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Cottered crank/BB vs newer crank/bb

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Cottered crank/BB vs newer crank/bb

Old 06-09-07, 07:56 AM
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chevy42083
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Cottered crank/BB vs newer crank/bb

So I'm putting together this old Royce Union with cottered cranks as a beater/commuter/fixie. The bottom bracket has some play in it (not sure if it's just loose, or trashed). It will wobble around.

I have NO idea about anything bottom bracket or cranks. Are they interchangeable (cottered and not)? I had considered swapping the cranks so I could use a different chainring... I have a small collection from when I raced BMX bikes. Wondering if i should/need to swap BB and cranks together. Any idea on a REALLY cheap set? It's a single speed now, and will have a flip flop hub.
What measurements do I need? I mean, I know the width of the BB shell. What else? Distance from center to the rear cog? BB diameter, where would I measure that?
What are the chances the BB and 1 peice crank from one of my old BMX bikes would fit the Royce Union? Is there a problem with 1 peice which use the practically solid chainring gear compared to the newer three peice cranks which use a chain ring? Available sizing? Strength? Pedal sizing?

Install myself, or just take it to a shop to have it done?
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Old 06-09-07, 12:14 PM
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Good luck getting the cottered cranks off. They are a PITA. If you are just going to use it as a beater, just adjust the play in the BB (loosen the lockring on the left side, move adjustable cup, tighten lockring), then pour some oil down the seatube to lubricate the BB. It will work forever.
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Old 06-09-07, 12:15 PM
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Good luck getting the cottered cranks off. They are a PITA. If you are just going to use it as a beater, just adjust the play in the BB (loosen the lockring on the left side, move adjustable cup, tighten lockring), then pour some oil down the seatube to lubricate the BB. It will work forever.
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1990s Raleigh M20 MTB--2007 Windsor Hour (track)
1988 Ducati 750 F1
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Old 06-09-07, 01:28 PM
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I'll try to tighten it up.
The bottom bracket part of the frame has a grease zirk/zert... whatever you call it. The nipple with a spring loaded ball that you hook a grease gun to. How much grease? Pump it till the old grease starts to come out the seams? Just a little?
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Old 06-09-07, 01:38 PM
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Originally Posted by chevy42083
So I'm putting together this old Royce Union with cottered cranks as a beater/commuter/fixie. The bottom bracket has some play in it (not sure if it's just loose, or trashed). It will wobble around.

I have NO idea about anything bottom bracket or cranks. Are they interchangeable (cottered and not)?
This bike will have a standard 68 mm threaded bottom bracket, like almost all adult bikes not made in Italy. Any normal crankset will fit if you install a bottom bracket appropriate for that crank.

See: http://sheldonbrown.com/cotters for tips on removing the old cranks.

and: http://sheldonbrown.com/tooltips for info on removing the old cottered bottom bracket.

Originally Posted by chevy42083
I had considered swapping the cranks so I could use a different chainring... I have a small collection from when I raced BMX bikes. Wondering if i should/need to swap BB and cranks together.
Yes, you will. Cotter type bottom brackets only work with cottered cranks.
Originally Posted by chevy42083
Any idea on a REALLY cheap set? It's a single speed now, and will have a flip flop hub.
What measurements do I need? I mean, I know the width of the BB shell. What else? Distance from center to the rear cog? BB diameter, where would I measure that?
You don't need to be concerned with any of that.
Originally Posted by chevy42083
What are the chances the BB and 1 peice crank from one of my old BMX bikes would fit the Royce Union?
Zero

Originally Posted by chevy42083
Is there a problem with 1 peice which use the practically solid chainring gear compared to the newer three peice cranks which use a chain ring? Available sizing? Strength? Pedal sizing?
No way a one-piece crank will fit a threaded bottom bracket.

As to pedals, one-piece cranks use the 1/2" pedal thread size.

Bikes with two- or three-piece cranks use the adult 9/16" pedal thread.

Originally Posted by chevy42083
Install myself, or just take it to a shop to have it done?
Depends on your level of competence, tools available, patience...

Sheldon "Interchangeability" Brown
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