They are called directional tires. They provide better traction when spinning in
the proper direction.
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On their track, engineered like most roads, backward tires performed
fine. That was my experience on motorcycles. I'd run at 80 or 90 in
Ice was more interesting, but the coefficient of friction for tires is
about .15, so it was okay. Wet ice was trickier, with a CF of about .05.
Still, riding was safer than walking because my tires held better than
my hiking boots. I just had to remember I wasn't on dry asphalt.
One morning on a deserted interstate in heavy rain, I hit the low point
between two hills. I guess that's a saddle. I felt something new to me.
It felt like a CF of 0. I guess the road was flooded deep enough that
the rubber wasn't reaching the road.
I was afraid that if my tires started to slide from under me and they
suddenly got a good bite on the pavement at the other side, I'd be
slammed on my head. Riding a bike, I'd never paid attention to balance.
I did now. I sat very carefully and used my knees and hands to try to
hold the machine perfectly upright.
I'll bet invisible flooding like that is what causes most hydroplaning.
I guess directional tires can handle slightly deeper flooding if they
are mounted frontwards.
I believe hydroplaning occurs when surface has water, does not have to
be puddle(deep flooded water). Once I was heading down on a local
freeway doing 100kph in the rain when another guy merged in front of me
at very high speed, suddenly his car flew across median and speeding up
opposite direction perfectly and then caame to a stop slowly. He must
have realized how lucky he was and know by now hydroplaning.
When they tested on the wet track to see how fast they could maneuver,
they had no trouble. Maybe there was puddling too shallow to see, where
the guy lost control. The faster you go, the less water it takes to
float you. I see another possibility.
In the late 1970s, there were a lot of wrecks at a curve on I-95 in
Providence in the first few minutes of a rain storm. Engineers said more
rubber and oil than usual had been deposited there during a long spell
without rain. The water loosened it, making a slick surface. They said
it could happen anywhere. So if you want to race your motorcycle in the
rain after a dry spell, give the rain a few minutes to wash the roads!
On both motorcycles and bicycles some people mount the tires backwards
on purpose and swear by the results. While I'm sure tire engineers do a
lot of testing and computer simulation I sometimes think 'the pattern
looks kewl' plays a part.
Most definitely, particularly for mountain bike tires. Even slicks tend
to have arrows but the direction isn't all that important.
Most of the braking on bicycles (most wheeled vehicles for that matter)
is done by the front tire, while the driving force is transmitted by the
rear wheel. This leads to markings like
<--- rear front -->
since you want the most aggressive part of the pattern oriented
differently. Or sometimes not. When I'm riding in the desert I don't
like a really aggressive pattern on the front since it tends to dig in
and send you off in strange directions. I'd rather live with the
Motorcycles are the same. I've run several different flavors of DOT
knobbies on the DR650. The more off road oriented ones like Dunlop 606's
are better in snow and mud but on the loose, rocky roads around here
they tend to deflect on rocks rather than just pushing through. Those
waterbars with the thick rubber strips can be interesting too.
After they told me I was no longer welcome at school, I began flashing
my diploma so people would know I'd been honorably discharged.
Everybody thought I'd be perfect in the heat-treating pit at a knife
plant. All day long, I'd load about 1600 pounds of blades onto a
300-pound cart, push them up a steep concrete ramp, and unload them.
A lot of cars didn't weigh much more than my loaded cart. When somebody
parked in my way and I couldn't get the door open, I'd pick it up and
move it. I had a little secret: don't try to pick up both ends at the
Picking up a car by the bumper hurt my fingers because I didn't own
gloves. As long as I didn't get blisters, I figured it was okay. Bumpers
are so flimsy these days that I wouldn't dare try to turn my car around
in my driveway that way.
On Sunday, May 10, 2015 at 1:45:44 AM UTC-4, micky wrote:
My '86 Thunderbird Turbo Coupe came with unidirectional tires. I never unde
rstood what that was all about but when I rotated the tires, I made sure th
at the directional arrows on the sidewalls went the right way, figuring tha
t it couldn't hurt and might help.
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