16Victor 

What's the difference between chainwheels/sprockets for 1pc. cranksets vs. 3pc? Can one be converted to another?

I'm upgrading my boy's bike from a 1 pc. to a 3 pc. crankset, so I'd like to know if I can mod his existing chainwheel or do I have to buy a new one?

Sorry for the easy question but I'm an old road bike guy, never have been a BMXer myself.

(edited to correct terminology)

SoonerBent

Assuming you mean changing from a 1 pc crank to a 3 pc crank. You will have to get a crankset, bottom bracket, and a set of adapters to fit the bottom bracket to the shell.

SS

16Victor 

Thanks, got all that on the way. I just have to figure out the sprocket compatibilty issue and get some 9/16" pedals.

sxe fbm rider

The term chain-ring isnt really used for bmx commonly.. usually just called a sprocket. BMX 3 piece cranks usually come with Bottom Brackets and the sealed cups will fit in the same as did the un-sealed ones. You can use the same spocket/chainring, but if you're upgrading the cranks it would be a good idea to upgrade the sprocket as well.

16Victor 

Thanks - that's good info.

It's just that I see on ebay some sprocket auctions that say "fits 1pc. cranks" or "fits 3pc cranks" or "fits 1pc and 3pc cranks." I just needed to know what, if anything, is different between them.

sxe fbm rider

You will usually get a little adapter ring with your cranks to put in the hole of the sprocket to make a 3 piece spindle fit into it.. The sprocket will still work with a 1 piece.. I'm 99% sure, I haven't used a 1 piece in a few years.

Tazz

That only applies as to how thick your crank axel is (e.g. 22mm or 19mm) 1pc are usaly 19mm. also find out what bb your son's bike has. it probably has a american bb but if buy chance it has a euro bb then if you get cranks with a american bb you fekked . what bike is it?

Tazz

sorry 1pc cranks dont have a euro bb so 4get wot i jus sed.
you have to get a 3pc crank with a american bb and if you buy a new sprocket it should come with a adapter for 22mm or 19mm

[B]make sure you get the right sized sprocket!!

BMXpert

i just upgraded from a 1 pc to a 3 pc. all i had to do was get a chainwheel adaptor or whatever u wanna call it and i still use my sprocket that i had. i use profile 3 pc race cranks. if u getr those u'll have to buy a chainwheel adaptor it doesn't come with them

CMcMahon

No, they are not. They are usually larger than 22mm, probably about 22.2mm (7/8").

Tazz

well ACTUALY 2-3 years back mine wer 19mm cuz i had to use the adapter that came wit tha sprocket

Freebyrd

I hate it when people type like that.

Tazz

like what?

Freebyrd

wot i jus sed, wit tha, wer, cuz

Nothing against you, but it just annoys me. I don't really know why...

Tazz

well maybe you have a little to much time on your hands, i dont so i type how i wanna type. problem?

Freebyrd

Nothing against you was my way of saying I don't want to start trouble, so no problem.

pnj

learn to type.

people that can type can type faster then those that can't, saving time.

Tazz

I can type very fast actualy, i work in a bmx shop and have to fill out lots of orders while on the phone. Verry confusing :s

sxe fbm rider

I dont like it, but it doesent bother me that much, but it really doesent save time, and I really have to put effort into reading it. Do it if you want, I just dont like it.