My bottom bracket appears to be failing, again, for the third time in almost as many years.

The drive side bearings feel not smooth (the first symptom is clicking as I pedal). Adding grease improved the situation slightly, but, since they are sealed, it's only a momentary fix.

Any thoughts as to what could be causing the premature wear?

The last time I changed to a BB where the right and left thread to each other, to try to improve stiffness. This is on a PF-30 BB shell.

Does the BB shell for a PF-30 need to be faced? I only know basic square-taper cartridge BBs and Campag Power- and Ultra-Torque, but my first thought is that your BB faces aren't square and you're putting undue stress on your bearings.

PF30 shells don't get faced.

PF30 can suffer from alignment problems, though not as much as BB30. The thread together unit addresses those issues. I would examine how well the spindle fits into the bearing. It should be smooth but full contact with the inner bearing race.


Of course, the crank also needs to be properly mounted and adjusted for BB preload. Who is doing your work?

What bike, what bottom bracket, is it being installed by a shop with the proper tools and knowledge or is it being installed at home and if so do you truly know what you are doing and have the correct tools (and that is not a judgement call) ? So many questions to be answered before we can diagnose things. You could be installing improperly or maybe you are letting a lot of dirt and grime get into things or you are a powerful rider or the frame hasn't been prepped for the bottom bracket or maybe it is something else like the crank arms not being installed properly or something else entirely. We have very minimal information that is easily rectified.

Just to note once again no judgement I know a lot of mechanics or home mechanics who aren't familiar with certain processes or don't have the correct tools or whatever who make mistakes that they may not even know they are doing.

What about bearing manufacturer, and what kind of use? I recently donated a bike that had an FSA crank with 19 mm PF bearings and they wore out every year I had it, about 5000 miles each time, always drive side. They were just cheap bearings, or just too small for my use. I got tired of that.

You are certain it's not the pedal bearings causing the click. Is this a click you hear or mostly just feel? And if it's more of a squeak or groan, then maybe just noise that some press fit BB's are known to make if everything isn't perfect. Not usually bad. Just annoying if you are of the mindset that your bike should be a stealth bike.

A few comments- A poor fitting cartridge bearing can move about within the BB shell and this can and does cause noises quite often.

For three BBs to "go bad" (my term) in so short a time (notice I didn't say miles yet) suggests some basic issue is still present. Issues might be a poor BB shell factory finishing, and the bearings are not best held in place. Or so much environmental exposure (the simple example is riding in the rain or transporting one's bike outside a car during driving in the rain. Add salt or mud...). Or the assembly was poor (as in too much preload or not fully seated bearings). Or other stuff, including just way more miles a year than what the manufacturer designed for.

More data would be nice but nothing we can say will fix the problem. That's up to those who can actually touch the bike. Andy

larger spindle equals more tiny balls and thinner races.... larger shaft diameter equals less flex to cushion sudden shocks

the bearing becomes the weakest link, accelerating wear....
add a few rainy rides and you end up with shorter bearing life.

add extra grease to the seals before install, and re-grease the exterior seals every few months, or even weeks, if the weather gets nasty.

my first experience with short external bearing life was a GXP setup... a CX racer complained about a "grungy noise" from the cranks... he was getting about 6 months per BB assy...
frequent re-greasing stretched that to one year or so, per assy.
the GXP BBs feature an external "Seal Plate" even... i took to re-greasing between them and the bearing seals too...

tiny balls equal higher contact point pressures... no way around that factor.

my old Shimano 600 Bottom bracket on my '82 trek is still going strong... it got re-greased regularly, once a year, for 10 years, and carried me for well over 20K miles(just a lowball guess.. it was my ONLY transportation, other than mass transit for long hauls)... the bike sees far less miles now. the DA hubs got the same 1 year re-greasings... they are still perfect too.

re-greasing a PF30 isn't so easy....
the old stuff is better, in that respect.

OK, I looked at my receipts, and it's not quite as bad as I said. The most recent BB was installed 3 years ago, and is this one:

https://www.amazon.com/dp/B018HHRC6W made by Wheels Mfg.

I installed it, as well as the earlier BBs, including the original, which lasted a good number of years. (to one of the Qs--I'm positive the problem is the BB, since I took the cranks off, and found the difference in bearing feel, as I described).

The one thing that is different from the original install is that I switched cranks from a SRAM crank to one compatible with Shimano, and needed the following adapter:
https://wheelsmfg.com/bottom-bracket...o-fsa-etc.html

"tiny balls equal higher contact point pressures... no way around that factor." maddog34

This! The load capacity of a ball bearing is geometrically related to its diameter. Double the ball count with half their diameters and you lose 50% of the load capacity. Add in 3X the initially stated life span and the wear rate sounds more typical. Andy

My experience with square taper BB cartridges is that once there is the slightest slack detected, wear accelerates; Lack of original bearing preload concentrates ball loading, and any radial slack wears the seals more. And that slack cannot be adjusted out with a cartridge BB.

Going to a hollow spindle crank with external bearings, any slack can immediately be adjusted out, even readjust preload before any slack presents itself. After initial installation, I think slack presented after 4 months, adjusted out, haven't needed to adjust again since, coming up on 4 years (total) and a lot of miles; I guess that first slack was from the bearing races burnishing in from grinding marks to smooth. Anyway, this is the number one thing I like about this newer BB system, greater bearing durability.

So why continue to use the SRAM BB with adapters when you can replace it with one that is right sized for Shimano? I think this is the one you need - PF30 to Shimano Outboard BB

BBInfinite has an option too BBInfinite

Good point! I think when I first switched cranksets, I was unsure if it would be permanent. Now it appears so. Thanks!

I just watched the video referenced in this article: https://www.roadbikerider.com/day-at-enduro-bearings/
one quote that stuck with me from the head bicycle bearing guy is that 95% of bearing failures are due to corrosion. Especially at the bottom bracket which drains everything from the weather, environment, rider etc. Don’t know if this is actually true, but Enduro do sell a class of bearings that they guarantee for life.

I'm using the Wheels Mfg adapter PF30 to Shimano adapter on a Synapse Alloy I just built and it is nice. When setting it up, I discovered preload to be VERY important with less being better than more. I had to remove the crank to run cables and upon reassembly I can see I had too much preload. I can also see how too much preload would impact bearing longevity.

Gary from BBInfinite suggests tightening it finger tight preload is adequate. When I replaced the 105 crank with GRX 600 with the BBInfinite BB, I followed his lead as I did when I did the original install. It will spin for days without much effort.

What's the "right" preload when your device (like a hub) has both free play and no play, at different points, as you spin the axle? Andy (knowing the question has no single answer>>>)

The answer is that something is worn unevenly, or bent, or originally manufactured with a runout (defect). I'd swap out parts or measure to see what is bad, and if unable, then I'd run the preload to the upper limit of tolerance at the orientation of highest preload, in the hope of minimizing the free play.

Agree. Back in the day when only the highest-end components could be adjusted so as to have no play with no binding, you just had to accept some play. If you ran with a bit of binding of the bearings, their life was pretty short.

The only problem I have with the answer being replace parts is when you have a customer (neighbor/friend for most here I suspect, not that the courts make much difference between the three when working on other than your own bikes) that can't afford the replacement parts costs. This should be a part of the before service discussion and the shop (or the person turning the wrenches) always has the right to refuse what they would consider unsafe practices or results. But I have to say that I have never considered rear hub bearing adjustments having any practical safety concerns. I've seen way too many broken axles and so trashed a bearing that it has metal flowing going on and can't remember anyone falling off their bike due to the condition of a rear wheel bearing. How and why one makes their judgements is up to them and where they draw their line in the sand is up to each of us and will be different from person to person. For myself, when I wrench I continually balance the current condition of the system, the amount of improvement I can likely result in with only labor, the amount of improvement with new parts and their costs against the cost of all this and the owner's expectations balanced with their own budget limitations (be they by lack of financial resources or by personal preferences).

Now other bearings are a different mater. Like one's headset, perhaps the most safety sensitive bearing on the bike. We do want the bike to go where we steer it to

My usual answer (note I say "usual" as every case is a bit different) to what to do with a bearing that is both tight and loose is to adjust the preload to a point where the looseness is REALLY small and live with the tight spot's added wear. A compromise for sure but like and bike repairing is full of them. Andy

Oh I'm totally on board. More than once I have rebuilt hub bearings with a spalled cone, marked the location on the wrench flats, and assembled into the frame with that UP, so not loaded when rolling. Makes a huge difference. Other times I have rebuilt a cup and cone BB, with a spall on drive side reversed to non drive side if a symmetrical spindle, and/or oriented so under the least load with crank arm orientation on that side. In both cases, spalls happened because bearing had slack; rebuilding with proper preload, and even with spall, durability inproved greatly.

I'm a pro-bono mechanic, this is common for me. Crack at rim spoke hole? I fab a socket for the spoke to pull on the inner wall just under the rim strip, lasts for years. Back in the UniGlide cog days, clean and reverse the cogs when putting on a new chain (no way around replacing a chain that needs it).