Tire Rotation

new tires are always faster than old tires!!
why? well, why not no seriuosly when new and scribbed in and or beaten
with larch,
soaked in boredoe the intended designed capacity is correct
when worn the intended designed capacity was flogged to death and no
longer holds true.

the flabby worn gives better grip is a special application as 28 inch
rims for stoned cobbled highways

new tires, once "scrubbed in" or beaten with larch
are always faster than
old worn tires.

why. well, why not no seriously becaws the design is right on the money
when new
the design capacity fades with wear.

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

Quoted message said:

Question: even if a flat profile on the rear tire isn't a safety issue, at
what point does it become a performance issue, if at all, in terms of
cornering ability, rolling resistance, etc.?

When there is no more rubber and all you see is casing. I usually end up
replacing the rear when it starts to get flats on a regular basis.
-----------
Alex

<[email hidden]> wrote a typical post.
^^^^^^^^^^^^^^^^
I love challenges. Trying to understand what you are saying is one of
life's pleasures.

If you did not recalibrate your cyclometer for the worn and new tyre
circumferences, and all else being equaI, I would expect to see a
slower reading for the new tyres. No?

Pete

:
: <[email hidden]> wrote a typical post.
: ^^^^^^^^^^^^^^^^
: I love challenges. Trying to understand what you are saying is one of
: life's pleasures.

Not for me. When he starts on that drivel, I just tune out and go to a
different post. Life's too short to try and figure out gibberish....

:
:

Tom Nakashima said:

I recently purchased two new tires to replace my old tires which have
developed a flat profile after approximately 4000 miles. I also have been
rotating the tires from front to rear every 500 miles to prolong the profile
(keeping it round) as the rear wears faster than the front. I've also been
making sure the tires have been properly inflated. There have been
articles about rotating a tire from front to rear may not be a good idea for
safety reasons. It seems to me if you don't rotate the tires what you'll
have is a very flat profile on the rear and not getting best mileage out of
the tires.
-tom

Perhaps but the best tire should go onto the front, not the rear. As
the rear wears out, buy a new one, put it on the front, put the old
front on the rear.

"Sheldon Brown" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Tom Nakashima said:

After pilling on the miles, my tires had developed a square profile from
the original round radius, which is slightly more pronounced on the rear.
I've heard when this happens, it's time to change tires, as it could be
dangerous to ride on this profile on the front....and there is also a
slight performance loss, which the experts call "rolling resistance".

I'm not convinced of this. I would expect worn tires to have _less_
rolling resistance, because as they get thinner they get more flexible.

The reason for replacing worn tires is that the thinnest part becomes so
thin that it takes a smaller and smaller sliver of glass or whatever to
poke through to the tube, so you start getting more flats.

Quoted message said:

I've been riding the same weekday training ride just about everyday for
the last 9 years, so I know the road well and speed checks along the
whole route. There's one section on the descent that I gauge as my
maximum speed of 33-35mph before the tire change. When I put on the new
tires (yes I purchased 2 and the same size and brand, same air pressure)
with the rounded profile my speed increased to 39-41 mph on the
descent....averaged checked over 10 rides as I reset my cyclometer before
I begin each ride.
On the flats my speeds have increased 1 to 2 mph, but on the climbs I see
no difference in speed.

I can't believe that this is due to the use of new vs old tires.

Rolling resistance is such a small percentage of total retarding force,
especially at high speeds like that that even if you installed totally
frictionless tires I don't believe it would give you half a mph of speed
improvement. I think there's some placebo effect involved here.

Sheldon "Skeptic" Brown
+-----------------------------------------+
| Well, the truth is usually just |
| an excuse for a lack of imagination... |
| --Garak, DS-9 |
+-----------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

Sheldon, sounds strange, and I was just as surprised as you were,
the only thing I could say is; "try it". You probably ride and wear out
tires just as fast as I do.
Find yourself a straight 6-8% grade slope, 1/2 mile long. No pedaling, just
push off to get started.
Carl mentioned wind resistance, (could be) I'm thin, 147 lbs 5'8".
Bibs with cycling jersey, hands on top bar near the stem with arms tucked
into the side of my body, and chin touching the stem. Feet in the horizontal
position parallel to the ground. I'm riding the Avocet Fasgrip SL Carbon 12
700x23C, weight 200g, 127 tpi, 110psi rear, 100psi front.
Record the max speed and repeat at least 5x for each of the tire sets
between the worn and new, record the average max speed.
-tom

pore favor-
which tire flats most often?
which tire slides more?
which tire carries more weight?
which tire is more important heading into the corkscrew?
which tire is more important heading out of the corkscrew?

one more thinga

the expletive deleted slime liner's overlap-mione overlap and if cut
yours to meet end to end
there's more room here for your post-we'll bring the rose bush-
the overlap is killing my tubes.
doing long distance commuting last winter, i'd blow a tube and put a
new one in soas to save time.
said tubes went into a box. yesterday i went thru them to patch a
couple having shot my mouth off about
no flats and no broken spokes, the ep wheel promptly..
and i found multiple-30-40%-leaks, stresses and cuts from the slime
liner's overlap. a case for rotation on the same rim at intelligent
intervals
say 1/4 to the mississippi.

thye other is the tube going into the co0nti tt is a thick bottomed
specialized thorn proof.
like the flat profile, not intended by the designer to porkduce specs.
the thicker tube sudues the conti's liveliness. a solid safe secure
tire yes but no longer lively.
kinda belgian taxi not french route not yet wooden
i asszoom the designer took this thickness into account for those folk
yemani bound but didn't center the thickness idea into producing sales

Tom Nakashima said:

Sheldon, sounds strange, and I was just as surprised as you were,
the only thing I could say is; "try it". You probably ride and wear out
tires just as fast as I do.

Nah, I hardly ever wear out tires. I've got something over 30 bikes, so
they average maybe 100 miles/year.

It's true that some get ridden a lot more than that, but I'm also a
terrible tire junkie, always trying out new ones, replacing perfectly
serviceable tires with the newest and hottest...

Current faves are Panaracer Rolly-Poly, Avocet FasGrip and the
unfortunaely extict Continental Avenue...

Sheldon "Tire Junkie" Brown
+-----------------------------------------+
| If a fool would persist in his folly, |
| he would become wise. |
| --William Blake |
+-----------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

Tom Nakashima said:

"Sheldon Brown" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Tom Nakashima said:

After pilling on the miles, my tires had developed a square profile from
the original round radius, which is slightly more pronounced on the rear.
I've heard when this happens, it's time to change tires, as it could be
dangerous to ride on this profile on the front....and there is also a
slight performance loss, which the experts call "rolling resistance".

I'm not convinced of this. I would expect worn tires to have _less_
rolling resistance, because as they get thinner they get more flexible.

The reason for replacing worn tires is that the thinnest part becomes so
thin that it takes a smaller and smaller sliver of glass or whatever to
poke through to the tube, so you start getting more flats.

Quoted message said:

I've been riding the same weekday training ride just about everyday for
the last 9 years, so I know the road well and speed checks along the
whole route. There's one section on the descent that I gauge as my
maximum speed of 33-35mph before the tire change. When I put on the new
tires (yes I purchased 2 and the same size and brand, same air pressure)
with the rounded profile my speed increased to 39-41 mph on the
descent....averaged checked over 10 rides as I reset my cyclometer before
I begin each ride.
On the flats my speeds have increased 1 to 2 mph, but on the climbs I see
no difference in speed.

I can't believe that this is due to the use of new vs old tires.

Rolling resistance is such a small percentage of total retarding force,
especially at high speeds like that that even if you installed totally
frictionless tires I don't believe it would give you half a mph of speed
improvement. I think there's some placebo effect involved here.

Sheldon "Skeptic" Brown
+-----------------------------------------+
| Well, the truth is usually just |
| an excuse for a lack of imagination... |
| --Garak, DS-9 |
+-----------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

Sheldon, sounds strange, and I was just as surprised as you were,
the only thing I could say is; "try it". You probably ride and wear out
tires just as fast as I do.
Find yourself a straight 6-8% grade slope, 1/2 mile long. No pedaling, just
push off to get started.
Carl mentioned wind resistance, (could be) I'm thin, 147 lbs 5'8".
Bibs with cycling jersey, hands on top bar near the stem with arms tucked
into the side of my body, and chin touching the stem. Feet in the horizontal
position parallel to the ground. I'm riding the Avocet Fasgrip SL Carbon 12
700x23C, weight 200g, 127 tpi, 110psi rear, 100psi front.
Record the max speed and repeat at least 5x for each of the tire sets
between the worn and new, record the average max speed.
-tom

Dear Tom,

For a 67 kg rider on a 9 kg bike at 0 watts down a -7% grade
on this calculator:

http://w3.iac.net/~curta/bp/velocityN/velocity.html

area->0.4 m^2 0.3 m^2 0.2 m^2
speed increase
rr km/h km/h km/h km/h
0.0040 54.13 62.51 76.56 0.41..0.59
0.0050 53.72 62.03 75.97 0.41..0.58
0.0060 53.31 61.55 75.39 0.42..0.59
0.0070 52.89 61.07 74.80 0.43..0.60*
0.0080 52.46 60.58 74.20

* The largest predicted speed increase between reasonable
steps in rolling resistance for new versus worn tires is
only 0.60 km/h, or about 0.37 mph

As mentioned elsewhere in this thread, this table compared
rolling resistance for some used/worn tires with new
versions at various psi:

http://www.legslarry.beerdrinkers.co.uk/tech/JL.htm

Some tires improved with wear, some stayed the same, and
some even got worse. It's likely that precise inflation and
speed calibration played some role in the erratic results.

The larger and thinner the tire to start with, the less the
effect should be of wear--the contact patch shape should
change less, and the difference in thickness between new and
worn tread should be less.

Again, the problem with roll-out tests is that we tend to
forget how many other variables affect the speed.

Here are some examples using the same calculator and making
small changes to headwind, temperature, and frontal area for
a 7% grade, 67 kg rider, 9 kg bike, 0.0050 rr, 0 watts, 0C,
0.30 m^2:
km/h km/h
defaults 62.03 change

1.61 kmh headwind 60.42 -1.61 (undetectable 1 mph wind)
15 degrees C 61.50 -0.53 (6drop from 68F to 59F)
0.31 m^2 61.02 -1.01 (shirt a little loose)

all three changes 58.88 -3.15

Notice that any one of these changes is about as much as
expected from changing the rr from 0.0080 to 0.0070 with 0.2
m^2 frontal area, which gave the greatest improvement.

However, the calculator probably ignores any improvement due
to a change in the shape of the contact patch.

A flattened profile on a formerly rounded 700c bicycle tire
might improve more than expected just from the loss of
material. The side casing wouldn't change, but the contact
patch should shorten and fatten from a long, thin ellipse to
a shorter, thicker, squarer shape of the same area:

<<<xx>>> new, rounded profile contact patch
XXXX worn, flattened profile contact patch

The difference is exaggerated, but the idea is that the
deformation is concentrated on a shortened section of the
tire sidewall.

A shorter contact patch is usually offered as the
explanation for why wider-section tires have lower
rolling-resistance at the same pressure--their contact
patches are shorter (and wider) and this means that they are
deforming a smaller section of sidewall.

I'm still skeptical that minor wear or slightly improved
road surface can make an easily noticeable difference in
coasting speed down 7% hills.

But you've noticed a speed increase with worn tires, and I
keep breaking 40 mph several times a week now down the upper
part of a smoothly re-paved descent where reaching 40 mph on
the old chip-seal used to be cause for excitement.

As a side note, the rain yesterday reminds me that I keep
wondering if a thin film of water on the asphalt reduces
rolling resistance. I seem to notice higher speeds when I'm
coasting downhill in light rain.

Carl Fogel

Tom Nakashima said:

Quoted message said:

Quoted message said:

There's one section on the descent that I gauge as my
maximum speed of 33-35mph before the tire change. When I put on the new
tires (yes I purchased 2 and the same size and brand, same air pressure)
with the rounded profile my speed increased to 39-41 mph on the
descent

I think you were seeing different wind conditions for these cases.
According to my calculations the rolling resistance would have to
change from .005 to .023 to cause the 6 mph difference you noticed.
That is huge.

But, a wind difference of only 6 mph would do it.

Quoted message said:

Quoted message said:

Quoted message said:

on the climbs I see
no difference in speed.

If the rolling resistance had actually changed that much, you would
have seen about a 1.5 mph difference going back up the hill.

Data from the "beer drinkers" site indicates a small reduction in
rolling resistance as a tire wears... on average. As Carl noted, there
is a lot of variation with the RR sometimes increasing, sometimes
decreasing, and sometimes staying about the same. But if we average the
values for each tire at different inflation pressures, then take the
average change for each tire that was tested both new and used (6
samples), we get a .0004 (about 6%) improvement in rolling resistance
for the used tires. This isn't conclusive because of the small number
of samples and the large variations, plus we don't know exactly what is
meant by the terms "used" and "worn" (how much?). It certainly doesn't
show that a used tire tends to get worse, though.

-Ron

Quoted message said:

As a side note, the state of Colorado very nicely repaved my
long daily downhill recently. When the chip-seal turned into
smooth asphalt, the rolling resistance dropped quite
dramatically with the same tires. I now hit over 40 mph
about half the time on the long, gentle upper section, where
34-37 mph used to be my maximum. But the wind can knock me
right back to the old speeds without being very noticeable.

Using 0.0090 and 0.0030, I still get only a
predicted difference of 40.1 mph versus 38.3 mph, less than
2 mph for an awfully generous estimate of best versus worst
rolling resistance.

I suspect the effective "rolling resistance" of a rough road could be
much higher than .009. When we are talking about smooth pavement it's
just losses due to tire deformation, but on a rough road there is a lot
of motion and vibration that effects the whole bike/rider... and must
get absorbed... somewhere. Even on fairly smooth pavement this is
noticeable.

There is a downhill section I ride regularly where the pavement changes
suddenly for the worse, and it feels like I'm putting on the brakes.

Has anyone seen test data where they got some numbers for effective RR
on rough asphalt? I haven't been able to find any...

-Ron

Quoted message said:

Sharp's 1896 "Bicycles & Tricycles" has a table at the end
of chapter 20, but it uses speeds of 4 to 12 mph; heavy and
wet mud; "asphalte," flint, and flag pavement; and similar
charming archaisms.

Whitt and Wilson's "Bicycling Science" 2nd edition may have
used some the same sources as Sharp for their table 5.2,
which features flint, flag, macadam, and broken granite.

I have the 3rd edition, and that table has been omitted. Wilson says
all the data was gathered by Frank Whitt (deceased), and the sources
are unknown and the results are questionable. Could you post some of
the values anyway, Carl?

Wilson does show one graph that gives about .0045 for 27x1.25 @ 100psi
on a "smooth hard" surace, and .0070 on "medium-rough"... no further
clarification.

It seems to me that the only accurate way to test this is with an
actual bike and rider, or something that simulates it well... the
vibration induced by the roughness and absorbed by the bike and the
rider's body would be a key "loss" wouldn't it? It seems to me that a
rough road has a substantial resistance.

Ron Ruff said:

Quoted message said:

As a side note, the state of Colorado very nicely repaved my long
daily downhill recently. When the chip-seal turned into smooth
asphalt, the rolling resistance dropped quite dramatically with the
same tires. I now hit over 40 mph about half the time on the long,
gentle upper section, where 34-37 mph used to be my maximum. But
the wind can knock me right back to the old speeds without being
very noticeable.

Quoted message said:

Quoted message said:

Using 0.0090 and 0.0030, I still get only a predicted difference of
40.1 mph versus 38.3 mph, less than 2 mph for an awfully generous
estimate of best versus worst rolling resistance.

Quoted message said:

I suspect the effective "rolling resistance" of a rough road could
be much higher than .009. When we are talking about smooth pavement
it's just losses due to tire deformation, but on a rough road there
is a lot of motion and vibration that effects the whole
bike/rider... and must get absorbed... somewhere. Even on fairly
smooth pavement this is noticeable.

Let's not conjecture about this. Rolling resistance of tires consists
of elastic deformation of tire, tread, casing and inner tube.
Obviously roughness of road surface deforms at least the tread if not
more so that will increase rolling resistance. That is why RR tests
are done on smooth steel drums, so that road roughness is not a
parameter but rather the deformation of the tire cross section by
wheel load.

Quoted message said:

There is a downhill section I ride regularly where the pavement
changes suddenly for the worse, and it feels like I'm putting on the
brakes.

I doubt that you can feel that because roughness changes the
perception of the road substantially. What is it you think you feel?
Wind drag does not change enough nor does visible perception of passing
objects.

Quoted message said:

Has anyone seen test data where they got some numbers for effective
RR on rough asphalt? I haven't been able to find any...

As I said, it isn't measured because it affects all tires about the
same. Therefore automotive tire tests as well as better bicycle tests
are don on a smooth steel drum.

Why do you care? What counts is the basic comparative RR value among
tires.

Jobst Brandt

Quoted message said:

Ron Ruff said:

Quoted message said:

As a side note, the state of Colorado very nicely repaved my long
daily downhill recently. When the chip-seal turned into smooth
asphalt, the rolling resistance dropped quite dramatically with the
same tires. I now hit over 40 mph about half the time on the long,
gentle upper section, where 34-37 mph used to be my maximum. But
the wind can knock me right back to the old speeds without being
very noticeable.

Quoted message said:

Quoted message said:

Using 0.0090 and 0.0030, I still get only a predicted difference of
40.1 mph versus 38.3 mph, less than 2 mph for an awfully generous
estimate of best versus worst rolling resistance.

Quoted message said:

I suspect the effective "rolling resistance" of a rough road could
be much higher than .009. When we are talking about smooth pavement
it's just losses due to tire deformation, but on a rough road there
is a lot of motion and vibration that effects the whole
bike/rider... and must get absorbed... somewhere. Even on fairly
smooth pavement this is noticeable.

Let's not conjecture about this. Rolling resistance of tires consists
of elastic deformation of tire, tread, casing and inner tube.
Obviously roughness of road surface deforms at least the tread if not
more so that will increase rolling resistance. That is why RR tests
are done on smooth steel drums, so that road roughness is not a
parameter but rather the deformation of the tire cross section by
wheel load.

Quoted message said:

There is a downhill section I ride regularly where the pavement
changes suddenly for the worse, and it feels like I'm putting on the
brakes.

I doubt that you can feel that because roughness changes the
perception of the road substantially. What is it you think you feel?
Wind drag does not change enough nor does visible perception of passing
objects.

Quoted message said:

Has anyone seen test data where they got some numbers for effective
RR on rough asphalt? I haven't been able to find any...

As I said, it isn't measured because it affects all tires about the
same.

really?

Quoted message said:

Therefore automotive tire tests as well as better bicycle tests
are don on a smooth steel drum.

so tell me, what is the benefit of measuring the rolling resistance of a
mountain bike tire designed for loose surface on a smooth steel drum?
sounds to me more like using a test that remains consistent and doesn't
fill with debris in an effort to obtain *comparative* measure rather
than trying to obtain *absolute* measure in real-world conditions.

Quoted message said:

Why do you care? What counts is the basic comparative RR value among
tires.

Jobst Brandt

Ron Ruff said:

Quoted message said:

Sharp's 1896 "Bicycles & Tricycles" has a table at the end
of chapter 20, but it uses speeds of 4 to 12 mph; heavy and
wet mud; "asphalte," flint, and flag pavement; and similar
charming archaisms.

Whitt and Wilson's "Bicycling Science" 2nd edition may have
used some the same sources as Sharp for their table 5.2,
which features flint, flag, macadam, and broken granite.

I have the 3rd edition, and that table has been omitted. Wilson says
all the data was gathered by Frank Whitt (deceased), and the sources
are unknown and the results are questionable. Could you post some of
the values anyway, Carl?

Wilson does show one graph that gives about .0045 for 27x1.25 @ 100psi
on a "smooth hard" surace, and .0070 on "medium-rough"... no further
clarification.

It seems to me that the only accurate way to test this is with an
actual bike and rider, or something that simulates it well... the
vibration induced by the roughness and absorbed by the bike and the
rider's body would be a key "loss" wouldn't it? It seems to me that a
rough road has a substantial resistance.

Dear Ron,

Table XI., taken from 'Engineering,' January 10, 1896,
giving results of experiments by Mr. H.M. Ravenshaw, serves
to show the variation of the resistance according to the
state of the road.

Table XI.--Resistance of Cycles on Common Roads
Machine Road Total Pounds Miles
Weight, per per
Lbs. ton Hour
--------- ---- --- ---- ----
Tandem Flint 120 37 4
Tricycles Flint 290 31 4
Pneumatic Flint 290 31 10.4
Tyres Flint 290 31 7
Flint 440 35 4
Flint 440 35 8.3
Asphalte 290 31 4
Asphalte 440 30 4
Asphalte 440 30 6
Heavy Mud 290 73 4
Wet Mud 290 65 12

Tandem Flint 200 33 5
Bicycles Flint 370 30 5
Pneumatic Heavy Mud 200 95 5
Tyres Heavy Mud 370 78 5
Flag Pavement 200 33 5

Single Flint 220 60 4
Tricycles Flint 220 60 8
Solid Flag Pavement 220 60 5
Tyres Heavy Mud 200 146 4

--"Bicycles & Tricycles," A. Sharp, 1896
p.256

[How Mr. H.M. Ravenshaw calculated or measured such low
speeds before digital electronic instruments is as much a
mystery as how he insured consistency in "Heavy Mud."]

[It's odd that a 200-lb single tricycle is claimed to
produce twice as much resistance at 4 mph (146 lbs per ton)
as a 290-lb Tandem tricycle at 4 mph (only 73 lbs). In heavy
mud, the difference between solid and pneumatic tires should
be minimized.]

[Oh, you meant Whitt & Wilson?]

Table 5.5. Rolling-resistance coefficients of four-wheeled
wagon (steel tires) and 1 1/2 ton stagecoach.

Surface Cr Speed Vehicle
-------- ----------- ----- -------
Cubical blocks 0.014-0.022 Slow Wagon
Macadam 0.028-0.033 Slow Wagon
Planks 0.013-0.022 Slow Wagon
Gravel 0.062 Slow Wagon
"A fine road" 0.034-0.041 4-10 mph Stagecoach
Common earth road 0.089-0.134 Slow Wagon

Source: J.C. Trautwine, "The Civil Engineer's Reference
Book," 21st edition, (Ithaca, N.Y.: Trautwine, 1937), p.
683.

--"Bicycling Science," Whitt & Wilson, 2nd edition, 1982, p.
122.

[A bit out-of-date, but laudably honest about the speeds
involved. "Cubical blocks" are what we would call
cobblestones. One shudders to contemplate the bearing
friction in traditional wagon wheels lacking bearings.]

[Sorry, you probably wanted bicycles, not stagecoaches.]

Table 5.2 Rolling Resistance of early tires
Coefficient
of rolling friction
Surface Solid-tire Pneumatic-tire Speed(m/sec)
------------------ ---------- -------------- ---------
Racing track x 0.004 x
road(a) x 0.005-0.010 x
Smooth macadam (b) 0.022-0.027 0.013-0.016 x
Flag pavement (c) 0.027 0.015 2.23
Flint (d) 0.027 0.014-0.017 1.79-4.47
Flag pavement x 0.017 x
Macadam road x 0.016 x
broken granite x 0.023 x

x = no data

a. Cycle tires; data from A. Sharp, "Bicycles & Tricyclces"
b. Car tires; data from A.W. Judge, "The Mechanism of the
Car," vol. III (London: Chapman and Hall, 1925), p. 150.
c. Heavy cycle tires; data from A. Sharp, ibid.
d. Thomson's early pneumatic tires (figure 1.22) on a
horse-drawn carriage; data quoted in "Mechanics Magazine,"
vol. 50 (1848).

[Er, not the most reassuringly modern data, is it? The
careful conversion of Sharp's quoted 4-10 mph to 1.79-4.47
meters per second lends a wonderful but spurious air of
accuracy.]

Carl Fogel

Ron Ruff said:

Quoted message said:

Sharp's 1896 "Bicycles & Tricycles" has a table at the end
of chapter 20, but it uses speeds of 4 to 12 mph; heavy and
wet mud; "asphalte," flint, and flag pavement; and similar
charming archaisms.

Whitt and Wilson's "Bicycling Science" 2nd edition may have
used some the same sources as Sharp for their table 5.2,
which features flint, flag, macadam, and broken granite.

I have the 3rd edition, and that table has been omitted. Wilson says
all the data was gathered by Frank Whitt (deceased), and the sources
are unknown and the results are questionable. Could you post some of
the values anyway, Carl?

Wilson does show one graph that gives about .0045 for 27x1.25 @ 100psi
on a "smooth hard" surace, and .0070 on "medium-rough"... no further
clarification.

It seems to me that the only accurate way to test this is with an
actual bike and rider, or something that simulates it well... the
vibration induced by the roughness and absorbed by the bike and the
rider's body would be a key "loss" wouldn't it? It seems to me that a
rough road has a substantial resistance.

Dear Ron,

Here's a pdf, whose figure 1.5 compares rolling resistance
for various asphalt, concrete, and chip-seal:

http://media.wiley.com/product_data/excerpt/19/04713546/0471354619.pdf

The chip-seal comes out about 33% worse than smooth asphalt.

Carl Fogel

carl fogeled in part:

Quoted message said:

As a side note, the rain yesterday reminds me that I keep
wondering if a thin film of water on the asphalt reduces
rolling resistance. I seem to notice higher speeds when I'm
coasting downhill in light rain.

It's an interesting question. It certainly reduces
friction (something I learned early on), but
there's something 'thicker' than air that the tire
has to push through.

Robert