Replacing old cottered cranks/bb

[brainpolice]

trying to replace the bb and cottered cranks on an old murray road bike (early-mid 80s is my best guess on date) - i want to replace them with modern parts (square-taper spindle and cranks). took the bb off and measured it, and it's something like 78 x 149mm (78mm being the length from outside of one cup to the other, 149 being length of the spindle). this seems really weird... am i measuring it wrong? if it's right, can i use a normal 68 x whatever bottom bracket (i'd assume not, but)? how do i size it? or do i have to track down a bb of the same size? thanks!

[Bill]

I really can't answer this one, but I am intrigued on how you got the cotters out though?

[nfmisso]

BP - pictures please !!! Ignore the overall length - it will have to match up with the new crankset you get. Remove the existing stuff from the frame (cups, axle, etc) the measure the housing on the frame.

Hi Bill - I always used a center punch and hammer after removing the nut and washer.

[Bill]

(02-25-2012, 09:16 PM)nfmisso Wrote:  BP - pictures please !!! Ignore the overall length - it will have to match up with the new crankset you get. Remove the existing stuff from the frame (cups, axle, etc) the measure the housing on the frame.

Hi Bill - I always used a center punch and hammer after removing the nut and washer.

Hi my friend. I have a couple of older bikes ,as everyone here knows lol, that have the cottered cranks. Hammer and punch is a way to do it with a block just under the spindle on the side of the cotter that is being driven out. I use this neat little tool... http://www.bikesmithdesign.com/CotterPress/index.html .

Sorry didn't mean to high jack the thread.

[RobAR]

Bill - you are the Nut on the threaded end of a 9 mm cotter.

[Bill]

LMAO!!!! Your the cap at the end of the bar tape keeping everything smooth and together in a neatly fashioned lol.