Author Topic: oversized bottom bracket!! (Read 923 times)

wadagangker · « **on:** March 16, 2008, 12:30 PM »

as a few of you may know, i am building a bmx from scratch (just frame). I have been enquiring around about a bottom bracket and have been told that i need an "oversized bottom bracket". i didnt really understand what the hell this guy was talking about

, but he said there is pretty much only 2 sizes of bottom bracket and i need the bigger one?!?! can anyone shed some light onto this? all i know is that the hole where the BB goes is quite big!! and there is no thread there (as this was one of the questions i was asked when enquiring). I would greatly appreciate any suggestions or any help people could offer.

RATTY · « **Reply #1 on:** March 16, 2008, 12:37 PM »

The one you probably want is a USA bottom bracket, it has no threads and the bearing cups just push in to the frame.

TwoBobRob · « **Reply #2 on:** March 16, 2008, 12:47 PM »

What is your frame? If its old school and the BB shell looks around 2" in diameter, then Ratty is right, You need a US BMX bottom bracket. It's gotta suit your crank obviously, so you'll ask for either a one piece or three piece BB when you order.

I did hear on here somewhere that some Mongoose cranks and BBs are different to the norm? I don't know a thing about this other than the threads are different i think. If you're running a Mongoose one piece crank, then a bit more research is in order I think

wadagangker · « **Reply #3 on:** March 16, 2008, 12:50 PM »

Quote from: TwoBobRob on March 16, 2008, 12:47 PM

What is your frame? If its old school and the BB shell looks around 2" in diameter, then Ratty is right, You need a US BMX bottom bracket. It's gotta suit your crank obviously, so you'll ask for either a one piece or three piece BB when you order.

I did hear on here somewhere that some Mongoose cranks and BBs are different to the norm? I don't know a thing about this other than the threads are different i think. If you're running a Mongoose one piece crank, then a bit more research is in order I think

the frame is an apollo (yes i know their crap) im trying to prove a point to someone that i can turn a piece of crap halfords bike into something to be proud of!!

TwoBobRob · « **Reply #4 on:** March 16, 2008, 12:54 PM »

That'll be a US BB.

So all you need to do now is match you BB type to the crank. Of course if you're going posh, then a brand new three peice crank will come complete with a BB and you needn't worry

Rombloke · « **Reply #5 on:** March 16, 2008, 12:55 PM »

yip usa bb

Dave

wadagangker · « **Reply #6 on:** March 16, 2008, 01:12 PM »

Quote from: TwoBobRob on March 16, 2008, 12:54 PM

That'll be a US BB.

So all you need to do now is match you BB type to the crank. Of course if you're going posh, then a brand new three peice crank will come complete with a BB and you needn't worry

so i need a usa BB? do they come in different sizes? what do you mean match the BB to the type of crank?

TwoBobRob · « **Reply #7 on:** March 16, 2008, 06:37 PM »

Sorry bud.... going a bit quick there....

Right.

Bottom brackets sizes curiously seem to be named based on geography, for example;

Yorkshire
Spanish
Euro
USA

In other words, the name depicts the size. There is only one size of USA BB, but there are two different designs, to suit crank types.

So, your actual crank arm assembly will be only one of two types. The one piece crank which as its name suggests is a single lump of steel that looks like a big letter 'S'.

Or,

The three piece crank which comes as individual parts; 2 crank arms and an axle to join them together, hence the name three piece crank.

So what you need to do is:

a) determine what size BB shell the frame has. I think we're all agreed it is USA sized. No threads and around 2" in diameter.

b) identify the crank as either one or three piece.

c) go out and buy said BB

4) come back here so we can give you the lowdown on fitting it all together

So, do you have a crank already, or do you need to buy one?

Three piece cranks are the better made stronger setups mostly, one piece cranks are the cheaper option and most people would say I reckon, the crank more identifiable to BMX. I'd certainly never seen one till BMX hit my town way back when....

You crank decision if you need to buy one will affect your BB decision.

Crank first, BB to suit afterwards.

Hope that helps, feel free to bombard us with questions

wadagangker · « **Reply #8 on:** March 16, 2008, 07:25 PM »

Quote from: TwoBobRob on March 16, 2008, 06:37 PM

Sorry bud.... going a bit quick there....

Right.

Bottom brackets sizes curiously seem to be named based on geography, for example;

Yorkshire
Spanish
Euro
USA

In other words, the name depicts the size. There is only one size of USA BB, but there are two different designs, to suit crank types.

So, your actual crank arm assembly will be only one of two types. The one piece crank which as its name suggests is a single lump of steel that looks like a big letter 'S'.

Or,

The three piece crank which comes as individual parts; 2 crank arms and an axle to join them together, hence the name three piece crank.

So what you need to do is:

a) determine what size BB shell the frame has. I think we're all agreed it is USA sized. No threads and around 2" in diameter.

b) identify the crank as either one or three piece.

c) go out and buy said BB

4) come back here so we can give you the lowdown on fitting it all together

So, do you have a crank already, or do you need to buy one?

Three piece cranks are the better made stronger setups mostly, one piece cranks are the cheaper option and most people would say I reckon, the crank more identifiable to BMX. I'd certainly never seen one till BMX hit my town way back when....

You crank decision if you need to buy one will affect your BB decision.

Crank first, BB to suit afterwards.

Hope that helps, feel free to bombard us with questions

Hi mate. great advice, cheers for that.

no i dont have a crank yet i just have a hole!! so does it matter wether i get a 1 piece or a 3 piece crank? you said i need to identify the crank as 1 or 3 piece, how do i do this? cheers bud. Dan

priv · « **Reply #9 on:** March 16, 2008, 07:37 PM »

gunna add to the confusion now,what axle will you be running if your going 3 piece?

some are 19mm or 22mm

19mm are the majority but primos for example are 22mm

and to answer your last question
1PIECE

3 PIECE

priv

wadagangker · « **Reply #10 on:** March 16, 2008, 08:12 PM »

Quote from: priv on March 16, 2008, 07:37 PM

gunna add to the confusion now,what axle will you be running if your going 3 piece?

some are 19mm or 22mm

19mm are the majority but primos for example are 22mm

and to answer your last question
1PIECE

3 PIECE

priv

I have no clue what axle i will be running mate, im new to this whole thing. I normally just stick to spraying bmx's!!! startin to wish id kept it that way! lol. whats the difference with the axles then, apart from the size obviously?

priv · « **Reply #11 on:** March 16, 2008, 08:35 PM »

wow where do we start?

if you buy 3 pc make sure it comes it comes with an axle,as there is alsorts of differences,splined,all number of teeth,square,

priv

TwoBobRob · « **Reply #12 on:** March 16, 2008, 09:33 PM »

The difference between the two is as in my previous post.

The real world difference used to be that cheap bikes came with one piece cranks, and if you were a lad with some money then a three piece crank upgrade was the thing to do.

For racers, aluminium three piece cranks were lighter than one piece.

Do yourself a favour and have a browse through the museum here. You're bound to find a crank you like the look of in there.