Technical & Reference Section > Tech and Restoration

bottom bracket sizes ?

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calmac:
Right i'm baffled........ordered a set of 3 piece cranks to upgrade from my 1 piece currently fitted to my Mid School Haro Zippo.

Was advised it came with US sized BB kit & axle to suit, axle is for a conversion because it is threaded internally like a 1 piece axle to allow tightning ( frame obviously non threaded & about 52mm internal size)

On inspecting BB kit, cups supplied almost perfectly sit inside existing frame cups being a lot smaller.

On doing a bit of research appears there's a Mid/US bearing type--does this sound like what i have ?

I am reasonably knowledgable in BMX (at least i thought i was), but this has me pullin' my hair out   :rant:

PLEASE HELP ME !!!!!!!!!!!!!!!!!!

Thanks Calum

calmac:
Thanks for replies guys, what i have isn't a sealed bearing conversion,it's exactly like the 1 piece set up ie. cup & bearing.

Like i say new cup & bearing is just like a smaller version of the original 1 piece ones & if you sit the new cup inside original cup it sits perfectly inside .

I was going to build up ,but frame off being painted just now.

I've now established it aint a Mid/US as it (looking at pic posted in previous) def. not like that, or a pop in type like the blue one in the previous reply.

thanks

calum

calmac:
Sorry Glen, aint got a camera here.
tried fittings from 1 piece to see if i could just use them with new axle & cranks, but threads on new axle (look exactly same as 1 piece axle) are smaller sized too, so bang goes that option.
this is a link to what i should have but BB kit is deff. not the same
http://www.ukbikestore.co.uk/product/196/3302_175_02/khe-prism-3pctubular-cranks-wbb---black.html

i measured new cups at 45 mm not 52 as they should be & bearings are obviously smaller to suit.

calum

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