Hollowtech BB installation frame prep ??
Got my new Hollowtech crankset and BB bearings, and I'd really like to install them today, but when I looked over the installation procedure on Park Tool's website, I saw that they recommend chasing the faces of the BB shell to make the left and right sides parallel to each other.
I don't have Park Tool's BFS-1 Bottom Bracket Facing Set, and probably will have to wait at least a week if I want to order one...
Is there an easy way to determine whether my BB shell's sides are parallel without this special tool?
My bike is a Gary Fisher Cobia.
Anyone know anything about the precision level of frame machining on GF bikes?
One way to find out is to make a trial installation. Thread in both bearing cups and then attempt to insert the crank spindle. If it slips through both bearings easily with out any obvious mis-alignment or side force, your bottom bracket shell is good. If you have to force the spindle to one side to make it fit, the shell should be faced.
Normally, individuals don't own bb facing tools as they are too expensive for a one-time use. This is a job almost always done by a good bicycle shop.
You should always face your shells. Take it to your LBS and get it done right.
Thanks for the replys so far...
I've got the frame completely stripped, and I suspect that my
LBS doesn't have the facing tools, so, ordering them and doing it myself will probably be faster, and more satisfying.
Still, if I could figure out whether the BB shell faces were already parallel without the tool...
Originally Posted by Halloween
I share your sentiment, and have actually thought about investing in a facing tool myself for the same reasons, but there are a few things to keep in mind: First, the facing tool you are considering purchasing is around $500 (US Dollars). Second, even if the cost is not an issue, you could still basically destroy your frame if you make a mistake with the procedure. Third, if the facing is off (but not so far off that you fail the test that HillRider described), I think the only major consequence is that you will experience decreased bearing life. But outboard bearings are relatively cheap compared to a Park BTS-1 (even the Dura-Ace ones are only like US$40), so IMHO it's not the end of the world to do without it for the short term and maybe get the BB faced at some later date. You might never have a problem. At worst you'd be out $40 for new bearings plus the cost of the facing service, which can be pretty pricey at some shops.
Also, you can get a set of calipers and measure the width of the BB shell at various points and make sure you get the same measurement (within some tight tolerance, like << .1mm) all the way around. That's not a foolproof check because it doesn't ensure that the faces are exactly perpendicular to the BB thread axis, but combined with HillRider's test, it should give you a pretty good idea how close you are.
Hmm... very good points! Especially your second one, Metaluna! Thanks!
Originally Posted by [B
Actually, I've already done the calipers check... and I got a very slight (barely noticeable on a millimeter scale) difference at a few points, which could possibly be due to paint. I'll swab a little acetone on the faces and measure again with the calipers.
As for the price of the facing tool versus a new bearing set; it's interesting that Shimano's own spec sheet makes no mention about close tolerances for BB shell face parallelism (that's the word... I looked it up!). Guess you could make the argument either way for Park Tools or Shimano angling for consumer overspending.
Just a bump in case any of the weekenders have ideas.
Check your facing?
Caliper the shell in Five places, in a star formation.
If more than one measurement is off from the others, you're boned.
That's how I do it. Or something close to that.
Edit: Oh, I actually read the whole thing through and someone said that.
Anywho, Depending on the quality of the frame in the first place, it CAN make a difference. I had a Diamondback frame that had a poorly faced BB, when I was done with it it was a hell of a lot better.