I hate to disagree with Richard since I have owned one of his bikes for almost 24 years. I have always liked to take twisty downhills as close to the limit as I can. One bike I used to own, a Peugeot PX-10, would develop a shimmy at the bottom most of a bunch of S turns just above Loch Raven Dam at the reservoir just north of Baltimore. The turn was reverse banked and a little wider than the rest, but I was usually a little over 30 mph by then. This shimmy was more of a violent harmonic shake that could only be cured by backing off speed, and it only seemed to happen there. The bike and I were eventually involved in an accident (unrelated) which resulted in the head tube being bent back just a little. A new chrome PX-10 fork and slightly bent top and down tubes, and that bike ended up handling better than new. I never had the shimmy or shake again.
Dan Artley, still trying to convince my brother to let me have the bike back, in Baltimore Maryland
... i think that notion of 'straighter' frames shimming more frequently than crooked frames is bullshit. ya' know what i think the real issue is? some people don't have balls. they don't know how to go down a hill without freezing up. period. i MEAN, do you ever here of guys descending in the pyrenees, in the pro ranks, on factory built bicycles...do you ever hear about these guys losing it at 62mph? no! because they have honed their bicycle handling skills. for the rest of us, when it comes to the issue of shimmy, and descending speeds, and the related issues, i say it's all pilot error....
e-RICHIE Richard Sachs Cycles No.9, North Main Street Chester, CT 06412 USA http://www.richardsachs.com ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ <Sterling@tns.net> writes: A couple of ideas regarding frame building/construction came together for me in the past few weeks.
There is an interesting article in this months Velo News , which discusses the elements of front end shimmy. Shimmy , head shake , high-speed wobble is caused by top tube rigidity or lack of it.
His frameset was constructed so that the top tube and down tube , in addition to the brazing at the lugs , were also brazed inside the head tube.
The French so clearly understood the elements of front end shimmy , that their tube sets also included an oversized top tube. It is also known that Rene Herse built racing bikes with oversized down tubes for extra rigidity , and I believe I saw a Rene Herse Randonneur bike on Ebay last year that also had the oversize down tube treatment . I'm sure there would have been more of oversized tube sets , if builders/constructors did not have to make the lugs themselves to fit the oversized tubes.
I would like to hear from the frame builders/constructors on the
list as to what they think of these ideas ( tubes brazed to the head
tube; oversized tube sets). This best reason for not brazing the
tubes inside the head tube is all the extra work , only Rene Herse
and Alex Singer were willing to go the extra mile.
Would having builders like Baylis and Sachs build bikes
with oversized tubes ruin the attempt to capture the past with this
type of build? Any comments from others?
Sterling Peters