Bottom bracket/crankset interchangability
 

I have an older 10-speed Triumph roadbike that has a cottered crankset in need of changing. It's warped, rusty and ugly.
Now I have a slightly newer 12-speed Norco moutainbike with a 3-piece cotterless crankset and bottom bracket that are in great shape. I even like the pedals better.

Would it be possible to take off the old stuff on the Triumph, and replace them with the parts from the Norco?
It looks like everything should fit, but I thought I'd ask the experts before I cross-thread something or wind up with a bunch of parts that won't fit.

It should work if the bottom brackets are the same width. I believe that the Triumph uses standard English threading and the Norco surely does.

Anyone who has never touched a cottered crankset, raise your hands. (Raises hand.)

/me raises hand.


Thanks for the quick response. A quick measure gave a pretty similar number on the widths. Guess the only thing left to do is bust out the tools and give it a go, let's hope for the best.

I've worked on a couple of them and if I never see one again, that will be just fine. :thumb:

good luck/hope it turned out ok

Your Triumph probably has the propriatary Raleigh threaded BB which is 26 tpi if I recall correctly. The cups from your other crankset won't fit. It might be possible to rethread the English BB to the modern British BB standard thread. I changed my wife's Raleigh Sport to a cotterless aluminum crankset and used the English BB cups. If your's are rusty/pitted you may be able to find them at a shop on the internet like Harris Cyclery. Use loose balls, not the ones in a pressed steel cage. The cotterless axle was a tight fit thru the English cups. I think I used an SR axle. I have a box of strange cotterless axles - it helps to be a packrat.

I'm almost at the point where we should start refusing work on cottered cranksets unless we start raising labour rates :)

Cottered cranks are easy to remove if you use the correct technique. On this one Sheldon is dead wrong. Do not use a hammer to pound on the threaded end of the cotter! 100% of the time this will destroy the cotter and may upset it in it's hole making it even harder to remove. The cotter is purposely made from soft stel compared to the axle and crank arm. The first thing you do is loosen the cotter's nut and soak the cotter and crank with Kano Industries Kroil. Nothing else works. Set it aside for a day, reapplying Kroil a couple of times. With the nut loose place a 3/8" drive socket backwards over the round unthreaded end of the cotter so the cotter can pass thru it. Use the biggest C-clamp you can find to press on the nut and socket with the swivel on the adjustable part of the C-clamp on the socket. I use a giant clamp that is a foot long. Really crunch down on the clamp. This may be enough to unseat the cotter. If not tap the C-clamp with a steel hammer. Tap, not bash. A good part of the time the clamp will shift and you may have to reset it on the cotter. I have worked on many neglected cottered cranks and have never found one this technique won't do the deed on.