Middleburn crank not compatible with Shimano bottom bracket
So, I have a Middleburn Uno square taper crank and a Shimano UN55 square taper bb. When I start to tighten the crank bolt the crank presses against the casing of the bb before its anywhere near tight enough, so that you can’t turn the crank. Has anybody else experienced this?Posted 4 years agoTurnerGuyMember
Take a hack saw and cut through the centre of the BB cartridge shall, but don’t saw through the spindle.
Then file roughly 3mm away from each of the inside surfaces of the cartridge shell and then glue it back together, so it now measures 67mm.
Then file the BB shell on the bike down to 68mm across, retap the threads, and refit the BB.
Put the cranks back on and they won’t hit the frame anymore.
Next problem is the chainline – anybody got any suggestions ?Posted 4 years agoTurnerGuyMember
must admit that chainline is something I am not too sure about.
All mtb rear hubs are 135mm, so why do different bikes need different BB spindle sizes, surely a parallel line back to the centre of the rear cassette is always going to be from the same spot above the crank arm?Posted 4 years ago
Yep, the hub width is fixed, hence the need for a shorter axle to bring my chainring I’m line with it. I’m running an internal hub gear so there is only one sprocket and one chainring. It runs fine but I’m presuming that it will all wear out quicker if it’s not aligned!Posted 4 years agotoppers3933Member
With a 113mm bb the chainline will probably be about 48mm I think. Which should be about 42mm for Alfine I think. I thought that alfine sprockets were dished and that it was possible to move the chain line over by flipping the sprocket? Could be wrong though. You could use chainring spacers to move the chainring overbuy it’s not the ideal solution.Posted 4 years agocoatesyMember
An expensive option, but I used to run my RS7s on a 107mm Royce BB, the cups sit flush with the BB shell so chainline can be much narrower. Not sure if relevant to the UNO, but my old 5 arm spider has a narrower chainline than the newer 4arm jobby that i’m now running, if it’s any use then you’re welcome to have it.Posted 4 years agoFieldMarshallSubscriber
I have previously had exactly the same problem. Had a long chat with Matt at Middleburn and according to him there are two possible reasons.
The taper in the cranks is worn. Thus it “sits” further up the axle.
The chainset is for an older/narrower chainline and thus the lock ring protrudes towards the bb shell.
I solved it by getting a wider axle.
But you could get a different spider.Posted 4 years ago
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