Bicycle Mechanics - Cartridge BB and cable guide mounting screw inteference
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I apologize if this topic has been dealt with previously. I'm converting a spindle/ballbearing BB to a Shimano cartridge BB (think: UN54 etc). The bike (Miyata 916 steel frame) has a plastic cable guide below the BB housing. The guide is mounted with a screw that protrudes into the BB. This interferes with the cartridge BB.
On my daughter's Specialized Sirrus (also steel), I have actually shaved down the length of that screw. But I am wondering if there is a better way e.g. a cartridge BB that has a narrow diameter than the Shimano series of square taper BBs.
08-03-09, 07:03 PM
I've always done what you did with your daughter's bike -- shorten the bolt. Cable tension holds the guide against the shell; the bolt is only there to prevent it from moving. Some guides just use a molded-in plastic plug instead of a bolt. So you're unlikely to cause any problems by shortening the bolt.
08-03-09, 07:12 PM
By all means, file down the screw or buy a shorter one. The threads sticking into the bb shell have no structural value and only get in the way. As JDT noted, the cable guide is mostly held in place by cable tension so the screw does little except add a measure of security.
I have had that happen numerous times. File that baby down. There might be a BB out there with a narrow middle diameter, but it seems easier to spend 3 minutes with a file then searching for such a cartridge.
08-03-09, 10:08 PM
Depending on the BB and guide screw in question, you may do fine by just backing off the screw when installing the BB, and then retightening it once the BB is installed. I've found that at least for my Campagnolo cartridge BB, that has somewhat of an hourglass shape, the guide screw is only just long enough to interfere with installation but not long enough that it will actually touch the middle portion of an installed BB body.
Or put a small washer under the head of the screw - faster and painless ...
Thanks for all the inputs!
08-05-09, 08:24 AM
Depending on the BB and guide screw in question, you may do fine by just backing off the screw when installing the BB, and then retightening it once the BB is installed.
To be followed at a later date by not remembering the interference and swearing profusely at why the bb won't come out! :roflmao2:
File or shorten the screw now and save yourself grief later.
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