Tires

Terry Morse said:

Jobst Brandt said:

So again, how do
you tell is one tire grips better than the next?

I measure a tire's wet traction by how much it slips when climbing a
steep, wet road.

I do too, but I seem to get the "wrong" answer this way. Out of the
3 different tires I've tried against my favorite steep hill in the
wet the best I've had so far by this measure are yellow-colored, treaded,
25 mm Continental GP 3000's.

Not that this makes the tires worth buying, mind you, since they are
normally really expensive (if you can't find tires in an ugly,
discontinued color at a deep discount) and add insult to injury by
wearing out incredibly quickly.

Dennis Ferguson

Terry Morse said:

Jobst Brandt said:

So again, how do
you tell is one tire grips better than the next?

I measure a tire's wet traction by how much it slips when climbing a
steep, wet road.

OK, so exception to the rule that slicks have more traction than treads b/c
of more surface contact with the road? How is this different climbing a wet
surface, if you'll forgive my ignorance?

-B

Terry Morse said:

Quoted message said:

So again, how do you tell is one tire grips better than the next?

Quoted message said:

I measure a tire's wet traction by how much it slips when climbing a
steep, wet road.

Wait a minute. Tires don't slip on wet pavement unless there is a
glossy tar or paint strip, or a metal [cover or RR track]. In that
event, any tire will slip. Road traction is a measure of how well the
tire corners on wet pavement and this is interaction of the tread
rubber with micro-roughness of the aggregate used in the pavement,
concrete or asphalt. I have seen riders fall off the bicycle while
climbing with Clement tubulars (250g Criterium and 300g Campionato del
Mundo) many years ago for ignoring tar stripes on pavement cracks. I
doubt anyone took that as a measure of wet traction.

Jobst Brandt
[email hidden]

Badger South said:

Quoted message said:

Quoted message said:

So again, how do you tell is one tire grips better than the next?

Quoted message said:

Quoted message said:

I measure a tire's wet traction by how much it slips when climbing
a steep, wet road.

Quoted message said:

OK, so exception to the rule that slicks have more traction than
treads b/c of more surface contact with the road? How is this
different climbing a wet surface, if you'll forgive my ignorance?

Because climbing does not make a tire slip but crossing slick spots
that one would not dare to corner on, descending, tires can be made to
slip. What is less apparent is that if the hill is moderately steep,
this "test" can cause a fall. It's not a valid test.

Jobst Brandt
[email hidden]

Jobst Brandt said:

Terry Morse said:

I measure a tire's wet traction by how much it slips when climbing a
steep, wet road.

Wait a minute. Tires don't slip on wet pavement unless there is a
glossy tar or paint strip, or a metal [cover or RR track]. In that
event, any tire will slip.

Not true. The next time it rains around here, let's go for a ride
and I'll show you a rear tire slipping on a climb. It happens to me
often, without the benefit of tar snakes or metal grates. Maybe you
can't make the rear tire slip with those monstrous big gears you
like to use, but I certainly do with a 42" gear.
--
terry morse Palo Alto, CA http://bike.terrymorse.com/

Terry Morse said:

Quoted message said:

Quoted message said:

I measure a tire's wet traction by how much it slips when climbing
a steep, wet road.

Quoted message said:

Quoted message said:

Wait a minute. Tires don't slip on wet pavement unless there is a
glossy tar or paint strip, or a metal [cover or RR track]. In that
event, any tire will slip.

Quoted message said:

Not true. The next time it rains around here, let's go for a ride
and I'll show you a rear tire slipping on a climb. It happens to me
often, without the benefit of tar snakes or metal grates. Maybe you
can't make the rear tire slip with those monstrous big gears you
like to use, but I certainly do with a 42" gear.

How does the gear affect slip on a hill? If the wheel torque is
sufficient to propel the bicycle, what does the contact patch care who
supplies the torque? Does your wheel slip when descending the same
grade when applying the brake? Something does not add up here.

Just for comparison, I have ridden up Filbert St in SF, the steepest
street in the city (31.5%) in the rain. It is a smooth hand finished
sheen concrete paved street with stairs for a sidewalk. It produced
no wheel spin.

http://www.mistersf.com/high/index.html?highsteep.htm

Jobst Brandt
[email hidden]

Quoted message said:

Terry Morse said:

Quoted message said:

> I measure a tire's wet traction by how much it slips when climbing
> a steep, wet road.

Quoted message said:

Quoted message said:

Wait a minute. Tires don't slip on wet pavement unless there is a
glossy tar or paint strip, or a metal [cover or RR track]. In that
event, any tire will slip.

Quoted message said:

Not true. The next time it rains around here, let's go for a ride
and I'll show you a rear tire slipping on a climb. It happens to me
often, without the benefit of tar snakes or metal grates. Maybe you
can't make the rear tire slip with those monstrous big gears you
like to use, but I certainly do with a 42" gear.

How does the gear affect slip on a hill? If the wheel torque is
sufficient to propel the bicycle, what does the contact patch care who
supplies the torque? Does your wheel slip when descending the same
grade when applying the brake? Something does not add up here.

Just for comparison, I have ridden up Filbert St in SF, the steepest
street in the city (31.5%) in the rain. It is a smooth hand finished
sheen concrete paved street with stairs for a sidewalk. It produced
no wheel spin.

http://www.mistersf.com/high/index.html?highsteep.htm

Jobst Brandt
[email hidden]

Cool. I note the description says in part: "...Valley for the distinction
of being the steepest driveable street in San Francisco.)"

IOW, there are steeper streets, they're just not driveable! <g>

-B

Quoted message said:

Terry Morse said:

Quoted message said:

> I measure a tire's wet traction by how much it slips when climbing
> a steep, wet road.

Quoted message said:

Quoted message said:

Wait a minute. Tires don't slip on wet pavement unless there is a
glossy tar or paint strip, or a metal [cover or RR track]. In that
event, any tire will slip.

Quoted message said:

Not true. The next time it rains around here, let's go for a ride
and I'll show you a rear tire slipping on a climb. It happens to me
often, without the benefit of tar snakes or metal grates. Maybe you
can't make the rear tire slip with those monstrous big gears you
like to use, but I certainly do with a 42" gear.

How does the gear affect slip on a hill? If the wheel torque is
sufficient to propel the bicycle, what does the contact patch care who
supplies the torque? Does your wheel slip when descending the same
grade when applying the brake? Something does not add up here.

Just for comparison, I have ridden up Filbert St in SF, the steepest
street in the city (31.5%) in the rain. It is a smooth hand finished
sheen concrete paved street with stairs for a sidewalk. It produced
no wheel spin.

http://www.mistersf.com/high/index.html?highsteep.htm

Jobst Brandt
[email hidden]

Cool. I note the description says in part: "...Valley for the distinction
of being the steepest driveable street in San Francisco.)"

IOW, there are steeper streets, they're just not driveable! <g>

-B

Jobst Brandt said:

Terry Morse said:

The next time it rains around here, let's go for a ride
and I'll show you a rear tire slipping on a climb. It happens to me
often, without the benefit of tar snakes or metal grates. Maybe you
can't make the rear tire slip with those monstrous big gears you
like to use, but I certainly do with a 42" gear.

How does the gear affect slip on a hill? If the wheel torque is
sufficient to propel the bicycle, what does the contact patch care who
supplies the torque?

The gear affects slip on a hill because lower gears produce higher
wheel torque at the peak of pedal force, when standing. Mountain
bike riders know this phenomenon all too well, since traction is far
less on the dirt than on pavement. If my rear wheel begins to slip
when climbing, I click up a gear or two and try to move my hips
farther over the back wheel. It works.

Quoted message said:

Just for comparison, I have ridden up Filbert St in SF, the steepest
street in the city (31.5%) in the rain. It is a smooth hand finished
sheen concrete paved street with stairs for a sidewalk. It produced
no wheel spin.

But then you climb using comparatively high gears. Try the same
stunt with a low gear, and you might be surprised at how easily the
back wheel slips.
--
terry morse Palo Alto, CA http://bike.terrymorse.com/

In article <[email hidden]>,

Quoted message said:

Terry Morse said:

Quoted message said:

> I measure a tire's wet traction by how much it slips when climbing
> a steep, wet road.

Quoted message said:

Quoted message said:

Wait a minute. Tires don't slip on wet pavement unless there is a
glossy tar or paint strip, or a metal [cover or RR track]. In that
event, any tire will slip.

Quoted message said:

Not true. The next time it rains around here, let's go for a ride
and I'll show you a rear tire slipping on a climb. It happens to me
often, without the benefit of tar snakes or metal grates. Maybe you
can't make the rear tire slip with those monstrous big gears you
like to use, but I certainly do with a 42" gear.

How does the gear affect slip on a hill? If the wheel torque is
sufficient to propel the bicycle, what does the contact patch care who
supplies the torque? Does your wheel slip when descending the same
grade when applying the brake? Something does not add up here.

Just for comparison, I have ridden up Filbert St in SF, the steepest
street in the city (31.5%) in the rain. It is a smooth hand finished
sheen concrete paved street with stairs for a sidewalk. It produced
no wheel spin.

http://www.mistersf.com/high/index.html?highsteep.htm

I believe your data point Jobst, but I have also spun my rear tire while
climbing (20mm IRC Triathlon tire; it was cheap is why) on wet but
apparently clean asphalt. This happens periodically on my commute, which
goes up a 1 km climb of moderate steepness: 10-15%, I'd guess.

I found a paper which quotes a notably higher coefficient of friction
for wet concrete than wet asphalt:

http://scholar.lib.vt.edu/theses/available/etd-5440202339731121/unrestric
ted/CHAP3_DOC.pdf

http://tinyurl.com/5v6n3

Page 5 of the PDF quotes values of 0.5-0.6 for wet asphalt, and 0.8 for
wet concrete. That latter figure is as good as the quoted low-end figure
for dry asphalt.

One thing I notice is I only seem to get slippage when out of the
saddle, so this may be due to light wheel loading at the rear.

--
Ryan Cousineau, [email hidden] http://www.wiredcola.com
Verus de parvis; verus de magnis.

Ryan Cousineau said:

One thing I notice is I only seem to get slippage when out of the
saddle, so this may be due to light wheel loading at the rear.

I notice the same thing: rear wheel slippage only when standing. I
attribute this to a combination of less weight on the rear wheel and
higher peak torque on the cranks.
--
terry morse Palo Alto, CA http://bike.terrymorse.com/

Terry Morse said:

Ryan Cousineau said:

One thing I notice is I only seem to get slippage when out of the
saddle, so this may be due to light wheel loading at the rear.

I notice the same thing: rear wheel slippage only when standing. I
attribute this to a combination of less weight on the rear wheel and
higher peak torque on the cranks.

I too have noticed it in several different forms.

On a MTB on dirt (seems the substrate would simply vary the
amount of torque required for the given coefficient of friction
to cause wheel spin for a given tire tread and material), as
well as steep asphalt climbs in low gear on a touring bike
(essential MTB gearing). On asphalt, I need to be out of
the seat and on the pedals. Off road the substrate has a
lower coefficient of friction so in or out of the saddle
doesn't matter; grade and "wetness" of the ground does.

Off road 4-wheelers as well as motorcycle hill climbers
know that you often shift to a *higher* gear when losing
traction. The inexperienced often *down shift* and bury
themselves in a hole.

SMH

Terry Morse said:

Quoted message said:

Quoted message said:

The next time it rains around here, let's go for a ride and I'll
show you a rear tire slipping on a climb. It happens to me often,
without the benefit of tar snakes or metal grates. Maybe you can't
make the rear tire slip with those monstrous big gears you like to
use, but I certainly do with a 42" gear.

Quoted message said:

Quoted message said:

How does the gear affect slip on a hill? If the wheel torque is
sufficient to propel the bicycle, what does the contact patch care
who supplies the torque?

Quoted message said:

The gear affects slip on a hill because lower gears produce higher
wheel torque at the peak of pedal force, when standing. Mountain
bike riders know this phenomenon all too well, since traction is far
less on the dirt than on pavement. If my rear wheel begins to slip
when climbing, I click up a gear or two and try to move my hips
farther over the back wheel. It works.

Quoted message said:

Quoted message said:

Just for comparison, I have ridden up Filbert St in SF, the
steepest street in the city (31.5%) in the rain. It is a smooth
hand finished sheen concrete paved street with stairs for a
sidewalk. It produced no wheel spin.

Quoted message said:

But then you climb using comparatively high gears. Try the same
stunt with a low gear, and you might be surprised at how easily the
back wheel slips.

These outings to Filbert street were with several riders and they all
used the lowest gear on their good quality racing bicycles. There was
no wheel spin. Not all of them made it to the top but that has no
bearing on traction demands. Just the same, if you believe slip is
gear dependent, then we don't need to go to a steep hill. This can be
done accelerating on a flat road. If that doesn't offer enough
resistance then a road overpass can be used for a simulated hill, many
of these having as much as 10% grade.

Jobst Brandt
[email hidden]

Quoted message said:

Terry Morse said:

Quoted message said:

> The next time it rains around here, let's go for a ride and I'll
> show you a rear tire slipping on a climb. It happens to me often,
> without the benefit of tar snakes or metal grates. Maybe you can't
> make the rear tire slip with those monstrous big gears you like to
> use, but I certainly do with a 42" gear.

Quoted message said:

Quoted message said:

How does the gear affect slip on a hill? If the wheel torque is
sufficient to propel the bicycle, what does the contact patch care
who supplies the torque?

Quoted message said:

The gear affects slip on a hill because lower gears produce higher
wheel torque at the peak of pedal force, when standing. Mountain
bike riders know this phenomenon all too well, since traction is far
less on the dirt than on pavement. If my rear wheel begins to slip
when climbing, I click up a gear or two and try to move my hips
farther over the back wheel. It works.

Quoted message said:

Quoted message said:

Just for comparison, I have ridden up Filbert St in SF, the
steepest street in the city (31.5%) in the rain. It is a smooth
hand finished sheen concrete paved street with stairs for a
sidewalk. It produced no wheel spin.

Quoted message said:

But then you climb using comparatively high gears. Try the same
stunt with a low gear, and you might be surprised at how easily the
back wheel slips.

These outings to Filbert street were with several riders and they all
used the lowest gear on their good quality racing bicycles. There was
no wheel spin. Not all of them made it to the top but that has no
bearing on traction demands. Just the same, if you believe slip is
gear dependent, then we don't need to go to a steep hill. This can be
done accelerating on a flat road. If that doesn't offer enough
resistance then a road overpass can be used for a simulated hill, many
of these having as much as 10% grade.

Jobst Brandt
[email hidden]

I think slip is more weight dependent than gear dependent.

--
Bob in CT
Remove ".x" to reply

Bob Viggen said:

I think slip is more weight dependent than gear dependent.

Could you expand on that theory. What effect does weight have on
tire to road contact and how does this affect tire slip?

Jobst Brandt
[email hidden]

jobst.brandt said:

Bob Viggen said:

I think slip is more weight dependent than gear dependent.

Could you expand on that theory. What effect does weight have on
tire to road contact and how does this affect tire slip?

F = N * Cf

N = normal force
Cf = coefficient of friction

--
Chris BeHanna
Software Engineer (Remove "allspammersmustdie" before responding.)
[email hidden]
I was raised by a pack of wild corn dogs.

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Peter Cole said:

"Claire Petersky" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

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

Quoted message said:

Any opinions out there on road tires for commuting on steep hills in the
rain? I had some continentals but they wore out pretty quick and the
vittorias are a little slick on wet pavement.

I ride with Avocet Cross II tires for commuting. These are very durable and
in my experience, grip well. I can also get them over the rims, something
that wasn't true with the Michelins I used to have. Biggest drawback: the
bike shop sometimes has to order these for me because they don't always have
them in stock.

Really heavy, lots of rolling resistance -- these tires are made for unpaved
surfaces.

_ Not really, they are a pretty good compromise tire if you do
both pavement and dirt. If you do just dirt there are better
tires. They are a pretty good choice if you want a heavy duty
tire that rolls fairly well on pavement. Due to the extra tread,
they will also hold up to lots of miles and be potentially more
flat resistant. They are the only "cross tire" that I would
consider for everyday pavement use. You do pay a weight penalty,
but in my experience they roll nearly as well as a slick tire
of the same dimensions.

_ Booker C. Bense

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Quoth [email hidden] ...

Quoted message said:

Road traction is a measure of how well the
tire corners on wet pavement and this is interaction of the tread
rubber with micro-roughness of the aggregate used in the pavement,
concrete or asphalt.

Does this mean that the only way an 'average buyer' could find out if
a certain tire have good traction is to: 1. ride faster and faster
until it slip out on you or: 2. take a decision after listening to
marketing plays by makers?
I do not know which of the two would hurt you most physically, but
number two would probably dig the biggest hole in your wallet 😉

How did you come to the conclusion about colored thread, I gather this
is not something you just say?

thanks
mike anderson

Mike Anderson said:

Quoted message said:

Road traction is a measure of how well the tire corners on wet
pavement and this is interaction of the tread rubber with
micro-roughness of the aggregate used in the pavement, concrete or
asphalt.

Quoted message said:

Does this mean that the only way an 'average buyer' could find out if
a certain tire have good traction is to:

Quoted message said:

1. ride faster and faster until it slip out on you fall

Quoted message said:

or:

Quoted message said:

2. take a decision after listening to marketing plays by makers?

Quoted message said:

I do not know which of the two would hurt you most physically, but
number two would probably dig the biggest hole in your wallet.

Quoted message said:

How did you come to the conclusion about colored thread, I gather this
is not something you just say?

The colored tread was a try to match colors of mini cars in Europe to
work as a sales gimmick. I read about the development in Automotive
News and that the idea was scrapped for lack of durability and wet
traction. This dawned on me immediately because in the days of
Clement tubular tires that we all rode, red TT tires were available
for low RR but caused crashes in the wet. Umma Gumma light colored
tires from Specialized were furnished to the 7-11 team in Europe,
where several riders promptly crashed in the rain. The road tires
were promptly withdrawn from the market although with knobby tires
that seemed to make no difference.

The best track TT tires in the days of fine silk tubulars used latex
treads that didn't last more than a few kilometers but were touted
(logically so) as having low RR. Otherwise the same tires could be
had with a carbon black tread strip. As I recall these were called
Tipo-00. The inner tubes looked like condoms and held air long enough
for a track session.

http://www.bikepro.com/products/tires/spec_over.html

Jobst Brandt
[email hidden]

Thank you, for the info and for the link, very interesting.

First, 'RR' stands for: rolling resistance, right?

Not so long ago I saw a two-colored tire at one of my LBS, mainly
black with a light gray, elevated, center. Unfortunately I did not ask
what brand it was but I ask about the two colours, the guy said he was
not sure exactly why only that it was: 'better than normal tires'. I
saw it as a sales department gimmick and now I am sure of it, it might
even be dangerous.

To come back to the question on how to know if a road tire has good
traction. Is trial and error really the only possible solution, it
seems so antiquated?

We know certain aspects, slicks have best traction, at least on a dry
surface. Track cars has probably used slicks the longest, I assume
bicycle slicks is a spin-off effect. One thing: racing cars have
special, high traction, rain tires, do they not, but how about bicycle
rain tires, do they exist, I guess not?

Thanks again,
mike anderson

Quoth [email hidden] ...

Quoted message said:

The colored tread was a try to match colors of mini cars in Europe to
work as a sales gimmick. I read about the development in Automotive
News and that the idea was scrapped for lack of durability and wet
traction. This dawned on me immediately because in the days of
Clement tubular tires that we all rode, red TT tires were available
for low RR but caused crashes in the wet. Umma Gumma light colored
tires from Specialized were furnished to the 7-11 team in Europe,
where several riders promptly crashed in the rain. The road tires
were promptly withdrawn from the market although with knobby tires
that seemed to make no difference.

The best track TT tires in the days of fine silk tubulars used latex
treads that didn't last more than a few kilometers but were touted
(logically so) as having low RR. Otherwise the same tires could be
had with a carbon black tread strip. As I recall these were called
Tipo-00. The inner tubes looked like condoms and held air long enough
for a track session.

http://www.bikepro.com/products/tires/spec_over.html

Jobst Brandt
[email hidden]