I didn't intend to contribute to this debate and was happy to read other more learned, better educated and more experienced people's emails on the subject. However since Frank Cohen has been deported from the List and because he did invoke my support in his contri of the 24th May, I thought it might be the decent thing to do..to give some little support to some of Frank's too aggressively held opinions.. I can only asssume that Frank still rides a "None Licentia Regit" model of frame.
I can't claim that I have any knowledge or experience of 1 1/8" top-tubes that isn't matched and probably surpassed by other frame-builders and riders alike on the List, and like most of them, I assume, I have used my fair share of these fatter tubes for top-tubes...even on smaller frames. It had to be stated that the majority of these were on lugless time-trial machines on which I simply thought that the result was more aesthetically pleasing..the transitions from polished welded bead to tubes of similar diameter being more attractive. At the same time I did have that "gut-feeling" that so many builders tend to rely on, that I was also producing a stronger, more responsive frame, by eliminating some proportion of the flexing produced by the torsional forces applied in racing. I have also used the 1 1/8" tubes for top-tubes in lugged frames when employing some of the investment cast lugs that flooded out of Taiwan in the 90s..but in these cases it was the lug that dictated the choice of diameter rather than me. I was never sure whether Whenever I thought that a larger frame needed oversize tubes and I didn't want to have the choice of lug dictated by Mr Chang of Ideation Creation or his counterpart at Everest, or Long Shen., I simply opted to use the "bi-laminated" technique. It's amazingly versatile.
In most cases I was more than happy to use the standard 1" top-tube for the majority of my lugged frames, simply because I thought that the tube makers knew what they were doing, and that they would beef up the gauges of the tubes, as necessary to respond to the constraints to which a frame was subjected. Gerald O'Donovan, at Raleigh took that same approach, relying upon Reynolds to supply the tubes that Raleigh needed to respond to certain demands, particularly for Pro racing. Raleigh did not carry out much testing and stress analysis. It wasn't until I started importing TVT carbon frames with their 1 1.8" all-round, that I saw any real testing carried out. That company's decision to use all three tubes in the same diameter was simply a commercial one, in that they only needed one mould for making the tubes, not two. But..they thought, as I had done with my lugless frames , that the end-product looked more homogeneous. In any case even a 1" dia RTM multi-layer carbon tube has some astonishing mechanical properties
I must admit that I have never used a 1.18" top tube, consciously, at any time, with the intention of improving the steering. If as a result of using such a tube in the main triangle, the steering improved, so be it. It was a bonus. I have always considered that good predictable steering to be a result of a combination of other factors such as head tube angle, fork rake and trail ., frame alignment. Had I wanted or had a "gut-feeling" that increasing the diameter of any tube would improve the steering, I would have, and did in fact, use oversize down tubes, as have Longstaff, Chas Roberts, Mercian etc..and of course Cannondale. Coincidentally I have just taken in yesterday, as a P/X, a lugless road frame of mine. It uses a 1 1/4" D/T, and 1 1/8 top and seat tubes.
The trend towards bigger diameter steel tubes in average sized frames, has resulted, in my cynical opinion, from a need for manufacturers to go with the flow and copy the bigger tubes produced for aluminium tubes. As far as I know from use and reading, the wall thicknesses of some of these new generation tubes are no thinner than those of certain "series" or tube sets that I was using in the late 70s and early 80s. OK.. I admit it..the ability of the fatter tubes to resist twisting is greater than the conventional tubes of yesteryear, but some of the steels produced by Reynolds, Vitus, Excell, Camus, and Gauthier-Troussel did actually result in some pretty stiffish frames.. It was the candid opinion of several tube manufacturers that their tubes were made "over-specced", and that even a top level Pro rider never actually pushed any of the tubes to their limits. Companies such as Columbus produced their popular series of tubes such as SL, SLX etc with thicker-gauged down and seat tubes - SP SPX etc, to provide stiffer tubes to be used in larger frames for stiffening up the lower regions of the frame. Their TSX with its helical grooving at the steering end of the top and down tubes was another step in that direction, in trying to eliminate twisting in the head-tube and steering area. But in all cases the top-tube remained at 1".
Like many frame-builders I have experimented with all manner of top-tubes, from twin ones like those used by Rensch for his Paris Galibier., to "double-D section ones.(also used for twin down-tubes long before Ernesto tried them out, but long after R O Harrison, of London), via fluted, grooved, helically twisted etc etc and for a long time most of my lugless frames used Tange oval tubes (quite beautiful, I thought), but none of these applications were intended to improve the steering, but just to stiffen up the triangle and / or create aesthetically pleasing frames.
I wonder if there isn't a point at which too stiff a front end is not counter-productive. The French "cycling" vocabulary, like the French language, is full of nuances resulting in a conversation with a French cycle manufacturer that will include terms such as "rendement" (very important that quality in a frame), "compliance", "performance", "maniabilite", whereas as in the UK it is more likely that a frame will be described as "feels good" or "has some get-up-and-go" ( that term for the old-timers!). But I recall a learned, and well documented and researched article in "Le Cycle" in the early 90s , that questioned whether an over- stiff front end might not in fact contribute to poorer steering and more crashes. This theory was also linked to the growing wide-spread use of the straight steel fork, as pioneered, in a sense, by Colnago. The article claimed that too stiff a front end, combined with a very stiff straight fork, could lead to the cycle pivotting rather than steering. The very high incidence of crashes by Pro riders, particularly Dutch ones such as the Ariostea team riding Colnago frames was fully discussed. In this respect I recall the comments on one top young amateur time-triallist and National Champion for whom I built frames. He had demanded the ultimate in a new T/T frame to be made of steel because I didn't use aluminium. It was to use a monoblade fork. Clearly this blade had to be STIFF!. The bike was a huge success..was light, rigid etc etc..but it did not corner at all well. As the rider explained, "..it doesn't so much corner as.. well ..sort of skips" The explanation we felt was that the beefed up monoblade allied to a very short very stiff head-tube was TOO STIFF resulting in a lack of "compliance"..there I go..that French word again.
Not so much a justification of anything....more of the sort of well-meaning discussion that goes on in most frame-builders' workshops as we endeavour to make the most out of our ill-researched, poorly documented and essentially Black Art...although I prefer to think of it as a craft or combination of skills.
Norris Lockley, Settle UK