8/2/14 7:02 PM

So, in three years I have totally trashed three SRAM bottom brackets. The one I just pulled had the left bearing seized up tight. GRRRR! I miss the good old days of replacing balls and repacking them. At least those would work forever with minimal care.

At least I have the tools for pulling the old ones.

8/2/14 8:50 PM

Of course I am a low mileage rider compared to most of you, but all my bikes, including a Motobecane Super Mirage from the 70's and my Trek 950 MTB circa 1990, have the original BB's. Never been serviced, either.

8/2/14 9:16 PM

I still have the same 9 speed BB since 2000 in my Strong. That's got over 30k on it. Funny that I read they were not good BBs more than a few times, the 7700 that is. re-greased twice.

Last edited by Sparky on 8/2/14 10:57 PM; edited 1 time in total

8/2/14 9:58 PM

If you're spraying any aerosols near the bb, or if you allow suds to get near it, the liquid will wick it's way in, contaminate the ball races and the bearing life will then be 1/10x.

8/2/14 10:54 PM

It's pretty unusual to go through BBs that fast unless you ride in the rain and mud.

Sandiway

8/2/14 10:59 PM

Is one side or the other going each time? Maybe Sandi is onto something, one side not faced/parallel etc.

Agree also on too vigorous cleaning regimes possibly issue.

8/2/14 11:35 PM

If the BB shell wasn't chased and faced before the BBs were installed, it may be that the BB threads and faces are not properly square and parallel, which will cause the bearings to sit at an angle to the axle and shorten their life. The old UN-72 square taper BBs and their siblings didn't care, because the bearings sat on shoulders in the housing of the bottom bracket, and that kept everything in alignment even if the BB shell threads and faces were slightly out of whack. With an external bearing bottom bracket, the BB shell is performing the same function as the housing on a UN-72 in keeping everything in alignment.

I have a bottom bracket tapping and facing set, and I always use it on a new frame. I don't think I've ever had a frame that didn't require some work to make everything properly square and parallel.

8/3/14 2:43 AM

I did ride about 140 miles in the rain two weeks ago. I believe that trashed it. The other two times the bearings just got worn and the the crank got loose.

FWIW this BB lasted about 4k miles counting trainer time. It is also the Rival level BB from SRAM so it is only a $30 part.

8/3/14 5:14 AM

I don't do near the mileage of many here, but I do ride in "all conditions"--which includes some very broad temperature ranges and a lot of snow/water/mud. I recently pulled a UN52 that had been through around 15,000 miles and that had been submerged a couple of times (pulled because I was selling the frame), and it's still smooth as butter.

And the UN52 is a pretty cheap part...

4,000 miles is a very short lifespan for a BB.

8/3/14 6:03 AM

Cheap BB, cartridge bearings.

8/3/14 6:38 AM

+1 on the durability UNXX cartridge bottom brackets and even on the often-criticized BB-6500/5500 (Octalink) versions. I have a BB-6500 with over 35,000 miles, many of those on my rain/beater bike, and it's still smooth and free of play. I've never worn out or seized any of them.

8/3/14 9:16 AM

External BB's need the threads chased and the shell faced. Its classic symptoms since yours is eating them. I chased and faced all mine and I have some BB's that are over a decade old.

8/3/14 12:22 PM

From a pure cost perspective, $30/year doesn't seem bad for a bike that is being ridden to some extent in the rain. Although I would certainly expect a Shimano outboard bearing to last longer than one year on a road bike.

I switched cranks a few months ago on the rain/winter bike, going from outboard BB to ISIS cartridge. I was amazed at how much smoother and more easily the cartridge BB spins.

I run ISIS cartridge on my good weather road bike and usually get around 2 years out of a BB.

8/3/14 12:29 PM

Isis may have been the worst idea anybody ever had for a bh. Square taper Shimanos last far longer.

Hasn't the industry made a mess out of this?

8/3/14 12:37 PM

I could be wrong, but I believe that even the cheaper aluminium frames all have their bb's faced post-welding, due to the severe expansion that aluminum undergoes while part of the weldment is transitioning from a liquid to a solid.

And I've wondered how a steel steel bb shell would ever distort from brazing heat alone, assuming that the threading/facing was done at a factory that used standard/good machining procedures, how would the faces not be almost perfectly square?

I've certainly seen many examples of how a head tube, with lugs brazed on each end, is too far out of parallel to allow bearings to spin freely, but how would a bb shell get this way unless it's tig'd steel with no post-weld machining?

I've also noticed how Shimano's bearings are typically shielded far better than most others, the key to long life it seems.
Doesn't Chris King make external-threaded bb cups for all of the popular cranksets? I would expect them to hold up to almost anything.

ISIS bb's were the industry's answer to Shimano's Octalink with it's greater stiffness and strength.
Problem was that apparently no one made an ISIS bb the way Shimano did, by machining the raceway directly into the spindle.
So, with bearing size compromised by the need for a pressed-on inner race, these bb's didn't last very long.
Some even came with double ball bearing cartridges on the drive side, but then the non-drive side bearing still often failed.
Not that many of these ISIS bb's were shielded as effectively as Shimano's, or that they had outer races on both ends machined from one solid tube...

8/3/14 3:57 PM

I used my BB tap/facer set on about 12 bikes, and every one of them yielded material. After chasing, the BB's turn in by hand, and marking the faces with a permanent marker showed that a certain area was contacted by the facing tool first, as the marker wore off in a small spot and that spot grew as I kept facing.

Why? I don't know for sure, but I suspect worn taps and facers and poor techniques in the process of using the tools. I'm betting that those tools are used/sharpened way beyond where they should be tossed, due to expense.

8/3/14 7:01 PM

Thanks for the data point.

I would somewhat expect the tapping to result as it did (i.e. dull/worn taps, and the fact that frame makers sometimes tap only to the depth of the oem production bb's threading.

But what frame material/construction were the frames you faced? What brands and quality level?

8/4/14 3:16 AM

I've had the same experience as dfcas - I think that every frame on which I've used the BB taps and facing cutters - that's probably somewhere between 15 and 20 frames - had some problem with either the threads in the shell, and/or (more usually) the BB shell faces not square to the threads or each other, as the cutters would initially only remove material from one side of the face. On some BB shells a reasonable amount of material had to be removed to get the entire circumference of the face square to the threads. From the markings on the faces when I received the frames, some of the shells had obviously previously been faced, but that was presumably before they were welded/brazed in place, and the welding or brazing had distorted the shell.

I've seen this with Al frames - good quality factory frames from Klein and Co-Motion; Ti frames, both factory (Litespeed) and custom (Hampsten, Baum, etc); also with both lugged and tigged steel frames - the lugged were either good quality Japanese factory frames or quite expensive custom frames from well-known builders, and the tigged frames were Surly and Jamis (both manufactured by Maxway).

And paying a lot of money for an expensive custom frame made is no guarantee of things being done correctly. I've received some very nice looking custom frames which I've had to reject for reasons such as:

- head tube and seat tube not in the same plane when viewed from the front.
- chainstays slightly different length so that a correctly dished wheel wouldn't sit evenly between the chainstays (on a fairly cheap factory frame I'd take a file to the dropouts to fix this, but I'm damned if I'll accept it on a custom costing several times as much).
- frame out of alignment, so that the front and rear wheels didn't track each other.
- brake bridge incorrectly positioned so that the tyre size I'd specified that I wanted to use wouldn't fit under the bridge.
- some fairly glaring omissions, too, such as one frame I received where everything seemed correct except that the builder had forgotten to braze the stop for the rear derailleur cable onto the drive side chainstay.

8/4/14 9:59 AM

Thanks for the info. It surprises me that a brazed bb shell would lose it's parallelism if it were machined parallel in the first place, but of course the threading could be cut off-axis.
Seems like a shoddy cost-cutting move if a welded shell were not at least faced after welding, as some distortion is inevitable with an asymmetric portion of the shell reaching the melting point during the welding process.

Also it sounds like building custom frames with good quality control is not as easy as we might think.

I've had to correct a few obviously factory-induced alignment defects over the years, the best one was a 1984 Trek 720, the cheapest one was a Kobe Kona.

Most others I had to correct were more-likely the result of lateral force into the fork or rear stays, sometimes the result of an owner spreading the rear triangle and only getting one side to bend out.

I've never bothered to get any head tubes or shells faced, or even tapped, even when I had to compromise headset adjustment on a Peugeot to provide a proper adjustment with the wheel pointing forward (headset bearings bound up a bit as the bars turned sharply).

The use of Shimano cartridge bottom brackets would seem to eliminate any concerns of bearing mis-alignments, as the inner and outer races of both the left and right bearings are machined into the same continuous piece of metal (not so with external-bearing types though).

8/17/14 3:42 PM

One of the selling points when I bought a Habanero Ti cross frame years ago to replace my fatigue-cracked Airborne Carpe Diem Ti frame was that the Habanero BB and HS were already prepped and ready to go. The BB sure did thread in a LOT better!

BTW, still love that Hab. Have close to 25,000 miles on it now. Don't ride it or any of them nearly as much since I have retired....

8/17/14 5:16 PM

"Don't ride it or any of them nearly as much since I have retired"


Aren't you supposed to ride more now? ;)

8/17/14 6:26 PM

Most of my riding - 95% - was commuting. Not doing that anymore! Need to get out more. Now that son has graduated HS and off to college (next week!), maybe I can get out more.

Things don't always turn out as you expect them to!

8/17/14 6:27 PM

Congrats on your son, and life sure can get in the way. ;)