How far can you lean?

Chris Malcolm said:

For various technical reasons, including that fashion dictates poor
engineering design, bicycle suspension is not much good at keeping
grip in road cornering.

Can you expand on this? What are the technical reasons? How does
fashion dictate poor engineering design?

--
Gareth Rees

In article <[email hidden]>, Chris Slade
<[email hidden]> writes

Quoted message said:

I've had pedal strike while going quite slowly. Taking a left hand corner
and suddenly finding myself flying over the handles to the right! Perhaps
Bromptons are more prone to this sort of thing than other bikes?

My mates and I used to get pedal strikes all the time when cornering
hard round a local village hall (when we young and invincible).
Typically the pedal/crank arm would hit the ground, then lever the back
wheel off the ground, which would then slip a few inches before landing
with a bump as the pedal rotated a bit more. Big grin, that was fun,
let's do it again...

These were 'racers', I can't remember anybody ever falling off as a
result, even though we were often riding close in a group.

--
John

in message <[email hidden]>,

(' ') said:

Chris Malcolm said:

For various technical reasons, including that fashion dictates poor
engineering design, bicycle suspension is not much good at keeping
grip in road cornering.

Can you expand on this? What are the technical reasons? How does
fashion dictate poor engineering design?

We don't currently have any suspension on most road bikes beyond that
supplied by tyres and spokes. These aren't very tunable for compliance.
There are exceptions, of course; the (no longer manufactured) Cannondale
Silk Road, and various Paris-Roubaix specials with elastomer inserts in
the forks and seatstays (commercialised by Specialized as 'zerts'😉.

And, of course, many recumbents and small-wheeled bikes use suspension.

I think Chris is implying that road bike design would benefit from
controlled and tunable suspension both front and rear. If he was, I agree,
and I think it's becoming more and more possible. It's worth watching what
the manufacturers bring to the Belgian classics over the next few years.

Simplicity in bikes is a good thing. Suspension (if it's any good, and
isn't heavy) will make things more complex and more expensive. But on the
limit, handling on less than perfect surfaces will improve.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/
Wannabe a Web designer?
<URL:http://userfriendly.org/cartoons/archives/97dec/19971206.html>

Quoted message said:

Chris Malcolm said:

For various technical reasons, including that fashion dictates poor
engineering design, bicycle suspension is not much good at keeping
grip in road cornering.

Quoted message said:

Can you expand on this? What are the technical reasons? How does
fashion dictate poor engineering design?

If you want suspension to improve your cornering adhesion you want the
suspension to be able to hold the wheel down on the road despite bumps
in the road trying bounce it out of contact. The best suspension for
that job is interposed at a point where the sprung weight is at a
maximum and the unsprung weight (what bounces up and down) is at a
minimum. Ideally you want the lightest possible suspension supporting
nothing but the wheel. In practice you need some extra stuff to keep
the wheel properly aligned and connect the suspension controlling
elements of spring and damper into the system.

The front wheel suspension has copied the telescopic fork design
popular in motorcycles. This is much heavier than a leading or
trailing link design (for example), much more so proportionally in a
bicycle with its very light wheels compared to the much heavier wheels
of a motorcycle. But the expanse of telescoping shiny tube looks much
more heroically macho and toughly engineered than does a leading or
trailing link design, which often look a bit flimsy to the
engineeringly uneducated eye of the consumer.

But there's worse to come. In order to control the movement of the
sprung mass and keep the tyre as firmly in contact with road as
possible we need a properly tuned spring and damper system. In a
telescopic system the obvious place to put the spring is round one of
the telescopting tubes. In effect half of that big steel coil spring
is unsprung weight. Much lighter springs could do the job, but not if
they're constrained by the aesthetics of the telescopic idea and
economy of manufacture to be wrapped around one of the sections of the
telescope.

The final horror is the damping. One popular way of doing that is some
kind of sealed piston. In order to minimise unsprung weight and seal
stiction the piston should as small as possible and move as little as
possible, e.g. by using link leverage to keep the motion and the seal
area small.

If you've already got telescoping front forks (that's right -- *two*
of them, one on each side -- looks nice doesn't it? :-) then
"obviously" you should use one of your telecoping tubes as the piston
of the hydraulic damper. Since they're also keeping the wheel aligned
etc. these are strong hollow tubes which means the seal has to operate
around the tube, which means a big grippy seal which means high
stiction. That means your suspension needs a bit of a wallop to break
the stiction and start it moving. That's one of the rather serious
problems in the performance of current bicycle front wheel
suspensions.

A disgusting series of engineering compromises which leads to a very
inefficient design of suspension which doesn't do the job well at
all. But big fat shiny tubes look like heroic engineering in the
shop. And it's easy and cheap to make. So you're left with the choice
of selling the customer a [censored] cheap design which looks attractive, or
educating them to appreciate a much more flimsy looking design which
actually performs an awful lot better.

The marketing types would have explained this grinningly to the
disappointed engineers in the boardroom, if the bicycle company was
actually forward looking enough to have any engineers at that kind of
management decision level. But the tradition in Anglophone capitalism
countries is to avoid having engineers anywhere near the managerial
decision making process. It makes profit making so much easier if you
don't have to waste time explaining the facts of life to upset
engineers. And we know what kind of consumers we're dealing with
here. Hell, we've already sold them a polystyrene crash helmet and a
commuting bicycle without mudguards :-)

--
Chris Malcolm [email hidden] DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
[http://www.dai.ed.ac.uk/homes/cam/]

Chris Malcolm wrote on 02/06/2007 10:00 +0100:

Quoted message said:

Quoted message said:

Chris Malcolm said:

For various technical reasons, including that fashion dictates poor
engineering design, bicycle suspension is not much good at keeping
grip in road cornering.

Quoted message said:

Can you expand on this? What are the technical reasons? How does
fashion dictate poor engineering design?

The front wheel suspension has copied the telescopic fork design
popular in motorcycles. This is much heavier than a leading or
trailing link design (for example), much more so proportionally in a
bicycle with its very light wheels compared to the much heavier wheels
of a motorcycle. But the expanse of telescoping shiny tube looks much
more heroically macho and toughly engineered than does a leading or
trailing link design, which often look a bit flimsy to the
engineeringly uneducated eye of the consumer.

Leading and trailing link designs have been tried but have not been
successful. Remember the old Girvin forks and more recently Jon Whyte's
quadlink fork?. Generally more pivots on a bicycle fork are bad news
which is why single pivot rear designs are so much more popular than the
theoretically better multipivots. On a bicycle the sprung mass is
dominated by the rider's weight unlike a motorbike where the frame is a
major part of the unsprung weight. Even so leading and trailing link
front suspension is pretty rare on motorbikes which mostly go for the
telescopic fork.
http://en.wikipedia.org/wiki/Motorcycle_fork

--
Tony

"The most savage controversies are those about matters as to which there
is no good evidence either way."
- Bertrand Russell

in message <[email hidden]>, Chris Malcolm

(') said:

Quoted message said:

Chris Malcolm said:

For various technical reasons, including that fashion dictates poor
engineering design, bicycle suspension is not much good at keeping
grip in road cornering.

Quoted message said:

Can you expand on this? What are the technical reasons? How does
fashion dictate poor engineering design?

If you want suspension to improve your cornering adhesion you want the
suspension to be able to hold the wheel down on the road despite bumps
in the road trying bounce it out of contact. The best suspension for
that job is interposed at a point where the sprung weight is at a
maximum and the unsprung weight (what bounces up and down) is at a
minimum. Ideally you want the lightest possible suspension supporting
nothing but the wheel. In practice you need some extra stuff to keep
the wheel properly aligned and connect the suspension controlling
elements of spring and damper into the system.

The front wheel suspension has copied the telescopic fork design
popular in motorcycles. This is much heavier than a leading or
trailing link design (for example), much more so proportionally in a
bicycle with its very light wheels compared to the much heavier wheels
of a motorcycle. But the expanse of telescoping shiny tube looks much
more heroically macho and toughly engineered than does a leading or
trailing link design, which often look a bit flimsy to the
engineeringly uneducated eye of the consumer.

But there's worse to come. In order to control the movement of the
sprung mass and keep the tyre as firmly in contact with road as
possible we need a properly tuned spring and damper system. In a
telescopic system the obvious place to put the spring is round one of
the telescopting tubes. In effect half of that big steel coil spring
is unsprung weight. Much lighter springs could do the job, but not if
they're constrained by the aesthetics of the telescopic idea and
economy of manufacture to be wrapped around one of the sections of the
telescope.

The final horror is the damping. One popular way of doing that is some
kind of sealed piston. In order to minimise unsprung weight and seal
stiction the piston should as small as possible and move as little as
possible, e.g. by using link leverage to keep the motion and the seal
area small.

If you've already got telescoping front forks (that's right -- *two*
of them, one on each side -- looks nice doesn't it? :-) then
"obviously" you should use one of your telecoping tubes as the piston
of the hydraulic damper. Since they're also keeping the wheel aligned
etc. these are strong hollow tubes which means the seal has to operate
around the tube, which means a big grippy seal which means high
stiction. That means your suspension needs a bit of a wallop to break
the stiction and start it moving. That's one of the rather serious
problems in the performance of current bicycle front wheel
suspensions.

USE SUB:
http://www.kinetics-online.co.uk/html/use_sub_fork.shtml

This is mountain bike technology, not road bike technology of course. But
single sided has to be right, and the anti-dive linkage makes a lot of
sense too. There's a similar system on the Canadian-designed GoBike:
http://www.gobikeonline.com/
Although this doesn't appear to have any damping.

Birdy also has a leading link system but it's dual sided and nothing like
as simple as the GoBike. I cannot believe that in the twenty-first century
we're still using forks, not monoblades.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

;; have mercy on the slender grass

Simon Brooke said:

I cannot believe that in the twenty-first century
we're still using forks, not monoblades.

If they all cost as much as that USE SUB, I think I can see a reason.
--
Chris

People usually get what's coming to them ... unless it's been mailed.

In article <[email hidden]>, Chris Slade
[email hidden] says...

Quoted message said:

Simon Brooke said:

I cannot believe that in the twenty-first century
we're still using forks, not monoblades.

If they all cost as much as that USE SUB, I think I can see a reason.

Economies of scale could easily halve that, but first you have to sell
the idea to the masses ...

Rob Morley wrote on 02/06/2007 13:41 +0100:

Quoted message said:

Economies of scale could easily halve that, but first you have to sell
the idea to the masses ...

They haven't in the much higher volume motorbike market where they could
stand a higher cost of goods. Selling the idea to the masses is not
really a problem if the idea is half reasonable. After all its not so
long ago that Paul Turner sold mountain bikers on fitting front
suspension at all and that with a pretty ropey product. The fact that
the link suspensions have not sold therefore is likely to be because the
masses have not seen any benefit over the simple telescopic fork.

--
Tony

"The most savage controversies are those about matters as to which there
is no good evidence either way."
- Bertrand Russell

In article said:

Leading and trailing link designs have been tried but have not been
successful. Remember the old Girvin forks and more recently Jon Whyte's
quadlink fork?.

Moultons seem to be fairly successful, if only in a limited niche.

Tony Raven said:

Chris Malcolm wrote on 02/06/2007 10:00 +0100:

Quoted message said:

Quoted message said:

Chris Malcolm wrote:
> For various technical reasons, including that fashion dictates poor
> engineering design, bicycle suspension is not much good at keeping
> grip in road cornering.

Quoted message said:

Can you expand on this? What are the technical reasons? How does
fashion dictate poor engineering design?

The front wheel suspension has copied the telescopic fork design
popular in motorcycles. This is much heavier than a leading or
trailing link design (for example), much more so proportionally in a
bicycle with its very light wheels compared to the much heavier wheels
of a motorcycle. But the expanse of telescoping shiny tube looks much
more heroically macho and toughly engineered than does a leading or
trailing link design, which often look a bit flimsy to the
engineeringly uneducated eye of the consumer.

Quoted message said:

Leading and trailing link designs have been tried but have not been
successful. Remember the old Girvin forks and more recently Jon Whyte's
quadlink fork?. Generally more pivots on a bicycle fork are bad news
which is why single pivot rear designs are so much more popular than the
theoretically better multipivots. On a bicycle the sprung mass is
dominated by the rider's weight unlike a motorbike where the frame is a
major part of the unsprung weight. Even so leading and trailing link
front suspension is pretty rare on motorbikes which mostly go for the
telescopic fork.

For reasons which, as the late lamented LJK Setright often pointed
out, had a lot more to do with fashion than with engineering.

--
Chris Malcolm [email hidden] DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
[http://www.dai.ed.ac.uk/homes/cam/]

Tony Raven said:

Rob Morley wrote on 02/06/2007 13:41 +0100:

Quoted message said:

Economies of scale could easily halve that, but first you have to sell
the idea to the masses ...

Quoted message said:

They haven't in the much higher volume motorbike market where they could
stand a higher cost of goods. Selling the idea to the masses is not
really a problem if the idea is half reasonable. After all its not so
long ago that Paul Turner sold mountain bikers on fitting front
suspension at all and that with a pretty ropey product. The fact that
the link suspensions have not sold therefore is likely to be because the
masses have not seen any benefit over the simple telescopic fork.

That's my point. Generally speaking the masses are very far from being
good judges of good engineering.

--
Chris Malcolm [email hidden] DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
[http://www.dai.ed.ac.uk/homes/cam/]

Chris Malcolm wrote on 03/06/2007 11:48 +0100:

Quoted message said:

For reasons which, as the late lamented LJK Setright often pointed
out, had a lot more to do with fashion than with engineering.

Ah yes a man who despised speed limits, diesel cars and
environmentalists and was notorious for scaring his passengers with the
speed of his driving. Someone whose opinions we should all value.

--
Tony

"The most savage controversies are those about matters as to which there
is no good evidence either way."
- Bertrand Russell

Chris Malcolm wrote on 03/06/2007 11:58 +0100:

Quoted message said:

That's my point. Generally speaking the masses are very far from being
good judges of good engineering.

I know, customers are a [censored].

--
Tony

"The most savage controversies are those about matters as to which there
is no good evidence either way."
- Bertrand Russell

In article <[email hidden]>, Tony Raven
[email hidden] says...

Quoted message said:

Chris Malcolm wrote on 03/06/2007 11:58 +0100:

Quoted message said:

That's my point. Generally speaking the masses are very far from being
good judges of good engineering.

I know, customers are a [censored].

Pity the tobacco industry, eh?

in message <[email hidden]>, Tony Raven

(') said:

Chris Malcolm wrote on 03/06/2007 11:48 +0100:

Quoted message said:

For reasons which, as the late lamented LJK Setright often pointed
out, had a lot more to do with fashion than with engineering.

Ah yes a man who despised speed limits, diesel cars and
environmentalists and was notorious for scaring his passengers with the
speed of his driving. Someone whose opinions we should all value.

He was, however, a commentator on automotive technology who gave a very
credible impression of knowing what he was talking about. I confess that
he influenced my opinion of telescopic forks, and that I have not yet been
persuaded that he was wrong.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

;; I'll have a proper rant later, when I get the time.

Tony Raven said:

Chris Malcolm wrote on 03/06/2007 11:48 +0100:

Quoted message said:

For reasons which, as the late lamented LJK Setright often pointed
out, had a lot more to do with fashion than with engineering.

Quoted message said:

Ah yes a man who despised speed limits, diesel cars and
environmentalists and was notorious for scaring his passengers with the
speed of his driving. Someone whose opinions we should all value.

Given that your reasons for sneering at his very well educated and
well expressed engineering opinions are that you don't like his
politics or personality I doubt that there's any point in our
continuing this discussion. For all I know my politics would
invalidate my opinion on bicycle wheel suspension too -- as you see
these things.

--
Chris Malcolm [email hidden] DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
[http://www.dai.ed.ac.uk/homes/cam/]

In news:[email hidden],
Simon Brooke <[email hidden]> tweaked the Babbage-Engine to tell us:

Quoted message said:

I think Chris is implying that road bike design would benefit from
controlled and tunable suspension both front and rear. If he was, I
agree, and I think it's becoming more and more possible. It's worth
watching what the manufacturers bring to the Belgian classics over
the next few years.

ISTR one team turned up to Paris-Roubaix a few years ago with bikes fitted
with Rock Shox boingy forks. The UCI's Blazer Brigade took one look at them
and said "take those things away and don't come back until you've got proper
Edwardian technology like everyone else".

--
Dave Larrington
<http://www.legslarry.beerdrinkers.co.uk>
Maffeo Barberini (1568-1644) was made entirely of salmon.

in message <[email hidden]>, Dave Larrington

(') said:

In news:[email hidden],
Simon Brooke <[email hidden]> tweaked the Babbage-Engine to tell
us:

Quoted message said:

I think Chris is implying that road bike design would benefit from
controlled and tunable suspension both front and rear. If he was, I
agree, and I think it's becoming more and more possible. It's worth
watching what the manufacturers bring to the Belgian classics over
the next few years.

ISTR one team turned up to Paris-Roubaix a few years ago with bikes
fitted
with Rock Shox boingy forks. The UCI's Blazer Brigade took one look at
them and said "take those things away and don't come back until you've
got proper Edwardian technology like everyone else".

On the other hand, Gibo rode Paris Roubaix on a Cannondale Silk Road with
the suspension hidden in the head tube. All the Saeco Cannondale riders
used Silk Road suspension forks in the 2004 Paris Roubaix except Salvatore
Commesso. Silk Road forks were also used in the 2003 race for sure, can't
find whether they were in 2005 (they were not used this year). So the
UCI's Blazer Brigade don't mind the technology being there provided it's
discreetly hidden.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

IMHO, there aren't enough committed Christians, but that's care
in the community for you. -- Ben Evans

In news:[email hidden],
Simon Brooke <[email hidden]> tweaked the Babbage-Engine to tell us:

Quoted message said:

On the other hand, Gibo rode Paris Roubaix on a Cannondale Silk Road
with the suspension hidden in the head tube. All the Saeco Cannondale
riders used Silk Road suspension forks in the 2004 Paris Roubaix
except Salvatore Commesso. Silk Road forks were also used in the 2003
race for sure, can't find whether they were in 2005 (they were not
used this year). So the UCI's Blazer Brigade don't mind the
technology being there provided it's discreetly hidden.

Or else, being exponents of Thinking Under The Influence Of Ramsey
MacDonald, they haven't noticed that there's any suspension there at all :-)

--
Dave Larrington
<http://www.legslarry.beerdrinkers.co.uk>
Where's the gin?