RE: [CR]Italian use of Reynolds tubes Was: Gitane vs Peugeot

(Example: Component Manufacturers:Campagnolo)

Subject: RE: [CR]Italian use of Reynolds tubes Was: Gitane vs Peugeot
Date: Tue, 2 Aug 2005 00:43:16 -0700
Content-class: urn:content-classes:message
Thread-Topic: [CR]Italian use of Reynolds tubes Was: Gitane vs Peugeot
Thread-Index: AcWXKilcmCgNIvn7QM2ZVAUqJclsCQAAHWTw
From: "Mark Bulgier" <Mark@bulgier.net>
To: <classicrendezvous@bikelist.org>


Brian B wrote:
> The reason a
> builder would choose to use Columbus tubing in the forks and
> stays is because Columbus forks and stays are "taper gauge"
> tubes, meaning that the wall thickness of the fork blade is a
> consistant thickness throughout the length of the tube. The
> way Reynolds tapered their stays resulted in a tube with a
> thin wall at the larger end and a very thick wall at the
> bottom end. The result is a heavier and less resiliant fork
> blade for racing bikes. The Reynolds method was OK for
> non-racing bikes, generally speaking.

But Brian, "taper gauge" is a Reynolds trademark, and their forks definitely are. They start as single-butted tubes with a long transition between the thick and thin, so when they (inevitably) thicken through tapering, they are left almost constant-thickness. Columbus had some of the same action going on, maybe the same technology though I haven't heard a description of how they achieved it. They never used that term taper gauge, to my knowledge.

Cheap fork blades thicken up toward the bottom, but Reynolds 531 blades never did, not any I got my hands on anyway. Oh wait, I did get to hold one Reynolds fork blade that was tapered at the wrong end - they stuck the thick end into the tapering machine and got a humorous but unusable paperweight. You could even see the markings they stamp into the big end of the blades, all scrunched down and tiny at the small end of this one.

The only stays I remember getting REALLY thick at the small end were Columbus SP - some batches of those suckers got so thick-walled at the dropout end that I used to chuck them up in a lathe and drill out the small end, to have 'em hollow enough to be rightly called tubing! They were "pipe" without the drilling! And really really rough, ugly, non-circular inside, though you could never see that on the finished frame without cutting it up.

Now, pre-1975 or so, Reynolds blades WERE definitely more harsh-riding, for two reasons: One, they were significantly heavier (thicker) than Columbus blades, even thicker than SP; and Two, they were more ovalized - that is, longer front to back, making them stiffer in the forward-and-back or vertical directions. (Surprisingly, they weren't less stiff side-to side either, contrary to popular belief - despite the long skinny oval, they made up for it with the thicker walls.) This is from actual measurement of stiffness of Columbus vs Reynolds blades we did at R+E Cycles in the early 80s, as well as calculating what the stiffness ought to be, from the measured dimensions and stiffness formulae.

BUT: they weren't more harsh-riding due to being thick at the small end - remember they were taper gauge, and nearly the same thickness top to bottom. They were harsher because of the stiffness UP NEAR THE CROWN - which is where most fork flex occurs anyway!! The raked area actually provides a rather insignificant portion of the overall flex. The AMOUNT of rake is important, to the geometry and ride, but two equally-raked blades will feel largely the same if their dimensions up near the crown are the same - the thickness down near the dropout is almost irrelevant. Except thick blades weigh more, and the strength down there isn't needed, so taper gauge blades save some weight, with no downside.

Some of the extremes of the pencil-thin variety probably get some flex down there, but probably still less contribution to the overall flex than even the steering column, due to the magic of leverage. The wheel transmits the road shock to the fork at the dropouts, and that force works on over a FOOT of leverage up near the crown, vs. around 2 inches of leverage in the middle of the rake.

This long-skinny oval (called ironically enough the "Continental" oval by Reynolds, though that shape wasn't used by tube makers on the Continent) was designed for strength and durability, but people started to notice the Columbus forks were more comfortable and a bit lighter, so eventually (probably about 1975 or '77) Reynolds released the "New Continental" oval - an almost exact copy of the Columbus oval, a smart move because their new blade fit all the crowns that were made for Columbus blades. I believe all 531 SL and 753 sets came with this new oval. The old oval was still offered alongside the new one for quite a number of years - I don't remember when they stopped making it. 1990?

Putting it in perspective: That "Old Continental" long skinny oval is the classic Reynolds fork blade as seen on all the pre-'75 Reynolds-tubed bikes we love, and quite a few after that date: the PX-10s, early-70s Raleigh Pros and Internationals, Gitane TdF and Service Course, LeChampions, Paramounts, Singers... So while true that these forks are in fact stiffer and harsher, they are found on so many bikes that were regarded as very comfortable. How can this be? It just shows that there are so many other variables that go into the overall feel, that the brand, and even shape and thickness of the tubing, can be overwhelmed by differences in design and the selection of the other parts that go into the bike.

Mark Bulgier
Seattle, WA USA