Re: [CR] Campy NR Headset & Brinelling

(Example: Framebuilding)

From: "David Snyder" <dddd@pacbell.net>
To: <classicrendezvous@bikelist.org>
References: <E1NCOHN-0008WJ-Jq@elasmtp-banded.atl.sa.earthlink.net>
In-Reply-To:
Date: Sun, 22 Nov 2009 22:00:24 -0800
Subject: Re: [CR] Campy NR Headset & Brinelling


Subject: Re: [CR] Campy NR Headset & Brinelling

I have never seen a headset brinnelled quickly except by being over-tight (which damages the bearings as soon as the bike is ridden over a few bumps). Note that I have quite-heavily tightened headsets (to settle the cups) in many, many (many!) a frame with no damage whatsoever, but riding with tight bearings is different. The difference is that, when ridden, steerer flex concentrates peak load to a small number of balls while the steerer length between upper and lower races is effectively shortened (locally) as the fork crown rocks slightly with every bump encountered. Mark makes an excellent point about setting bearing tension with a stem installed(!) and also about the retainer not being the problem (I always fit a lone similar-type stem with no wheel or handlebar to obscure a proper adjustment).

With the NR headset, I have done fit experiments to verify that the races should be full, with not one bearing omitted. There is plenty of running clearance this way (about 1mm cumulative gap between balls) and the balls are thus not free to fall into previous divots in the races. IIR, Campa retainers hold 20 balls, but 24 loose balls can be fitted for best results.

Always better to have a headset too loose than too tight! A too-tight headset will not allow minute self-center corrections to the steering and can cause an immediate crash when riding hands free. When combined with the inevitable brinnelled races, a too-tight adjustment can also cause unsteady cornering, and on some bikes can trigger a speed wobble. A mildly-loose headset, otoh, seems to cause no immediate harm or effect other than an occasional clanking sound.

Lastly, I often re-adjust headsets on beater bikes with wheel and bars installed. I'll first tighten to the point of slight detenting, then back off the adjustment by the now-familiar amount. This on headsets already traumatized and with but a squirt of oil fed thru the cup-cone clearances. This does gives surprisingly long-lasting service in most cases while sparing the expense of a proper rebuild.

David Snyder Auburn, CA usa

Mark Stonich wrote:
> In my experience Option A is Plan A.
>
> However I don't believe that using the retainer was the cause of your
> indexed steering. High quality headsets are so smooth that they feel good
> when too tight. I've seen more ruined due to this than neglect. Doesn't
> take many miles either.
>
> When adjusting good headsets I make sure the stem is installed and
> tightened, as this microscopically shortens the steerer. Then, when the
> headset "feels good" I start backing off the adjustment in tiny increments
> till I can just detect some slop, then re-tighten just a tiny amount.
> Properly adjusted NR headsets should last many, many years, even in
> tandems.
>
> Also, IIRC Campi retainers hold as many, or nearly as many, balls as you
> can fit when loose. I just took apart a 1st Gen DA headset and the
> retainers didn't hold much more than half the balls that could have been
> fitted loose. Though badly pitted it feels pretty good now with a full
> compliment of loose balls
>
   > Jeff holt wrote:
>>Need some CR advice....
>>Made the "mistake" of installing an Campy NR headset using the ball
>>bearing retainer v. loose balls when I re-assembled my Cinelli this
>>summer. The result, brinelling (a/k/a indexed steering).
>>I've received some conflicting advice:
>>Option A) Simply replacing the ball bearing retainer with loose balls can
>>eliminate the problem. Option B) Replace the entire headset as the only
>>way to eliminate the problem.
>>Option C) Leave it alone & ride the bike. (This option seems plausible, as
>>when I actually ride, I don't notice a problem.)