Back in the mid 70s we were having a lot of problems with "pitting" in the crown race and bottom cup in Campy NR headsets. We took 17 headsets to a friend's machine shop and ram a hardness test on them. These included a number of new and used Campy headsets, Zeus, and Stronglight P3, V4 and S5 headsets plus some el-cheapos.
We were surprised to find that the 5 or so Campy headsets all had a Rockwell C hardness of 47-48 in the bearing race area. The Zeus and Stronglight headsets were all over 60Rc while the cheap ones were all over the place because most of them were only case hardened.
I was at a Jobst Brant presentation last fall and the subject of headset wear came up. The conventional wisdom was alway that pitting was caused by "brinelling" due to vertical impact. Jobst suggested that the pitting was caused by fretting due to the back and forth motion of the fork in the headset. I thought that it was a very reasonable answer.
Perhaps it can be a combination of both actions in some situations. I've frequently found loose headsets on other people's bike, sometime REAL loose.
One emergency fix that I've done for pitted headsets is to rotate the cup or crown race enough so the the balls are not sitting in the pits. Bearing retainers are primarily utilized for ease and speed of assembly. Some of them have reduced bearing count. They encourage to stay in one position especially since headsets are thrust bearings with very little rotational movement.
I use the tables in "Sutherland's Handbook for Bicycle Mechanics" for correct bearing size and count. Also I prefer to use the thickest grease I can find. It helps in holding the loose balls in place during assembly plus it can help keep dust out of an unsealed headset.
Charles Colerich oakland, CA
-----Original Message----- From: Ken Freeman <firstname.lastname@example.org> To: KvnMuadib@aol.com Cc: email@example.com Sent: Wed, 11 Mar 2009 4:59 am Subject: Re: [CR] headset wear?
What I've seen most often trashed are the crown race and the lower fixed cup. This comes from my own bikes and my attempts to replace a Record headset by buying some used ones.
Feel in headsets is interesting. A crunchy or notchy feeling can be due to grit inside. It can also be due to old, dried grease that has lost its suspended oil, and is now nothing more than a hardened trail of little dirty mountains, providing obstacles to your bearing balls. "Don't want to touch an old headset" is not wise - it can turn an old good bearing into trash needing replacement.
I haven't really had loose ball replacement result in a bad headset turning good. I do think it's a good idea because it better divides the load, the parts are easier to source, and it might reduce further degradation. It's always a trial and error to find the maximum number of balls that will allow the bearing to seat (then subtract one). You need to do test fittings, in my experience.
Test fittings are also what tell me an old HS is not usable. If it fit well into the frame once, and I re-install (with a press), and if the correct adjsutment point is a matter of which way the fork is turned, I replace the headset. This leads to delays. To clarify, if I can adjust the HS correctly with the fork straight ahead, but it tightens upwhen I turn it 90 degrees, that isn't right, and I haven't found that turning the parts and re-installing it does any good. Reaming and facing might help, but I'm dealing with work parts anyway, so first I replace the HS. This usually gets it. If not, then I have it reamed/faced.
I call this dance "headset hell," especially if have a hard search to find a HS that meets the vintage requirements and the stack height.
I hope this isn't more than you wanted to hear about.
Ann Arbor, MI USA
On Tue, Mar 10, 2009 at 4:19 PM, <KvnMuadib@aol.com> wrote:
> hi all. what in your opinon is most likely part to wear in a trad. threaded
> headset? would pitting in fork crown race be most obvious to" feel" or
> negligible. can crunchiness due to minor pitting of cup or race be
> alleviated by
> loose bearings as oppoced to caged?do you add one more to the total if cage
> removed?if all of this has been discussed before forgive me ,my browser and
> operating system is having more than its share of timeouts freezes etc.so
> comp time is a little reduced .thanks in advance kevin ruberg howell nj
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