Technical & Reference Section > Tech and Restoration

Bottom Bracket Fitting Help Needed

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TwoBobRob:
No Marty, you're right.   They're not supposed to be loose.....

Moose:

--- Quote from: perry on January 28, 2008, 08:14 PM ---this is bmx right  ::)

ive seen cups literally fall into the shell when on its side and others that were simply the wrong size

to use a lathe you need to know what size the shell is in the first place and once that calipers out i can guarantee no shell measured will be the same

decent chrome will add no notable thickness and skimming it will have it flaking off and rusting the frame

if anything more than hand tools are needed to pop some cups in then doesnt that say they are the wrong size  :uglystupid2:

id love to know do those peoples bearings spin freely or do they require a little "push" ( and thats without the cranks on )

if the cups are alloy get a file and take your time , if they are steel get measuring ( precision tools ) and if they are a close tolerance warm the shell

--- End quote ---

Perry, I'm left a little confused by this post - I don't quite understand what your solution is to the question, is it to warm the BB shell? With new chrome - I certainly wouldn't.

perry:
yes

to over one hundred degrees hahaha

no

nothing more than a few degrees with a hairdrier on anything bike related

still dont know what the frame is
what the cups are . one piece , open bearing , sealed , alloy , steel , new , old etc
has the frame taken a knock in the past , ie is the shell still round ? , was it round in the first place ? has it ever been submitted to a measuring device ?

were the parts for the build trial fitted before the chroming ?

could wax lyrical about what machinist to take it to but would be nice to know what the parts are first lol

have you considered a 68mm threaded bb  :)

Paulo:
Struth!!!!

Loads of suggestions thanks.

The cups are for an OPC. Although the cups in question weren't test fitted before chroming, the frame did have some in which were removed. My gut feel is that these new ones are not the best quality ups and are a fraction too big.

I'll try filing them a little first, and then make up a more robust clamp to fit them. Failing that, I'm going to hit the fook out of them with a hammer! :shocked:

My concern is that if the frame gives a little to accept the cups then the chrome will flake.

I guess I'm going to have to take my time with a file.

Thanks all :daumenhoch:

Moose:
Try this, but be gentle and watch that new chrome

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