Chasing and Facing
 

OOOOk. According to a search that I did on the Bike Forums, chasing a bottom bracket cleans the threads so it threads more easily. However, the facing of a bottom bracket is the cutting of the face of the BB shell so that the plane of the face is perpendicular to the axis of the Bottom Bracket.

However, an assumption that I am making as of now is that facing and chasing are not always necesary, at least not facing. Would a frame builder not face the bottom bracket before painting? I can understand needing to chase a bottom bracket after having it shipped to you, but the facing?

Ill probably bring it in anyway for insepction at the LBS.

HEre is the thread which I found:
http://www.bikeforums.net/archive/in.../t-132357.html

Im just wondering what your thoughts are on having to chase/face brand new frames direct from builder, and not that it makes a difference indicating the maker, but its an Iro Frame XD. IDK if it also makes any difference, but the Crank im using is SRAM Omnium. External bearings.

According to what ive read in addition to the indicated thread, im assuming that chasing and facing are not always necessary, and that I can install the crank with no facing/chasing at all (of course with copious amounts of grease=p).

Ive had a bike before, but this is the first time that I will build it from the ground up.

I just need help and hope you guys will bear with me as I go through the process.

iro frames are chased and faced from the factory. you shouldn't need to do any of that to a new frame.

really, any new frame should be ready to assemble with a gxp or any bb.

if you paint it or powdercoat it, then you'll need to do one or both depending on what was masked and how.
usually that isn't necessary... but you need to take great care when installing a bb on any frame as crossing the threads can quickly destroy the frame. just make sure it's not difficult to install the cups/shells and if it is difficult that it's not getting significantly more difficult the farther in the shell goes. if you're not sure about what you're doing, get it installed at a shop unless it's a frame you can afford to mess up.

Ok. Thanks man. Well, other than the factory paint, i haven't added anything to the frame. And yeah. I would think that as important as chhasing and facing are, i would think that builders today would face and chase them prior to shipping them to their distributors.

But thanks CC.Ill double check though just to make sure. Better safe than sorry.

I've built numerous bikes with both steel and aluminum frames, and have never faced the BB, but have had the threads chased on the steel frames by my lbs. I've never had a problem with the BB. The head tube, however, might need facing and reaming to ensure proper alignment of the headset cups.

Facing the BB is important for those bottom brackets where both cups have a flange, and they rest against the shell face when tighened to the proper torque - e.g shimano octalink, any external bottom bracket system. For those that are not this type - having coaxial bottom bracket threads is next similarily important - otherwise the BB binds when properly torqued. Due to sideloads on the bearings = e.g old campy square taper.

Proof is always in the installation, and comparison between non installed spin resistance an installed spin resistance.

Since there is never a sure answer, facing and chasing the BB always removes all doubt.

If the threads are indeed not coaxial, how will chasing the threads remedy this?

If you are getting Omniums (or any other external bearing crank for that matter) PLEASE spend the extra few bucks and get the frame faced. I work at a shop and for the longest time I was one of those that thought it was not THAT important to face the frame for external BB cranks. We recently bought a facing tool and all of our cranks are running soother than before. We've even gone as far as calling customers who recently bought external BB cranks and offered to face their cranks for free if they wanted to come by and drop the bike off for a bit.

Sure, the bearings are not going to explode if you don't face your BB shell but you'll extend the longevity of the entire system. I would say that in the case of some high end bikes like my Tarmac which have a machined BB shell it is not necessary but pretty much required to anything else.

I recently purchased an Argon 18 Electron which appeared to have a faced shell. There was no paint on the shell faces and the Aluminum was smooth as if someone had faced it but after a few turns of the facing tool metal began so shave off. The Omniums I installed are the smoothest external BB system I've encountered (next to campy).

If the bb faces have paint on them, they ought to be faced, but doesn't seem to be particularly necessary nowadays.

Not once have I had a customer complain about bb noise and upon actually facing a bb with paint on the faces from the factory, found that the faces were even.

I face the ht and bb of every bike I build for myself; any high end build in the shop. OEM bikes could probably use it, but is not a common part our usual bike prep and setup routine with anything other than bare frame builds.

It depends how far off they are. A piloted tap set should be able to correct minor misalignment.

FWIW, my IRO Mark V didn't come faced or chased, even the serial number is covered by paint and I couldn't read it.

Campagnolo made a "go/no-go" gauge that shows whether the head tube needs milling:
http://www.os2.dhs.org/~john/passa-nonpassa.jpg

Thanks for all the great replies. I did notice on both the Cane Creek and Chris King websites they recommend chasing and facing. That would make sense since they sell their units to older/used bikes as well as new builds. I just picked up a 2007 Cannondale (USA made) F1 frame (RAW). When I run my finger along the edge of the bottom bracket it feels rough. I'll take it into the LBS for their take.

proper frame prep should be a one-time precision operation, and is absolutely worth doing if the frame is worth hanging on to. face/chase bb, head tube, disc mounts, ball-hone seat tube, check alignment if so equipped.

would i do a kilo? unlikely. did i do my sputnik? everything but an alignment check.

Phil Wood BBs eliminate the facing issue...just sayin'

Non sequitur.