Re: Braking 101

[frankbauer@thevine.net]

john sez:
>Now why don't we all just lock up our brakes each time we go into turn one
>at PIR?  Well, besides severly reducing overall tire life (due to flat
>spotting of the tires), you actually don't stop as quickly if the wheels
>are locked up as you do if you or the ABS is modulating the brakes
>properly.  Why?  Because the cf between the tire and the road gets worse
>too as critical temperatures are passed and because of other reduced force
>"sliding effect" issues I don't remember from my Engineering Dynamics
>classes of 10 years ago.

it's a fairly simple concept.  static friction is typically higher than
dynamic friction.  this means it is harder to get something to slide
than to maintain the slide.  (one notable exception is viscous coupling.)
of course it is a simplification to call the road/tire interaction static
since there is also tire slip and rubber deformation involved.

mike sez:
>>It seems to me that the kinectic energy contained in the forward motion of
>>the vehicle must be converted to heat and the bigger the mass (rotor) the
>>better to absorb/dissipate the heat. (vented rotors).

a more important reason for increasing the rotor diameter is to increase
swept area which directly affects heat transfer from friction material
to rotor.

another way of solving the reduced friction at high heat problem is to
use materials that maintain their Cf at higher temps (kevlar pads,
carbon fiber disks)

frank

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