The NR head set stack is about 39.5mm. The same vintage Pista version was about 33.9mm. A difference of about 7/32". Not much but when you're looking for the Nth degree of advantage maybe enough. Being a small guy the stem/bar height can often be higher then I would like already so I can appreciate the lower stack, not that I ride the track. Don't let your frame of reference make you think that the Pista came second, dimensionally. If I had more historical knowledge I might be able to make the argument that the Strada's 3/16" balls were the improvement from the then standard (5/32")... Maybe trackies talk about how heavy road stuff is, unnecessarily so for their track needs. Lastly this is racing equipment. It doesn't have to last longer then the event. Just ask Lotus (F1 campaigns in the 1970s)about building to the edge. ----- Original Message ----- From: Dean Nixon To: Andrew R Stewart Sent: Sunday, January 10, 2010 6:38 PM Subject: Re: [CR] Identifying Campagnolo Pista vs. Strada Headsets
How much lower for the stack height? 1/32nd of an inch? That doesn't make sense either. Usually a lower position is achieved with a a more aggressive stem angle as well as deeper handlebars. The stack height seems irrelevant other than for cutting the steerer as short as possible? Also - why go through the extra trouble and cost to 'under engineer' a road headset so it can handle less load?
On Sun, Jan 10, 2010 at 6:19 PM, Andrew R Stewart <onetenth@earthlink.net> wrote:
Ken- Your take on bearing load capacity is the opposite that I understand. I've always heard (and see in my work) that the load a bearing is a geometric factor of it's diameter. So half the balls of twice the diameter will result in the unit having twice the load. If the ball count remained the same (and the overall size of the unit then grew) the unit would have 4 times the load capacity.
My take on the smaller balls in the Pista unit was two fold. First the smooth track conditions didn't require maximum load capacity and the overall stack height could be lower. this allowed a lower bar/stem position.
Any one out there have more definitive information?
----- Original Message ----- From: "Ken Freeman" <kenfreeman096@gmail.com> To: "Dean Nixon" <vintage.lugged@gmail.com> Cc: <classicrendezvous@bikelist.org> Sent: Sunday, January 10, 2010 9:34 AM
Subject: Re: [CR] Identifying Campagnolo Pista vs. Strada Headsets
For the same race diameter, smaller balls allow more balls in that circumference. Half the ball diameter would allow twice as many balls. More balls allow more points of contact and better load sharing, i.e. the contact pressure at each contact point is less than for a larger ball.
No, bigger is not always better!
On Sun, Jan 10, 2010 at 8:46 AM, Dean Nixon <vintage.lugged@gmail.com>wrote:
In particular for the Super Record models - they seem identical even in the old catalogs. Other than the bearing size (3/16 vs. 5/32) is there any way to tell the difference visually? Measuring the diameter of the races would be difficult I think. Also, will the races get damaged if they are used with bearings that are either to large or too small? What is the rational behind using 3/16" bearings for the pista version anyway? Just wondering...
Dean Nixon
Toronto, Canada
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Ken Freeman
Ann Arbor, MI USA
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Andrew R Stewart Rochester, NY
Andrew R Stewart
Rochester, NY