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Play in the Headset

Old 09-11-19, 04:25 PM
  #26  
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Originally Posted by Andrew R Stewart View Post
There are many thousands of bikes with a threadless headset that also use the cup as the bearing contact surface. The bearings are typically held in place with a plastic seal/snap ring.
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.
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Old 09-11-19, 10:25 PM
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Originally Posted by cyccommute View Post
The "vibration" in the indexing of a headset is the pounding. It's not erosion due to wear but denting due to brinelling. According to Wikipedia



Headset bearings are stationary for most of the time. If the headset is loose, the cup moves away from the bearing on the upward travel of impact and and then moves back down on the bearing in the downward phase. Repeated enough times with enough load and the cup are dented or "brinelled". A brinneled headset will have regular indentations at each of the bearings on the lower cup with deeper ones on the trailing edge where impact is worst.

.
A good example.
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Old 09-11-19, 11:28 PM
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Originally Posted by Doug64 View Post
A good example.
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
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Old 09-12-19, 07:50 PM
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Originally Posted by Andrew R Stewart View Post
There are many thousands of bikes with a threadless headset that also use the cup as the bearing contact surface. The bearings are typically held in place with a plastic seal/snap ring. I've service a few dozens over the years.
Indeed. Not all threadless headsets use cartridge bearings. The original Aheadset used caged bearings.
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Old 09-12-19, 08:15 PM
  #30  
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Originally Posted by terrymorse View Post
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
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 doesnít the damage occur on the leading edge as well? Especially if as Brandt says

Damage to head bearings seems to be twofold in this case because properly adjusted steering, can only get looser from dimples and it cannot be immobilized by them. Therefore, the head adjustment was too tight. However, dimpling is not caused by impact, but rather by lubrication failure that occurs while riding straight ahead. This occurs more easily with a correctly adjusted bearing than with a loose one that rattles and clunks. Rattling replenishes lubricant between balls and races that would otherwise not be present. Off road bicycles suffer less from this malady than road bicycles because it occurs primarily on long straight descents where no steering motions that would replenish lubrication occur.
From the above, it is fairly clear that Brandt didnít 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 donít loosen under vibration.
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Old 09-12-19, 10:21 PM
  #31  
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Originally Posted by cyccommute View Post
...it is fairly clear that Brandt didnít have much off-road experience.
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.

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Old 09-12-19, 11:47 PM
  #32  
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Originally Posted by cyccommute View Post
From the above, it is fairly clear that Brandt didnít 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.
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.
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Old 09-13-19, 07:10 AM
  #33  
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Originally Posted by terrymorse View Post
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.

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I donít know much about Brandt and his riding style but his statement above isnít 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.

Originally Posted by HTupolev View Post
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.
It is poorly worded now that I look at it again. However, as I stated several times, road bikes didnít 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 shouldnít 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 donít develop index steering. Loose headset will in almost all cases. And they do it very quickly.
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Old 09-13-19, 09:27 AM
  #34  
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Originally Posted by cyccommute View Post
Bottom line: Brandt is wrong on his hypothesis of why headsets get (got) dented.
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.

Originally Posted by cyccommute View Post
Pitting of cones and bottom bracket spindles is likely through fretting.
Incorrect. Pitting of cones and bottom bracket spindles is due to metal fatigue.

Originally Posted by cyccommute View Post
But properly adjusted headsets don’t develop index steering.
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.
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Last edited by terrymorse; 09-13-19 at 09:31 AM. Reason: spelling correction
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Old 09-13-19, 09:30 AM
  #35  
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Originally Posted by cyccommute View Post
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 doesnít the damage occur on the leading edge as well?
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.
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