Today I ordered a new bicycle through MASH SF. I bought a fixed gear track bike built up from the Cinelli MASH Histogram frame. I'm going to write about this bike once I've had it for a while, but for now I want to write about the bike that the Histogram will be semi-replacing.
About a year and a half ago I bought a bike from Mission Bicycle Company. If you're not familiar with them, they make their own steel frames with horizontal dropouts which means that their bikes are built as single-speed/fixed gear or with internally geared rear hubs (in contrast to how most road bikes are built with a rear derailleur). I already had a Surly Pacer and was looking to build something a bit cooler and more unique. Thus, I built up this bike in a pretty unusual way. I asked them to build it with an SRAM Automatix hub. This is an interally geared rear hub with a "centrifugal clutch", and is the only such hub on the market that I know of. The way this works is when the rear wheel is spinning at about 11.5mph the rear wheel shifts "up" with a 137% step. These are pretty unusual---I ride a lot and check out other people's bikes somewhat obsessively as I'm riding (and walking) around, and since I got this bike I've only seen one other bike built up with this hub. Mine is built with a 46t front chainring and a 19t cog on the rear hub. This means that when the bike shifts up, it's similar to riding with a 46t/14t ratio or thereabouts. Since the shifting is automatic, there's no cabling to the rear wheel. I also built the bike with only a front brake, so the only cabling at all on the bike is a small cable going from the handlebars to the front brake caliper. The hub is really small (much smaller than other internally geared hubs you may have seen), and the small size of the hub and lack of cabling aesthetically makes it look like I'm riding a fixed gear or single-speed bike.
The rest of the bike was built with mid tier components and with bull handlebars. I got security bolts for the front wheel and security bolts for the seat. The whole thing cost something like $1300 with tax which is kind of pricey for an unbranded bike with two gears, but includes the price of the hub and a fancy seat. One change I did make a few weeks after buying the bike is to get the traditional pedals with steel toe clips swapped out for double-sided SPD mountain biking pedals. I thought I was going to want standard pedals so I could get around town with regular shoes, but I found that after riding for so long with SPD cleats on my road bike I just liked the feeling of being clipped in too much to go without. I just throw an extra pair of shoes in my backpack if I'm heading out (and at work I have an extra pair of regular shoes for the office).
The main function of this bike has been as a commuter bike, although I have done a few intense weekend rides (2000' elevation gain) on this bike. As a commuter bike, this bike is awesome. I'm really happy with it. Because it's not branded and is built up with security bolts everywhere, I feel like I can lock it up anywhere in the city with only the rear wheel/triangle locked. This means I only carry a single mini U-Lock and I haven't had any issues.
I can go surprisingly fast on this thing. I'm a pretty aggressive rider in general, so I'm always sprinting wherever I go, but that said I'm able to pass people in spandex on expensive carbon fiber bikes all the time on straight stretches. Over the distances you can typically go in the city between lights, the lack of gears isn't a problem at all, and actually when the higher gear is engaged the ratio is pretty high. I've timed my work commute on my road bike, and it takes me exactly the same amount of time to commute on both bikes (the commute time is mostly dependent on the lights I hit or don't hit). I have a weekend loop that I do, and the loop that I do from my apartment to the top of the Legion of Honor takes 40-45 minutes on my road bike and is about 700' of climbing. The loop takes about 50 minutes on the Mission Bicycles bike, and I'm able to get up from the bottom of Sea Cliff to the top of [Legion of Honor](https://en.wikipedia.org/wiki/Legion_of_Honor(museum)) which is a Category 4 climb on Strava. The steepest segment I've gotten up on this bike is the 43rd Ave Climb which is 275' and is an 11% grade on the steep block. My time on this bike on the 43rd Ave segment is actually only a few seconds off from my road bike, although subjectively the climb is a lot harder on the Automatix hub.
Overall I'm pretty happy with the Automatix hub, but there are a few minor issues with it. The first is that because it engages the higher gear at a particular speed, there are certain grades where it's really hard to not engage it. What I mean is that there are certain grades (5% or 6%? I'm not sure) where I naturally want to get out of the saddle to climb. However, getting out of the saddle delivers enough power that I end up hitting the speed threshold, and all of a sudden the climb is beyond my max power output. If this happens I have to stop pedaling for a fraction of a second and then try to re-engage the bike on the lower gear. I've never actually fallen this way, but I've gotten pretty close a few times, and it's pretty scary when it happens. To counteract this I end up having to be really careful about my cadence on certain hills which is annoying and inefficient. This tends to be an issue for me when navigating The Wiggle where I have to bike at a really unnatural speed unless I want to go all out and bike up in the high gear.
Another problem is that sometimes the gear can egnage unexpectedly at lower speeds. This typically happens when going over potholes or bumps in the road, especially when I'm close to the shifting speed. Again, this is particularly annoying on hills where it can be dangerous. Another thing I've noticed is that when going below the shifting speed, if you keep pressure applied to the cranks in just the right way you can keep the gear engaged in the higher gear basically all the way down to when you're stopped. This doesn't happen too frequently, but it's caught me off guard when coming to a rolling stop at stop signs. What happens is I'll get down to nearly 0mph, and then try to start pedaling with the cranks vertical. When the cranks are vertical I have almost no mechanical advantage, so I've almost fallen before when this happens.
The last issue is that the hub has the tendency to rattle when going over bumps/potholes. I haven't had any mechanical problems as a result of this, so I don't think it indicates a real problem, but it's definitely disconcerting. On a previous bike I once had the bottom bracket slip out when going over a pothole, and I occassionally get flashbacks of this happening, or worry that my rear wheel is going to slip out of the rear dropouts since a loose rear wheel can also cause rattling.
Despite these minor issues, I want to reiterate that I like this bike a lot, and I plan to keep it and probably still mostly commute on it. I will definitely continue to use this bike for around-town chores and when I have to go places where I'll have to lock my bike up outside. The only thing I'd really consider changing if I were to rebuild it is the lack of a rear brake. 99% of the time I don't need the additional braking power, but descending from the Legion of Honor or down Clipper from the top of Portola can be really terrifying since the front brake will get really hot and loud and it's literally my only braking mechanism.
Update (2015-10-15): I just checked, and the front chainring on my Mission Bicycles bike is a Sugino Messenger 46t. Changing the front chainring is incredibly easy (the only slightly complicated thing is you'll have to adjust your chain length) and will make the bike easier to ride if you're having difficult on hills, or will make it faster if you find that you're always on straightaways or going downhill and are spinning too fast.
I have nothing but good words to say about the Sugino Messenger series, and will be sticking with it. The Sugino Messenger is their mid-tier series (higher end is the "Sugino Zen" series). You can change the front chainring to have more or fewer teeth if you want to trade off speed for climbing/starting power. One thing to note is that the Sugino Messenger 46t is 130mm BCD (a.k.a. PCD) where as the bigger more professional track chainrings tend to be 144mm BCD. This BCD number is how far out from center the cranks and the chainring are drilled for the screws that attach the two pieces. If the diameter is off, you won't be able to attach the crank to you chainring because the screw slots won't line up.
For instance you can actually get 44t 144mm BCD front chainrings which are a smaller gear than what I have but attach to the cranks at wider diameter. If you had 130mm BCD cranks you wouldn't be able to attach the cranks to a 144mm BCD chainring, even if the cranks themsleves were much longer (say 175mm). If you're confused check out Sheldon Brown's authoritative site, or ask anyone at your LBS for 60 seconds of their time to explain to you how it works.