Re: [CR] Campy NR Headset & Brinelling - Adendem

(Example: Production Builders:Tonard)

Date: Mon, 23 Nov 2009 20:49:55 -0800
From: "verktyg" <verktyg@aol.com>
To: Mark Petry <mark@petry.org>, <Classicrendezvous@bikelist.org>
References: <00cd01ca6c81$97eb1f30$c7c15d90$@org>
In-Reply-To: <00cd01ca6c81$97eb1f30$c7c15d90$@org>
Subject: Re: [CR] Campy NR Headset & Brinelling - Adendem


1. Correction, I suggested that files had a hardness of 55Rc. Well that probably applied to common hardware store files. That number came from the crude "Mohs scale of mineral hardness" based on the idea that a harder material will scratch a softer one.

Modern jewelers files are rated at about 72RC which would indicate that they've probably been nitrided to get the hardness over the maximum 66Rc-67Rc for most tool steels.

Even so, the scratch test should tell you something. It's very difficult to make any marks on the surface of a 58Rc - 62Rc part. If you can easily scratch the surface of a crown race in the bearing track area then it's below the optimum hardness.

2. Headset alignment. I recently prepped a 1985 Gitane Team frame (a real one). Everything on that frame was very accurate except the head tube faces (the fork crown was good). They had been faced at one point but I still had to remove a little material to get them parallel. Most frames I've worked on or prepped have needed the head tube and fork crown refaced.

Refacing the fork crown and head tube faces should be done anytime a headset is removed or installed. Even if the frame had been well prepped, you have no idea what kind of hammer mechanic removed the previous headset, especially on parted out frames from eBay (the case with the Gitane Team frame).

One other thing, I've frequently had to readjust a headset after the first or second ride as the components seem to settle in a little no matter how carefully they were pressed in.

3. Lights went off when I first heard Jobst describe his theory of headset brinelling. I don't want to get into a discussion of that at this time. But as I mentioned before about the parable of the blind men and the elephant, there are many causes for brinelling in a headset (and brinelling is a word).

Back in the day working on entry level Bike Boom bikes, they frequently came in with loose headsets that were severely brinelled. I made what seemed like a logical conclusion that the indentations had been pounded in from repeated impact from the loose headset. These bikes had cheap case hardened races plus most of them were on French bikes with the difficult to adjust toothed washers.

I don't think that there is one simple cause for the brinelling problems with Campy headsets. I have well over a dozen bikes with them including a 1965 Swiss Tigra that's still smooth as glass. Inconsistent hardness could be a major factor. I've never seen a fretting or brinelling problem in Campy hub cones.

4. Finally, headsets are thrust bearings. Like other rotary bearings they permit rotation between parts but they were designed to support high axial loads. Ball thrust bearings are meant for low thrust applications where there's little radial load. Because of the head tube and fork angle there is considerable radial thrust applied to the front and rear of the crown race on lower headset cup. There are extremely high pressures applied to a very small contact area.

I don't ever recall seeing a problem on old bikes that used much larger ball bearings!

Chas. Colerich Oakland, CA USA

Mark Petry wrote:
> Interesting info on the hardness testing!
>
> My technique for adjusting headset is (after fully clean and adjust
> everything, assuming properly milled and faced, stem installed and
> tightened) set the upper cup to where it's clearly loose and "rattles" when
> you bounce the front wheel.
>
> Then very slowly tighten the cup until the rattle just disappears, and snug
> the locknut down.
>
> Now lock the front brake and wiggle the bike back and forth. Do you feel
> any play? If so tighten just a tiny bit more.
>
> Then clamp the front wheel between my knees and using two wrenches (I use a
> Campy flat wrench and the Park 7-sided wrench which will not slip) carefully
> tighten the locknut and upper cup against each other, repeating the test
> above if necessary.
>
> Final test - to make sure it's not too tight - when you lift the bike and
> tilt it from side to side, the headset should be loose enough to allow the
> front wheel to "flop" or fall under its own weight.
>
> I believe that the Stronglight A9 roller bearing headset is a much better
> headset than a Campy. And I recommend "extreme pressure" grease, not Campy.
> Use black moly-sulfide.
>
> Mark Petry
> Bainbridge Island, WA