Re: Bicycle Quarterly Rolling Resistance Tests: No Surprises

[Ron Ruff]

On Mar 25, 3:48 pm, Tim McNamara <[email protected]> wrote:
> You're making that assumption and taking it as fact, which is a logical
> error, but that was one of the main assumptions that Jan's test
> challenged. I don't know with certainty one way or the other, but it
> may be that the differences in rolling resistance resulting from higher
> or lower inflation pressures may be of far smaller magnitude than smooth
> drum tests would suggest.

That is one of the issues... the IRC, Tour, and BQ test actually agree
on the effect of pressure on rolling resistance. The BQ results were
misinterpreted however, as they report that the effect of pressure was
much smaller than that shown in roller tests. This is a reprint from
my earlier post:

"They say that roller test show that a drop in pressure from 105 to
85
psi resulted in a Crr increase of 15%, whereas their testing showed a
drop in speed of only 2%. Apples to oranges... Crr is not speed. An
increase in Crr of 15% *is* equivalent to a drop in speed of ~2%...
so
they have verified the drum tests."

 

[Ron Ruff]

Tim McNamara wrote:
> There seems to be some difficulty in this thread in understanding how
> what tests mean in terms of statistically significant measurements, and
> in turn what that means for interpretation of results. IIRC, without
> rereading the article before going to work this morning, Heine wrote
> that the effects of inflation pressure were smaller than the error of
> measurement (unless the differences in inflation pressure were very
> large that is). If my recollection of this is accurate, then the BQ
> tests do not verify the findings of the Tour Magazine and IRC drum
> roller tests regarding inflation pressure as a factor in rolling
> resistance.

The author makes the statement that roller testing shows a 15%
difference and his test shows only a 2% difference, and this is
because roller testing misses the suspension losses. But he is
wrong... since these two results are in fact equivalent. This shows a
misunderstanding of how Crr effects speed. A 15% change in Crr is not
trivial IMO, but yes the BQ test should have very large error bars. He
makes other statements regarding latex tubes and comparisons between
tires that his test simply doesn't have the resolution to have
confidence in.

 

[[email protected]]

Ron Ruff writes:

>> There seems to be some difficulty in this thread in understanding
>> how what tests mean in terms of statistically significant
>> measurements, and in turn what that means for interpretation of
>> results. IIRC, without rereading the article before going to work
>> this morning, Heine wrote that the effects of inflation pressure
>> were smaller than the error of measurement (unless the differences
>> in inflation pressure were very large that is). If my recollection
>> of this is accurate, then the BQ tests do not verify the findings
>> of the Tour Magazine and IRC drum roller tests regarding inflation
>> pressure as a factor in rolling resistance.

> The author makes the statement that roller testing shows a 15%
> difference and his test shows only a 2% difference, and this is
> because roller testing misses the suspension losses. But he is
> wrong... since these two results are in fact equivalent. This shows
> a misunderstanding of how Crr effects speed. A 15% change in Crr is
> not trivial IMO, but yes the BQ test should have very large error
> bars. He makes other statements regarding latex tubes and
> comparisons between tires that his test simply doesn't have the
> resolution to have confidence in.

I don't see what is so difficult about measuring RR. We, in
particular, are interested only in relative rolling losses among tires
offered and that is much simpler. What you do with suspension or
rough ride is a different matter and should not be mixed with rolling
loss.

For the relative merit of one tire over another, I still believe the
IRC tests:

http://www.sheldonbrown.com/brandt/rolling-resistance-tubular.html

Is the best comparison and shows the most pertinent information in a
credible table because it shows the effects of inflation pressure and
thereby is self validation for the curves.

Jobst Brandt

 

[Tim McNamara]

In article <[email protected]>,
"Ron Ruff" <[email protected]> wrote:

> Tim McNamara wrote:
> > There seems to be some difficulty in this thread in understanding
> > how what tests mean in terms of statistically significant
> > measurements, and in turn what that means for interpretation of
> > results. IIRC, without rereading the article before going to work
> > this morning, Heine wrote that the effects of inflation pressure
> > were smaller than the error of measurement (unless the differences
> > in inflation pressure were very large that is). If my recollection
> > of this is accurate, then the BQ tests do not verify the findings
> > of the Tour Magazine and IRC drum roller tests regarding inflation
> > pressure as a factor in rolling resistance.
>
> The author makes the statement that roller testing shows a 15%
> difference and his test shows only a 2% difference, and this is
> because roller testing misses the suspension losses. But he is
> wrong... since these two results are in fact equivalent. This shows a
> misunderstanding of how Crr effects speed. A 15% change in Crr is not
> trivial IMO, but yes the BQ test should have very large error bars.
> He makes other statements regarding latex tubes and comparisons
> between tires that his test simply doesn't have the resolution to
> have confidence in.

When I read the test results I wondered about the discriminative power
of the tests and the risk for noise in the data, since lots of potential
problems are introduced when you're measuring the elapsed time of a
cyclist coasting down a hill. Part of why drum tests are the norm is to
reduce the degrees of freedom and confounds as much as possible. I am
hoping that the new information that was published in the most recent BQ
will resolve some of my questions one way or the other. The magazine
arrived today but I haven't had time to read it.

Jan's an intelligent guy and the team involved included a few PhDs who
are familiar with scientific method, as well as some attempts at peer
review which was perhaps not as strong as it might have been from an
academic standpoint. So I have confidence that they did take as many
steps as they could think of to eliminate confounds- I am just not as
sure that they actually succeeded.

We also, I think, have to contextualize the BQ viewpoint which is
randonneuring, and consider Jan's conclusions within that framework. In
a crit, TT or a (relatively, for randonneurs) short road race of 100
miles maximum efficiency is more important than comfort so tires are
inflated as hard as possible. If inflation pressure provides very small
practical effects on rolling resistance that's very useful for a
randonneur because running tires at 100 rather than 115 psi can be
noticeably more comfortable, and over 375 miles in a weekend that can
mean faster times due to reduced fatigue.

A lot of us here in r.b.t, myself included, tend to contextualize these
discussions in a racing framework. That may lead us to interpret the
same set of data very differently.

 

[Jan Heine]

Did Bicycle Quarterly's test simply confirm the test results of the
drum tests?

The answer is yes and no:

Yes:
1. wider tires roll faster.
2. tires with more supple casings roll faster.
3. Tubular tires appear to roll slower than clinchers, all things
being equal.

No:
4. The ranking order of the tires tested both by TOUR magazine on a
drum (Continental's test lab) and by us on real roads was not the
same:

Tire TOUR Crr BQ time
Deda Tre Giro d'Italia 0.0038 25.3 s
Vittoria Open Corsa CX 0.0039 25.8 s
Michelin Pro Race 0.0042 27.1 s
Conti Ultra Gator Skin 0.0058 27.1 s

As you can see, the Michelin scored much better on the drum than on
real roads, or inversely, the Conti is better on real roads than the
drum tests indicate.

5. We found that tubular tires rolled slower at higher pressures.

6. We found a very distinct speed increase with tire pressure until
about 12% tire drop, then the speed increase flattened off almost
completely. This is very different from the curve shape found at
http://bike.terrymorse.com/imgs/rolres.gif

Bicycle Quarterly is a magazine by riders for riders. Riders don't
care about the rolling resistance of their tires, but about the
overall resistance of the tires. Our tests compare this overall
resistance of tires, at typical speeds. We did not single out rolling
resistance, suspension losses and aerodynamic losses, because riders
don't care. They simply want to go faster. Unfortunately, by narrowly
defining and measuring "rolling resistance," drum tests do not provide
the answers riders need. Unfortunately, many riders have taken them to
do, so tires that are not very fast, such as Avocet Duros, have been
ridden by many in the hopes that they were. Using drum tests for
research into tire casings may be useful, but the suspension losses
also need to be considered, and to my knowledge, they haven't been.
For example, TOUR used the drum test to predict tire speed, concluding
that the Michelin was a lot faster than the Conti - even though on our
real roads, they were the same.

Somebody asked how long the Deda tires lasted. Bicycle Quarterly tests
always specify the test distance of any piece of equipment or bike we
test. The Deda tires were run for 2000 km (1250 miles), without a
single flat. However, our conclusion states: "Its limited tread life
and overall durability makes it most suited to special events, where
its superior comfort and speed are especially attractive."

Anyhow, I wish people would read the test articles before jumping to
conclusions based on erroneous assumptions. If you cannot afford the
magazine, check your local library. If they don't have it, suggest
they get it. Or spend the $ 30 for a subscription. If you don't like
the magazine, we'll refund the unused portion of the subscription.
Here is the link:

http://www.vintagebicyclepress.com/subscriptioninfo.html

And as Mark said, we love to get contradicting views, either as
letters to the editor, or even full articles. If somebody wrote a good
piece titled "In Defense of Tire Testing on Steel Drums," I'd give you
at least a few years' worth of BQ subscription, perhaps even pay some
cash for the article!

Jan Heine
Editor
Bicycle Quarterly
140 Lakeside Ave #C
Seattle WA 98122
www.bikequarterly.com

 

[[email protected]]

On 27 Mar 2007 19:29:02 -0700, "Jan Heine" <[email protected]>
wrote:

[snip]

>Tire TOUR Crr BQ time
>Deda Tre Giro d'Italia 0.0038 25.3 s
>Vittoria Open Corsa CX 0.0039 25.8 s
>Michelin Pro Race 0.0042 27.1 s
>Conti Ultra Gator Skin 0.0058 27.1 s
>
>As you can see, the Michelin scored much better on the drum than on
>real roads, or inversely, the Conti is better on real roads than the
>drum tests indicate.

[snip]

Dear Jan,

In hopes of preventing another outburst of format indignation, I've
taken the liberty of adjusting the spacing in your table:

Tire TOUR Crr BQ time
Deda Tre Giro d'Italia 0.0038 25.3 s
Vittoria Open Corsa CX 0.0039 25.8 s
Michelin Pro Race 0.0042 27.1 s
Conti Ultra Gator Skin 0.0058 27.1 s

There! Another senseless tragedy averted!



Cheers,

Carl Fogel

 

[Tim McNamara]

In article <[email protected]>,
[email protected] wrote:

> On 27 Mar 2007 19:29:02 -0700, "Jan Heine" <[email protected]>
> wrote:
>
> [snip]
>
> >Tire TOUR Crr BQ time
> >Deda Tre Giro d'Italia 0.0038 25.3 s
> >Vittoria Open Corsa CX 0.0039 25.8 s
> >Michelin Pro Race 0.0042 27.1 s
> >Conti Ultra Gator Skin 0.0058 27.1 s
> >
> >As you can see, the Michelin scored much better on the drum than on
> >real roads, or inversely, the Conti is better on real roads than the
> >drum tests indicate.
>
> [snip]
>
> Dear Jan,
>
> In hopes of preventing another outburst of format indignation, I've
> taken the liberty of adjusting the spacing in your table:
>
> Tire TOUR Crr BQ time
> Deda Tre Giro d'Italia 0.0038 25.3 s
> Vittoria Open Corsa CX 0.0039 25.8 s
> Michelin Pro Race 0.0042 27.1 s
> Conti Ultra Gator Skin 0.0058 27.1 s
>
> There! Another senseless tragedy averted!

Oddly enough, Carl, in my newsreader Jan's table was more accurately
formatted than yours.

 

[Joe Riel]

Tim McNamara <[email protected]> writes:

> In article <[email protected]>,
> [email protected] wrote:
>
>> On 27 Mar 2007 19:29:02 -0700, "Jan Heine" <[email protected]>
>> wrote:
>>
>> [snip]
>>
>> >Tire TOUR Crr BQ time
>> >Deda Tre Giro d'Italia 0.0038 25.3 s
>> >Vittoria Open Corsa CX 0.0039 25.8 s
>> >Michelin Pro Race 0.0042 27.1 s
>> >Conti Ultra Gator Skin 0.0058 27.1 s
>> >
>> >As you can see, the Michelin scored much better on the drum than on
>> >real roads, or inversely, the Conti is better on real roads than the
>> >drum tests indicate.
>>
>> [snip]
>>
>> Dear Jan,
>>
>> In hopes of preventing another outburst of format indignation, I've
>> taken the liberty of adjusting the spacing in your table:
>>
>> Tire TOUR Crr BQ time
>> Deda Tre Giro d'Italia 0.0038 25.3 s
>> Vittoria Open Corsa CX 0.0039 25.8 s
>> Michelin Pro Race 0.0042 27.1 s
>> Conti Ultra Gator Skin 0.0058 27.1 s
>>
>> There! Another senseless tragedy averted!
>
> Oddly enough, Carl, in my newsreader Jan's table was more accurately
> formatted than yours.

Than your newsreader isn't using a fixed-width font.

--
Joe Riel

 

[Ron Ruff]

On Mar 27, 7:29 pm, "Jan Heine" <[email protected]> wrote:
> As you can see, the Michelin scored much better on the drum than on
> real roads, or inversely, the Conti is better on real roads than the
> drum tests indicate.

Jan... if "suspension losses" can explain why some tires perform
better on real roads, then shouldn't these tires have a smoother ride?
In the article you state that the Contis had a poor ride compared to
the Pro2. You also state that latex tubes have a smoother ride, yet
they are slower on the road... but they perform better on drum tests.
I can't think of any mechanism for this to occur... the concept of
suspension losses certainly doesn't do it.

> 6. We found a very distinct speed increase with tire pressure until
> about 12% tire drop, then the speed increase flattened off almost
> completely. This is very different from the curve shape found athttp://bike.terrymorse.com/imgs/rolres.gif

Is this curve published somewhere? I don't see it in the article.
There are only 2 data points for most of the tires you tested. There
are 4 for the Rolly Polly, but the drop-off looks about the same as
the IRC tests to me... plus, it is necessary to convert your run times
to Crr if you want to make a comparison. Converting to Crr will make
the differences more pronounced.

 

[Michael Press]

In article
<[email protected]>,
[email protected] wrote:

> I can't get embroiled in an internet debate about this stuff, so I'm
> afraid I won't be posting additional responses here. If you really
> think we are off our rockers, write a letter to BQ, or better yet,
> write an article critiquing ours. If you haven't at least read the
> article(s) though, arguments that they are "nutty" simply show closed-
> mindedness.

I appreciate that you do not wish to engage in an
extended discussion; and sympathize fully with your
position. Nobody would be served by such a discussion.
Therefore I am puzzled at your Parthian shot: a vague
accusation of nutty-ness and close-mindedness in this
forum. My email address is valid.
--
Michael Press

 

[Michael Press]

In article
<[email protected]>,
Tim McNamara <[email protected]> wrote:

> In article <[email protected]>,
> [email protected] wrote:
>
> > On 27 Mar 2007 19:29:02 -0700, "Jan Heine" <[email protected]>
> > wrote:
> >
> > [snip]
> >
> > >Tire TOUR Crr BQ time
> > >Deda Tre Giro d'Italia 0.0038 25.3 s
> > >Vittoria Open Corsa CX 0.0039 25.8 s
> > >Michelin Pro Race 0.0042 27.1 s
> > >Conti Ultra Gator Skin 0.0058 27.1 s
> > >
> > >As you can see, the Michelin scored much better on the drum than on
> > >real roads, or inversely, the Conti is better on real roads than the
> > >drum tests indicate.
> >
> > [snip]
> >
> > Dear Jan,
> >
> > In hopes of preventing another outburst of format indignation, I've
> > taken the liberty of adjusting the spacing in your table:
> >
> > Tire TOUR Crr BQ time
> > Deda Tre Giro d'Italia 0.0038 25.3 s
> > Vittoria Open Corsa CX 0.0039 25.8 s
> > Michelin Pro Race 0.0042 27.1 s
> > Conti Ultra Gator Skin 0.0058 27.1 s
> >
> > There! Another senseless tragedy averted!
>
> Oddly enough, Carl, in my newsreader Jan's table was more accurately
> formatted than yours.

Luckily, this question can be settled. Here is a scale.

1234567890123456789012345678901234567890123456789012345678901234567890
^ ^ ^ ^ ^ ^ ^
abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ

Do the carats align with the zeroes?
Does the `z' align at 26 characters?
Does the `Z' align at 52 characters?
--
Michael Press

 

[Tim McNamara]

In article <[email protected]>,
Michael Press <[email protected]> wrote:

> In article
> <[email protected]>,
> Tim McNamara <[email protected]> wrote:
>
> > In article <[email protected]>,
> > [email protected] wrote:
> >
> > > On 27 Mar 2007 19:29:02 -0700, "Jan Heine" <[email protected]>
> > > wrote:
> > >
> > > [snip]
> > >
> > > >Tire TOUR Crr BQ time
> > > >Deda Tre Giro d'Italia 0.0038 25.3 s
> > > >Vittoria Open Corsa CX 0.0039 25.8 s
> > > >Michelin Pro Race 0.0042 27.1 s
> > > >Conti Ultra Gator Skin 0.0058 27.1 s
> > > >
> > > >As you can see, the Michelin scored much better on the drum than on
> > > >real roads, or inversely, the Conti is better on real roads than the
> > > >drum tests indicate.
> > >
> > > [snip]
> > >
> > > Dear Jan,
> > >
> > > In hopes of preventing another outburst of format indignation, I've
> > > taken the liberty of adjusting the spacing in your table:
> > >
> > > Tire TOUR Crr BQ time
> > > Deda Tre Giro d'Italia 0.0038 25.3 s
> > > Vittoria Open Corsa CX 0.0039 25.8 s
> > > Michelin Pro Race 0.0042 27.1 s
> > > Conti Ultra Gator Skin 0.0058 27.1 s
> > >
> > > There! Another senseless tragedy averted!
> >
> > Oddly enough, Carl, in my newsreader Jan's table was more accurately
> > formatted than yours.
>
> Luckily, this question can be settled. Here is a scale.
>
> 1234567890123456789012345678901234567890123456789012345678901234567890
> ^ ^ ^ ^ ^ ^ ^
> abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ
>
> Do the carats align with the zeroes?
> Does the `z' align at 26 characters?
> Does the `Z' align at 52 characters?

What does this have to do with tires? If you must yank threads off
topic like this, please at least fork it off into its own thread.

 

[A Muzi]

Michael Press wrote:
-snip tabulation query-

> Luckily, this question can be settled. Here is a scale.
> 1234567890123456789012345678901234567890123456789012345678901234567890
> ^ ^ ^ ^ ^ ^ ^
> abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ
> Do the carats align with the zeroes?
> Does the `z' align at 26 characters?
> Does the `Z' align at 52 characters?

aligns perfectly in Netscape News
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[41]

Tim McNamara wrote:
> In article <[email protected]>,
> "Ron Ruff" <[email protected]> wrote:
>
> > On Mar 25, 3:48 pm, Tim McNamara <[email protected]> wrote:

> > > I don't know with certainty one way or the other,
> > > but it may be that the differences in rolling resistance resulting
> > > from h igher or lower inflation pressures may be of far smaller
> > > magnitude than smooth drum tests would suggest.
> >
> > That is one of the issues... the IRC, Tour, and BQ test actually
> > agree on the effect of pressure on rolling resistance. The BQ re sults
> > were misinterpreted however, as they report that the effect of
> > pressure was much smaller than that shown in roller tests. This is a
> > reprint from my earlier post:
> >
> > "They say that roller test show that a drop in pressure from 10 5 to
> > 85 psi resulted in a Crr increase of 15%, whereas their testing
> > showed a drop in speed of only 2%. Apples to oranges... Crr is not
> > speed. An increase in Crr of 15% *is* equivalent to a drop in speed
> > of ~2%... so they have verified the drum tests."
>
> There seems to be some difficulty in this thread in understanding how
> what tests mean in terms of statistically significant measurements, and
> in turn what that means for interpretation of results. IIRC, without
> rereading t he article before going to work this morning, Heine wrote
> that the effects of inflation pressure were smaller than the error of
> measurement (unless the differences in inflation pressure were very
> large that is).

Yes, the resolution of the BQ test method was not sufficient to hear
the signal due to inflation pressure: it got smothered in the noise.
That is (one of the reasons) why one does roller tests, to reduce the
noise and find that otherwise drowned out signal which is nevertheless
still athletically very significant: 13 sec per hour, roughly. Both BQ
and IRC tests come to that same conclusion, just that in the BQ tests
the noise levels were about that much too, while in the IRC tests they
were much smaller.

An important point to emphasize- so I will do it again in reply to JH
and MM's posts- is that the BQ tests prove that, for paved roads such
as used in the BQ tests, suspension losses ARE NOT a factor. We know
this because, all other things being similar, air pressure is by far
the major determinant of suspension losses. Yet, changing the air
pressure within an important range did not change the times any more
than one would have expected due to their influence on rolling
resistance alone, based on the IRC tests. Just as Jobst has been
saying all these years.

 

[Ron Ruff]

On Mar 29, 6:56 am, "41" <[email protected]> wrote:
> An important point to emphasize- so I will do it again in reply to JH
> and MM's posts- is that the BQ tests prove that, for paved roads such
> as used in the BQ tests, suspension losses ARE NOT a factor. We know
> this because, all other things being similar, air pressure is by far
> the major determinant of suspension losses. Yet, changing the air
> pressure within an important range did not change the times any more
> than one would have expected due to their influence on rolling
> resistance alone, based on the IRC tests. Just as Jobst has been
> saying all these years.

I think it would be more accurate to say the suspension losses were
small enough to be lost in the noise of the BQ test. I believe they
are there, but appear to be fairly small. Alan Morrison has been
testing tires on rollers with a powermeter, and his data is posted at
the Bike Tech Review site. He also tried testing on a "rough"
roller... one that had a series of wires attached to the surface. This
lessened the effect of tire pressure on Crr, but up to at least 140
psi there was no pressure where the resistance started to increase. I
had actually expected to see a clear "optimum" at a lower pressure.

 

[41]

Tim McNamara wrote:

> Ja n's an intelligent guy and the team involved included a few PhDs who
> are familiar with scientific method, as well as some attempts at peer
> review which was perhaps not as strong as it might have been from an
> academic standpoint. So I have confid ence that they did take as many
> steps as they could think of to eliminate confounds- I am just not as
> sure that they actually succeeded.

Since I am the one who started this thread, I should emphasize that I
find that they did succeed: within the limits of resolution of their
tests, they confirmed conventional tire theory as explained e.g. by
Continental or Schwalbe, with regard to tire width and thickness:
<http://www.schwalbetires.com/wider_faster_page>
<http://www.schwalbetires.com/tech_info/rolling_resistance>
<http://www.cyclingnews.com/tech/?id=2005/features/conti_tech>


Likewise they confirmed both the IRC tests, and the interpretation of
them that Jobst has been offering all these years:

-For paved roads, suspension losses acting in any way different from
ordinary rolling resistance losses ARE NOT a factor in how fast the
bike rolls. We know this because they found the effect of air pressure
within the relevant ranges to be no different from that found in the
pure rolling resistance tests as done by IRC.

-Tires are slower the more hysteretic their construction: thicker,
harder rubber; heavier, stiffer casing; tubular glue.


Equally important is what the tests DID NOT show (or test for):


> We also, I think, have to contextualize the BQ viewpoint which is
> randonneuring, and consider Jan's conclusions within that framework. In
> a crit, TT or a (relatively, for randonneurs) short road race of 100
> miles maximum efficiency is more important than comfort so tires are
> inflated as hard as possible. If inflation pressure provides very small
> practical effects on rolling resistance that's very useful for a
> randonneur because running tires at 100 rather than 115 psi can be
> noticeably more comfortable, and over 375 miles in a weekend that can
> mean faster times due to reduced fatigue.


Since the BQ tests were over a short downhill test course, they did
not and COULD NOT test for the effect on event times as influenced by
comfort and fatigue. That trade off is individual anyway, since riding
styles and positions and body masses and bicycle wheelbases are
different. As I say, they DID prove, within the limits of their test
resolution, that the direct suspension effect (i.e. not via the
intermediary of how it fatigues the rider) as different from rolling
resistance per se IS NOT a factor on paved roads (at least, for
whatever particular surface they used). Just as Jobst has been
propounding all these years.

Another item they did NOT and could not test for: which is faster,
thin hard rubber or thick soft rubber, so as to give equal durability?
And: what to make of that question, since one simply doesn't find soft
rubber treaded tires, of any reasonable thickness, with the durability
of thin hard rubber.

 

[Tim McNamara]

In article <[email protected]>,
"41" <[email protected]> wrote:

> Tim McNamara wrote:
>
> > Jan's an intelligent guy and the team involved included a few PhDs
> > who are familiar with scientific method, as well as some attempts
> > at peer review which was perhaps not as strong as it might have
> > been from an academic standpoint. So I have confid ence that they
> > did take as many steps as they could think of to eliminate
> > confounds- I am just not as sure that they actually succeeded.
>
> Since I am the one who started this thread, I should emphasize that I
> find that they did succeed: within the limits of resolution of their
> tests, they confirmed conventional tire theory as explained e.g. by
> Continental or Schwalbe, with regard to tire width and thickness:
> <http://www.schwalbetires.com/wider_faster_page>
> <http://www.schwalbetires.com/tech_info/rolling_resistance>
> <http://www.cyclingnews.com/tech/?id=2005/features/conti_tech>
>
>
> Likewise they confirmed both the IRC tests, and the interpretation of
> them that Jobst has been offering all these years:
>
> -For paved roads, suspension losses acting in any way different from
> ordinary rolling resistance losses ARE NOT a factor in how fast the
> bike rolls. We know this because they found the effect of air
> pressure within the relevant ranges to be no different from that
> found in the pure rolling resistance tests as done by IRC.
>
> -Tires are slower the more hysteretic their construction: thicker,
> harder rubber; heavier, stiffer casing; tubular glue.

The resolution of the BQ tests, IMHO, was not fine-grained enough to
claim that they confirmed or disconfirmed "conventional" tire theory.
And indeed, the authors of the test appear to disagree with your
conclusion on several points- including finding that suspension losses
were a significant factor. There were several points of difference
compared to the IRC tests and the Tour tests.

Tests always have to be interpreted in the context of what was being
examined. In the case of the BQ tests they were not examining rolling
resistance but overall tire performance. Rolling resistance is one
factor in tire performance.

> Equally important is what the tests DID NOT show (or test for):
>
> > We also, I think, have to contextualize the BQ viewpoint which is
> > randonneuring, and consider Jan's conclusions within that
> > framework. In a crit, TT or a (relatively, for randonneurs) short
> > road race of 100 miles maximum efficiency is more important than
> > comfort so tires are inflated as hard as possible. If inflation
> > pressure provides very small practical effects on rolling
> > resistance that's very useful for a randonneur because running
> > tires at 100 rather than 115 psi can be noticeably more
> > comfortable, and over 375 miles in a weekend that can mean faster
> > times due to reduced fatigue.

I wrote the above, not anyone from BQ, just to make sure that is clear.

> Since the BQ tests were over a short downhill test course, they did
> not and COULD NOT test for the effect on event times as influenced by
> comfort and fatigue. That trade off is individual anyway, since
> riding styles and positions and body masses and bicycle wheelbases
> are different. As I say, they DID prove, within the limits of their
> test resolution, that the direct suspension effect (i.e. not via the
> intermediary of how it fatigues the rider) as different from rolling
> resistance per se IS NOT a factor on paved roads (at least, for
> whatever particular surface they used). Just as Jobst has been
> propounding all these years.

Their conclusion about that is much the opposite of what you claim they
found. Again I ask: have you actually read the source article and the
follow up article? If not, you are really not in any position to say
what their findings were, let alone to rebutt them.

 

[41]

Ron Ruff wrote:
> On Mar 29, 6:56 am, "41" <[email protected]> wrote:
> > An important point to emphasize- so I will do it again in reply to JH
> > and MM's posts- is that the BQ tests prove that, for paved roads such
> > as used in the BQ tests, su spension losses ARE NOT a factor. We know
> > this because, all other things being similar, air pressure is by far
> > the major determinant of suspension losses. Yet, changing the air
> > pressure within an important range did not change the times any more
> > than one would have expected due to their influence on rolling
> > resistance alone, based on the IRC tests. Just as Jobst has been
> > saying all these years.
>
> I think it would be more accurate to say the suspension losses were
> small enough to be lost in the noise of the BQ test. I believe they
> are there, but appear to be fairly small.

Sure. All statements should be taken as having "within the resolution
of the test" implicit. I make it explicit much of the time but
sometimes one does want to abbreviate.

> Alan Morrison has been
> testing tires on rollers with a powermeter, and his data is posted at
> the Bike Tech Review site. He also tried testing on a "rou gh"
> roller... one that had a series of wires attached to the surface. This
> lessened the effect of tire pressure on Crr, but up to at least 140
> psi there was no pressure where the resistance started to increase. I
> had actually expected to see a clear "optimum" at a lower pressure.

Do you have a link? I searched for a while but found nothing except
his old <AFM_tire_testing_rev4.pdf>, all done on smooth rollers.
e

 

[41]

Tim McNamara wrote:
> In article <[email protected]>,
> "41" <[email protected]> wrote:
>
> > Tim McNamara wrote:

> > > So I have confid ence that they
> > > did take as many steps as they could think of to el iminate
> > > confounds- I am just not as sure that they actually succeeded.
> >
> > Since I am the one who started this thread, I should emphasize that I
> > find that they did succeed: within the limits of resolution of their
> > tests, they confirm ed conventional tire theory as explained e.g. by
> > Continental or Schwalbe, with regard to tire width and thickness:

> The resolution of the BQ tests, IMHO, was not fine-grained enough to
> claim tha t they confirmed or disconfirmed "conventional" tire theory.

What is not clear? I said, within the limits of resolution of the
tests.


> And indeed, the authors of the test appear to disagree with your
> conclusion on several points- including finding that suspension losses
> were a significant factor.

What is not clear? The original article presented their findings as
surprising, overturning previously held beliefs. The title of this
thread, which I started, is "Bicycle Quarterly Rolling Resistance
Tests: No Surprises". In the post that began this thread I said:

#Nevertheless, although the BQ tests were presented as overturning
tests done on #polished drums, in fact they are yet another
vindication of them.


In other words, the whole point of this thread was to argue that their
data should be seen as demonstrating something other than what they
originally concluded. Is it possible to be any clearer?


> Their conclusion about that is much the opposite of what you claim they
> found. Again I ask: have you actually read the source article and the
> follow up article? If not, you are really not in any position to say
> what their findings were, let alone to rebutt them.

What an amazing paragraph. Why would I have to "rebutt" them if I were
agreeing with them? Obviously I am disagreeing. And I certainly am in
a position to know what the findings I disagree with are, because Jan
and Mark have been kind enough to clearly state them here. I am taking
their explanations and saying that in fact they indicate something
other than what they have taken them to indicate. Is it possible to be
any clearer?
a

 

[[email protected]]

I suspect that all these indirect test methods, arguing about how
rough a surface must be and arriving at a single data point are used
because the testers are not willing to spend the money of making a
repeatable large diameter drum tester on which to perform tests that
repeatably encompass all the results they are getting form derivative
experiments that are blurred by wind resistance, vehicle inertia,
rider compensation and small timing variations with large effect.

The tests shown from the IRC tests:

http://www.sheldonbrown.com/brandt/rolling-resistance-tubular.html

Give the effects of road roughness because lower inflation pressure
effectively shows increases in RR caused by more flexing on rougher
surfaces. In fact when riding on reasonable pavement, the results are
that of a smooth drum and the value of higher inflation visible in the
graph. The people most interested in RR are road raiders and they
don't have much suspension to worry about.

Moreover, that a series of data points measured directly from strain
gauges are verified that the data is repeatable because they fit a
"power fit" curve. All the dodges of smooth drums not being realistic
that we've seen here boil down to "we don't have the means to measure
it directly".

All the discussion seems to be misdirected in my assessment. Get a
testing rig that works.

Jobst Brandt