Braking while turning

Chalo Colina writes:

Though I've not actually seen video of it, the crash that took
Beloki out of the Tour this year (which commands its own thread
right now) has been described as a highside.

I've highsided both pushbikes and motorbikes, and motorbikes are
worse.

That's why he hit so hard and it was from losing traction on a tar
stripe, that with the hot weather was gooey. It was a classic
slippery surface type crash as we see more often in Paris-Roubaix on
wet cobbles. Motos just throw the rider farther and with greater
speed.

Jobst Brandt

Palo Alto CA

ah yes:
that's one way to solve the question. drive a bald tired whatever but
several extensively framewheel tire combos on a geased surface or put
snow tires with studs on all two or four's or 18 if available.
but yagotta work up, gently whatever your relative ground speed(as
opposed to ur mitty speed) to the experimental level in the first
paragraph. experience it. develop awareness of what your doing. hey,
the dead are buried just outside the wall, dude.
and some can't get there. they're not fast enough to reach a
conclusion. they think they're fast enough and that's ok 'cause it
saves the ins. burial expenses we all share when budman meets live
axle and wooden wheels.

one question? front grip minus turning friction minus brake friction
gives us X grip. but the front does go in the "right direction" more
or less whereas the rear has no differential-the rear gets dragged
along. What does "drag along" mean in terms of grip and brake balance?

On Sun, 20 Jul 2003 19:44:15 -0000, Ray Heindl may
have said:

Doug wrote:

It's an important discussion, I don't mean to be flippant. But I
find there is more to worry about than skidding with the front.
If, for example, a stone large enough to lift the wheel off the
ground is hit, the front wheel will stop. When it hits the ground
again, an end over is a given. So on turns on steep grades coming
out of hills like in Malibu where rocks are prevalent, I am very
reluctant to use the front brake.

Why does the front wheel stopping cause an endo? I would think that
once it hits the ground again, it will either skid or start to rotate
again, depending on the amount of traction available. Is it because
the coefficient of friction between the brake and the wheel is higher
once the wheel stops rotating?

Yes. It requires more rotational force to break the grip of pads that
are in contact with a motionless wheel; this is a well-known principle
in physics. The gradient can be remarkable.

--
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anonymous snipes surreptitiously:

If, for example, a stone large enough to lift the wheel off the
ground is hit, the front wheel will stop. When it hits the ground
again, an end over is a given. So on turns on steep grades coming
out of hills like in Malibu where rocks are prevalent, I am very
reluctant to use the front brake.

Why does the front wheel stopping cause an endo? I would think that
once it hits the ground again, it will either skid or start to
rotate again, depending on the amount of traction available. Is it
because the coefficient of friction between the brake and the wheel
is higher once the wheel stops rotating?

Yes. It requires more rotational force to break the grip of pads
that are in contact with a motionless wheel; this is a well-known
principle in physics. The gradient can be remarkable.

I don't know where you get these mechanical models on which these
theoretical results are based but they are not true. One can easily
stop the front wheel on s spot of gravel and without letting up on the
brake continue a descent with the wheel again rotation when solid
pavement is reached. This assumes the length of the skid is not long
and not at a strong lean angle. This is not difficult for a ride who
knows how to descend.

The reference to static friction being higher is commonly called
stiction but it does not have significant effect on bicycle braking.
Riding over a wet tar stripe or a bit of ice is a more common form of
a wheel stopping but it isn't even slightly as treacherous as it is
made out to be by the worry warts.

I don't see why writers to these forums take pleasure in creating
horror scenarios supported by pseudo-science. They seem to themselves
be inept enough that they crash and and find pleasure in transferring
their pain and fear to others so they won't dare have it any better
than they.

Jobst Brandt

Palo Alto CA

anonymous snipes surreptitiously:

If, for example, a stone large enough to lift the wheel off the
ground is hit, the front wheel will stop. When it hits the ground
again, an end over is a given. So on turns on steep grades coming
out of hills like in Malibu where rocks are prevalent, I am very
reluctant to use the front brake.

Why does the front wheel stopping cause an endo? I would think that
once it hits the ground again, it will either skid or start to
rotate again, depending on the amount of traction available. Is it
because the coefficient of friction between the brake and the wheel
is higher once the wheel stops rotating?

Yes. It requires more rotational force to break the grip of pads
that are in contact with a motionless wheel; this is a well-known
principle in physics. The gradient can be remarkable.

I don't know where you get these mechanical models on which these
theoretical results are based but they are not true. One can easily
stop the front wheel on a spot of gravel, and without letting up on
the brake, continue a descent with the wheel again rotating when solid
pavement is reached. This assumes the length of the skid is not long
and not at a strong lean angle. This is not difficult for a rider who
knows how to descend.

The reference to static friction being higher is commonly called
stiction but it does not have significant effect on bicycle braking.
Riding over a wet tar stripe or a bit of ice is a more common form of
a wheel stopping but it isn't even slightly as treacherous as it is
made out to be by the worry warts.

I don't see why writers to these forums take pleasure in creating
horror scenarios supported by pseudo-science. They seem to themselves
be inept enough that they crash and and find pleasure in transferring
their pain and fear to others so they won't dare have it any better
than they.

Jobst Brandt

Palo Alto CA