terrymorse 

A headset like this?



It seems to me that this design doesn't fix the fretting wear (aka "false brinelling") problem at all. It's the same as a threaded headset, minus the threaded bits at the top.

Doug64

A good example.

terrymorse 

Looks like an example of false brinelling, as there appears to be no raised edge around the dents.



Profile differences between true and false brinelling

cyccommute 

Indeed. Not all threadless headsets use cartridge bearings. The original Aheadset used caged bearings.

cyccommute 

First, it would be difficult to see a raise edge in person. Trying to see it in a photo taken from a distance is next to impossible. But if it were due to a corrosive effect...which is what false brinelling is...why is the damage localized to the rear of the headset? If the bearings are galling and breaking loose, why doesn’t the damage occur on the leading edge as well? Especially if as Brandt says

From the above, it is fairly clear that Brandt didn’t have much off-road experience. There are few instances where mountain bikes make long straight runs. We are always steering to adjust our fall line. Road bikes have much longer, straighter runs.

There is also the tightness of the bearing to consider. In my experience, a properly tighten headset bearing will never dimple. The problem, especially when it came to off-road riding, was keeping the headset properly tightened. The act of riding off-road caused the headset to loosen. A loosened headset was a ruined headset in 10 to 15 miles. There were dozens of companies that made locking mechanisms to solve the problem. It was never really solved until the advent of headsets that don’t loosen under vibration.

terrymorse 

It is clear you know very little about Jobst Brandt. His rides always included off-road riding. In fact, he was leading people like Gary Fisher and Tom Ritchey off-road in the Santa Cruz Mountains, on road bikes, before these guys built the first mountain bikes.

Haul Road Memories

HTupolev

Re-read the Brandt paragraph you quoted. He's claiming that mountain bikes are less prone to the issue because they're not doing long straight downhill runs.

cyccommute 

I don’t know much about Brandt and his riding style but his statement above isn’t in keeping with what was known to be a problem in the early days of mountain biking. In that era, seldom did we see dented headsets in road bikes but they were very, very common in mountain bikes.

It is poorly worded now that I look at it again. However, as I stated several times, road bikes didn’t have the problem. Mountain bikes did and mountain bike headsets were very prone to loosening. It was so common that CoolTools offered a headset add-on. I used it more then once and I always carried a small adjustable plier for tightening headsets. If the mechanism that Brandt proposed is true, then mountain bikes shouldn’t have suffered from dented headsets at all.

Bottom line: Brandt is wrong on his hypothesis of why headsets get (got) dented. I agree that a loose headset would be less prone to fretting for the very reason he lays out. If fretting is occurring, it requires a strong metal to metal contact. Pitting of cones and bottom bracket spindles is likely through fretting. I would also suggest that properly adjusted headset should be prone to fretting for the reasons he lays out. But properly adjusted headsets don’t develop index steering. Loose headset will in almost all cases. And they do it very quickly.

terrymorse 

You are the one who is wrong in thinking that headset bearings get dented through true brinelling. Your error in thinking can be demonstrated by clamping a headset in a vise, then going at it with a hammer as hard as you can. No indentations will develop.

In contrast, take a properly adjusted bearing of any design and subject it to vibration. Wear will appear in short order. This phenomenon has been known and documented for at least 80 years.

Incorrect. Pitting of cones and bottom bracket spindles is due to metal fatigue.

Incorrect. Properly adjusted bearings develop indentation from wear when subject to vibration. Bicycles are not exempt from this fundamental fact of tribology.

You press me as someone who has confidence in his opinions, yet hasn't studied material science, stress of materials, or tribology. If you had, you wouldn't be making these errors.

terrymorse 

Damage is on the rear and front of the bearing surface, because that is where the vibration movement is the highest. Indentation is greater in the rear, because the displacement is greater there.