zero_B

i just found an old diamond back frame
and it's got a 1 piece crank

generally speaking, is it possible to put 3 piece cranks
in a bike that originally had 1 piece cranks?

miamijim

Generaly speaking? Yes.

mykesbykes

yes you can, bearing in mind that its not the crank that has to fit, but the bottom bracket (the roundy thingy the stick thingys go round on.

there are 3 types, American (the standard), Mid (slightly smaller than american?) , Euro (old school, higher end, smaller).

but generally old bmxs had american bottom brackets, and most 3 pc cranks are american.

post some pics of that diamond back, Im rebuilding a DB Viper right now, myself..

Greyryder

Mid supposedly uses the same size bearings as American, but doesn't use cups. Some brands do use larger bearings, in their American bottom brackets, though. There's also Spanish, which is similar to Mid, but smaller.

If it came with one piece cranks, it most likely uses an American Bottom bracket. Most three piece cranks have an American BB available for them. You just have to know the spindle diameter of the new cranks. Most use a 19mm, but a few, like Primo, use 22mm. There are a couple of high end two piece cranks out there that use an odd size spindle, but their only available with a European BB

Older bikes, and low end bikes made for big box stores will likely have American bottom brackets. Newer BMX bikes use European bottom brackets, but the width is different than what's used on road or MTB bikes. Newer freestyle bikes will most likely use a Spanish BB. Some newer freestyle bikes might use a Spanish BB, but I don't think that size ever really caught on.