More thoughts on tubing specifications and ride qualities

In a previous post, I noted that some highly respected people in the bike world assert that the frame tubing specifications make little or no difference to the ride.  However, in my experience, there are some circumstances in which tube choices make a huge difference.

For example, there was a Monark Siver King at Stu’s for repair.  It was an American balloon-tire kid’s bike, the frame of which was made from 1” round aluminum tubing.  If I remember correctly, the bottom bracket deflection could be measured in inches as you pedaled, yet it had a surprisingly lively ride.  My time with it was short, and I did not try it with a load, nor did I dive into any tricky corners; I suspect that with that much flex the handling could have been challenging.

Close to the same time (early 1980’s), I was at a Portland cyclocross race.  Jim Merz, then a Portland frame builder, brought a bike to the race that appeared to be nearly as flexy as the Monark.  The frame was steel (I think), and I don’t know anything about the specifications, but it must have had very thin walls.  He was using the flexibility as a substitute for suspension and he was riding over some of the obstacles that made the rest of us dismount.  He said something at the time about a good competition bike being “on the hairy edge of breakdown”.  I did not ride the bike, and I don’t know how long that frame survived.

I have ridden two tandems that had frames that were clearly too flexible.  Tandems are an extreme example because of the long tubes, double power input, and double human payload compared to a single bike.

One tandem was an American coaster-brake balloon-tire bike with 1” steel tubing, which usually means low strength steel and thick walls.  While riding placidly it was pleasant enough, but anything other than a gentle change in direction would cause the frame to twist, bend, and buck and generally become a challenge to keep under control.  Another tandem, a Gitane of traditional-diameter (unknown wall thickness but possibly tandem gauge) Reynolds 531 was better, but still could be a handful at low speeds and when cornered hard, and there was a lot of flex when accelerating or climbing.  On the other hand, I have ridden tandems built with oversize and presumably heavier gauge tubing that handle just like single bikes.

In this vein, Mr. Weiss, over at  Bike Snob NYC posted a  link  to a magazine article published in 1996 (back when steel was still taken seriously). The article is an account of a blind test of seven bikes with different frame tube specifications but otherwise identical design. It is remarkable that they assembled this group of bikes, but they could have made more of the opportunity.

In fact, they blew it.  This group of bikes could have been ridden by a group of testers whose pooled observations might have yielded some real insights.  And they could have performed some objective testing, like keeping track of lap times and measuring frame deflection.  Instead, one rider/writer recorded his hurried impressions.

The writer, Alan Cote, had a great deal of trouble telling the tube sets apart by their riding properties. With only one observer (contrary to the impression given by the graphics accompanying the article), this could either mean that differences were truly too subtle to distinguish, or there were too many bikes and too little time to sort out all the sensory information, or maybe that Mr. Cote was not a good observer.

Cote reaches some preliminary conclusions, then appears to second guess himself when he is informed of the construction material of each bike. “I think my ride impressions were essentially random”, he says after he discovers that the tubing specifications do not necessarily correlate with his initial ride impressions.

All of these tube sets are steel, so the specific steel alloy (or associated tensile strength) makes essentially no difference in tube rigidity, and the alloy, by itself, should make no difference in ride qualities.  Ride characteristics are determined by a combination of tube diameter and wall thickness.  Of course a higher-strength alloy does allow thinner walls and lighter weight without reducing the total strength, so the alloy characteristics can influence the long-term usefulness of a frame.

Using my  previous analysis  and a subjective analysis of the other frame specifications, most of these frames should have similar characteristics, but there is enough of a range that differences should have been perceptible, at least in the frames at the extremes.

The most flexible frame should have been the one constructed from SLX tubing.  It has the most flexible main triangle and the lightest chain stays, seat stays, and fork blades.  Cote identified this bike as the “softest”, apparently only for power transmission.  I don’t see any reason it would not also be the softest in its over-the-bumps ride.

I am surprised that he could not distinguish the straight-gauge (Aelle) frame.  Unless we have been defrauded about the value of butted tubing over the last 120 years (a possibility I cannot entirely eliminate) there should be a noticeable difference between this and the other bikes.  I found my Schwinn Sports Tourer, with similar tubing, harsher and less lively than comparable butted frames (though I recognize that that perception could have been because I knew it was straight gauge).

The stiffest frame should have been the Thron, with stout oversize tubing and heavier chain stays and seat stays.  This frame should be 30% or more stiffer than the SLX, a difference I would expect a rider to feel both in lateral flex during pedaling and over the bumps.  Cote called this the best at shock absorption, an impression that is surprising.

Cote’s favorite (which he called the “stiffest”) was the Neuron frame, made from tubing that used a complicated elliptical butting pattern.  Based on its specs, I would expect that it should be only incrementally stiffer than the SLX.  It is possible that the unique butting patterns provide a noticeably better ride, but if so, that fact did not save Neuron tubing from being eliminated from the Columbus catalog.

For a wine drinker who is happy with generic white wine, the difference between chardonnay and pinot gris is too subtle to bother with.  But a wine journalist worthy of the name would easily identify the two, wax poetic about the contributing tastes and mouth feel, and maybe tell you what vineyard the grapes came from.  A bike journalist should have a similarly well-calibrated sense of the contribution of frame construction to ride characteristics.  Maybe the differences between these frames were subtle, and maybe any differences really don’t matter when it comes down to the overall riding experience, but I have a hard time believing that the differences were indiscernible.  Bike journalism is driven too much by manufacturers’ (advertisers’) claims rather than educated, calibrated experience.  This was a unique opportunity to improve the writer’s ability to judge ride characteristics (maybe bike magazines should have a stable of test bikes with known and validated characteristics for training aspiring writers).

Or, if a panel reached consensus, this test would have reached a defensible conclusion that frame material really doesn’t matter (at least within this range).

Instead, it was a lost opportunity.

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