part of my fixed gear bicycle saga

My second try at finding a suitable bike for a fixed-gear conversion was an oldish Motobécane Mirage. A generic 1980s road bike, with an unexciting (and not too light) steel frame. But it has the features I wanted for a fixed gear bicycle: horizontal dropouts, roomy geometry (for fenders and stout tires), steel frame.

Unfortunately it has some features that I don’t like. The bottom bracket is Swiss-threaded – very obsolete and impossible to get parts for. (Fortunately I was able to put in new ball bearings and get it to work just fine, thanks.) The fork has issues too – either the threading is messed up, or it’s another weird French thread. The handlebars are steel, too narrow, and heavy. The stem is too short to be usable. The seat and seatpost are garbage.

So I’m making do. I bought a new seatpost. But it won’t go in all the way, because there is an internal “ridge” inside the seat tube. I may have to cut off the bottom of the post!

The alloy wheels are usable. I removed the old freewheel, respaced (so the hub is centered on the axle) and redished (so the hub is centered in the frame) the rear wheel, and using this trick I tightened the track cog down hard.

I’m proudest of my job salvaging the cranks. At first I thought I couldn’t use them. I wanted a 42 tooth front chainring; these cranks had a 52 and a 40 tooth – but I couldn’t simply take off the 52 tooth ring and use only the 40 (which is a fine size), because the 52 tooth ring is part of the spider – the 4- or 5-pointed radial star that connects the crank to the chainwheel.

I was going to give away or sell the cranks for cheap, but on closer inspection noticed that the 52 tooth ring was badly worn. Teeth were halfway chipped off, or their sides were worn away. So I pulled out my trusty hacksaw and file, and hacked off the big ring, leaving a “spider” that I attached the 40 tooth ring to. It worked out really well! Here is what it looks like:

bodged crank!

bodged crank!

Close ups of the rear 17 tooth track cog (sorry about the grease – it looks like someone blew their nose on it!):

greasy rear axle/cog

greasy rear axle/cog

Here are some pix of the whole bicycle – but this is not its final form. The pedals, handlebars, stem, seatpost, and seat will change, and I may put the fenders back on (but maybe not – maybe I’ll be lucky and be able to wait till October, like last year ;-).

moto side view

moto side/above

moto angle shot

Here is a pic of the 42mm chainline:

42mm chainline!

... and the rest of the drivetrain. But those pedals are temporary. However, it is easier to learn to trackstand without falling over if you’re not clipped in!



Sadly – or maybe not! – this project is dead. I connected the front brake and rode the bike around Portland a bit. It was scary, and not a lot of fun. The bike didn’t fit me too well, and because of its cranky Frenchness finding parts (like a higher stem) was going to be a big drag. And I was worried that eventually I’d have to replace the Swiss-threaded bottom bracket. I didn’t want to deal with a quirky frame that required hard-to-find (and obsolete) parts.

So I gave up on it. The wheels and cranks went onto a Schwinn Le Tour frame that I built up for my dad. The frame and handlebars are still sitting in the garage. If anyone here in Portland (OR) is interested, contact me (via comment link). The remains are likely to go to the Community Cycling Center.

I’m working on turning a Nishiki Olympic twelve into a city/utility bike. It’ll start out fixed and stay that way if I like it. Otherwise: singlespeed bicycle!