MrLucky

Will only bmx fit? No mtb cranks at all? Thanks to anyone who replies in advance!

Zef

I think you will have better luck on the BMX forum for product recommendations specific to the BMX genre. You will find that a lot of the discussions on this forum tend to skew more towards road and mt bike repair related things. Plenty of that can criss-cross with BMX so don't be dismayed but I believe the true BMX experts can be found here: https://www.bikeforums.net/forumdisplay.php/13-BMX

-j

Wilfred Laurier

i believe there are adapters available
that have press fit threads in place of the american
or ashtabula
bottom braket cups
in the frame

then you thread your english bb into the threads of the adapter
english being the common modern standard
also called euro by bmx types
and use whatever cranks work with that bb

cny-bikeman

I am not aware of anything called an American BB - English yes - 68mm wide, x 1.37 diameter x 24tpi thread pitch. Cranks fit on the end of the spindle, so they don't care about the bottom bracket threads or shelll diameter. If your bottom bracket, whether English (Euro?), Ashtabula, or something else, can (with or without some sort of adapter) accept a spindle that is the right length and the right type end for a given crank, then it will work. I suggest you Google bottom bracket types and educate yourself about the different factors to consider.

techsensei

You can get adapters if you want to fit bottom brackets using traditional English threading. There are probably adapters for the various pressed-in bearings; I know one is made for using a BB30.

Zef

Yah...like I said...check out that BMX forum.

-j

Wilfred Laurier

ashtabula is also sometimes called american bb

you cant say that anymore

cny-bikeman

OK, but it appears (from a Google search) that American refers mainly to the shell size, as most of the parts referred to as American are for 3 piece cranks, not Ashtabula/one-piece. I almost never dealt with BMX equipment when I wrenched, and until this post do not recall anyone here referring to the large shell as American, but rather one-piece or Ashtabula.

surreal

American bottom brackets fit into bikes with American BB shells; these are the same used for one-piece cranks (you referred to Ashtabula, which was one brand of OPC that dominated the US market for quite some time...). An American BB shell is about 51.3mm in diameter, and is threadless; it accepts press-in cups that house the bearings. Many American BB shells are somewhere close to 68mm wide, but there is some variation seen among frames; most cranks compatible with American BBs will be designed to accommodate slightly wider or narrower shells. The term "American bottom bracket" typically refers to BB sets sized for American shells for 3-piece (or 2.5 piece, nowadays) bmx cranks.

Most 3piece BMX cranks are sold with the crankarms, bolts, and spindle. B/c bmx frames come with several different BB styles (American, Mid, Spanish, "Euro"*), the BB's are sold separately and consist of bearings, tube spacers, often some other spacers, and in the case of Euro or American BB's, the cups. The idea is, you match the BB to both your frame's BB shell, and your crank's spindle diameter. Eg, in order to run Redline Flights on my neo-Klunker, I had to get an American BB to match the frame, and that American BB had to specifically accept the 19mm spindle of the Flights.

Mr.Lucky: as we discussed in the other thread, you're pretty much limited to bmx cranks, although most will accept a spider if you want to run multiple chainrings. Most modern bmx cranks use either a 19mm or a 22mm spindle, although there are other sizes as well--- you'll need to get a BB with bearings to accept the specific size of your crank's spindle.

*"Euro BB= BSA threaded, aka "English" to those who forgot that the English had a few different threaded BB standards themselves....This is probably the most common BB style among most bikes, excepting cruisers and BMX