I recently installed an A9 (thank you, Greg Parker!) in my Mondonico, replacing a worn Shimano 600 with the wavy nuts. My first installation was to simply lube and install the Stronglight parts and set the bearing. This resulted in uneven turning over 360 degrees. I didn't think this was right, so I took the frame/fork to my LBS. The tech there reamed and faced the frame and re-installed, resulting in smoothness and freedom very close to that of an excellent ball-bearing headset.
I'm still in the middle of rebuilding this bike so I don't know if it'll no-hand well, but it certainly did before the rebuild and I expectit to be as good after. Certainly the frame has not shifted and the head bearings move well.
I think if people are having trouble no-handing it could be a headset, but it's not simply because it's an A9. It's more likely because it's not installed perfectly or perhaps worn. Besides, this is a design with long exposure in the field, and if residual friction was a major problem it would be much better known.
Tony Oliver in his book "Touring Bicycles" said that he greatly prefers roller-bearing headsets for robustness and longevity, but they need to be installed correctly. I've just seen initial evidence of the difference between correct and incorrect installation.
Ken Freeman Ann Arbor, MI USA
-----Original Message----- From: classicrendezvous-bounces@bikelist.org [mailto:classicrendezvous-bounces@bikelist.org] On Behalf Of John Thompson Sent: Monday, February 04, 2008 10:49 PM To: Classic Rendezvous 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.
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John Thompson (john@os2.dhs.org)
Appleton WI USA