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The plan: move spacers around on the rear wheel to get the cassette about 8mm farther in for better range of access from the small chainring; re-dish wheel for proper alignment; shorten the chain a little bit; remove the front derailleur. Maybe remove the big chainring.

Am I missing anything in this plan?

UNNECESSARY DETAILS:

This is an old steel road bike frame with a franken-drivetrain: 8 speed Campy cassette with a Sora rear derailleur and an SRAM chain. I'm going shell out and buy a nice road bike for training and long rides, and my plan is to make this older bike a lock-up commuter. I'd like to avoid sinking money into it, as it faces good odds of being stolen at some point in the next four years.

The main problem I have is the front derailleur is an endless pain. If the chain gets even a little dirty the shifting becomes very fiddly: dropped chains or sometimes stuck on the big ring. None of the parts are worn or stretched. I think there's just a certain amount of incompatibility in the mismatched drive-train parts. (Maybe I'm wrong.)

Using it as basic transportation & commuter I don't even really need the large chainring. It seems to me that it should be possible to move some spacers around and get the cassette about 8mm farther in so more of the gears are properly usable from the small chainring. Then I'll have enough gears to never be annoyed. And if I maybe switch out the indexed shifter for a friction bar-end shifter I'll barely have to do any maintenance; no indexing worries. Just clean the drivetrain maybe once every 7 weeks.

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    Something is wrong – 75 mm is almost 3 inches, the spacing on the rear dropouts is around 130 - 135 mm. Do you mean 7.5 mm? – dlu Oct 18 '15 at 17:46
  • yes. edited.... – rjt_jr Oct 18 '15 at 17:52
  • By accepting the first answer within a few hours, you discourage others from contributing alternative answers. There is always more than one way of doing things. – andy256 Oct 18 '15 at 22:49
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You definitely don't want to redish the rear wheel. The dishing is to center the wheel between the locknuts. It is necessary to accommodate the cassette, but it is more of a function of the hub than the cassette or the cassette position.

If I'm reading the right you'd like to convert to a single chainring in front and adjust the chain line (to center the single chainring on the cassette) so that you can utilize all of the cogs on the cassette while maintaining reasonable chain deflection.

The usual way to do this is by adjusting the length of the bottom bracket axle, but since you'd like to minimize spending on the project you're wondering if you can do this with the cassette. As best I know the only way you'll be able to do this is to drop on cog from the cassette and replace it with a spacer, so that you're moving the cassette relative to the chainring.

I think you could do that, but you may want to start by just using one chainring and see if you're happy with the bike in that configuration. You may be running with more chain deflation than would be ideal, but it should work. Then if you like it consider your options for improving the chain line.

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  • Is putting in a longer bottom bracket spindle expensive or difficult? I wouldn't think so. Is it that simple? – rjt_jr Oct 18 '15 at 19:15
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    Pretty much, you can get nice "standard" square taper bottom brackets for under $20, I would think an individual spindle would be even less. Swapping out spindles is easy – as long as you have a crank arm puller. That's another maybe $20 if you don't have the tool, but it is a good one to have since it makes it possible to do your own maintenance. – dlu Oct 18 '15 at 19:44

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