Have questions or want to discuss cycling? Join Now or Sign In to participate in the BikeRide community.

New: Take part in the May Giveaway for a Road Electric Bike Hurricane from KBO


Ch-2n bottom bracket
#1
I have a kona smoke and want to upgrade the bottom bracket to a shimano un54.

I removed the original bottom bracket which has no sizes written on it just ch-2n (i think its chin haur).

I measured the shell of the frame which is 68mm and the length of the spindle is 119.7mm.

My problem is that the spindle length doesn't appear to be a standard size the un54 does 118 or 122.5, will any of these work.

I have had a look on the drive side and there is a fair size gap between the crankset and the frame so maybe could go for the 118mm?

the spindle also is asymmetrical and is slightly longer on the drive side will this affect what size i need to order.

sorry for so many questions but this has stumped me as i am a newbie just wish it had been a standard size.
  Reply
#2
(04-19-2011, 03:12 PM)contender1 Wrote:  I have a kona smoke and want to upgrade the bottom bracket to a shimano un54.

I removed the original bottom bracket which has no sizes written on it just ch-2n (i think its chin haur).

I measured the shell of the frame which is 68mm and the length of the spindle is 119.7mm.

My problem is that the spindle length doesn't appear to be a standard size the un54 does 118 or 122.5, will any of these work.

I have had a look on the drive side and there is a fair size gap between the crankset and the frame so maybe could go for the 118mm?

the spindle also is asymmetrical and is slightly longer on the drive side will this affect what size i need to order.

sorry for so many questions but this has stumped me as i am a newbie just wish it had been a standard size.

I've opted for the un54 68mm x 122mm as i thought there would be less chance of the inner chainring fouling on the frame, hope it works.
  Reply
#3
Chain line might be an issue. BB length always is dependent upon how the crankset is matched with it. You may be good with 122mm but could be off as well. Those who know much more than me can perhaps chime in.
  Reply
#4
The chances are that the UN54 will be symmetrical so will put the chainrings nearer the chainstay if you get the 118mm size.
Obviously this will also move the other crank away from frame.
I like to go with the smallest BB I can and have used a spacer behind the BB to offset it to the right giving the chainrings a bit of clearance.
Ride hard or ride home alone!
  Reply
#5
Fitted the 122mm cartridge and it works fine. all gears still working perfectly
  Reply


Possibly Related Threads...

Forum Jump:

[-]
10 Latest Posts
I think I might of been a little too has...
Today 02:03 AM
Have you Ever Tried an Electric Bike?
05-09-2021 09:14 AM
2018 Specialized Stumpjumper Comp Alloy ...
05-08-2021 09:31 PM
Schwinn 3rd Avenue 700C hybrid
05-08-2021 02:33 AM
Trek 720 (1997) Drive Train (Crank & Der...
05-07-2021 04:06 PM
Square-Taper BB 68 (1.37 24T) Crank-Arm ...
05-07-2021 01:52 PM
How to Approach Questionable Deals
05-07-2021 01:23 AM
2021 Pro Road Cycling
05-05-2021 01:10 PM
Loose seat stem housing on Trek Madone 9...
05-05-2021 08:53 AM
1962 Varsity - Move Stem Shifters Ok?
05-05-2021 12:40 AM

[-]
Top 5 Posters This Month
no avatar 1. Jesper
27 posts
no avatar 2. ChaseCal
6 posts
no avatar 3. Stephen111
4 posts
no avatar 4. Papa Dom
4 posts
no avatar 5. Sagan97
3 posts