The importance of frame compliance over rigidity

[Barrowman]

Perhaps I didn't express exactly the point I was trying to make.
Design and materials are the key. I suspect the majority of off the shelf Alloy frames are much of a muchness
(No direct experience in riding one to be fair) whereas a good steel frame made from the right tubing is a much better bet. More expensive ? Inevitably I am afraid. I observe most modern machines have 'fat' tyres, is this to compensate for lack of frame compliance?

[NickJP]

my take on it is this; frames that are likely to be too flexible are also likely to be noticed and rejected, well before the flexibility actually slows you down much. Some people even think flexible frames are faster. My view is that it might be true in some cases, if perhaps the flexible frame makes you pedal better.

Yes, Sean Kelly certainly didn't seem to be hindered by extremely flexible Vitus frames that he rode. Here's his skinny tube aluminium frame Vitus 979 (aluminium fork as well) from 1986, a year in which he won (amongst many other races) Milan-San Remo, Paris-Roubaix, Paris-Nice, Tour of the Basque Country, Volta a Catalunya, and in addition came second in Tour of Flanders and Giro di Lombardia.

[slowster]

Fairlight's approach is interesting. They have the now almost standard tapered carbon forks (or 1 1/8" steel fork) with accompanying oversized headtube and an oversize downtube, but the top tubes are 1" Reynolds 631 and 853, which are ovalised for their entire length. (So the 853 tubes have to be ovalised in the UK, heat treated by Reynolds, and then shipped to the contract manufacturer in Taiwan, rather than just being drawn down from whatever general stock of tubing Reynolds and/or the manufacturer have in Taiwan.)

Effectively they take one of the things that contributed to the ride and compliance of a traditional narrow tubed frame, and they increase that tube's flexibility in the vertical plane even further than on a traditional narrow tubed frame. I don't think there was ever a need felt to do that on a traditional frame, because it also benefited from flex of the forks and steerer. I doubt the Fairlight frames get close to the compliance of a narrow tubed frame with quill stem, but it would be interesting to compare one with a more standard modern oversized tube frame.

From page 10 of their design notes for one of their models:

The tube starts life as a 25.4mm round tube and is fully ovalized to 20 x 30mm. This tube is critical in providing the excellent comfort of our frames. The stiffness in the horizontal plane is equivalent to that of a 30mm tube, while the narrow 20mm tube in the vertical plane means it provides excellent comfort, effectively flexing as the wheels try to move away from each other under load. A more standard round 28.6mm or 31.8mm top tube would be torsionally (twisting forces) stiffer, but we design the downtube and top tube to work together in how they deal with the various loads/forces. The tube is butted at 0.8/0.5/0.8.

https://fairlightcycles.com/?v=79cba1185463 / https://fairlightcycles.com/wp-content/ ... s-V1.2.pdf

[pjclinch]

Another approach is a stiff frame (possible a space frame...) combined with suitable suspension.

This introduces its own issues, of course, but done right it is a workable solution.

Pete.

[mig]

my take on it is this; frames that are likely to be too flexible are also likely to be noticed and rejected, well before the flexibility actually slows you down much. Some people even think flexible frames are faster. My view is that it might be true in some cases, if perhaps the flexible frame makes you pedal better.

Yes, Sean Kelly certainly didn't seem to be hindered by extremely flexible Vitus frames that he rode. Here's his skinny tube aluminium frame Vitus 979 (aluminium fork as well) from 1986, a year in which he won (amongst many other races) Milan-San Remo, Paris-Roubaix, Paris-Nice, Tour of the Basque Country, Volta a Catalunya, and in addition came second in Tour of Flanders and Giro di Lombardia.
KellyKAS.jpg

whilst i understand the thrust of what you are saying i'm not sure that the conclusion is that he wasn't hindered. it was just that he was fastest on those days amongst other riders on tech of the same time.

[Carlton green]

my take on it is this; frames that are likely to be too flexible are also likely to be noticed and rejected, well before the flexibility actually slows you down much. Some people even think flexible frames are faster. My view is that it might be true in some cases, if perhaps the flexible frame makes you pedal better.

Yes, Sean Kelly certainly didn't seem to be hindered by extremely flexible Vitus frames that he rode. Here's his skinny tube aluminium frame Vitus 979 (aluminium fork as well) from 1986, a year in which he won (amongst many other races) Milan-San Remo, Paris-Roubaix, Paris-Nice, Tour of the Basque Country, Volta a Catalunya, and in addition came second in Tour of Flanders and Giro di Lombardia.
KellyKAS.jpg

whilst i understand the thrust of what you are saying i'm not sure that the conclusion is that he wasn't hindered. it was just that he was fastest on those days amongst other riders on tech of the same time.

I see both sides to that ‘argument’, one might also say that if he was hindered then the degree to which that was so was insignificant. There’s a school of thought that argues that being shaken around by frames, wheels and tyres that are too stiff actually stops you performing to the best of your ability - it would certainly stop me enjoying the ride and I’d be either altering or changing the bike too.

Since the original post I’ve not commented but I have been watching it with interest. My thanks to all who have contributed and please do keep the posts coming in.

[mattheus]

my take on it is this; frames that are likely to be too flexible are also likely to be noticed and rejected, well before the flexibility actually slows you down much. Some people even think flexible frames are faster. My view is that it might be true in some cases, if perhaps the flexible frame makes you pedal better.

Yes, Sean Kelly certainly didn't seem to be hindered by extremely flexible Vitus frames that he rode. Here's his skinny tube aluminium frame Vitus 979 (aluminium fork as well) from 1986, a year in which he won (amongst many other races) Milan-San Remo, Paris-Roubaix, Paris-Nice, Tour of the Basque Country, Volta a Catalunya, and in addition came second in Tour of Flanders and Giro di Lombardia.
KellyKAS.jpg

Your data also suggests that toe-straps are the best equipment to use for winning races.

[Brucey]

..... I observe most modern machines have 'fat' tyres, is this to compensate for lack of frame compliance?

yes, I think so.

[Cugel]

my take on it is this; frames that are likely to be too flexible are also likely to be noticed and rejected, well before the flexibility actually slows you down much. Some people even think flexible frames are faster. My view is that it might be true in some cases, if perhaps the flexible frame makes you pedal better.

Yes, Sean Kelly certainly didn't seem to be hindered by extremely flexible Vitus frames that he rode. Here's his skinny tube aluminium frame Vitus 979 (aluminium fork as well) from 1986, a year in which he won (amongst many other races) Milan-San Remo, Paris-Roubaix, Paris-Nice, Tour of the Basque Country, Volta a Catalunya, and in addition came second in Tour of Flanders and Giro di Lombardia.
KellyKAS.jpg

whilst i understand the thrust of what you are saying i'm not sure that the conclusion is that he wasn't hindered. it was just that he was fastest on those days amongst other riders on tech of the same time.

I had and raced one of those Vitus 979 frames in the late eighties. it was horrible - flexy in an alarming way, especially in sprints and going down fast bendy descents. I got rid toot sweet and went back to me 531SL frame.

The 531SL frame was a handbuilt (Alan Dent) frame that was a perfect fit to me and did have a degree of compliance that improved the ride quality without feeling like a rubber bike, as the Vitus frame felt. Nevertheless, an eventual move to a well-designed carbon fibre - resin frame was a revelation in terms of both comfort from compliance but a compliance that still managed to get the energy of every pedal thrust down to the back tyre patch on the road far more effectively than any steel frame I'd ever ridden (and I've ridden quite a few over the decades, from gas-pipe and scaffolding pole to that handbuilt 531SL, with many other tubesets of various designs in between).

No doubt there are comfortable and efficient steel frames about, now and then; but I have my doubts that any of them can match the combined efficiency & comfort of a well-designed CF frame. If they could, there'd be a presence in racing. I know there have been one or two revivals using particularly exotic tubing but these soon faded away.

Of course, racing is not touring. But carbon fibre frames can be designed for any style of bike to maximise what's wanted of it and minimise the unwanted aspects. Steel tubes can be ovalised, butted, etcetera and put together in clever designs but steel tubing doesn't have the malleability of carbon fibre in plastic, like it or not.

Although there are also plenty of badly designed and thus poor to ride CF framesets of course. And a steel tourer can probably take more serious damage whilst remaining functional than a CF frame, if touring out in the sticks .... where CF frame fixing is also less likely available than steel frame fixing. But fixability has nothing much to do with frame comfort and efficiency.

[Cugel]

my take on it is this; frames that are likely to be too flexible are also likely to be noticed and rejected, well before the flexibility actually slows you down much. Some people even think flexible frames are faster. My view is that it might be true in some cases, if perhaps the flexible frame makes you pedal better.

Yes, Sean Kelly certainly didn't seem to be hindered by extremely flexible Vitus frames that he rode. Here's his skinny tube aluminium frame Vitus 979 (aluminium fork as well) from 1986, a year in which he won (amongst many other races) Milan-San Remo, Paris-Roubaix, Paris-Nice, Tour of the Basque Country, Volta a Catalunya, and in addition came second in Tour of Flanders and Giro di Lombardia.
KellyKAS.jpg

Your data also suggests that toe-straps are the best equipment to use for winning races.

[rareposter]

But fixability has nothing much to do with frame comfort and efficiency.

Good post (all of it) but this point is worth a mention too - when choosing a frame material, the designer is considering the intended purpose of the bike, fatigue strength, joining and forming options, corrosion resistance, weight, price, availability of raw material, aesthetics, ease of repair (should it be necessary), cost of the final product... Plus many other considerations.

Ultimately, the ride property is determined by the design rather than the material. You can build insanely stiff or really noodly frames in pretty much any material - the sweet spot of course is along a range between those extremes, one optimised for that type of bike and riding as well as the intended customer.

However at very low / mass production price points, much of the above is given only a cursory glace at best. Very few people buying a £300 Carrera (for example) are going to care about any aspect of bike design and production, material strength or anything as esoteric and subjective as "ride feel" whereas someone buying a semi-custom Fairlight (to use the example from slowster above) are spending very significantly more money on it and they will be discerning enough to care as well as (generally) a bit more capable of subjectively categorising ride feel.

[peetee]

[
The 531SL frame was a handbuilt (Alan Dent) frame that was a perfect fit to me and did have a degree of compliance that improved the ride quality without feeling like a rubber bike, as the Vitus frame felt. Nevertheless, an eventual move to a well-designed carbon fibre - resin frame was a revelation in terms of both comfort from compliance but a compliance that still managed to get the energy of every pedal thrust down to the back tyre patch on the road far more effectively than any steel frame I'd ever ridden (and I've ridden quite a few over the decades, from gas-pipe and scaffolding pole to that handbuilt 531SL, with many other tubesets of various designs in between).

531SL certainly can get the job done. I know of a rider on a 531Pro (that’s what SL became in the mid 80’s) frame that set a hill-climb course record in 1997. I occasionally look up Strava times on this course and others I’m familiar with and his time hadn’t been beaten two years ago and probably still holds today.

[Carlton green]

[
The 531SL frame was a handbuilt (Alan Dent) frame that was a perfect fit to me and did have a degree of compliance that improved the ride quality without feeling like a rubber bike, as the Vitus frame felt. Nevertheless, an eventual move to a well-designed carbon fibre - resin frame was a revelation in terms of both comfort from compliance but a compliance that still managed to get the energy of every pedal thrust down to the back tyre patch on the road far more effectively than any steel frame I'd ever ridden (and I've ridden quite a few over the decades, from gas-pipe and scaffolding pole to that handbuilt 531SL, with many other tubesets of various designs in between).

531SL certainly can get the job done. I know of a rider on a 531Pro (that’s what SL became in the mid 80’s) frame that set a hill-climb course record in 1997. I occasionally look up Strava times on this course and others I’m familiar with and his time hadn’t been beaten two years ago and probably still holds today.

Which kind of goes to reinforce a recently discovered truth: ‘I don’t need the best but I do need at least good enough, affordable and reliable’.

Ultimately, the ride property is determined by the design rather than the material. You can build insanely stiff or really noodly frames in pretty much any material - the sweet spot of course is along a range between those extremes, one optimised for that type of bike and riding as well as the intended customer.

My daily ride is built from 18-23 which I had thought was likely not of any worthwhile quality. However research elsewhere says it’s perfectly fine (fit for purpose) and your post suggests to me that that should be the case too (if designed and built well). It glides along and seems to get me up the hills too … the fitter I get the better it climbs.

[Brucey]

..I had one of those Vitus 979 frames in the late eighties. it was horrible - flexy in an alarming way, ....without feeling like a rubber bike, as the Vitus frame felt.......

me too; I sold my vitus to a chum, explaining it was way too floppy for me (I could, at will, easily cause the FD to scrape on both sides) and he absolutely loved it.

[531colin]

..................
My daily ride is built from 18-23 which I had thought was likely not of any worthwhile quality. However research elsewhere says it’s perfectly fine (fit for purpose) and your post suggests to me that that should be the case too (if designed and built well). It glides along and seems to get me up the hills too … the fitter I get the better it climbs.

"18-23" is a Raleigh trade mark for tube; theres a (2007) post here from CJ viewtopic.php?p=30668&hilit=18+23#p30668 saying what it is and how its made; but to me more importantly CJ also says all varieties of steel have the same density and the same Young's modulus (stiffness); where fancy steels differ is in their strength, so you can have less of the fancy steels, this usually means thinner walled tube. The backside of this is that some frames made of cheap oversize tube (which is also relatively thick-walled) are really stiff; good for powerful riders' flat-out efforts, or a camping load; less good for light riders all-day comfort on an unloaded bike.