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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 05-14-12, 04:24 PM   #1
bsrepur0232
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Going nuts trying to figure out which BB!

I pulled the Shimano BB-UN71 (68x107) out of my bike because it was constantly creaking and driving me nuts. Also wondered if maybe it was too short since the chain ring would occasionally nick the frame. I thought finding a slighly longer replacement UN71 would be a simple task but only now realize it's been discontinued. I read somewhere on here that the UN73 was made to replace the UN71/72 by integrating the drive-side threads into the cartridge body itself instead of using a separate cup (presumably because the union between cartridge and cup was the cause of the creaking?) So trying to figure out what to do

Should I replace the UN71 with UN73 (ebay?) to solve the creaking problem? And if so, aren't the 107 and 110 the same on the drive side? If so, would I need to go with a 113 in order to push the chainring out enough?

Other option is to go with UN55, but because it tightens from the opposite side, not sure if the 110 is actually the same as the 107? In other words, will the 110 UN5x give me 3mm more than the on the drive side than the 107 UN5x? And if I go with the UN55--are the threads part of the cartridge or do they use separate rings with creaking issues?
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Old 05-14-12, 04:37 PM   #2
bikeman715
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go with the UN73 . the 3 extra mm will be on the drive side ,moving the chainrings ,when doing this it will requre readjustment of the front derailer . also it can affect the chinline .
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