Frkl

"Vertically compliant/laterally stiff:" the holy grail of modern bike design. I can't stand the phrase, personally. Maybe there are others here too?

Anyway, I was recently reading old Cannondale catalogs, because, why not?, and I found the term used in 1996.* This surprised me, but I guess "old" stuff becomes new again all the time. I guess the concept has been around for a while, but has anyone encountered the phrase itself earlier than this?


* yes, I know 1996 isn't vintage, but what other forum here would appreciate this?

El Chaba

June 14, 1817 is often cited as the date of invention of the first bicycle. I think the term “vertically compliant/laterally stiff” came into wide use on June 15 of the same year….

abdon 

You may want to ask on the frame building forum. They would be more familiar with the practical implications of this.

cudak888 

I'd wager that it came from the marketing department after listening to framebuilders.

Anyone have an example older than the '96 Cannondale catalog? I can see this term being cooked up to allay any fears about the lack of seat stays.

-Kurt

smd4

I don't know when it was first phrased like that, but lateral stiffness was always a much-talked-about feature in 1980s bike reviews. Not sure when "vertically compliant" became a thing.

Trakhak

I don't remember ever encountering claims about vertical compliance/lateral stiffness characteristics until Gary Klein started promoting his aluminum frames.

I have a Klein catalog from around 1983 or so. It includes the following statements:

POWER TUBING: High-strength aluminum/magnesium alloy tubes in large diameters are used.

POWER EFFICIENCY: The Klein has the most deflection-resistant power train made. This minimizes the energy lost to frame deflection. While the increased efficiency occurs under all riding conditions, it is particularly evident under the high stress of a steep climb or a hard sprint, as it rigorously resists lateral (bottom bracket) deflection and transmits more of the rider's energy into forward motion. You can easily feel this performance advantage. Laboratory tests performed at M.I.T. show the Klein to be over 60% more rigid than the best steel frames.

RIDE COMFORT: The frame has a significant effect on ride comfort. In order to achieve a smooth ride, it is desirable for the frame to absorb road shock in a vertical suspension fashion. The Klein construction does this better than any other frame. The lightweight Power Tubing(TM) has more overall suspension ability than super light gauge steel tubing. This results in the incredibly smooth ride.

Frkl

Oh, i really don't care about the practical implications at all, if by that you mean regarding actual frame design, what it physically means, or whether it imparts an actual benefit.

I am just wonder out of curiosity regarding the phrase or idea itself being used by companies to describe a positive attribute of their bike.

Frkl

I just quickly looked at some before posting this. In the earlier catelogs it was all about how absolutely flex free and rigid their frames were.

https://vintagecannondale.com/catalog/

has them going back further.

Frkl

and ovalized tubing was around well before as well, and at obviously served the lateral stiffness goal.

Frkl

oh cool. that is really interesting. thank you

repechage

‘when Cannondale extended the chainstays beyond the seat stay attachment point, that was an attempt to have both.

smd4

God that was ugly...

Frkl

Oh, I always thought that was so that the frames broke and the owner would "upgrade."

But seriously, it's true that Cannondale realized they didn't have this (vertical compliance) and needed it. The Silk Road Headshok bikes for instance.

jeirvine 

Google Ngram charts the usage of words and phrases. https://books.google.com/ngrams/

Here's what it shows for vertically complaint, and laterally stiff. (I can't get it to do both phrases at once.) Looks like the former took off in 1978.

-J

Trakhak

Regardless of what the marketing department might have claimed at the time, our Cannondale rep said that the design with the dropouts that extended behind the seat stay connection was a means of circumventing the terms of Gary Klein's patent.

mpetry912 

I think attributed originally to Damon Rinard ?

many hype cycles drove this particular line of discussion

/markp

Trakhak

Cannondale was all about innovation, with any number of wild deviations from design norms. They're still selling at least one model with a Lefty fork, for example. But I can't help wondering: if the HeadShok represented an effort to compensate for the unique stiffness of their aluminum frames, then why did Specialized come up with their Future Shock for all those reputedly comfy carbon bike models?

Vertical compliance: the myth that won't die. Double diamond bike frames are essentially two-dimensional, perfectly designed to offer effectively no vertical shock absorption.

Enough. I just did a search, and this was the first result:

Frame Stiffness

What I got from that page: measurements of vertical compliance of four frames (and, separately, forks, plus wheels and tires), including a Trek 1200 (aluminum frame), a Specialized Sirrus (steel frame), a De Rosa (steel frame), and a Cannondale, were compared. The compliance was measured with various vertical loads. The values are expressed in 0.001-inch increments.

The table of data doesn't reproduce well, at least on my screen (the values in the final column wrap around under the designations in the first column), but the results are clear. The largest difference in frame vertical compliance, comparing like for like, was 0.003"!

The guy who did the measurements went on to say (in part; the whole thing is worth reading) the following:

"What is going on here? I read the bike mags and this net enough to know
that people have strong impressions about the things that affect ride
comfort. For example, it is common to hear people talk about rim types
(aero vs. non-aero), spoke size, butting and spoke patterns and how they
affect ride. Yet the data presented here indicate, just as Jobst predicted,
that any variation in these factors will essentially be undetectable to
the rider."

He's finally driven to starting a later paragraph with "Being a psychologist, I am naturally inclined toward the psychological explanation."

Having ridden racing bikes since the mid-1960's, which included high-end track and road bikes in steel, aluminum, and carbon, I long since figured out that I can predict how "comfortable" a bike will be for me (whatever that means for racing bikes) by looking at the wheelbase measurement. There are probably effects related to frame angles, rake, etc., but I don't care. If a bike is built with my preferred wheelbase, I'm going to like it, and frame material doesn't enter into it.

Exception: my preference for maximal lateral stiffness, which is why all the bikes I've ridden consistently for the last 15 years have been aluminum. (Carbon would probably be fine, too, but I made the mistake of buying my one carbon bike without checking the wheelbase figure, and it's a little over a centimeter too long for my liking.)

Frkl

thanks, this is interesting: here is the combined.


But this doesn't tell us when they happen together as a connected concept. I tried to search for the whole phrase but it isn't working for me.

iab

Suzy Rottencrotch said it to me in the spring of 1978.

Frkl

As I mentioned, I'm not really so much interested in this case with whether it is a "real" thing or makes a "difference," more just the idea that people had.

But since you brought it up: There has been some renewed discussion about the whole vertical compliance "myth." The thing about the "triangles don't flex" argument (and by extension, diamond frames composed of triangles) against the existence of (meaningful) vertical compliance is that it overlooks the fact that most bicycle frames are by far not diamonds composed of triangles. Actually, the head tube usually results in a trapezoid front "triangle" and the rear dropouts in trapezoid rear "triangles" (albeit much more triangle like). And trapezoids or any quadrilateral are super prone to flex.

It also overlooks the fact that any non-straight portion or weaker portion of a tube will encourage in some deflection, even if very small, thus shortening the effective length of the tube and resulting in "vertical compliance". This seems to me especially true with the seat stays, and we can see with eg some Litespeed frames, that the designers took advantage of this by slightly bowing the stays "down" to increase their tendency to deflect. Many frames also don't have completely straight seatstays in the plane perpendicular to the wheel (whether a small bend near the seat cluster or a more radical S shape). Brakes also cause deflection, which leads to a shortening of one side of the trapezoid: cantilever brakes outward and caliper brakes in the direction of travel.

Ie, a triangle cannot flex if a) it's really a triangle and not actually a quadrilateral, and b) the sides of the triangle are immune to deflection (or compression and extension, but I give you these are essentially 0). Both of these are not met with a bicycle.

But most importantly, i think this becomes clears in bikes actually being ridden. I would expect that static tests that simply apply a load (80lbs in the example you cite) wouldn't show much (but it does show something, and if you applied real world loads we would see more). And 80lbs is nothing; I exert a 175lb load while sitting on the stationary bike; when i hop the pothole and land it, there is a bit more than that.

steelbikeguy

There is an ad in the Jan/Feb 1980 issue of Bicycling with similar statements. Nothing as simple as "vertically compliant, laterally stiff", but definitely addressing the issues of comfort and efficiency.
I wonder if "vertically compliant, laterally stiff" only shows up where people are mocking these sorts of claims? It seems too concise to be written by the marketing folks.



Steve in Peoria

Trakhak

'But since you brought it up: There has been some renewed discussion about the whole vertical compliance "myth." '

Where? Links?

You object that bike frames are not composed of triangles but instead of two trapezoids. That, of course, would have been the case for all the frames tested, which renders that objection irrelevant. In any event, at a maximum of 0.003" of difference in vertical frame deflection, it's clear that the contribution to flexibility the trapezoids make is vanishingly small.

I agree that 80 lbs would be insufficient to tease out the differences between frames and between forks. However, he also made the following (annoyingly vague) statement:

"For some of the measures, I applied pressures from 20 to 270 lbs
to check for any significant nonlinearity."

We have to guess, but I can't imagine that he applied 270 lbs to the wheels and tires: that would be broadly equivalent to simulating a total bike-plus-rider load of over 500 lbs (270 lbs per wheel).

Thus, the 270 lbs was almost certainly applied to the frame, and possibly the fork, too. But all the bikes were either 1986 or 1987 models, so they all had steel forks, and so those numbers are irrelevant with respect to comparing aluminum to steel.

Anyway, the point of using the greater weight was, as he says, to check for nonlinearity. He didn't find any.

Again, I'll provide a couple of myth-busting links. The videos are from a bike racer with a degree in mechanical engineering and a low tolerance for bike-related BS. The first is an overall discussion of bike stiffness; in the second, he's talking about the myth of the superiority of titanium bikes with respect to riding comfort, but he also notes (around 2:45) that any difference you think you feel between bikes built of different frame materials is essentially imaginary.

Hope you don't mind a bit of salty language. He's clearly irritated by the persistence of the myth that one frame material versus another = comfort versus harshness, given how simple the calculations are that disprove it.

Bicycle Stiffness - The Truth. Ep 2. Second Moment of area, stiffness & compliance explained.

Titanium Bikes - The truth and Physics of 'ride feel' marketing.

campfire

In simplifying the videos, you've missed a key point. The statement in bold is only true if the frames in question have equal geometries (I.E., section moduli in corresponding tubes). Aluminum, titanium, and steel may all have similar specific modulus values, but they are used in different ways. Aluminum is prone to cracking when allowed to deflect. Aluminum frame builders keep the section modulus (what the video calls "modulus of area") high to prevent fatigue failures. Steel doesn't have such a problem, and steel frame builders often use tubes with a lower section modulus (less stiffness).

The videos are correct, materials don't automatically determine a frame's comfort. But they do affect the compromises that a frame builder must choose, and some of those compromises, in turn, impact a frame's comfort/harshness. Steel frames can be built stiff or flexible, but Aluminum flexibility comes at the cost of short fatigue life. The resulting different geometries ride differently.

steelbikeguy

okay... back to the point of the thread (I think...)!

I was poking through my old Bicycle Guide issues that I've scanned. No OCR when scanning, so I'm just perusing each page that looks like it might discuss stiffness.
In the July 1989 issue, there is an article looking at the different frame materials and how they compare.



on the top right of one page discussing the Kestrel, I spied a discussion about stiffness...


and I found the magic phrase "laterally stiff but vertically compliant"!!




It does say that "everyone dreams about" this characteristic, so it seems reasonable to assume that it was already a common phrase and had been around for some time. This does suggest that the origin has yet to be discovered.

Steve in Peoria

Trakhak

That would all make sense if double-diamond frames deformed significantly under vertical load. They don't. An article linked to early in this thread reported that under the tested vertical load, two frames built of steel (a 1987 DeRosa and a 1988 Specialized Sirrus) and two of aluminum (a 1987 Trek 1200 and a 1988 Cannondale; model unspecified) differed in vertical deflection by a maximum of 0.003".

If someone has data that show significant deviations from that finding, I'd love to see them. Otherwise, I'll trust those results, which mirror my experience---that double-diamond bike frames with identical geometries ride more or less the same with respect to vertical compliance and differ significantly only in torsion. The latter factor is what influenced me to consign my Reynolds 531 and 853 frames to the basement and ride aluminum bikes exclusively for the last 15 years.

In pointing out these facts, I feel like a compact disc fancier arguing with vinyl record proponents. Yes, poorly mastered CDs can sound bad. But, correctly mastered, they can take advantage of their roughly 90 dB dynamic range, versus a maximum of 70 dB for the very best vinyl.

But vinyl records can still sound good, despite their limitations, and steel frames can be satisfying to ride. In fact, I rode pro-level steel racing bikes from 1964 until about 2005, and I loved every one of them---some more than others, of course.

Then I bought my first aluminum race bike, and became instantly addicted to the immediacy of response, especially accelerating and sprinting up hills, to say nothing of the perfect tracking of the wheels in fast, twisty descents. I'm still as enthusiastic about those qualities as I was 18 years ago.