overpowering the brakes with the engine

On Oct 13, 1:41*pm, XR650L_Dave > wrote:
> On Oct 13, 3:43*pm, gpsman > wrote:
>
> > On Oct 13, 8:46*am, XR650L_Dave > wrote:
>
> > > I think you've been driving something with a tiny engine so long you
> > > are not aware of the recent uptick in engine output even for many
> > > econo-boxes.
>
> > Or, as usual, you don't know what the **** you're talking about.
> > *-----
>
> > - gpsman
>
> Contributing absolutely zero as usual, I see.
>
> ****in' useless troll.
>
> I happen to know quite a bit about all the engineering/physics/
> thermodynamics of what's going on in the suggested situation.
>
> Dave

On dry pavement, stopped. Lock your brakes. Floor it. Notice all
that tire smoke that is _NOT_ appearing?

Granted that changes a few things. Brakes are not in 'antilock' mode
and vehicle momentum is not present. It does, however showthat the
engine (even after shifting down) cannot overpower the brakes.

Harry K

In article
>,
XR650L_Dave > wrote:

> On Oct 14, 10:22*am, harry k > wrote:
> > On Oct 13, 11:12*pm, Arif Khokar > wrote:
> >
> > > harry k wrote:
> > > > On dry pavement, stopped. *Lock your brakes. *Floor it. *Notice all
> > > > that tire smoke that is _NOT_ appearing?
> >
> > > There's a significant difference between static and dynamic friction.
> >
> > I do believe I made that clear in my post.
> >
> > Harry K
>
> The brakes can hold the rotor from moving against a larger torque than
> they can apply against a moving rotor, because static friction is
> greater than dynamic (sliding) friction.

Brake pad materials are chosen such that there is as little difference
as possible between static friction and dynamic friction.

The reason should be obvious.

--
Alan Baker
Vancouver, British Columbia
<http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>

"Alan Baker" > wrote in message
...
> In article
> >,
> XR650L_Dave > wrote:
>
>> On Oct 14, 10:22 am, harry k > wrote:
>> > On Oct 13, 11:12 pm, Arif Khokar > wrote:
>> >
>> > > harry k wrote:
>> > > > On dry pavement, stopped. Lock your brakes. Floor it. Notice all
>> > > > that tire smoke that is _NOT_ appearing?
>> >
>> > > There's a significant difference between static and dynamic friction.
>> >
>> > I do believe I made that clear in my post.
>> >
>> > Harry K
>>
>> The brakes can hold the rotor from moving against a larger torque than
>> they can apply against a moving rotor, because static friction is
>> greater than dynamic (sliding) friction.
>
> Brake pad materials are chosen such that there is as little difference
> as possible between static friction and dynamic friction.
>
> The reason should be obvious.
>
Still, there is very little heat generated with static friction (obviously,
since the rotors are not rotating and creating dynamic friction against the
brake pads), and yet there is a lot of heat generated with dynamic friction.

Look beyond just the brake pads--assuming the pads are not glazed or near
their wear indicators, or have some other brake pad issue--since there are
at least two other variables involved in the brake system:

Rotors: thickness (near the discard specification value, between the machine
to and discard value, at the machine to value, above the machine to value?),
and condition (any heat checks/cracking, any hard spots where brake pad
material has accumulated?) both matter in terms of braking effectiveness.

Brake fluid: cleanliness and mileage (i.e., when was it last changed? brake
fluid does get dirty and also absorbs water over time) matters most if the
brake fluid may be close to its boiling point.