Right way to install a BB cartridge.

[Andy in Germany]

I'm replacing a BB this afternoon: Elder Son has progressed on his bike mechanic apprenticeship from "I don't know how to do this", through "Hey, I can do this..." to "I've done this so often it's boring so here's some tools."

My memory is that I should screw the cartridge in first, then the plastic nut on the other side to tension it, but he thinks it should be done with the plastic nut first. Which is it?

And how many newtons should I use? Some people seem to say 40, others say 60.

 

[sleuthey]

And how many newtons should I use?

That depends on the distance that you apply the force from the BB
If you mean how many NewtonMeters (Nm) then surely it will say in the BB litriture/spec?
If I had your guidance only Id go for around 55Nm (upper end but not maxed out).
From memory I put the plastic ring on first just by a few turns to guide the spindle through then fit and tighten the BB before tightening the plastic ring. Seemed to work quite well on both occasions

 

[presta]

Cartridge first, and 50-70Nm.

 

[Nigelnightmare]

Look here:

View: https://www.youtube.com/watch?v=xUtOeFJJycg


HTH

 

[12boy]

Good to grease the threads before you screw in the BB with heavy grease or anti seize. My LBS guy says go easy on the plastic threads on the left side, they can crack if you try to get them flush with the frame. All the left does is provide a little support as t he drive side holds it in place. I tighten mine with an 18 inch breaker bar until I can't and they have never come loose or creaked. I've cracked a few of the plastic side though, and now only get metal on both sides.

 

[si_c]

I tend to grease the threads then put in the plastic cup first - but only so that it is in far enough to support the loose end of the cartridge. Put the main body in then as far as it will go, tighten it up and then tighten the loose cup.

I don't tend to use a torque meter for BBs same as I don't for pedals - the rotary motion of the cranks turning will tighten it up as you ride anyway.

 

[Andy in Germany]

Many thanks one and all, the BB is now fitted and I'm about to clean the frankly disgusting chainwheel before putting that back on too.