Re: [CR]Frame Flex Testing

(Example: Events:Cirque du Cyclisme:2004)

Date: Thu, 29 Sep 2005 09:53:06 +0000
From: "Steve Maas" <>
Subject: Re: [CR]Frame Flex Testing
In-reply-to: <000601c5c46a$18dd2210$71bffea9@CharlesNighbor>
References: <000601c5c46a$18dd2210$71bffea9@CharlesNighbor>

My best instincts tell me to stay out of this; I've got work to do today. Nothing to be gained by getting into a technical discussion with people who can't even agree on how a spring works. My internal bleeding, however, motivates me to do otherwise.

I made the point a couple weeks ago that these highly subjective assesments of things like frame flex are not reliable. The discussion, at the time, was on frame softening, a phenomenon that simply doesn't occur. The idea that it does occur, however, comes precisely from this type of subjective assessment.

I'm still waiting to see some hard data showing that (1) frames flex to a degree that is genuinely perceptible to a human, and (2) that there is a significant difference between any two frames of the same general type. This is especially unlikely in our case, since we are dealing with frames made of identical materials to virtually identical dimensions, for a given size.

On the other hand, it is well known that people will perceive whatever they expect to perceive. It is startling to see how strong this tendency is, and how easily people can be led to feel that they can experience something that doesn't really exist. For this reason, all academic research which could be influenced by subjective effects is made doubly or even triply blind. Most laymen look at this as just an academic nicety, but it decidedly is nothing of the kind. If even the best researchers are subject to it, the rest of us are, too.

I haven't seen the article that started this thread, and I'm not going to take the time to look for it. The hard data that I have seen indicates what I would expect, namely that any degree of frame flex in a conventional lugged steel frame is very small, probably imperceptible. Especially, it is orders of magnitude below the amount of movement in other parts of the bicycle: the tires, seat, bar covering, looseness in the bearings, and so on. It's just not credible to me that anyone could perceive frame flexing--let alone DIFFERENCES in flexing between two frames--within this large cloud of confusion. It's a sneeze in a hurricane.

I suggest that frame flex proponents take a close look at, especially the last two or three paragraphs.

Steve Maas School of Electrical, Electronic, and Mechanical Engineering, University College, Dublin Dublin, Ireland