I did search but haven't really found what im looking for. I have some kind of euro frame. it had a cottered 3 piece crank, the bb shell is smaller in diameter than an American. the spindle was threaded with screw in cones. I didn't knock the cups out yet, but I think they are just pressed in. is there an adapter to switch over to modern bmx 3 piece crank? or am I on my own to come up with something?
cotter 3 piece crank
- Thread starter jamesdart
- Start date
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They're probbly male-thread cups, and depending on where and when they were made, you might have it easy as far as putting on a better 3 piece crank, or you maybe S.O.L.
Any idea on the frame's manufacturer?
Any idea on the frame's manufacturer?
Not surprising that a vintage Orbea would have French threads, as Orbea is a Basque marque...
anyone ever successfully convert from a Thompson? I have a couple ideas. i think i want to just run some run of the mill, modern, cheap, bmx crank.
I saw some kind of threadless adapter that was sort of like a threaded bottom bracket. it had like a plastic spacer that fit into the frame, for square drive cranks. 128mm. im not sure how that works out in the end for chainline. Im not sure I want square drive.
another idea, is to make a sleeve press fit inside my bb shell, to fit spanish bb bearings. can put a step so the bearings cant slide in. can also plug weld it into the shell.
OR look at what it would take to bet a 41mm "mid" bb bearing into that 40mm shell. I guess i should check the width.
I saw some kind of threadless adapter that was sort of like a threaded bottom bracket. it had like a plastic spacer that fit into the frame, for square drive cranks. 128mm. im not sure how that works out in the end for chainline. Im not sure I want square drive.
another idea, is to make a sleeve press fit inside my bb shell, to fit spanish bb bearings. can put a step so the bearings cant slide in. can also plug weld it into the shell.
OR look at what it would take to bet a 41mm "mid" bb bearing into that 40mm shell. I guess i should check the width.
I like this idea; with the right tools and persistence, you could probably make it work.
The threadless square taper BB probably won't work on your frame. The one I am familiar with is offered by Velo-Orange: http://store.velo-orange.com/index....ets/grand-cru-threadless-bottom-brackets.html
They say it's too loose to use on even an Italian BB shell (36mm); it's designed for English shells, which are 1 3/8" (or @34.8mm)-- you'd need to sleeve-down the Thompson shell to accept this, and if you're going that route, I'd say you're better off looking at something to fit mid or Euro bmx bearings... more later.
Here is a sealed unit. http://en.hollandbikeshop.com/bicyc...acket-cotterless-127-40mm-thompson-press-fit/
There are some different lengths offered too http://en.hollandbikeshop.com/thun/
There are some different lengths offered too http://en.hollandbikeshop.com/thun/
Awesome that they offer those adaptors.... but i'm thinking @jamesdart has some really cool ideas kickin' around in his head. James, you can run most bmx cranks an any bearings with a 3/4" ID. Yeah, they sell them as 19mm, but 3/4"=19.05mm, and most cranks use r12-rs (3/4x1 5/8x7/16") sized bearings in mid or American BB shells. (and 19-37-9mm bearings for Euro or Spanish BB shells...)... the key is running the proper ID; the OD and width can vary depending on whatever "sleeve" you use to reduce the frame's BB shell....
