xxguitarist

I found a fairly cheap frame/crank/etc (bike minus wheels, basically) that I was eyeing as a conversion, but it seems to have a one-piece crank. Hoping for some input on chainline with this crank, as I've only worked with the usual 3 piece sort.
Is this too much work for an older columbia frame? https://providence.craigslist.org/bik/1133635289.html

While I'm at it, beyond sighting, how do you know if you have your chainline *just right*

bmw5nkj

i did a conversion last summer that has a one piece crank. using that and a
formula hub, the chainline is pretty good.


i would advise not to bother with frames with one piece cranks. they are quite heavy. i sort of regret converting that bike (and losing money), but it was a good learning experience for me.

Raiden

In this case, the only way to know is to pop your wheel in there and see if it fits. If not, get a new set of cranks and a bb the width that the manufacturer suggests.

^ I've just been reminded- make sure that frame will accept a standard English- threaded bb, or you might be SOL if you try to upgrade later.

fuzz2050

generally, if a frame takes a one piece crank, it's not worth converting. I'd look elsewhere, not everything with horizontal dropouts needs to be a fixed gear

Build your own

Since the chainring sits relatively close to the bb shell on a single piece,the chainline should be pretty close.If it's in too far it can be moved out a bit by using a spacer between the chainring and the bearing race.As far as converting that bike,it depends what you are looking for.Wile there's better frames out there if you don't mind having a heavier bike and just ride it as is (check out simple living cycles in framingham for excellent deals on wheels) ,why not.If you envision turning it into a tricked out,blingy racemachine,don't bother.

Andy_K 

All you ever wanted to know about chainline and more:

https://www.sheldonbrown.com/chainline.html

He doesn't mention one-piece cranks, probably for the reason that fuzz2050 mentioned.

I would guess that your options are:

1. getting lucky and having it match as is
2. respacing/redishing the rear wheel (eliminates flip-flop use)
3. buying an American to European bottom bracket adapter and getting a three-piece crankset

EatMyA**

He does talk about One piece "ashtabula" cranks and mentions that they are the strongest cranks you can get.

https://www.sheldonbrown.com/harris/opc.html

"The most distinctive part of this type of bike is the one-piece steel crank. The better ones are a solid forging, incorporating the left arm, axle, and right arm in a single piece of steel. These are the strongest cranks available. This is what makes them popular for BMX and children's bikes that are subject to rough usage. They are also the only type of crankset that can be serviced with ordinary household tools...all you need is a large adjustable wrench and a screwdriver."

more on the subject: https://www.sheldonbrown.com/opc.html

sheldon has great chainline articles as well. This IS NOT an issue. You might have to adjust things but thats it. You do not NEED to get new cranks. Alot of BS on this thread. The only reasons to convert to 3 piece are: 1 you hate *how they look. 2. you are trying to save weight. Aluminum cranks are lighter (not better, not stronger, just lighter).

JJPistols

ain't nuthin' wrong with some good ol' ashtabula

Andy_K 

I meant that he doesn't talk about them in the chainline article.

I would disagree that there isn't anything wrong with them. What's wrong with them is that you only have like one choice for decent pedals. And the bikes they're on are usually (though not always) low end department store bikes.

Andy_K 

3. You don't want to be limited to 1/2" pedals.