dunderhi

The loose bearings that I have inspected usually cracked, broked in half, or develop flat spots. I have also had races pit and split. Lately, most bearings that I have used are sealed and they just feel like that are a bunch of rocks tumbling around in the race. Like broken chains, bad bearings area part of my life and I just toss them without a second thought anymore. I do ride in the rain from time-to-time, but it's not that often.

I'll submit that a 300+lb guy climbing a 12 percent grade out of his seat is putting down 300+lbs of force with each pedal stroke on most likey 4-6 bearings at a time. Those 4-6 bearings would have a contact patch of maybe 0.01 square inches, so I'm looking at 30-40kpsi with my crude approximation. High grade steel bearings should be able to withstand almost an order of magnitude higher pressure, but my bearings don't fail immediately, so I know I'm not generating failure types of pressures immediately. It usually takes maybe a year to fail, so I suspect spherical imperfections, metallurgical imperfections, lubricant breakdown, or contamination can reduce the bearing contact point by an order of magnitude, thus reaching failure loading at those small points and starting the failure mechanism which leads to eventual failure over time. As a guy who has snapped a crank arm in half (ended up in a ditch), little things like bearings don't really stand a chance with me. Hopefully, the new lighter me won't have to replace so many parts in the future.

https://www.schaeffler.com/remotemedi...ures_us_en.pdf

Minion1

I don't see why ceramic bearings wouldn't be a sensible option given they were installed and sealed properly - people still get hung up on problems from new bike technology from the first or second generation of a product, and the "myth" of the issue persists long after the issues have been resolved (BB30 creaks, carbon rims melt tires, carbon frames explode). If they are installed properly, and last well, I don't really see anything unreasonable there.
Buying speed by installing ceramic bearings for the majority of riders, though, is very, very expensive and marginal at best.

queerpunk

Like Ondrej Sosenka's heavy-as-f wheels that he used to set his (redacted) Hour Record?

carleton

What makes them not sensible is the high price for the marginal (at best) gains.

No one is saying that ceramic bearings are worse than quality steel bearings.

In my humble opinion, ceramic bearings have, by far, the lowest benefit/cost ratio of any changes we can make (equipment, bike fitting, coaching, diet, etc...) of all of the things that we can do to be faster or more efficient.

I've never heard anyone say or write, "I installed ceramic bearings and experienced an improvement." People say that about wheels, skinsuits, diet, aero bars, aero helmets, training, coaching, bike fitting, wind tunnel testing, etc... all the time.

I think that the money we'd spend on ceramic bearings could be spent on something that has a better chance of providing measurable results.

If dunderhi says that steel bearings fail for him and ceramics are reliable, then that's about durability, not speed or efficiency. That solves a real problem for him.

Minion1

Yeah, we're on the same song sheet. If they're more durable for Dunderhi, and his experience with them seems to say they are, and he's happy to pay for them, I reckon they're a good idea. I'm not, er, svelte, but I don't think I'm as big, or climbing as much, as Dunderhi, so I don't have any experience with them in that regard.

What I was really getting at, and this is a totally tangential mini-rant, is at the myths that persist about some newer bike tech, when the issues have been resolved with an update, a bit of common sense, decent installation and sensible use. Because I work in a bike shop, I hear this sort of stuff every day when some of the issues have been resolved years ago - people still think bike saddles lead to erectile dysfunction, for instance.

Another is that ceramic bearings turn to dust really quickly and are too fragile for use on a bike - with the first generation ceramic bearings, and lower quality/poorly designed bbs, this is probably true, and some people certainly got stung by these products. But they have improved considerably, and the newer ones seem to me much better. That they last well in Dunderhi's case kind of makes my point, so long as I'm not just relying on confirmation bias. It's basically a semantic argument, so apologies for that.


But yeah, they are the worst bang for buck in terms of actual performance by quite a long way.

dunderhi

This might be somewhat timely, but I noticed a pedal was starting to creak this evening. So I checked it out and it wasn't spinning smoothly. So rather than just chuck it and grab a spare, I decided to take a look at why it failed to satisfy the curiousity of some of the members here. First, a little background. This was a Shimano Dura-Ace 7800 SPD-SL pedal, the same model as I used on the track last year. This particular pedal was on my indoor trainer bike in the basement and has been getting a lot of riding time this winter. I would estimate that this pedal has less than 10kmi of use. Anyway, I took the pedal apart and there was ample grease that looked to be of a decent consistency. While I was cleaning out the pedal I was seeing little metal particles on my rag. I cleaned and then checked out the bearings. Both the roller and ball bearings looked good. See below.



So, this leaves the spindle or the bearing race. Well it was obvious with the grease cleaned off that the bearing race failed.

Velocirapture

Thats not very regular-looking bearing race damage. I'm surprised that the bearings themselves were good, considering what they were running over

dunderhi

Well, when I say good, I mean they look round and not broken in half to my 50 year old eyes. Larger bearings, like in BBs, are more easily inspected. These bearings did their best to roll away from me once I got the grease off. From the looks of it, I would say the spindle and bearings were steel, but the race was aluminum which is the the weaker material. I'm tempted to take apart one of my carbon-bodied D/A pedals to look at the race material. Hopefully it's steel.