tyre suspension effect (from Are touring bikes old fashioned)

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CJ
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tyre suspension effect (from Are touring bikes old fashioned)

Post by CJ »

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kylecycler wrote: 19 Jan 2022, 11:46amThe caveat concerning ride quality is that if you go with wider tyres - 50 mm or wider still - you can run them at low enough pressures without sacrificing rolling resistance such that the tyres' suspension effect tends to outweigh the fork's, so then a disc fork's relative lack of compliance matters far less.
The tyre's suspension effect ALWAYS outweighs anything you might get from even the most compliant fork - short of an actual suspension fork. Tony Oliver has calculated and Mike Burrows has measured it. And although I can't find the figures on the internet just now, as I recall, a narrow 25mm tyre at high pressure gives something like FOUR TIMES AS MUCH as the curly-ended style of steel fork recommended by Tony Oliver for maximum compliance. To all intents and purposes, so-called rigid forks are rigid, compared to ANY pneumatic tyres. So we can all stop worrying about comfort when choosing our brakes.
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kylecycler
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Are touring bikes old fashioned?

Post by kylecycler »

CJ wrote: 20 Jan 2022, 11:46am
kylecycler wrote: 19 Jan 2022, 11:46amThe caveat concerning ride quality is that if you go with wider tyres - 50 mm or wider still - you can run them at low enough pressures without sacrificing rolling resistance such that the tyres' suspension effect tends to outweigh the fork's, so then a disc fork's relative lack of compliance matters far less.
The tyre's suspension effect ALWAYS outweighs anything you might get from even the most compliant fork - short of an actual suspension fork. Tony Oliver has calculated and Mike Burrows has measured it. And although I can't find the figures on the internet just now, as I recall, a narrow 25mm tyre at high pressure gives something like FOUR TIMES AS MUCH as the curly-ended style of steel fork recommended by Tony Oliver for maximum compliance. To all intents and purposes, so-called rigid forks are rigid, compared to ANY pneumatic tyres. So we can all stop worrying about comfort when choosing our brakes.
I should have known that, Chris - any time you read anything on the subject by a real proper engineer like yourself, you learn that the 'suspension effect' of a frame and/or fork is grossly exaggerated, certainly compared with that of tyres. I thought the fork might have had more of an effect but evidently not.

There's a retired bridge engineer in California called Rick Jorgensen who built frames BITD, most notably tandem frames for Ibis. Some time in the 1980s or early '90s, just out of curiosity, he built a rig and instrumented different bicycles to see what effect frame (and fork) stiffness had on ride quality...
"I found a lot of things that don't jibe with what everybody in the world tells you. Road shock is a function of air pressure and tires. Everything else is secondary. Yes, a Vitus [light gauge aluminum frame] absorbs more road shock than one of my bikes with oversize chrome-moly, but how much? About five pounds of air pressure [laughs]. With air pressure and tire size and tire shape, you have so much more control over road shock than with anything else."
https://www.obatik.com/wp-content/uploa ... gensen.pdf

It's drifting away from the subject of the thread but anyone with any interest in tandem design should read that interview. I've only ever been on a tandem once, as the stoker, and I nearly had the poor old captain off - couldn't get a handle on it at all - but I still found the interview fascinating.
Jdsk
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Re: Are touring bikes old fashioned?

Post by Jdsk »

kylecycler wrote: 20 Jan 2022, 3:05pmThere's a retired bridge engineer in California called Rick Jorgensen who built frames BITD, most notably tandem frames for Ibis. Some time in the 1980s or early '90s, just out of curiosity, he built a rig and instrumented different bicycles to see what effect frame (and fork) stiffness had on ride quality...
"I found a lot of things that don't jibe with what everybody in the world tells you. Road shock is a function of air pressure and tires. Everything else is secondary. Yes, a Vitus [light gauge aluminum frame] absorbs more road shock than one of my bikes with oversize chrome-moly, but how much? About five pounds of air pressure [laughs]. With air pressure and tire size and tire shape, you have so much more control over road shock than with anything else."
https://www.obatik.com/wp-content/uploa ... gensen.pdf

It's drifting away from the subject of the thread but anyone with any interest in tandem design should read that interview. I've only ever been on a tandem once, as the stoker, and I nearly had the poor old captain off - couldn't get a handle on it at all - but I still found the interview fascinating.
Haven't seen that before. Thankyou.

Jonathan
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Re: Are touring bikes old fashioned?

Post by jimlews »

CJ wrote: 20 Jan 2022, 11:46am The tyre's suspension effect ALWAYS outweighs anything you might get from even the most compliant fork - short of an actual suspension fork. Tony Oliver has calculated and Mike Burrows has measured it. And although I can't find the figures on the internet just now, as I recall, a narrow 25mm tyre at high pressure gives something like FOUR TIMES AS MUCH as the curly-ended style of steel fork recommended by Tony Oliver for maximum compliance. To all intents and purposes, so-called rigid forks are rigid, compared to ANY pneumatic tyres. So we can all stop worrying about comfort when choosing our brakes.
And yet... some bicycles are indisputably more comfortable and less fatiguing than others irrespective of the rubber.

CJ, I wonder how much of the acclaimed comfort of your old Thorn Audax was down to the shape of the fork.

FWIW. it is my opinion that straight forks act as a beam with road shock transmitted directly along their length, up the steerer and into the riders wrists. And they are pig ugly.

When I am belting along rutted tracks on my old iron I can see significant deflection of the elegantly curved lower portion of the fork (531).
Perhaps not a "scientific" observation but it is definitely there and may be repeatedly observed; if you can keep up.
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Re: Are touring bikes old fashioned?

Post by rareposter »

jimlews wrote: 21 Jan 2022, 7:23pm And yet... some bicycles are indisputably more comfortable and less fatiguing than others irrespective of the rubber.
Frame geometry, frame / fork material, tyre width and pressure and the loading (front panniers / bar bag etc) and the type / material of the handlebars will all have a significant input. More loading tends to result in more damping.
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Re: Are touring bikes old fashioned?

Post by pwa »

jimlews wrote: 21 Jan 2022, 7:23pm
CJ wrote: 20 Jan 2022, 11:46am The tyre's suspension effect ALWAYS outweighs anything you might get from even the most compliant fork - short of an actual suspension fork. Tony Oliver has calculated and Mike Burrows has measured it. And although I can't find the figures on the internet just now, as I recall, a narrow 25mm tyre at high pressure gives something like FOUR TIMES AS MUCH as the curly-ended style of steel fork recommended by Tony Oliver for maximum compliance. To all intents and purposes, so-called rigid forks are rigid, compared to ANY pneumatic tyres. So we can all stop worrying about comfort when choosing our brakes.
And yet... some bicycles are indisputably more comfortable and less fatiguing than others irrespective of the rubber.

CJ, I wonder how much of the acclaimed comfort of your old Thorn Audax was down to the shape of the fork.

FWIW. it is my opinion that straight forks act as a beam with road shock transmitted directly along their length, up the steerer and into the riders wrists. And they are pig ugly.

When I am belting along rutted tracks on my old iron I can see significant deflection of the elegantly curved lower portion of the fork (531).
Perhaps not a "scientific" observation but it is definitely there and may be repeatedly observed; if you can keep up.
As I have said before, I once had a race bike with Nivacrom steel straight blade forks and they were more compliant than 531ST forks with a curve that I had on another bike at the same time. The straight blade forks were on a bike with narrower tyres too! The important thing to bear in mind is that the blade is not vertical, so road vibrations don't simply go straight up the blades. Some bending is induced by hitting irregularities in the road, and as long as the blades are not made of scaffolding pipe they can offer some plushness. Blades like that tend to angle from the crown, so at the top section they are less vertical than the top section of blades that have a curve at the bottom. Cheap and nasty straight blade forks will, I expect, be harsh. But so too will be cheap and nasty curved forks.

But with the move to higher volume tyres, there is a lot less need for frame and fork compliance. In fact there is something to be said for having a very rigid frame and forks and relying on the tyres to do the comfort, because that way you can ditch all the unwanted handling quirks of flexy frames.
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Re: Are touring bikes old fashioned?

Post by jimlews »

pwa wrote: 22 Jan 2022, 8:41am
CJ wrote: 20 Jan 2022, 11:46am The tyre's suspension effect ALWAYS outweighs anything you might get from even the most compliant fork - short of an actual suspension fork. Tony Oliver has calculated and Mike Burrows has measured it. And although I can't find the figures on the internet just now, as I recall, a narrow 25mm tyre at high pressure gives something like FOUR TIMES AS MUCH as the curly-ended style of steel fork recommended by Tony Oliver for maximum compliance. To all intents and purposes, so-called rigid forks are rigid, compared to ANY pneumatic tyres. So we can all stop worrying about comfort when choosing our brakes.
As I have said before, I once had a race bike with Nivacrom steel straight blade forks and they were more compliant than 531ST forks with a curve that I had on another bike at the same time. The straight blade forks were on a bike with narrower tyres too! The important thing to bear in mind is that the blade is not vertical, so road vibrations don't simply go straight up the blades. Some bending is induced by hitting irregularities in the road, and as long as the blades are not made of scaffolding pipe they can offer some plushness.

But with the move to higher volume tyres, there is a lot less need for frame and fork compliance. In fact there is something to be said for having a very rigid frame and forks and relying on the tyres to do the comfort, because that way you can ditch all the unwanted handling quirks of flexy frames.


Nivacrom is a newer, much more 'high tech' steel than 531st; the latter being considered somewhat overbuilt even for a touring application. That is why Thorn, for example used 531c blades on their XTC model. Columbus forks are (or were) somewhat lighter built in terms of wall thickness - to the extent that if a columbus fork was involved in a front ender, the forks would be trashed. If 531 forks, the frame would be trashed and the forks remain largely unscathed.
So, you are not really comparing like with like. And you don't tell us what tyres you were using.
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Re: Are touring bikes old fashioned?

Post by cycle tramp »

20220122_120757.jpg
Admittedly larger tyres may roll faster and 27.5 may look more sexy... but for shear versatility 26 will always be around...

Above is my bike with 26 inch wheels, 2 inch wide tyres and full mudguards, carrying 10kg of chicken feed in the front paniers, my dinner (carried in my new bucket) and 9 kg of assorted stuff (more chicken feed, salt lick for the horse and some new tools) carried on the rear rack without any problems to the wheels...

...and if i get bored I can always change the tyres to 1.25 inch slicks for the summer time..

I really must get the sqr block sorted...
Last edited by cycle tramp on 22 Jan 2022, 12:51pm, edited 1 time in total.
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Re: Are touring bikes old fashioned?

Post by Jdsk »

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Re: Are touring bikes old fashioned?

Post by djb »

Hey, what is that click mount on the front of your seatpost for?
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Re: Are touring bikes old fashioned?

Post by andrew_s »

cycle tramp wrote: 22 Jan 2022, 12:36pm...and if i get bored I can always change the tyres to 1.25 inch slicks for the summer time..
The trouble with buying 26" now is that whilst relative oddball tyres like 1.25 slicks are available now, they are much less certain to remain so.
cycle tramp
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Re: Are touring bikes old fashioned?

Post by cycle tramp »

andrew_s wrote: 22 Jan 2022, 2:57pm
cycle tramp wrote: 22 Jan 2022, 12:36pm...and if i get bored I can always change the tyres to 1.25 inch slicks for the summer time..
The trouble with buying 26" now is that whilst relative oddball tyres like 1.25 slicks are available now, they are much less certain to remain so.
At the moment sjsc carry the same number of different 27.5 size tyres as they do 26 size tyre.
Within the space of a few years we've also seen a sharp fall in the number of mountain bikes sold with 27.5 size wheels. It's possible that we could see a shrinkage of tyre choice for that wheel size as a result of this over the next few years.

Whether 1.25 x 26 inch slicks will continue to be produced is down to customer demand. If enough people continue to use the 26 inch wheel then the answer will be yes.
And equally the reverse is true of the 27.5 inch wheel. If the gaint bicycle marketing machine begins to convience people that the 27.5 size wheel is dying and the 700 wheel size is the way forward then then the same fears could be said of the 27.5 wheel.

The only was to be really future proof us to either use the 700 wheel size (as CJ commented this size of wheel is so prevalent that no one is going to stop making tyres for it), or use hub or disc brakes which allows you the freedom to then use both 26 and 27.5 inch wheel.
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cycle tramp
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Re: Are touring bikes old fashioned?

Post by cycle tramp »

djb wrote: 22 Jan 2022, 2:13pm Thank you, my neck feels better.

Hey, what is that click mount on the front of your seatpost for?
It's my saddle bag support - it should be facing the rear of the bike, but I had to tighten the seat clamp, and needed to move it out of the way :-)
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Re: Are touring bikes old fashioned?

Post by rareposter »

In going on about his 531 forks, i think @jimlews has inadvertently answered some of the OP's original question:

Are touring bikes old fashioned?

Well yes and no - they've largely been ignored by the mainstream bike industry so they've been mostly immune to the fads and fashions and whims of the trade. The fact that the niche has mostly been filled by much smaller manufacturers and individual custom builders means they've stayed largely true to their roots but part of that is because the riders themselves have a very old-fashioned / traditional viewpoint - after all if you've been touring for years on a comfortable 531 steel bike that's carried you trouble free across continents, why would you ever feel the need to buy something newer?

Everything is focussed on comfort and reliability. The mainstream trends of lighter / faster / more aero simply don't apply and the mindset of the touring rider is very different - they want simplicity and reliability so they've never really been interested in buying the latest shiny new must-have or top end kit.

That does also have a downside though because you end up in a bit of a rut of traditionalist thinking and a refusal to consider new things because "we've always done it this way".
cycle tramp
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Re: Are touring bikes old fashioned?

Post by cycle tramp »

rareposter wrote: 22 Jan 2022, 5:31pm In going on about his 531 forks, i think @jimlews has inadvertently answered some of the OP's original question:

Are touring bikes old fashioned?

Well yes and no - they've largely been ignored by the mainstream bike industry so they've been mostly immune to the fads and fashions and whims of the trade..

Everything is focussed on comfort and reliability. The mainstream trends of lighter / faster / more aero simply don't apply and the mindset of the touring rider is very different - they want simplicity and reliability so they've never really been interested in buying the latest shiny new must-have or top end kit.

That does also have a downside though because you end up in a bit of a rut of traditionalist thinking and a refusal to consider new things because "we've always done it this way".
Yeah, absolutely... and to be fair the mainstream idea of 'faster' is a bit of a red hearing when touring. If we're taking a performance different of a few miles an hour, when comparing any equipment, then you're better off brushing up on your map reading skills (especially if you have to stop and read a map at every junction)...or have to repair an inner tube.
(On my organised Lejog ride, I was the first of any of my group, despite my 26 inch wheels and solid touring frame, on the day we rode from Cheddar to Monmouth, simply because I knew the area very well and never needed to stop to check where I was).
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