chasing and facing
 

i sort of hijacked a thread in the road forum about this.

do all framesets need to have this done? i've only seen a couple of references to it from on-line retailers. i recall one seller indicated that the frameset was completely prepped - chased and faced. all the rest never mentioned anything about it.

i'm buying a soma frame. since this is a "discount" frame, should i assume i need to take it to an lbs to have it prepped? what is the typical charge for this?

thanks

All frames should be chased and faced, allthough I know some people have forgone the procedure. The paint and metal reside in the BB shell threads can cause issues when installing the BB. Paint on the outside of the shell can cause the BB not to line up flush with the shell causing serious issues. A lot of frame manafactures do this prep work before selling the frame, but discount frame makers do not. You can tell simply by looking closely or asking the seller. Expect to pay $50 at the LBS.

It's not really needed with modern manufacturing. The component makers list it as a requirement mainly to cover their ass.

Example: A shade tree mechanic fubars a bottom bracket install due to his own incompetence. He calls the distributor to file a warranty claim. The distributor asks if the BB shell was chased and faced (knowing fully that it requires special tooling that the home mechanic most likely does not have). The home mech replies, "Uh, what's that?".

Result: Warranty denied.


Use some common sense (removing excess paint from threaded and press fit areas) and you'll be fine.

If you're using a shimano cart bb, or any modern non loose ball bb. you can almost always safely ignore this.

+1. My LBS charges $35 a piece to chase and face the bottom bracket and face the headset. That price includes the install of the bb or hs.

I made a set of thread chasers out of a set of old chrome bb cups. Take a dremel tool and cut 4 grooves in line with the bb axle direction and set a carriage bolt through it with the head inward. Set a pair of nuts on the end, tightened together to form a wrenching flat and voila, you have a thread chaser. I have used the same pair(you will need one for each side due to opposite threads) for several years. Be very generous about bolt torque.

Note: the parts list includes 1. a fender washer
2. A carriage head bolt
3. 3 Nuts

Most frames I encounter at work don't have this done and need reasonable amounts of prep work. The main reason this is needed is because metal frame tubing distorts from the heat applied from brazing or welding, so the bearing surfaces need remachining with special milling and tapping tools that are cheap enough so that a shop doesn't have to buy a vertical mill or thread tapping machine. Prep work doesn't simply remove paint in most cases, it just looks that way. The paint merely acts as a tracker when facing a BB shell or head tube; the paint that remains is just a low spot that can indicate more facing is needed for example.

BB shell threads should ideally be tapped with a piloted tap set (not just chased), so they are aligned on a common axis. The facing procedure then references the aligned threads so that everything is nice and square.

For Shimano-type cartridge BBs, tapping may be needed so that the plastic or aluminum left side cup doesn't get stripped from poor quality threads, but facing is unnecessary. Cartridge bearing BBs that have separate replaceable cartridge bearings in individual cups that reference the shell faces do benefit from tapping/facing, and for external bearing BBs it should be considered a necessity. Many of the external bearing BBs have little tolerance for unfaced shells (Truvativ cranks are the worst in my experience) and the bearings seem to crap out rather quickly if this is overlooked. I usually recommend that customers have this done before installing any external bearing BB.

Surprisingly, I've seen some of the mail-order frames (e.g. Douglas from CC) fully prepped, where as most frames from the bigger companies like Trek, Giant and Specialized usually forego any prep work. Most high-end small builders seem to do this. If you're investing in a nice Chris King headset or an external bearing crankset, it's worth paying a little more to get the frame prepped by a competent shop (you may have to try a few shops; find one you know has good mechanics and tools, a couple I've worked for either had no machining tools or had poorly maintained/abused tools). It only has to be done once, and it's usually cheap insurance for better bearing life and performance. HTH.

Agreed. I chase and face my BB and face my headtubes on every one of my own bikes and most of the bikes I sell. It does take some time, so it's not realistic for a shop to do it on every bike they sell. I would request it free on a bike $1000+ if it's not already done in the first place.

Yes, cartridge BBs will work fine on a painted BB shell. Remember though, even if the BB threads on straight, you can still have gaps between the shell and BB cup for water, dirt, sand, etc. to invade.

The headtube is just as bad if it's not faced. I've had more than a few bikes come through that felt like you were steering through a mixture of sand, mud, and glue. Surprisingly, one of these was a Gary Fisher Hi-Fi Deluxe. Simply prepping the headtube and reinstalling the headset did the trick.

Best case scenario in unprepped frames? Slightly increased bearing wear/overhaul intervals.

Modern as opposed to what? A smithy hand forging your frame from iron? Componant makers suggest it for a real reason otherwise they wouldn't bring it up and thereby open themselves up to warranty claims.

Since when do "shade tree mechanics" call distributors? Most distributor won't take your call. They'll refer you to an authorized retailer. If they don't, they're fools.


Any "modern" BB design that places the cups and bearings outside the BB shell needs to be faced. It is NOT done during manufacturing. You may get lucky but if your BB shell isn't faced properly you will certainly decrease the life of your bearings.

I have had BB (with the frame attached) come into my service center as a warranty claim. I remove the BB, chased and faced, and viola! Smooth as a baby's bottom.

Weight the cost of a chase and face with the cost of 1 BB. Then decide.

This comes up regularly and I always post the same old engineering maxim:

"A bearing is only as good as its mounting."

There's never time (or $) to do it right but always enough to do it over.

I don't buy it. Where's your proof? (Proof that the BB shell on an OEM frame isn't faced to close enough tolerances for adequate bearing life)

There are tens of thousands of production bikes out there with external bottom brackets mounted from the factory.

There is difference between OE installation on a new frame (and new BB shell) and installation on a "experienced" frame that could have been subjected to a myriad of conditions, that could have damaged the shell facing or threads over time. Since this is a mechanics forum and not an assembly factory forum, I will assume the later to be the case.

My proof is the internal memo I got from the Campagnolo Service Center in Italy telling us to remind distributors and retailers to face their BB shells.

My proof is in the 20+ years of wrenching for a living that has demonstrated to me, over and over again, the prudence of chasing and facing.

You may get away with not doing it but, then again, you may not. You'll never know just by looking at the shell (unless the threads are obviously damaged).

As to a new frame: Frames are built without paint (obviously) and the shell may be just fine. Slap some paint on there and suddenly you have a heap of paint that could cause the cups to not sit properly against the shell face. Again, I have seen this enough times to accept it as a fact. I'm sure there are other wrenches on BF who have seen the same thing.

I've seen how bare steel on the faces of a bottom bracket shell can rust and the rust can run under the paint and destroy a beautiful paintjob.

Couldn't the bottom bracket cup chip the paint and expose the bare steel?

Anyway, I normally face and chase shells if a customer brings in a frame and wants an external BB crank installed. I hardly ever take apart an OE build to face/chase unless its being build for a special customer or has specifically requested it.

One question for all you wrenches, what do you do with carbon bikes with aluminum or ti bottom bracket shell inserts? It seems risky to try to face those shells. I built up a carbon bike recently (I think it was an ADK frame) with a Al BB shell insert. The faces didn't look to be perfect but I played it safe and didn't face it. A ruined BB < ruined frame

I bought a new carbon frameset recently and the BB has been faced (visually & per checklist).

Question: On a steel frame, what do you do to the exposed metal after it has been re-faced? It does have an external BB now, but I'm still wondering if water can creep in and cause rusts. Thanks!

Good point. If your tools are sharp, you should get a nice edge to the paint. I then put a liberal amount of grease on the freshly faced shell for just this reason.

+1

For Aluminium: Since the inserts are often 2 pieces that are bonded into the carbon frame, you are at the mercy of the frame maker a bit more if there is damage (although maybe a damaged cup could be replaced by someone like Calfre? Not sure here). I'd still face and chase.

For Ti: If it's a Ti frame and isn't painted I'd leave it. Most shops don't have the proper cutting tools for Ti anyway. I'd be interested in hearing what others do here, as well.

Yep, they're covering themselves from fraudulent warranty claims. Where are the failed bearings?

That's hardly proof. Where are the piles of prematurely failed bearings?

In my experience (a mere 11 years in the shop), very few frames actually require re-facing the BB shell, and on those that do, it's pretty obvious that it's needed. Binding and difficulty in adjusting bearing preload are two signs that something is amiss.

I'm standing by what I first said. Unless there's a problem, facing/chasing is unnecessary.

This has come up before. Last time, a frame builder said that he did not want has BB's faced because of the rust issue. I can't remember who it was, maybe Richard Sachs. He's a member.

I have faced lots of BBs and headtubes. I have yet to have one that is square from the get go. SOme where pretty good but never square, the "out" section is always where the chainstays are welded or brazed in. More surprising is the headtube. The part is often "finished" before becoming part of the frame, but the faces are still off every time.
Does it matter? For the guy that whacks his junk together with a twobyfour and a hammer, ... NO. For guys that want their stuff right,... it matters. You can hone a cylinder with emory cloth and get by with it but a proper hone does it right. Get by or do it right, your choice.

In the recycling bin in my shop.


See above.

Perhaps we're just different types of mechanics. I prefer prudence and earing on the side of caution. You?

I consider frame prep analogous to blueprinting a car engine. Sure the engine will run just fine with mediocre tolerances, but mic everything and precision hone your cylinder bores and you can get substantial increases in HP and longer intervals between engine rebuilds. Same goes for bearing surfaces on a bicycle. And again, it's cheap insurance, you only do it once for the life of the frame.

Just two days ago I punched out the cups of a customer's Chris King headset. A little tight-loose pattern and a trashed lower bearing after a year of use. Guess what, head tube not faced. Probably contributed to that. Being anal-retentive, I machined it for him no charge. On a properly machined head tube I've seen those things go for several years with almost zero maintenance.

Frame prep is sort of a "specialty" service that a lot of shops I've been to (and worked for) don't offer. I've seen plenty of trashed tools too; I think a lot shops simply don't know how to do it or don't know how important it is. It's also easy to screw up your tools or the frame your prepping (use lots of cutting fluid, special fluid for aluminum, keep your taps/dies/reamers/facing mills nice and sharp, don't bang the cutters around or store them in a tool box where they'll bang around against other tools, don't turn your reamers and facers backwards when cutting). I've done some hobby-level machining, so I'm probably a little more knowledgeable about machining than the average mechanic (I am not a machinist however). When I started at the shop I'm currently at, I sent in all the cutting tools to get sharpened. The tool grinder ground off about half the lands of the BB taps to get a good edge again, they probably hadn't ever been sharpened with something like 10+ years of use! Cutting tools are unique among bicycle tools: they're expensive, very fragile and high precision. But many mechanics treat them like cone wrenches and vice grips, and they often get ruined (one shop I worked at had a Campy toolset; about a third of the tools were chipped or broken, nearly made me cry, now those are some expensive tools!).

I think what separates the good shops from the ordinary shops is service like this, where real mechanical expertise comes into play. Fixing a bike isn't a lego set or simply replacing worn parts; the best mechanics I've seen (or worked with) were masters of frame machining, alignment, overhauling hydraulic brakes and suspension, and diagnosing and fixing the puzzling repairs (e.g. mysterious noises or creaking) that other shops could not or would not do. The best ones were also the ones that could admit that they didn't or couldn't know everything there is to know about fixing bikes (bikes have gotten complicated!) at any given time.

I think a lot of shops got lazy. when Shimano introduced cartridge BBs you could easily get away without facing. Chasing only became needed if there were damaged threads. basically, an entire generation of wrenches gained their experience at a time when you usually didn't need to chase and face.

Now, with BB designs having changed back to a design which benefits from this machining, most of the mechanics simply don't know how any more.

sooooooo

anyone know of reputable chicagoland shops that perform this service? does performance bike do it?

Sure. I agree with "prudence and earing on the side of caution". But I'm also a realist. Most bicycle frames will accept another headset or bottom bracket without issue. My major disagreement is with the statement "All frames must be faced and chased - no matter what!". Most will.

Great work!

Everyone knows King only sold all of two headsets in that last five years.

You've single handedly corrected the only King headset installation screw-up in the past five years! (The other one was installed by a reputable shop with freshly sharpened facing tooling.)

We all know there aren't any King headset users out there that not only installed them without having the frame faced by a pro shop, but are curently using them without problems. :rolleyes: