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Old 04-05-06, 01:33 AM   #1
minastirith
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Very basic Bottom Bracket Question

My LBS just replaced my old BB to a new one and I got back my old-worn out BB. I have never fixed a bottom bracket before so I am new at this. How come the removable ring on the non-drive side just rotates and doesn't get detached from the BB body? According to Park Tool website, removable ring is either on the driver or non-drive side. If the removable ring doesn't detach, how are you supposed to install it onto your BB shell?
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Old 04-05-06, 03:15 AM   #2
cascade168
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Originally Posted by minastirith
My LBS just replaced my old BB to a new one and I got back my old-worn out BB. I have never fixed a bottom bracket before so I am new at this. How come the removable ring on the non-drive side just rotates and doesn't get detached from the BB body? According to Park Tool website, removable ring is either on the driver or non-drive side. If the removable ring doesn't detach, how are you supposed to install it onto your BB shell?
In most cases, the removable ring (which in the case of a UN-53 is plastic) will be on the non-drive side for an English BB. This type of cartridge BB is basically in two pieces - one being the BB cartridge body with the fixed flange being part of it's body, and, the second being the removable ring. Both of these two pieces install and are removed with the same tool (for this example - a UN-53), the 20-splined BBT-2. When you install the BB you take the fixed_flange/cartridge body assembly and screw it into the BB tube on the frame. After it is installed (remember - left hand threads on the drive side of an English BB tube) you then screw in the removable ring (regular right hand threads on the non-drive side). Aside from proper torquing both sides, that's it. The removable ring is pretty much there to keep the non-drive side of the spindle centered with the BB tube on the frame, and provide rigidity to the whole assembly. It does nothing as far as the bearings in the cartridge are concerned. The reason they can get away with using a plastic removable ring is because it's just a centering spacer. One thing they don't tell you on the Park site is that plastic removable rings don't require as much torque. If you put 360ft/lbs on them, often they will crack. I have started using 300 ft/lbs. This works fine and I have seen no problems with them backing out. Even if they do crack they will still do their intended job - keeping the spindle centered in the BB tube. I just don't like hearing that noise (the "crack") when I am installing a new BB.
I agree with just about everything they say on the Park site as pretty much gospel, but it's my experience that 350-360 ft/lbs will crack those rings at times. As they say, your mileage may vary.

I hope this answers your question ;-)

Last edited by cascade168; 04-05-06 at 03:24 AM. Reason: clarification
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Old 04-05-06, 09:13 PM   #3
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Cascade's numbers are right but his units are wrong. He means IN*lbs. not FT*lbs.

And while I'm correcting you, I'll also pose a question of my own

I'm replacing the generic square taper BB on my Specialized Hardrock with a Shimano UN-73 BB. The current one creaks after a few miles of pedaling and I guess it deserves to after 4000 miles of commuting. The only issue I'm having with the new BB is that my left crankarm won't seat down as far as it did on the old BB. I've torqued the bolt to 30 ft. lbs. (360 in. lbs.) per the spec I've read everywhere and it still has at least 2mm more to go before it's where it used to be in terms of distance from the BB shell. I don't want to ride the bike like this as I fear the minimal engagement will cause problems in the long run.

Have you ever experienced anything like this? I'm going to try installing the crankarm in a different orientation tomorrow along with trying the other UN-73 BB that I bought (for my other bike with a creaking BB). Worst case, I'm just putting the original back in and living with the noise.
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Old 04-05-06, 10:08 PM   #4
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Quote:
Originally Posted by joejack951
Cascade's numbers are right but his units are wrong. He means IN*lbs. not FT*lbs.
You are, of course correct. My bad.


Quote:
Originally Posted by joejack951
Have you ever experienced anything like this? I'm going to try installing the crankarm in a different orientation tomorrow along with trying the other UN-73 BB that I bought (for my other bike with a creaking BB). Worst case, I'm just putting the original back in and living with the noise.
I have not seen that. I think your idea of trying a different orientation is a good one. I think I'd try different orientations with the non-drive side crank arm first and see if you can find one that works. Assuming you can, then install the drive side crank. One other thing that I believe in is greasing the tapers. I know there is a lot of controversy about "to grease, or not to grease, the tapers", but I have always done so with no problem. Even Jobst Brandt - someone that I don't agree with on a lot of things - says to grease the tapers. He says if you don't that you can't accurately torque the crank arm bolt. So, there is at least that one thing I do agree with him on. Also, if you don't already use it, try teflon tape on the threads of the BB. I like this method the best and so do many other people. It's solved lots of "creaking BB" problems. Good luck!
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Old 04-05-06, 11:42 PM   #5
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Only thing that comes to my mind, with your crankarm not seating as far down on the Shimano BB as it did on the previous, is that you might have an ISO (Campy-taper) crank. Of course, it's only the left, and Specialized never made a mtn bike with Campy stuff. At least not at the HardRock level.

Test some things out. Does the left crankarm seat properly on both sides of the old BB? How about on the right side of the new one? Maybe there's a manufacturing imbalance somewhere.
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Old 04-07-06, 07:25 AM   #6
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I got a chance to mess around with the BB issue again last night. I used a pair of calipers and measured the Shimano BB near where the crank arms should be seating. It measured the same on both sides. I then measured my original BB in the same area and it measured the same as the Shimano on the drive side but about 0.2mm smaller on the non-drive side. Then, I measured the square on my crank arms and sure enough, the drive side was 0.2mm bigger than the non-drive side. So either Truvativ worked with this BB supplier to make a non-symmetrical BB or Specialized just lucked out when sourcing components.

I ended up putting the original BB back in with a lot of anti-sieze on threads (had to use a cheater bar to remove the original) and so far ( one ~7 mile commute) no creaking. We'll see how long that lasts.
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