Is it just machining the frame around the bottom bracket & headset to make sure the surface is perfectly flat?

If so, what tool do you use and how do you ensure both sides of the bottom bracket are parrallel?

Facing tool and they’re not exactly cheap either.
Get a shop to do it.

Just had a look, they’re not cheap are they, jesus!

Thanks for the info.

why would you want to face a BB, then fit plastic spacers which distort upon tightening also the bb shell is threaded so facing wouldn’t really be of much benefit as the cups will follow the angle of the thread not the form of the outside of the cups??

headsets are a different matter though ive never had any faced and have never ever had a problem with sets wearing out quickly etc etc.

fatmutha – totally agree. I’ve never got this argument that people with external BBs have to have their BB shell faced as it will make no difference. As long as the threads are parallel then it’ll all be ok.

And sometimes LBS will cut the threads too.

Get the LBS to do it.

Thanks for the advice 🙂

Facing a bottom bracket will make a significant difference and the B/B isn’t alligned just by relying on the threads.

Considerably more important on HT2 Bearings.

anthony – can you provide a bit more explanation please? the threads are all that contacts the metal parts of a ht2 bb, as the face of bb only meets the bb shell with a plastic washer in between. i really don’t understand all this bb facing nonsense that’s going round at the moment.

As far as I can see, the BB threads (Or any other thread for that matter) aren’t an exact fit, are they? As in if you screw the BB half way in, it will still move slightly within the threads: There’s some play, if you see what I mean
So it follows that as you tighten the threads down the cup will settle and then align on the outer edge of the BB shell, not by the threads, due to said ‘play’.
So, that’s why, I think, BB shell faces should be parallel

Yeah but you have to do up a bottom bracket really quite tightly, with a fair amount of leverage. Al isn’t the toughest of materials, so you could easily get a bit of deformation if the face/threads aren’t parallel.

there’s a lot less play in bb threads than other threads. also there’s still the plastic spacer issue. those spacers can’t be made to that high tolerances and they do deform under pressure.

Plastic spacer?
All my cranks have metal ones.

Al isn’t the toughest of materials, so you could easily get a bit of deformation if the face/threads aren’t parallel.

Exactly. That’s what facing does, isn’t it?
🙂

Plus of course, that every alloy frame I’ve owned since 2004 was faced at the factory…..

P.S My argument was in favour of facing…

I watch several of my frames faced, and it always surprises me how much metal has to be removed before the cutter is touching the whole surface. They may well have been machined at the factory, but this doesn’t seem to guarantee trueness.

Never had a frame faced, still alive. Don’t go through stuff any quicker, King H/S is 6 years old, and certainly make HT11 bearings last longer than a lot on this site.

Go for it, if it makes you happy.