Bicycle repair: Solving a puzzle without any edge pieces

IMG_7567 2

A bicycle in need of repair is a puzzle.

What shifter can you find to go with the freewheel or cassette you have? Is that dirty chain in the junk box a usable takeoff or something for a backyard sculpture? If the latter, how did it miss the garbage can?

The difference between a bicycle puzzle and a cardboard puzzle is you can usually replace the missing bits of a bicycle.

How old is it?

If the bicycle is mature enough—built before index shifting, press-fit bottom brackets, built before the word standard was redefined as non-standard—it doesn’t matter that the parts you have are not an exact match for the original parts.

In a friction-shifting puzzle you can swap rear derailleurs from different companies, as long as they all 1) sneak under the largest freewheel cog 2) handle all the chain it takes to shift from the smallest gear combination to the largest, and 3) come with a claw or fit the same dropout hanger.

It doesn’t matter that you’re exchanging the equivalent of blue sky for the middle of a cumulous cloud, a brick wall for a wooden spire, or a hydrangea for a redbud tree. When the puzzle piece fits, it works.

Analyzing the challenge.

When it doesn’t fit, the problem is sometimes obvious: A one-piece crank doesn’t play in a bicycle frame with a 68mm threaded bottom bracket; a 26-inch tire doesn’t mesh with a 24-inch rim.

Sometimes the problem is more subtle. Does the bearing cone for that one-piece crank have 24 or 28 threads per inch? Is the width of that 26-inch tire 1.75 or 1 3/4 inches? (Nope, not compatible; don’t do the math—it won’t help you).

What’s obvious and what’s subtle depends on who looks at the parts. If you don’t know left and right pedals unscrew in different directions, you’ll have a hard time understanding why the righty-tighty rule doesn’t apply to the left pedal.

A newer bicycle is a different kind of puzzle.

Some modern parts are more precisely made than they were in the past. This can be a good thing and a bad thing: a good thing because a drivetrain with oodles of cassette cogs can take you anywhere you want to go; a bad thing because a little inaccuracy—induced by a worn chain or jockey wheel, or a slightly misaligned derailleur hanger—can make you feel like you’re always going to be stuck in the Fifth Circle of Hell.IMG_7565

At the same time, some parts are problematic from the start.

I’m enough of a dinosaur to believe that a bottom bracket with proper British threading is not something to be lightly discarded in favor of a design that takes new parts and a freezer to fix.

(There are a ton of different bottom brackets out there. Maybe the problem with some of them isn’t the idea behind their designs—it’s the execution of it.)

I admire the clean lines of a bicycle with internal cable routing. However, tripling the time it takes the average rider to replace cables because internal guides weren’t part of the bill of materials is not a good strategy for manufacturers hoping for word of mouth leading to additional sales. Some makers do the engineering; others appear to be thinking out of sight out of mind. (If you’ve changed cables on one of the problematic bikes, you may also find yourself out of your mind.)

If you have a bicycle with a cheap bottom bracket and/or cable routing from hell, I feel for you. You don’t have a puzzle to solve. You have a torture chamber to escape.

If only it didn’t cost so much money to bribe the jailer.

Learning to make do.

Back to the old bike. Say you’re looking at an ancient front derailleur, a Simplex. No parallelogram swinging the cage from chainring to chainring—instead, it uses a pushrod design to shove the chain sideways. Maybe the screw that connects the cage to the rest of the mechanism is missing. Find a screw with the same thread as the old one and you’re good to go.

IMG_7574Almost.

The plastic clamp around the frame is broken and you don’t want to mess with it any longer. You pull off the Simplex, chuck it in a junk box (always saving parts—always) and bolt on a SunTour. Or maybe it’s time to install that Campy Nuovo Record you’ve been hanging onto since the 80s. Perfect.

Except the clamp of the new/old front derailleur is a different diameter than the bicycle’s seat tube. Ah, you need a shim. Maybe you cut one from an aluminum can; maybe you cut apart a reflector clamp for the right piece of plastic (shimmery being one of the better uses of plastic).

This is not what you’d do for a Handmade Bicycle Show entry, but if it gets your old bike on the road, shim up and ride.

Puzzle solving.

This is why you have a workshop—and by you I mean me. To make do. Tinker. Not always to spend money and bolt on someone else’s perfect solution. You’ve done that, you’ll do it again, and yep, there’s nothing like shiny, new and well-engineered bicycle parts.

Nope, today you’re doing the best you can with what you have because the solution works, it’s free and, most of all, because puzzles are fun.IMG_7569 2

They were fun when you replaced a broken coaster brake axle when you were 12, and they’re fun today.

Riding a bicycle? It’s a great thing. Fixing the bicycle used to quadruple your walking speed? Priceless. (Sometimes, literally priceless.)

It’s the best use of all those useless bits and pieces you have laying around, things that turned out to have a use after all.

Just as you hoped they might.

About 16incheswestofpeoria

Former bicycle mechanic, current peruser of books, feeder of birds.
This entry was posted in maintenance and tagged , , , , , , , . Bookmark the permalink.

1 Response to Bicycle repair: Solving a puzzle without any edge pieces

  1. Andy Stow says:

    This is why my most recent build had an English threaded BB with square taper spindle, and why I went with the Gevenalle instead of true brifters. I didn’t really want disc brakes, but they happened.

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