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bsa 68mm bottom bracket recommendation

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bsa 68mm bottom bracket recommendation

Old 05-03-21, 01:46 AM
  #1  
kracksmith
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bsa 68mm bottom bracket recommendation

I have a 2008 Cannondale Rush 5Z and would like to get a better chainring and bottom bracket (68mm threaded)combo.

Right now, somehow the chainring is too close to the frame and hitting the frame arm when it compress from a jump, the current chainring is 24 teeth makes the gearings way too low for me, don't plan to do much uphill pedaling, I would like something in the 30s and single chainring is fine.

Any recommendation would be appreciated. not something too cheap and not something too expensive.





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Old 05-03-21, 07:03 AM
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unterhausen
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I'm surprised that had a 68mm bb. Any 73mm mtb crank can be made to fit with spacers. Not sure what to recommend, I would go to a bike shop and see if they can get you anything.
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Old 05-05-21, 04:52 AM
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biker128pedal
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I had a similar issue with square taper BB. I needed to measure the overall spindle length and then found one longer to push the chain line out. Looks like your spindle length is too short for that crank. Was a hassle to find one. But the less costly path. Then you have to get the old BB out. Start soaking the threads with Aerokroil or equal. Iíve had to secure the tool in a bench vice and rotate the frame for leverage on occasion.

if you have the money look at upgrading the crank and BB.
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Old 05-05-21, 09:29 AM
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Yes due to the bad crank and short length spindle I will have to buy new. Threading to one of the arm is striped and couldn't get it removed the normal way, so had to bang it out since I wouldn't reuse the arm. The BB was very tight so had to secure it, and with a long breaker arm it finally came out.

"I needed to measure the overall spindle length and then found one longer" What size did you end up getting?






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Old 05-07-21, 10:28 PM
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running into a bit of trouble here guys, so my bottom bracket is 68mm and 127mm end to end. 127mm already seems too narrow, what other size are there that is longer?
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Old 05-08-21, 11:23 AM
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I think you have either a spacer problem or a crank problem, the spindle is fine.

Some bikes have (or can use) a chain guard or derailleur mount that is clamped in by the bb on the drive side. If that chain guard or derailleur mount is not present, then you need to have a 2.5mm spacer in place. The bike would use a 73mm bb even though the shell is 68. Some 73mm bottom brackets are sold as 68/73 and come with the spacer. This should be easy to find or rule out with your caliper.

The crank problem would be just that the crank's chain line is narrower than the original. The middle ring chain line on a MTB triple is like 48-50 mm from the center of the bike and that's where a single ring should sit. The inner ring should be about 8mm in from there.
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Old 05-08-21, 10:00 PM
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Originally Posted by kracksmith View Post
running into a bit of trouble here guys, so my bottom bracket is 68mm and 127mm end to end. 127mm already seems too narrow, what other size are there that is longer?
Sorry I had not been following this thread. Iíll have to see what I have. Overall in your case consider replacing both the crank and the BB.

Saw this 137mm on eBay

https://www.ebay.com/itm/Bike-Bicycle-Bottom-Bracket-68-x-137mm-Square-Taper-/264358046204?_trksid=p2349624.m46890.l49286

Edit: I looked and I went to a 127mm. Not sure what I had before. Enough so I could not shift to the granny gear on the triple.

Also crank drive sides have different chainring offsets. May be time for a new drive train. Iíve was eyeing a 1X conversion but parts are hard to find. I also want a FS bike and new road bike. The needs and wants are piling up.

Last edited by biker128pedal; 05-09-21 at 07:56 AM.
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Old 05-09-21, 12:26 AM
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thanks guys, 137mm should do the trick.
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