facing bottom bracket???

[Judderz]

Cheers Fossy

 

[PaulSecteur]

That would be great.

Just remembered this thread after the forum was down for the upgrade. I will get some pics up soon.

 

[Nebulous]

What about replacing like-for-like, a Hollowtech 2, with another one. Would that need anything done, or can I assume it would already be parallel?

I have a Tiagra compact, and have done somewhere over 3000 miles. The last time I wondered about dismantling it I took off the chain and couldn't believe how smooth running it was, so I decided to leave well alone. I doubt if I'll get off with that after another winter though, so might replace it in the spring.

 

[ACS]

Just remembered this thread after the forum was down for the upgrade. I will get some pics up soon.

Paul, no hurry I'm off the grid this weekend, taking mental health break, no computers, no cycling, no kids just me and the SWMBO and some R&R.

 

[TheDoctor]

I've never understood this. if the threads in the BB are in line with each other, then the faces are irrelevant. Similarly, if the threads are skewed, then facing the BB won't help.
Can someone explain?

 

[lpretro1]

Any bump in the surface where the bearing cup is inserted means that there is an extra bit of pressure on the bearing - the bearing itself is not totally rigid. Over time that bump will cause premature wear at that point on the bearing. That is why it should be faced so that is it a smooth as can be. It can just be a thickening in the paint finish. It is only carried out on a metal frame. It is not an issue if you have a carbon frame as the bb shell is inserted when the frame is built and will already be flat.

 

[mickle]

The BB manufacturer is covering their behind with the advice to face and chase. In the 'olden days' it wasn't uncommon to find BB shells which had faces or threads which were so skew-wiff as to make BB installation a almighty PITA. Usually a result of frame manufacturers threading the shell before welding, which left the shell warped, particularly in the early days of mass produced aluniman frames.

Standards are so much better now. If the bike was made in the last ten years I wouldn't bother.

 

[Smokin Joe]

I've never understood this. if the threads in the BB are in line with each other, then the faces are irrelevant. Similarly, if the threads are skewed, then facing the BB won't help.
Can someone explain?

That's what I've always thought.

The threads on a bb shell are quite fine and go along way into the shell allowing no play even before they are tightened. If the faces are not parallel surely the cups would just tighten against the high spots without being pulled out of line?

The few people I have known who fitted external bearings to an old frame never bothered with facing and had no problems with premature wear.