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Technical & Reference Section => Tech and Restoration => Topic started by: johnjo74 on February 24, 2010, 11:50 PM

Title: Junior /Mini Crank
Post by: johnjo74 on February 24, 2010, 11:50 PM

I am doing up an old 80's bmx up as a rider for my son . Not sure what the frame is , had no decals .
I want to replace the crank set up,  to something a little more attractive ! Not measured the arms , but it is a mini bmx with 16 " wheels  , so I'm guessing 140 /150mm ?
Will I need to replace the bb and look for a three piece crank / spider set up ?
Like i say , its nothing special , so dont want to be spending big bucks.
Anyway , can anyone point me in the right direction , as I am baffled with what to look for or put up a wanted for ??

(http://www.radbmx.co.uk/archive/albums/ae59/JOHNJO74/STA60066.jpg)

(http://www.radbmx.co.uk/archive/albums/ae59/JOHNJO74/STA60067.jpg)

(http://www.radbmx.co.uk/archive/albums/ae59/JOHNJO74/STA60071.jpg)

(http://www.radbmx.co.uk/archive/albums/ae59/JOHNJO74/STA60075.jpg)

(http://www.radbmx.co.uk/archive/albums/ae59/JOHNJO74/STA60078.jpg)

(http://www.radbmx.co.uk/archive/albums/ae59/JOHNJO74/STA60080.jpg)

Cheers johnjo74  8)

Title: Re: Junior /Mini Crank
Post by: MartyC on February 25, 2010, 12:06 PM

If you want to run alloy 3 piece cranks you will need to replace the bb as the one you have is for cranks that use cotter pins.  A set of old school 3 piece alloy cranks in a 165 length can be picked up for about forty quid or you can pick up a new school set for a similar price.  Best place to start looking is eBay as you might be able to pick up a bargain as junior/mini stuff is less sought after and therefore lower priced.  Thread wise you'll need an English thread bb and try and get one with the same width axle to ensure the proper chain alignment  :daumenhoch:.

Title: Re: Junior /Mini Crank
Post by: johnjo74 on February 25, 2010, 05:41 PM

Cheers for that , think I have a little more understanding of what I need now  :)
So is this the only way , or is a OPC set up possible ? If it is , what should I be looking for ?
Cheers , johnjo74 8)

Title: Re: Junior /Mini Crank
Post by: Bigfrawg on February 25, 2010, 05:53 PM

check the wanted adds , i think dazbmx has a mini opc  :-\

Title: Re: Junior /Mini Crank
Post by: MartyC on February 26, 2010, 08:33 AM

Quote from: bigfrawg on February 25, 2010, 05:53 PM

check the wanted adds , i think dazbmx has a mini opc  :-\

A mini opc is no good if he has a euro/english bb which going by the pics of his cotterpin setup that's what he has  :daumenhoch: