Rubbing the tire on the road, is it really mathematically simple?

When I was in high school I was taught, or I read, that it's bad to turn
the steering wheel when the car is not moving. It's hard on the front
tires, wears out the tread, and one should be moving the car at least a
little when turning the wheel. Did they say that? Do they still?

I've been thinking about this and now I have doubts.

Seems to me any extra wear on the tread because of turning the direction
in which the tires point will be the same whether the car is moving or
still. It's harder to relate to the sliding motion of the tire on the
road surface when the car is moving, but it's clear when the car is
still. That seems to me to be the difference, but the vectors that
indicate rubbing seem the same either way.

I included the math group first because it seems like they would have
opinions.

micky wrote:
> When I was in high school I was taught, or I read, that it's bad to turn
> the steering wheel when the car is not moving. It's hard on the front
> tires, wears out the tread, and one should be moving the car at least a
> little when turning the wheel. Did they say that? Do they still?
>
> I've been thinking about this and now I have doubts.
>
> Seems to me any extra wear on the tread because of turning the direction
> in which the tires point will be the same whether the car is moving or
> still. It's harder to relate to the sliding motion of the tire on the
> road surface when the car is moving, but it's clear when the car is
> still. That seems to me to be the difference, but the vectors that
> indicate rubbing seem the same either way.
>
> I included the math group first because it seems like they would have
> opinions.

I would think that total tire wear would be the same but wear per unit
area would be different.

On 5/11/2019 4:13 PM, micky wrote:
> When I was in high school I was taught, or I read, that it's bad to turn
> the steering wheel when the car is not moving. It's hard on the front
> tires, wears out the tread, and one should be moving the car at least a
> little when turning the wheel. Did they say that? Do they still?

obviously all the wear is on one spot on the tire


>
> I've been thinking about this and now I have doubts.
>
> Seems to me any extra wear on the tread because of turning the direction
> in which the tires point will be the same whether the car is moving or
> still.

na, it is distributed all along the tire face, not in one spot


> It's harder to relate to the sliding motion of the tire on the
> road surface when the car is moving, but it's clear when the car is
> still. That seems to me to be the difference, but the vectors that
> indicate rubbing seem the same either way.
>
> I included the math group first because it seems like they would have
> opinions.
>

micky amok-crossposted to sci.math, sci.physics, and rec.autos.tech:
^^^^^
Please post here using your real name.

> When I was in high school I was taught, or I read, that it's bad to turn
> the steering wheel when the car is not moving. It's hard on the front
> tires, wears out the tread, and one should be moving the car at least a
> little when turning the wheel. Did they say that? Do they still?

Yes, of course. However, this is just a rule of thumb; the amount of wear
depends on the surface and the type of tread. For example, the wear from
turning a still tire on ice or snow is negligibly small compared to the
turning on asphalt.

> I've been thinking about this and now I have doubts.

You have not thought this through.

> Seems to me any extra wear on the tread because of turning the direction
> in which the tires point will be the same whether the car is moving or
> still.

It is not. When the car is moving relative to the ground surface (road),
and the wheel and tire are rotating the tire’s tread is experiencing mostly
rolling resistance/friction/drag with the road. When the car is at rest
relative to the road, if the wheel is turned, the tread is experiencing
mostly kinetic friction with the road.

The magnitude of the friction (a force) between two surfaces is calculated
as the friction coefficient (commonly: µ, mu) for the contact of the two
surfaces for the respective situation times the magnitude of the normal
force F_n on the body with significantly less mass (lighter body):

F_f = µ F_n,

whereas

F_n = F_g cos α = m g cos α

is the force with which a body is pressed against the ground surface by
gravity (actually the force that the ground surface must exert on the
lighter body to prevent it from continuing to fall freely towards the center
of energy–momentum of the heavier body, e.g. the center-of-mass of Earth).

α is then the angle of the ground surface to the tangent surface of the
heavier body:

Paul in Houston TX amok-crossposted:
^^^^^^^^^^^^^^^^^^
Please post here using your real name, “Paul in Houston TX” #74656.

> I would think that total tire wear would be the same but wear per unit
> area would be different.

What is the basis for your assumption?

F’up2 sci.physics

--
PointedEars

Twitter: @PointedEars2
Please do not cc me. / Bitte keine Kopien per E-Mail.

On Saturday, May 11, 2019 at 11:13:23 AM UTC-10, micky wrote:
> When I was in high school I was taught, or I read, that it's bad to turn
> the steering wheel when the car is not moving. It's hard on the front
> tires, wears out the tread, and one should be moving the car at least a
> little when turning the wheel. Did they say that? Do they still?
>
> I've been thinking about this and now I have doubts.
>
> Seems to me any extra wear on the tread because of turning the direction
> in which the tires point will be the same whether the car is moving or
> still. It's harder to relate to the sliding motion of the tire on the
> road surface when the car is moving, but it's clear when the car is
> still. That seems to me to be the difference, but the vectors that
> indicate rubbing seem the same either way.
>
> I included the math group first because it seems like they would have
> opinions.

A lot of stuff you learn in high school is theoretical and a lot of the times not practical. As a practical matter, most times you can avoid turning the front tires while stopped. Sometimes you can't. All the math and theory in the world won't change that fact. Don't worry about this and be grateful that you have power steering. As they say, don't sweat the small stuff.

On 12/05/2019 7:13 am, micky wrote:
> When I was in high school I was taught, or I read, that it's bad to turn
> the steering wheel when the car is not moving. It's hard on the front
> tires, wears out the tread, and one should be moving the car at least a
> little when turning the wheel. Did they say that? Do they still?
>

More importantly, it's hard on the steering linkage, which tends to be a
lot more expensive to replace.

Mind you, with modern power steering, clueless drivers, and longer
warranties, manufacturers have probably beefed up that part of the
mechanism.

Still, when you trust your life to a machine, treating it well seems
like a no-brainer.

Sylvia.

On 12/5/19 11:15 am, dsi1 wrote:
> On Saturday, May 11, 2019 at 11:13:23 AM UTC-10, micky wrote:
>> When I was in high school I was taught, or I read, that it's bad to turn
>> the steering wheel when the car is not moving. It's hard on the front
>> tires, wears out the tread, and one should be moving the car at least a
>> little when turning the wheel. Did they say that? Do they still?
>>
>> I've been thinking about this and now I have doubts.
>>
>> Seems to me any extra wear on the tread because of turning the direction
>> in which the tires point will be the same whether the car is moving or
>> still. It's harder to relate to the sliding motion of the tire on the
>> road surface when the car is moving, but it's clear when the car is
>> still. That seems to me to be the difference, but the vectors that
>> indicate rubbing seem the same either way.
>>
>> I included the math group first because it seems like they would have
>> opinions.
>
> A lot of stuff you learn in high school is theoretical and a lot of the times not practical. As a practical matter, most times you can avoid turning the front tires while stopped. Sometimes you can't. All the math and theory in the world won't change that fact. Don't worry about this and be grateful that you have power steering. As they say, don't sweat the small stuff.
>
What they really say;
Don't sweat the petty things but
don't get caught petting the sweaty things.

--

Xeno


Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

On Saturday, May 11, 2019 at 8:28:26 PM UTC-10, Xeno wrote:
> >
> What they really say;
> Don't sweat the petty things but
> don't get caught petting the sweaty things.
>
> --
>
> Xeno
>
>
> Nothing astonishes Noddy so much as common sense and plain dealing.
> (with apologies to Ralph Waldo Emerson)

Don't pet the sweaty things? I like it. The Lord is a shoving leopard.

On Saturday, May 11, 2019 at 7:14:36 PM UTC-10, Sylvia Else wrote:
> On 12/05/2019 7:13 am, micky wrote:
> > When I was in high school I was taught, or I read, that it's bad to turn
> > the steering wheel when the car is not moving. It's hard on the front
> > tires, wears out the tread, and one should be moving the car at least a
> > little when turning the wheel. Did they say that? Do they still?
> >
>
> More importantly, it's hard on the steering linkage, which tends to be a
> lot more expensive to replace.
>
> Mind you, with modern power steering, clueless drivers, and longer
> warranties, manufacturers have probably beefed up that part of the
> mechanism.
>
> Still, when you trust your life to a machine, treating it well seems
> like a no-brainer.
>
> Sylvia.

My method of avoiding excessive tire slippage when parallel parked is to use a floor jack to lift the front tires off the ground and swing the entire front end clear of the car in front. This saves excessive strain on the tires, steering linkage, the steering rack, and the power steering pump. Never having to replace the entire front suspension is pretty much a no-brainer. Thanks to years of practice, I can pull out of a space in only 2 minutes!