Do I really need to face the BB shell?
 

Hey guys, question.

Say I want to upgrade my crank. Right now I have a square taper cartridge type BB (shimano). I'm upgrading to a hollowtech II BB. Do you think I should really face the bottom bracket shell? In other words, how common is it for the shell faces not to be square with relation to the threads? I don't have the cutting tool to do it, and it's expensive.

Some more information:
- cheap alu7005 frame (Ridley Ignite A30)
- same frame is also sold with SLX cranks on a higher model (A10)
- about 6 months old, BB has never been removed

Input greatly appreciated.

I'd say there's a good chance it's square. You should probably file the paint off the faces, at least.

You can probably get an idea how straight they are by colouring over the ends with a permanent marker, half-tightening the cups and then undoing them again to see where they've rubbed off the ink...

And if you take the bare frame into a shop, they shouldn't charge you much to face the BB of an ally frame.

I would do as Kimmo suggested. You can also measure the shell faces for parallelism and be fairly certain it's close enough for OBs. There was a case posted on this forum (can't find it now) where they had the BB faced and ended up with horrible chatter marks that couldn't be undone. I'm of the opinion that the cutting angles on the cutter was not proper for aluminum. Not saying this is the case with every tool, and every operator, but I'd not chance it.

xlDooM, It's more important to face the BB shell on an unbuilt bike. Use a flat file to remove any paint, being sure to keep it across the circumfrence at all times. This can also show whether you need to face the BB or not.

Brad

The dreaded chatter... it's a right bastard, that. A decent operator shouldn't let it get out of hand, though.

Why? Given the bike was specced with square taper, perhaps the BB wasn't faced, or faced to the same standard as it should be for an external BB.

It can't tell you how square the cuts are.

When I modified one of my bikes recently from an Octalink HT1 crank to an external bearing HT2 crank I first installed the external bearings snugly and did a try-fit with the new crank's spindle. The fact that the spindle slipped through both bearings with no binding or force indicated the bb shell faces were adequately parallel. If the spindle had been a force fit, I'd have had the shell faced.

Get the BB shell faced by someone who knows what they are doing. Bearing alignment is based upon the shell faces being parallel. Premature bearing failure can result from misaligned bearings. Decide whether you want to pay some money up front now for a bit a of machining or more money later for a bit of machining and a new bottom bracket.

Your choice. Al

And while you're at it, have them do your head tube. Chances are that if the BB wasn't properly faced, the HT wasn't either.

Cup and cone BBs need to be faced if there is any doubt. If using a cartridge, it probably doesnt make that much difference.

For the purpose of this discussion, outboard bearings have more in common with cup-and-cone than square-taper/ISIS/Octalink sealed units.

For the latter, the two bearings are in one unit and therefore parallel with each other by default, regardless of the BB shell. With cup-and-cone and outboard, how parallel they are is dependent on the BB shell faces being parallel.

facing at the LBS is a big waste of money IMO. i would much rather trust the manufacturer of the frame or BB shell to have faced it properly during the manufacturing process. (there was a time, many decades ago, when quality frames were only made by hand, and depending on the builder, tubes may have been cut out of square more often than today.)

for me to take the time and trouble and expense to present the frame to the mech at the LBS, i would first have to be convinced by someone that the BB was indeed OUT of square. my guess is that the LBS can't or wouldn't do that. and if they did manage to show me that the BB was out of square they would then have to show me that it had been fixed.

way, way too much trouble. and i wouldn't be surprised that even finding an LBS that would do it properly is unlikely.

but it's fashionable for BB facing and headtube facing to be recommended these days, so i guess some will recommend it no matter what...

My LBS mechanic is a cool dude who charges very reasonable prices, but he's of the old fashioned type and I don't think I trust him too much with precision jobs.

I can get a Saint or XTR BB for about 22 euros plus shipping, so I think I'll try it without facing first (I'll file off the paint with a flat, fine file as recommended). If it feels out of square or the bearings give up in less than 1000 miles I'll bring it to the shop and order a new BB. Thanks for the input. Now I just have to save my gas money in a jar and decide which crank :D Zee is 85 euros right now so that looks like a steal.

This is good advice.

Just as an additional useless comment - our shop prepped and built a $14,000 Italian machine for the Expocycle last year. The BB needed facing because the clear coat covered the external bearing interfacing surface but surprisingly enough - the BB had to be faced to bring it within dimensional tolerances too. Check the specifics for your own crank and you'll see some pretty hard numbers.

So if they were initially off on a hand built frame for a $14,000 bike - I wouldn't count on them being acceptable by default on anything mass produced with a much smaller price tag. But as noted - cartridge BB's and BB30 configs have slightly different tolerances.

Just the type TO trust, if we both mean the same thing by "old fashioned".

I'm not sure that's a valid comparison. Hand built frames are more likely to show dimensional variation than those built by modern machinery, no matter what the price. Obviously Wal-Mart bikes are machine built and the tolerances are likely to be pretty poor but any "big name" bike-shop quality volume builder probably does better on average than a small shop artisan.

I think you're being overly optomistic. In theory mass producing BB30 bottom brackets (without a requirement for plastic inserts) should then have produced frames with no issues. But thats not what happened.

kimmo, My first builds were with cup/cone BBs and facing the BB and HT and chasing the BB became my practice, which was taught to me by the owner of the LBS I worked for. Cartridge BBs are more forgiving WRT parallel faces, but still it's my practice.

Using a file on the BB can reveal high or low points, but can't help determine how parallel the faces are.

Brad

25 years ago , The Name Italian builders expected the selling shop to do the final threading , facing
and reaming with their own cutting tools .. They often had the lovely Campagnolo made set..

and so were shipped painted but not ready to install Headset or BB..

but that was then , and the frames were Steel.

Was there any issues with the BB that was installed at the factory? No? Then why "fix" something that ain't broke...?

Only upshot here is perhaps the opportunity to screw something up that wasn't wrong in the first place.

Unless you're moving from a cartridge BB to a crankset that uses an outboard bearing system like Shimano Hollowtech II, RaceFace X-type Crankset, FSA MegaeXo, and Truvativ Giga X Pipe - in which case its a different ballgame.

This is a direct quote from the RaceFace website regarding the installation of outboard bearings:

Don't bother with it. The BB's are more forgiving than we are led to believe. These things are not Swiss watches.

True but expect accelerated wear of the bearings if the faces are not parallel.

It's overly optimistic to expect all new frames to be faced and I've found un-faced BB shells on new bikes already fitted with outboard bearings. Surly frames do seem to face the shell, at least on the ones I've worked on. If you are going to change a square tapered BB for outboard bearings (and I can never understand why anyone would want to), then "a pennyworth of tar" comes to mind.

Ridley bike? doubt you will have problems, those are already faced from the factory, actually even with chinese no name cheap ass frames is really rare they need facing.

Good luck

The majority of the "fix" done by facing is removing uneven layers of paint. It tends to drip down towards the bottom and causes a trapezoidal shape to BB-faces. If it's been faced and built up before, you pretty much don't need to worry about it.

Put in and see how it feels.....if it binds,get it faced......or get some bluing or marker and a file and have at it.