Marketing parlance ?

[Jim]

From the zipp website...

We have known for years that tire pressures over 120 psi can actually increase rolling resistance as
the tire treads are pushed past their elastic limit and high local input stresses can lead to higher
than allowable strains which begin to actually fail the rubber in shear. High tire pressures only
feels fast, as an increase in pressure will increase the frequency at which the tire vibrates, and
in turn transfers more vibration into the hub and rider. This results not only in increased rolling
resistance as the rubber begins to build heat, but also to increased tire degradation and wear, not
to mention wear and tear on the rider

Really ?

 

[Ken]

"Jim" <[email protected]> wrote in news:[email protected]:
> We have known for years that tire pressures over 120 psi can actually increase rolling resistance

I don't know about that rolling resistance claim, but here are a couple of other articles that
recommend more moderate road tire pressures (like 100psi):

http://www.roadbikerider.com/ua4.htm#Are%20Narrower,%20Harder%20Tires% 20Better
http://www.sheldonbrown.com/tires.html#pressure

Their arguments make sense to me.

 

[Tc Rider]

Jim <[email protected]> wrote in message news:[email protected]...
> From the zipp website...
>
> We have known for years that tire pressures over 120 psi can actually increase rolling resistance
> as the tire treads are pushed past their
elastic
> limit and high local input stresses can lead to higher than allowable strains which begin to
> actually fail the rubber in shear. High tire pressures only feels fast, as an increase in
> pressure will increase the frequency at which the tire vibrates, and in turn transfers more
> vibration into the hub and rider. This results not only in increased rolling resistance as the
> rubber begins to build heat, but also to increased tire degradation and wear, not to mention wear
> and tear on the rider
>
> Really ?
>

Marketing?! What would Zipp have to gain by telling people how to make tires last longer? I'd say
it's probably on the level, though I have to wonder at the magnitude of some of the effects...

 

[Bfd]

Ken <[email protected]> wrote in message news:<[email protected]>...
> "Jim" <[email protected]> wrote in news:[email protected]:
> > We have known for years that tire pressures over 120 psi can actually increase rolling
> > resistance
>
> I don't know about that rolling resistance claim, but here are a couple of other articles that
> recommend more moderate road tire pressures (like 100psi):
>
> http://www.roadbikerider.com/ua4.htm#Are%20Narrower,%20Harder%20Tires% 20Better
> http://www.sheldonbrown.com/tires.html#pressure
>
> Their arguments make sense to me.
You may also want to add this to your reading... discussion
http://www.terrymorse.com/bike/rrdiscuss.html graphs http://www.terrymorse.com/bike/rolres.html

 

[Jobst Brandt]

Jim who? quotes:

> "We have known for years that tire pressures over 120 psi can actually increase rolling resistance
> as the tire treads are pushed past their elastic limit and high local input stresses can lead to
> higher than allowable strains which begin to actually fail the rubber in shear. High tire
> pressures only feels fast, as an increase in pressure will increase the frequency at which the
> tire vibrates, and in turn transfers more vibration into the hub and rider. This results not only
> in increased rolling resistance as the rubber begins to build heat, but also to increased tire
> degradation and wear, not to mention wear and tear on the rider."

> Really ?

No! Not the part about an increase in RR. That is pure fiction as the curves at:

http://www.terrymorse.com/bike/rolres.html

show. That is because, as often, manufacturers don't understand their products, the engineering
skills for that having sought more rewarding positions. Rolling resistance is not caused by road
scrubbing as myth and lore tells us, but rather through losses in elastic materials used in tires.
Old-timers may recall when the first durable clincher was offered by Specialized, it had a 1/4"
raised center ridge that was claimed to reduce RR by minimizing scrub (road contact). In fact the
tire had its highest RR when new and after the ridge was flush with the rest of the surface, was
lower. Elastomer losses include the inter-cord matrix that holds the casing together, and the tread.
The tube also becomes an integral part of the tire when inflated. The higher the pressure the less
the tire flexes, and therefore, the lower the RR. That's pretty simple but beyond the scope of the
folks in charge of the product who are, no doubt, in charge of the hype in the PR texts.

As to wear, they should show some wear curves to support their claim. That is to say, where is the
optimum. We don't want to ride flat tires and too high a pressure endangers the rider with tire
blow-off and greater wear.

Jobst Brandt [email protected] Palo Alto CA

 

[W K]

<[email protected]> wrote in message news:[email protected]...
> Jim who? quotes:
>
> > "We have known for years that tire pressures over 120 psi can actually increase rolling
> > resistance as the tire treads are pushed past their elastic limit and high local input stresses
> > can lead to higher than allowable strains which begin to actually fail the rubber in shear. High
> > tire pressures only feels fast, as an increase in pressure will increase the frequency at which
> > the tire vibrates, and in turn transfers more vibration into the hub and rider. This results not
> > only in increased rolling resistance as the rubber begins to build heat, but also to increased
> > tire degradation and wear, not to mention wear and tear on the rider."
>
> > Really ?
>
> No! Not the part about an increase in RR. That is pure fiction as the curves at:
>
> http://www.terrymorse.com/bike/rolres.html
>
> show.

Those tests were done on a smooth drum of course. How important are the energy losses associated
with going over a rough surface with less suspension (from higher pressure in the tires)?

Its not a personal pet theory of mine or anything, but I have seen theories based on something like
the above, in that when dealing with a slightly rough road surface the ability of a tire to act as
suspension may be more of an advantage than that given by the lower "smooth surface RR".

 

[Jobst Brandt]

W K snipes anonymously:

>>> "We have known for years that tire pressures over 120 psi can actually increase rolling
>>> resistance as the tire treads are pushed past their elastic limit and high local input stresses
>>> can lead to higher than allowable strains which begin to actually fail the rubber in shear. High
>>> tire pressures only feels fast, as an increase in pressure will increase the frequency at which
>>> the tire vibrates, and in turn transfers more vibration into the hub and rider. This results not
>>> only in increased rolling resistance as the rubber begins to build heat, but also to increased
>>> tire degradation and wear, not to mention wear and tear on the rider."

>>> Really ?

>> No! Not the part about an increase in RR. That is pure fiction as the curves at:

>> http://www.terrymorse.com/bike/rolres.html

>> show.

> Those tests were done on a smooth drum of course. How important are the energy losses associated
> with going over a rough surface with less suspension (from higher pressure in the tires)?

Maybe you can describe a model of what you believe happens on a paved road of typical asphalt
roughness that would change rolling resistance response of a tire. Do not omit an energy equation
that shows where these losses are converted to heat, the result of all energy losses. Note that tire
deflection from a rider sitting on the bicycle is greater than pavement roughness, that is if this
enters into the model you visualize.

> Its not a personal pet theory of mine or anything, but I have seen theories based on something
> like the above, in that when dealing with a slightly rough road surface the ability of a tire to
> act as suspension may be more of an advantage than that given by the lower "smooth surface RR".

Before repeating these pseudo-science tales, you might look into their validity. Myth and lore
survives on repetition, not fact.

You might also consider:

http://draco.acs.uci.edu/rbfaq/FAQ/8b.25.html

Jobst Brandt [email protected] Palo Alto CA

 

[Doug Milliken]

On Thu, 3 Apr 2003 [email protected] wrote:

<snipped comments on rolling resistance>

> As to wear, they should show some wear curves to support their claim. That is to say, where is the
> optimum. We don't want to ride flat tires and too high a pressure endangers the rider with tire
> blow-off and greater wear.
>
> Jobst Brandt [email protected] Palo Alto CA

Does anyone know of a good test procedure for bicycle tire wear tests?

I know that for truck tires (trucking fleets spend a lot of money on replacement tires) there has
been a lot of work done to characterize wear and none is really conclusive. The problem seems to be
that wear is very nonlinear with small changes in operating conditions. For example, different
drivers on the same delivery route may get 2:1 or even more difference in tread life.

-- Doug Milliken www.millikenresearch.com

 

[Phil Holman]

<[email protected]> wrote in message news:[email protected]...
> W K snipes anonymously:
>
> >>> "We have known for years that tire pressures over 120 psi can
> >>> actually increase rolling resistance as the tire treads are
pushed
> >>> past their elastic limit and high local input stresses can lead
to
> >>> higher than allowable strains which begin to actually fail the rubber in shear. High tire
> >>> pressures only feels fast, as an increase in pressure will increase the frequency at which
> >>> the
tire
> >>> vibrates, and in turn transfers more vibration into the hub and rider. This results not only
> >>> in increased rolling resistance as the rubber begins to build heat, but also to increased
> >>> tire degradation and wear, not to mention wear and tear on the rider."
>
> >>> Really ?
>
> >> No! Not the part about an increase in RR. That is pure fiction as the curves at:
>
> >> http://www.terrymorse.com/bike/rolres.html
>
> >> show.
>
> > Those tests were done on a smooth drum of course. How important are the energy losses associated
> > with going over a rough surface with less suspension (from higher pressure in the tires)?
>
> Maybe you can describe a model of what you believe happens on a paved road of typical asphalt
> roughness that would change rolling resistance response of a tire. Do not omit an energy equation
> that shows where these losses are converted to heat, the result of all energy losses. Note that
> tire deflection from a rider sitting on the bicycle is greater than pavement roughness, that is if
> this enters into the model you visualize.
>
> > Its not a personal pet theory of mine or anything, but I have seen theories based on something
> > like the above, in that when dealing with a slightly rough road surface the ability of a tire to
> > act as suspension may be more of an advantage than that given by the lower "smooth surface RR".
>
> Before repeating these pseudo-science tales, you might look into their validity. Myth and lore
> survives on repetition, not fact.

What is the essence of the contention here? Do riders use more energy rolling over chip seal at 140
psi than at 100psi? I know which is more comfortable and there is no doubt that riding over chip
seal is slower than on smooth pavement.

Phil Holman

 

[Jobst Brandt]

Phil Holman writes:

> What is the essence of the contention here? Do riders use more energy rolling over chip seal at
> 140 psi than at 100psi?

That is the contention as I understand it and it has been proposed many times before. Repetition
does not make it so. There is no evidence that comfort has any parallel in rolling losses in
tires unless it is inverse. Just the nature of tire rolling resistance, which arises from viscous
losses in tire elastomers, points to lower losses with increasing pressure within the limits of
actual tires.

Jobst Brandt [email protected] Palo Alto CA

 

[W K]

<[email protected]> wrote in message news:[email protected]...
> W K snipes anonymously:

My name is William Kemp BTW.

> > Those tests were done on a smooth drum of course. How important are the energy losses associated
> > with going over a rough surface with less suspension (from higher pressure in the tires)?
>
> Maybe you can describe a model of what you believe happens on a paved road of typical asphalt
> roughness that would change rolling resistance response of a tire. Do not omit an energy equation
> that shows where these losses are converted to heat, the result of all energy losses. Note that
> tire deflection from a rider sitting on the bicycle is greater than pavement roughness, that is if
> this enters into the model you visualize.

Ah, I see, If I cannot give you a realistic scenario based on science I am not allowed to even ask
whether there is an effect caused by rough roads.

Science needs simple questions before you arrive at a complex answer. Are there figures for how
rolling resistance varies with tyre pressure on a rough surface?

> > Its not a personal pet theory of mine or anything, but I have seen theories based on something
> > like the above, in that when dealing with a slightly rough road surface the ability of a tire to
> > act as suspension may be more of an advantage than that given by the lower "smooth surface RR".
>
> Before repeating these pseudo-science tales, you might look into their validity. Myth and lore
> survives on repetition, not fact.

Simple questions:

Do people riding on rougher roads experience more rolling resistance?

Sorry, I cannot explain if this is true in terms of energy loss.

 

[Jobst Brandt]

William Kemp writes:

>>> Those tests were done on a smooth drum of course. How important are the energy losses associated
>>> with going over a rough surface with less suspension (from higher pressure in the tires)?

>> Maybe you can describe a model of what you believe happens on a paved road of typical asphalt
>> roughness that would change rolling resistance response of a tire. Do not omit an energy equation
>> that shows where these losses are converted to heat, the result of all energy losses. Note that
>> tire deflection from a rider sitting on the bicycle is greater than pavement roughness, that is
>> if this enters into the model you visualize.

> Ah, I see, If I cannot give you a realistic scenario based on science I am not allowed to even ask
> whether there is an effect caused by rough roads.

Certainly there is an effect of rough roads but it is not one that will change the nature of
reducing rolling resistance as pressure is increased. The amount of tire distortion increases with
roughness as does rolling resistance. You can test that if you have a suitable road by riding on or
off the chip seal and noting the speed. I had the opportunity of doing that on the north slope of
Monitor Pass on US 395. There was a repeatably lower speed on the rougher surface.

> Science needs simple questions before you arrive at a complex answer. Are there figures for how
> rolling resistance varies with tyre pressure on a rough surface?

Not that I know of. Of course, from knowing that tread squirm, typical of patterned treads where
tread rubber bulges into tread voids, impressing angular pavement features into a smooth tread will
also cause tread squirm. Tread squirm is the principal loss in knobby tires rolling on smooth
pavement. This has been measured.

>>> Its not a personal pet theory of mine or anything, but I have seen theories based on something
>>> like the above, in that when dealing with a slightly rough road surface the ability of a tire to
>>> act as suspension may be more of an advantage than that given by the lower "smooth surface RR".

>> Before repeating these pseudo-science tales, you might look into their validity. Myth and lore
>> survives on repetition, not fact.

> Simple questions:

> Do people riding on rougher roads experience more rolling resistance?

Yes.

> Sorry, I cannot explain if this is true in terms of energy loss.

Tire losses are almost entirely due to tread, casing, and inner tube flexing while the least losses
are caused by tread scrubbing on the road. If this were not the case tires would wear out much
faster than they do.

Jobst Brandt [email protected] Palo Alto CA

 

[Phil Holman]

<[email protected]> wrote in message news:[email protected]...
> William Kemp writes:
>
> >>> Those tests were done on a smooth drum of course. How important are the energy losses
> >>> associated with going over a rough surface with less suspension (from higher pressure in the
> >>> tires)?
>
> >> Maybe you can describe a model of what you believe happens on a paved road of typical asphalt
> >> roughness that would change rolling resistance response of a tire. Do not omit an energy
> >> equation that shows where these losses are converted to heat, the result of all energy losses.
> >> Note that tire deflection from a rider sitting on the bicycle is greater than pavement
> >> roughness, that is if this enters into the model you visualize.
>
> > Ah, I see, If I cannot give you a realistic scenario based on science I am not allowed to even
> > ask whether there is an effect caused by rough roads.
>
> Certainly there is an effect of rough roads but it is not one that will change the nature of
> reducing rolling resistance as pressure is increased. The amount of tire distortion increases with
> roughness as does rolling resistance. You can test that if you have a suitable road by riding on
> or off the chip seal and noting the speed. I had the opportunity of doing that on the north slope
> of Monitor Pass on US 395. There was a repeatably lower speed on the rougher surface.
>
> > Science needs simple questions before you arrive at a complex answer. Are there figures for how
> > rolling resistance varies with tyre pressure on a rough surface?
>
> Not that I know of. Of course, from knowing that tread squirm,
typical
> of patterned treads where tread rubber bulges into tread voids, impressing angular pavement
> features into a smooth tread will also cause tread squirm. Tread squirm is the principal loss in
> knobby tires rolling on smooth pavement. This has been measured.
>
> >>> Its not a personal pet theory of mine or anything, but I have seen theories based on something
> >>> like the above, in that when dealing with a slightly rough road surface the ability of a tire
> >>> to act as suspension may be more of an advantage than that given by the lower "smooth surface
> >>> RR".
>
> >> Before repeating these pseudo-science tales, you might look into their validity. Myth and lore
> >> survives on repetition, not fact.
>
> > Simple questions:
>
> > Do people riding on rougher roads experience more rolling
resistance?
>
> Yes.
>
> > Sorry, I cannot explain if this is true in terms of energy loss.
>
> Tire losses are almost entirely due to tread, casing, and inner tube flexing while the least
> losses are caused by tread scrubbing on the road. If this were not the case tires would wear out
> much faster than they do.

On a rough surface, if the tires are inflated so high as to cause an upward velocity component of
the bicycle and rider, then surely the losses are not just limited to the flexing of the tires.

Phil Holman

 

[Jobst Brandt]

Phil Holman writes:

>>> Sorry, I cannot explain if this is true in terms of energy loss.

>> Tire losses are almost entirely due to tread, casing, and inner tube flexing while the least
>> losses are caused by tread scrubbing on the road. If this were not the case tires would wear out
>> much faster than they do.

> On a rough surface, if the tires are inflated so high as to cause an upward velocity component of
> the bicycle and rider, then surely the losses are not just limited to the flexing of the tires.

There is always a vertical component when not on glassy surfaces. You can feel even smooth concrete
decks of bridges in the handlebars. In that case, you should be able to explain where you see energy
being converted to heat. Rolling resistance refers to the losses in tires, not someone's flabby body
parts vibrating. In any case, that scenario may interest someone somewhere but comfort becomes more
of an issue in that domain. We're talking rolling resistance here and what you bring up is
classically where these discussions end, somewhere in someone's fat ass.

Think tires!

Jobst Brandt [email protected] Palo Alto CA

 

[Phil Holman]

<[email protected]> wrote in message news:[email protected]...
> Phil Holman writes:
>
> >>> Sorry, I cannot explain if this is true in terms of energy loss.
>
> >> Tire losses are almost entirely due to tread, casing, and inner tube flexing while the least
> >> losses are caused by tread scrubbing on the road. If this were not the case tires would wear
> >> out much faster than they do.
>
> > On a rough surface, if the tires are inflated so high as to cause an upward velocity component
> > of the bicycle and rider, then surely the losses are not just limited to the flexing of the
> > tires.
>
> There is always a vertical component when not on glassy surfaces. You can feel even smooth
> concrete decks of bridges in the handlebars. In that case, you should be able to explain where you
> see energy being converted to heat. Rolling resistance refers to the losses in tires, not
> someone's flabby body parts vibrating. In any case, that scenario may interest someone somewhere
> but comfort becomes more of an issue in that domain. We're talking rolling resistance here and
> what you bring up is classically where these discussions end, somewhere in someone's fat ass.
>
> Think tires!

You are absolutely correct in your definition of rolling resistance. Unlike the original post, I do
not include the effects of too high a tire pressure and rough roads in that definition. Phil Holman