OPC-->3PC cranks - bb conversion..
 

Hi All -

I have an old american road bike that i am converting to fixed gear and the one piece cranks need to be replaced as it is increasingly hard to find pedals with a 1/2" thread (and they are pretty well rusted out).

At any rate I have never encountered his situation before so I am looking here for help or to at least be pointed to an appropriate resource.

The BB measures ~50mm inside diameter and is ~68mm long and threadless.

I am pretty sure it is possible to convert these over to a 3 piece crankset relatively easily - I already have a spare set of cranks for a square taper BB but I guess I need help with the proper sizing and where to get what I need.

The cheaper the better - this project has already gotten more expensive than I had initially budgeted.

Thanks for all your help in advance!!!

-d

Try a BMX supplier. They'll have an adapter to convert your bottom bracket. They might call it a "euro" adapter or something like that.

These may be the least expensive option. I've seen fancier conversions from BMX suppliers, accompanied by much fancier prices.

oh cool - yeah those look liek they would do it - i am curious as to the sizing though..the one for single chainring apparently measures 127mm edge of tapered section to edge of tapered section. My bottom bracket is 68mm in length. That seems like a lot of axel...but what do I know...

Can anyone confirm that this is the right size - is 68mm a relatively standard length?

Thanks in advance!

No, 68 mm is NOT the length of the spindle, it's the length of the bottom bracket SHELL, the cylindrical part of the frame into which the bottom bracket goes. Since the spindle sticks out of the shell, it's gotta be longer :)

Basically any bottom bracket is longer than 100 mm... for newer Shimano cranksets something like 107 mm is typical for a double, 113 for a triple.

No, I know this ;) It just seemed long - 127mm is almost double 68mm so I guess thats what I was looking for confirmation for before I went and bought the wrong piece. Like I said i nthe original post I am only going to have the one chainring so it doesnt need to be too long.

I think I ll go ahead and make that purchase. thanks for the advice all - rock on!!