Author Topic: An important upset in the classical view of bicycle resilience  (Read 425 times)

Andre Jute

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Here's a really good discussion of the relationship between the various springing systems in the bicycle.

https://cyclingtips.com/2018/04/jra-with-the-angry-asian-does-frame-compliance-still-matter/

The general approach since forever has been to assume the "springs" of the frame/fork/seatpost plus wheels plus inflated tyres work in sequence, at which point it becomes obvious that only the tyres, being the softest spring, matters. But that is the classic view. Damon Rinard, whose work I've been following since the early 1990s, has now turned the conventional wisdom on its head, arguing that the controllability of carbon brings the spring rate of the frame much closer to (narrow) road tyres. Important consequences follow. The general trend towards wider tyres at lower pressures also has important consequences to bicycle system resilience and consequently comfort.

The article is commended to those interested in the technicalities of riding comfort in the certainty that you will find it well worth your time.

martinf

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Re: An important upset in the classical view of bicycle resilience
« Reply #1 on: April 22, 2018, 08:56:37 AM »
This seems to be focused predominantly on road bikes, so maybe not very applicable to those of us that ride very wide tyres on frames designed for luggage carrying.

On a bike like my Raven Tour, the frame/fork (and the racks bolted to them) have to be fairly stiff to stop the bike flopping around with a full load. Wheels also have to be sturdy to avoid collapse. The obvious way of getting back a reasonable degree of comfort is to use wide, high-quality, low-pressure tyres.

On this kind of bike, other comfort-enhancers can be sprung seatposts (Dan has one on his Nomad), sprung saddles (I fit these on most of the family bikes with relatively upright positions, but don't yet need them on my drop bar bikes), sprung stems (I've tried one in the past and abandoned it because of the play that developed), thick handlebar padding, there are probably a few other methods.

An alternative approach for a load carrying bike is full suspension. I've tried this as well - I had a Moulton APB space frame with spring and damper type mechanical suspension. This had a very rigid frame made of lots of small triangles. The front and rear racks were attached directly to the main frame, so completely suspended. It didn't take quite as much luggage as my large wheel tourers, but was a more stable load platform than my (contemporary) old mountain bike with the old Karrimor solid-wire racks. For me, the two downsides of the Moulton over a Thorn touring bike were the small wheels, which are good enough for road touring, but don't work as big wheels on rough tracks (I often like to take "short cuts") and the wear in the suspension system (this is only an issue in the long term).


Andre Jute

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Re: An important upset in the classical view of bicycle resilience
« Reply #2 on: April 23, 2018, 12:23:48 AM »
This seems to be focused predominantly on road bikes, so maybe not very applicable to those of us that ride very wide tyres on frames designed for luggage carrying.

I quite agree. However, sooner or later some adventurous manufacturer will offer a carbon fibre touring bike designed to distribute the "comfort zones", and then these considerations will become relevant.

On a bike like my Raven Tour, the frame/fork (and the racks bolted to them) have to be fairly stiff to stop the bike flopping around with a full load. Wheels also have to be sturdy to avoid collapse. The obvious way of getting back a reasonable degree of comfort is to use wide, high-quality, low-pressure tyres.

Actually, the wider touring tyres become, and the lower the air pressure in them, the further apart the frame stiffness and the tyre stiffness move. Rinard's overriding point is that it is no longer adequate to consider the tyre the softest spring in the bicycle system (at least in road bikes) because carbon frames can be built to approach the tyre quite closely, and in future closer still. What we've seen in steel and even ali touring bikes over the last generation or so is precisely the opposite: frames have become stiffer and tyres more compliant.

Wheels also have to be sturdy to avoid collapse.

It's difficult to see this fact change, even for stupid-light road bikes. For every other kind of bike, certainly, I reckon wheels will remain the stiffest part of the bike, probably forever.

***
I must say I appreciate the simplicity of my everyday bike, which has all the suspension in the tyres, with solid fork and and rear triangles on a very stiff cross-frame in three dimensions, plus of course the Brooks saddle, which has already translated into longevity. On one of my previous bikes, a Gazelle Toulouse, the suspended fork gave up the ghost around 2000 miles, which simply isn't good enough.

martinf

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Re: An important upset in the classical view of bicycle resilience
« Reply #3 on: April 23, 2018, 12:52:39 PM »
I quite agree. However, sooner or later some adventurous manufacturer will offer a carbon fibre touring bike designed to distribute the "comfort zones", and then these considerations will become relevant.

I had another reminder of why I avoid carbon fibre a couple of weeks ago.

A young racer passed me and a few other "ordinary" cyclists just before the river crossing, then, instead of using the (unusual for my area) decent cycle lane on the bridge, stayed with the cars.

When I caught up with him on the bridge he was holding half a carbon fibre bicycle in each hand, but he seemed OK apart from road rash. I didn't see how the accident had happened, there was a car stopped that seemed to have been involved and several people around the young racer, including two cyclists, so I carried on my way.


Andre Jute

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Re: An important upset in the classical view of bicycle resilience
« Reply #4 on: April 23, 2018, 11:02:48 PM »
When I caught up with him on the bridge he was holding half a carbon fibre bicycle in each hand...

Ouch!

PH

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Re: An important upset in the classical view of bicycle resilience
« Reply #5 on: April 24, 2018, 10:20:20 AM »
I regard this sort of technical article as little more than navel gazing, stiff for who, compliant for what ride?
Take my Mercury as a random example - Thorn's sizing guide is around 6'2" - 6'4", the recommended max luggage capacity is 25 kg for "sweet" handling.  The NHS healthy weight guide for people in that height range is 65kg to 95kg. 
It's not hard to see where this is going...  At the extremes we'll have a 65kg rider who carries no luggage and has a preference for smooth tarmac (Good luck finding some) and at the other extreme there's the 95 kg rider carrying 25 kg and accepting the sorts of surfaces that any touring cyclist will.  This is without considering that we're not all in that healthy weight band and never overload a bike, things a designer wouldn't dare ignore. Does anyone think that a frame designed to cover that range is going to be ideal for all, or even a high percentage?
It's not hard to see that despite the best efforts of any frame manufacturer or all the words in any brochure, there's huge compromises being made in what would be optimal for any given rider.  You'd need to spend mega money to avoid them, even many so called custom frame builders do little more than offer stock designs with some braze on options and a choice of paint.
We haven't even touched of personal preferences - one mans compliant will be another's floppy!

This is why tyres are the most important factor, not because of any technical data, but because the rider can use them to tailor the bike to their liking and then do so again and again and again.

Andre Jute

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Re: An important upset in the classical view of bicycle resilience
« Reply #6 on: April 25, 2018, 01:52:34 AM »
I regard this sort of technical article as little more than navel gazing, stiff for who, compliant for what ride?

It's possible to calculate many parameters of the median customer; all it takes is money and a savvy researcher. For the non-statisticians, the median is not an average, but the largest number of people in the universe that have the same or very close characteristics of interest, for instance the same weight, height, and luggage requirement. In the case of this article, it seems to me likely that they started by tailoring a bike to Mr Rinard; he's been building carbon fibre bikes for over 20 years that I know of. Most of the components that eventually achieve high reputations are originally the obsessions of individual engineers; vide those photographs of Jobst Brandt riding his Cinelli around and round the parking lot in front of the Avocet office, who marketed his innovations, among which the most revolutionary was the slick bicycle tyre.

.... tyres are the most important factor, not because of any technical data, but because the rider can use them to tailor the bike to their liking and then do so again and again and again.

For sure, experienced bicycle tourers like controlling the ride by the classic method of a stiff frame and control over tyre choice. But not everyone has the relevant knowledge or experience to conclude such matters competently. Since the discomforts of cycling are an important barrier to growing the market for bikes, manufacturers are spending money on staff and labs to tailor bikes, presumably for the median customer. We should welcome the intention, which goes against recent trends towards one-size-fit-all bikes. It's also good marketing to say that they are doing something about comfort. But, since carbon fibre frames are built one at a time, with a lot of manual labour, the more expensive bikes can possibly be individually tuned to the owner's weight, load and other preferences. There was a fellow on another conference who sold titanium bikes that were made for him in Taiwan, and he used to offer a service of having any individual frame tailored to the individual customer; he did pretty well. That sort of approach should be much easier with carbon fibre.

PH

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Re: An important upset in the classical view of bicycle resilience
« Reply #7 on: April 25, 2018, 11:38:56 AM »
I regard this sort of technical article as little more than navel gazing, stiff for who, compliant for what ride?

It's possible to calculate many parameters of the median customer; all it takes is money and a savvy researcher. For the non-statisticians, the median is not an average, but the largest number of people in the universe that have the same or very close characteristics of interest, for instance the same weight, height, and luggage requirement.
Point taken, but you need to brush up on your maths ;)
Of the three most common types of average (Mean, Median, Mode) median is simply the middle value, I think you meant mode which is the most common value.

Whatever, back on subject - once a frame designer has calculated the most common attributes of the most likely user (assuming that they've done that research which is a bit of a leap) what do they do with the information? However much they may like to build for that customer, do you not think they have to consider the usage by those at the top end of the range?

Andre Jute

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Re: An important upset in the classical view of bicycle resilience
« Reply #8 on: April 26, 2018, 12:50:57 AM »
I regard this sort of technical article as little more than navel gazing, stiff for who, compliant for what ride?

It's possible to calculate many parameters of the median customer; all it takes is money and a savvy researcher. For the non-statisticians, the median is not an average, but the largest number of people in the universe that have the same or very close characteristics of interest, for instance the same weight, height, and luggage requirement.
Point taken, but you need to brush up on your maths ;)
Of the three most common types of average (Mean, Median, Mode) median is simply the middle value, I think you meant mode which is the most common value.

Oh, quite. Thanks.  I must have been half asleep. The clue lies in "from: Andre Jute on April 25, 2018, 01:52:34 AM"

Whatever, back on subject - once a frame designer has calculated the most common attributes of the most likely user (assuming that they've done that research which is a bit of a leap) what do they do with the information? However much they may like to build for that customer, do you not think they have to consider the usage by those at the top end of the range?

I'm not defending these guys, and I'm not in their market (road bikes) at all, and never have been; my interest is simply in a good discussion point.

However, to answer your point, it seems to me that Rinard has long since done the research (the article gives you at least one of his answers, and hints at others); in fact, I've been following his research on the net since he built his first carbon fibre bike in his garage many years ago, since even then he seemed to me brighter than the guys at the big-name manufacturers, and it is to their credit that they too saw it, and brought him inside. The better designers for other niches have also done their research. To take an example familiar to everyone here: Andy Blance describes the genesis of his bikes at length and designs the Thorn for use by "those at the top end of the range", and by offering bikes of many sizes and riding styles within each range already goes a long way towards what these plastic bike manufacturers are just rediscovering as a possibility after going too far the other way into the land of Onesizefitsall.

PH

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Re: An important upset in the classical view of bicycle resilience
« Reply #9 on: April 26, 2018, 12:37:19 PM »
I think we're going to have to agree to disagree on this one, I have no doubt the research is sound, I just question the relevance in real world cycling.
Tom Anhalt sums it up for me in the comments
Quote
bike designers would do better to use their engineering resources making sure their products can accommodate larger tire widths rather than designing complicated/questionable flexing elements into the bikes
Not that it's ever going to be an issue for me, I wouldn't consider a frame that didn't take a suitable tyre for my use.  I am at the top end of any design range 1.89 meters and 95 kg, I've never had a frame I considered too stiff (steel, aluminium, titanium) when ridden with the appropriate tyres.

Andre Jute

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Re: An important upset in the classical view of bicycle resilience
« Reply #10 on: April 26, 2018, 02:54:17 PM »
I think we're going to have to agree to disagree on this one, I have no doubt the research is sound, I just question the relevance in real world cycling.
Tom Anhalt sums it up for me in the comments
Quote
bike designers would do better to use their engineering resources making sure their products can accommodate larger tire widths rather than designing complicated/questionable flexing elements into the bikes

Nope. We're in agreement, and for the same reason you gave. I too believe in stiff frames and fat tyres, rather than trying to bodge right a design never intended to take my 95kg plus shopping or luggage, or to ride through the unavoidable potholes on my lanes.

I just admire, intellectually, these guys taking on the established wisdom -- which currently is the perverse, and doubly so in carbon fibre when one considers its plasticity, onesizefitsall.