Tires

On Thu, 02 Sep 2004 18:12:35 GMT, wrote:

Terry Morse writes:

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.

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.

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


I think slip is more weight dependent than gear dependent.

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

Bob Viggen writes:

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

Bob Viggen writes:

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

On Thu, 02 Sep 2004 19:27:10 +0000, jobst.brandt wrote:

Bob Viggen writes:

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.)

I was raised by a pack of wild corn dogs.

On Thu, 02 Sep 2004 19:27:10 +0000, jobst.brandt wrote:

Bob Viggen writes:

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.)

I was raised by a pack of wild corn dogs.

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In article xVZYc.1499$3l3.1435@attbi_s03,
Peter Cole wrote:
"Claire Petersky" wrote in message
link.net...

"dreaded" wrote in message
...


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 ...

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 writes:

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 fall

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?

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

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 ...

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