem with my track hub set up. So what’s wrong with the standard screw on cog with reverse threaded lock ring?

    Come to think of it, I’ve logged my fair share of fixie miles with a standard hub and bottom bracket lock ring, no problems.

    Still, cool set up.

  2. Dan GoldbergApril 10, 2008 at 8:43 am

    Search any forum for people reporting that they’ve stripped a hub, and you’ll see the need. I don’t think that there’s a problem with a properly installed, high quality hub, threaded cog and lockring, but plenty of people manage to use either crappy parts or put them together wrong and wreck their wheels. A lot of people could use something foolproof.

    I wouldn’t mind such a setup just for my peace of mind (being able to swap out a cog with a hex wrench sounds pretty stellar too)… now, to wait for the US dollar to be actually worth something again

  3. Chip HaynesApril 10, 2008 at 10:12 am

    I’m running a vintage (35-year old) Campy track hub on my road fixie, and no problem-o. Of course, I’m no great gear gorilla, either. I’ve run the “suicide set up” using a standard freewheel hub, track cog and a British bottom bracke lock ring, and that’s always worked well for me, too- with a liberal application of JB Weld as a thread lock. Maybe I’m just too soft on the pedals.

    I’ve got the chain whip and tools to swap out cogs on a regular track hub, but yes, I can see the advantage of using an allen wrench instead.

    Here’s hoping this one catches on!

  4. sumadisApril 10, 2008 at 1:10 pm

    fuggly. and we all know how important looks are to both speed and safety.

    oh, and did anyone say been there, done that, LEVEL? http://www.levelcomponents.com/

  5. riderxApril 10, 2008 at 1:46 pm

    The Level is similar but different. The Level is cool and it’s a great idea (I’ve put many, many miles on one, full review here: http://tinyurl.com/6zpjgc) but it’s a proprietary hub and cog interface where the LondonFixie cog let’s you slap a cog on an existing disc hub setup. Since I don’t swap cogs out until they are worn out, a bolt on cog makes this much easier since the damn cog has been wrenched on there for so long. Even with anti-sieze and a quality chain whip it’s usually no easy chore to remove.

    Is bolt on better? That’s for you to decide. It’s just another option that might fit with what you have on hand, just like the suicide hub. I’ve currently got bolt on setups, Level, standard track hub and a suicide hub all successfully working in my quiver.

  6. tim zApril 10, 2008 at 4:40 pm

    i doubt this is the future of fixie cogs. if it’s already fixed, why add shit to the mix?

  7. Chip HaynesApril 11, 2008 at 6:42 am

    Because, like everything else out there, there are always people that have to have The Latest Thing.

    (I’m not one of them.)

  8. icon o'classtApril 11, 2008 at 11:28 am

    That’s all fine and good for the YooKayers, but here in the states, we got TomiCOG:


  9. FRYEApril 28, 2008 at 10:55 am

    why are they using hexagonal allen key compatible bolts, when the disc brakes use torx bolts that are multi sided, torque down better and are less prone to being stripped out by a novice?

    and what about the Miche track cog carrier system??


  10. LeonMay 11, 2008 at 12:09 am

    I have never had a problem with the ‘traditional’ screw on rear cog……but one little advantage of a bolt cog apart from stripped threads etc is ease of keeping the rear area clean. I never got round to it….too much of a fuss…i don’t have a chain whip etc etc…so when i got LBS to remove cog….total mess….as i said many may see that as minor…but?……just a thought.

  11. PistolpeteJuly 14, 2008 at 12:37 pm

    The real advantage is removeability after long miles in poor environments.Those fine threads on a standard setup,even with anti-gall goo,are a bee-atch to replace.Now if you are going to use it offroad a 19 is still too small.On my high country work 29er I’m currently running a Dingle 17/21 with a double chainring setup 34/38,and at the end of the day of patrol work it’s STILL too tall.Now,If I could stack up a 17 with a 22 that would be great.As for trying to make it fool-proof,don’t even think like that.As soon as you try they come up with a better fool…

  12. joseNovember 21, 2010 at 6:13 pm

    I am interested in a pinion of 6 agugeros to put it on mountain bike hub

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