[CR]Re: A9 headset (was: Riding no-handed)

(Example: Production Builders:Peugeot)

Date: Mon, 04 Feb 2008 21:49:20 -0600
From: "John Thompson" <john@os2.dhs.org>
To: Classic Rendezvous <Classicrendezvous@bikelist.org>
References: <3.0.6.32.20080202111211.013fcc78@mailhost.oxford.net>
In-Reply-To: <3.0.6.32.20080202111211.013fcc78@mailhost.oxford.net>
Subject: [CR]Re: A9 headset (was: Riding no-handed)

John Betmanis wrote:
> I just had a good look at a Stronglight A9 headset I have and the
> needles look cylindtical, not conical like the rollers in a true
> taper roller bearing. With a taper roller bearing the surfaces of the
> cups and cones and the axes of the rollers all converge at a single
> point. The surfaces of these needle roller headsets are all parallel
> and the needles only roll at one point on their surface and skid on
> the rest. I bet it's this extra friction that delays the front wheel
> from immediately steering in the direction the bike wants to tip.

You're right about the A9 headset and its cylindrical bearings. There is sliding contact on the bearings, but since the piece is not in constant rotation it does not significantly affect loaded performance. The cylindrical bearing was chosen over tapered bearings for at least two reasons: first, they are much cheaper to produce than tapered roller bearings; and second, they are much more forgiving of misalignment than tapered roller bearings. One of the reasons tapered roller bearing headsets never caught on to any great extent was their propensity to bind up unless the head tube and fork crown were perfectly prepared.

--
John Thompson (john@os2.dhs.org)
Appleton WI USA