Shimano BB-CS20 bottom bracket unable to assemble

[marcinkrk]

Hi,
I've serviced couple of Shimano's bottom brackets but that one seems strange. As in RJ's the bike guy tutorial I removed rubber seal from the one side where the flange is and undone the locknut, then undone the cone nut, cleaned, regressed and tried to reassemble. The problem starts when I want to torque the locknut because it drives in the cone nut with it because there's no washer in between with a tooth that stops it from rotating I end up with overtighten bearings. There's also no slit in the axel where the washer's tooth would fit. I can't also imagine how did they assemble it and torque it rather strong in the factory. There's no way to hold the cone nut properly and do the locknut because there's socket on the way. Do you guys have any idea what kind of sorcery did they use to tighten it down?

 

[was8v]

What I do normally is:

1) put old sealed BB in the metals scrap bin
2) buy another

Sorry I can't be of help but is it worth the faff? Maybe on a un7* at a push, but a cheapo one?

 

[marcinkrk]

I see. Out of curiosity how do they tighten it? Does involve some thin octagonal pipe socket which fits the cone nut to hold it and allows socket to go through it to tighten the lock nut? I've never encountered pipe socket which is octagonal in shape, only hexagonal and they will not fit that particular cone nut.

 

[was8v]

They will have a big purpose built machine to churn them out e.g. https://bikerumor.com/2018/05/23/shimano-factory-tour-this-is-why-theyre-masters-of-the-metal/

 

[Alembic 42]

I have just done mine and I used a small flat head screwdriver to hold the cone in position while I tightened the lockring (counter-clockwise) onto drive side the cone - takes a few goes to get the correct pre-load with no play and not too tight, but can be done. I used a long spark plug socket to tighten the lockring.