Yet Another Cook Bros RSR Bottom Bracket Length Thread [Merlin Edition]

worldcollapse

worldcollapse

Dirt Disciple
i've went through dozens of threads and still at a complete standstill with so many varying opinions.

i've got a 1995 merlin mountain, and a set of cook bros RSR's silver.
typically i see 122.5 recommended [will 123 suffice?] however some instances i see 127, 127.5 [here], hell even 125 suggested!

any first-hand suggestions before i further go insane?
 
Yes, I started my own similar thread a while back. I had some other non-spindle length questions answered but sort of lucked out with the bottom bracket already fitted to my frame being a good length. Oddly enough a 108mm Syncros spindle works with my 93' Cannondale M800 frame which is a lot shorter than usually recommended. Chainrings clear with sufficient space and crank arm ends have lot's of clearance from chainstays. I'm not 100% sure but have been led to believe my Syncros spindle is ISO taper rather than JIS. It also seems recommended to use ISO tapers with Cooks, RSRs at least.

I'm unsure if using Shimano JIS is a bad idea or not. I know riders that have used Shimano bottom brackets with Cooks without issue, I think the cranks sit a couple millimeters out using JIS compared to ISO.

Ultimately if someone has a 95' Merlin Mountain with RSRs fitted they would have your answer.

Do you have any spare bottom brackets to experiment with to see what lengths might provide the correct clearance?
 
I just realized you're probably dealing with a non threaded bottom bracket shell? Press in cartridge bearings with the Merlin?

If so my spare bottom bracket experimentation suggestion won't be much help
 
sorry, 95 = 68mm threaded shell!
which of course, UN55 are completely non-existent these days which is a shame. UN300 looks fair... but still unsure. at least dual metal cups.. though i am unsure of that little notched collar which in itself is it's own discussion. bizarre.

the JIS/ISO discussion is a weird one though i was never too concerned with it. i always figured over-torquing and ill fitting sizing resulted in the 'cracking'.

just wanted some user input because obviously test fitting would be best, but don't really want to buy a sack of bb's that i will likely never use again just for science.
 
🤣, no don't blame you!

Thought you may be like some of us with way too many old parts lying around. Too bad you weren't closer, I could lend you at least six different sizes to try out

I agree JIS is most likely safe with correct torque applied 👍
 
You must log in or register to reply here.

Latest posts

Back
Top