poor man's compact
12-06-11, 11:49 PM
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poor man's compact
I was thinking of using just the inner 2 rings of a triple (42-30) for my daughter to get a super compact crank. Essentially mountain gearing with a road look. So no triple shifter and no triple fd. Any problems with this?
12-07-11, 01:00 AM
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You can use the same shifter and front derailleur. (Replacing them would be the opposite of a poor man's solution.) Remove the large chainring, replace the crank bolts with BMX/single speed ones, and turn in the high limit screw to lock out the third position of the shifter.
12-07-11, 06:53 AM
#3
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This should work fine. A lot of people who think that the gearing on road compact cranks (typically 34/50) is too high for really hilly terrain (or long distance/endurance riding) look for a way to have a super-compact crank (something like a 30/46) and use the option that you describe - only using the inner and middle positions of a triple crankset. There are other options, but this is normally the cheapest and simplest.
With a 30/42 combination, most front derailleurs (double or triple) should work OK, although some will work better than others. Also, try mounting the derailleur at several heights until you find the one that achieves the best results (the best-performing position is occasionally with the outer cage significantly above the largest ring, but it's hard to predict).
If the person wants even lower gearing, then consider switching the inner ring for a 26 or 28 tooth ring. I have a commuter bike with 26/42 chainrings on a road triple that works very well. Since it is for commuting, I've added a chainguard in the empty outer ring position to keep my pants away from the rings and chain.
With a 30/42 combination, most front derailleurs (double or triple) should work OK, although some will work better than others. Also, try mounting the derailleur at several heights until you find the one that achieves the best results (the best-performing position is occasionally with the outer cage significantly above the largest ring, but it's hard to predict).
If the person wants even lower gearing, then consider switching the inner ring for a 26 or 28 tooth ring. I have a commuter bike with 26/42 chainrings on a road triple that works very well. Since it is for commuting, I've added a chainguard in the empty outer ring position to keep my pants away from the rings and chain.
12-07-11, 12:56 PM
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Chances are you're going to need the triple shifter, although you might be able to make it work with the right double. You just need to make sure the length of the cage is sufficient, and double derailers might be a bit short for effective shifting. Friction shifting can cover a lot though.
I did just what you're describing, although I swapped the middle and outer ring, leaving me with a 46-22. The shifting on my setup is less than precise, but I don't have to do it very often.
I did just what you're describing, although I swapped the middle and outer ring, leaving me with a 46-22. The shifting on my setup is less than precise, but I don't have to do it very often.
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