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Saturday, October 16, 2004

Fixed Gear 

I couldn't do the club ride today due to a scheduling conflict, but I did manage to run a few other errands, and kept pretty busy. I spent a few hours doing a major reconstruction of the fixed gear, one of my less-ridden bikes.

The reason I wasn't riding it so much is that in the first iteration, I had created a monstrously overgeared bike. A typical road-going fixed-gear will use a gear like 42-15 or so, but I was riding around on something like a 52-16. That's a crazy gear, super-high, so the bike was all but impossible to ride up a serious hill, and coming down was almost as bad, as the high gear ensured you couldn't slow the bike down much by backpedaling.

So, since I had the bike apart, I decided to correct most of the bike's other fixed-gear sins: quick releases are a fixie no-no, mostly out of a respect for track traditions and a serious desire for the rear wheel to not come loose while riding in the velodrome (if possible, a loose rear wheel is an even worse experience on a fixed gear than a geared freewheel bike, but then most drivetrain failures are). So I decided to respace to 110 mm at the rear, the traditional fixed-gear standard, so that I could use other hubs in the future, and so I could remove some spacers from my current axle, convert it to nuts from a quick-release, and possibly use the second set of threads on the other side (this is a good thing, because it means I can now put a second choice of gearing, or even a freewheel, on the spare side).

When a shop re-spaces your steel frame (usually to make it wider so you can use modern drivetrains with 8-10 speeds) they probably use the fancy term cold-set, which sounds nicer than "bend frame without using heat". Which is what they do, and what I did on the porch. The approved technique involves a 2x4 and judicious force, but since I was going narrower and felt lazy, I just stood on the frame a little, then un-bent it a bit to fix my overenthusiasm, then used my nifty dropout-alignment tools to make the final tweaks. Some string and cleverness nicely substitutes for a frame-alignment tool, and you can get away without using dropout-alignment tools, but the latter is fun to play with, and I got my set for free, more or less.

Changing the gearing was surprisingly involved. The old chainring I was using was permanently attached to the cheap original crank from the bike. This bit of unpleasantness was removed from the bike and put back on the parts pile, and out came a 5-bolt crank and appropriate ring. Two appropriate rings in the end, since the easiest way I had to solve some spacer issues with the chainring bolts was to add another, smaller chainring just outside the actual drive ring. It looks silly, but it works just fine, and gives me a theoretical option to drop the gearing slightly, from the 44 to a 40.

I got the project mostly reassembled before dark (there are some outstanding issues with re-centering the rim, adjusting the rear brake, and fixing a flat tire), and retired to the computer feeling quietly satisfied with a fairly well-executed bike project.

I also found the SCSI drives I needed this week (yay eBay), and have convinced my father to focus on the Canon A70 or A75 as his first digital camera. They're really good.

Uh-oh. There's some ready-made frosting in the fridge. I don't know what evil the frosting cartels work to make it so smooth and tasty, so close to being pre-mixed butter and sugar, but um, it's okay to just eat that stuff, right?

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