RE: What's the straight dope on SS brake lines?(long tech response)

[Brian McGarvey <brianm@zbt62.eastnet.gatech.edu>]

a cross drilled rotor is an engineering trade off in thermodynamics.
high performance motorcycles and autos nearly all have x-drilled for the
following reason.
the brake system works by friction (i know this is obvious to anybody who
has for got to disengage the rear p-brake, flames smoke etc...)
friction by definition creates heat at the braking surfaces. the heat gets
dissapated thru the brake system. If you are experiencing brake fade and
your system has good fluid the most common cause of this is the heat has
dissapated into the fluid and the fluid has heated the rubber flexible
tubing that goes from the rigid tubing to the wheels. Installing SS.
braided lines will eliminate this problem as the SS braid and the teflon
tube are not suseptable to expansion to the degree that the rubber ones
are. This comes at a cost the expanding lines will "save" your other
elements of the system at a cost of fade --> failure of the brake system.
The main problem is if you have upgraded alot brake failure can be caused
by boiling the fluid and turning it into a gas.<--- this is very bad. the
brakes go from hard to soft to zero in less than 2 - 3
applications.(experience on a Motorcycle and a Dodge omni)

next step.
You are still experiencing brake fade this is caused generally by the
elements of the system becoming too hot and causing rotor and/or pad
failure. ie. glazing as the recent poster talked about.

moving from solid rotors to vented rotors more than DOUBLES the heat
dissapation surface area. allowing the system to cool at faster rate.

<personal opinion>
I'm not sure what ppl think they are getting w/ slotted rotors other than
cool looks but the surface area increase for heat dissapation is very
small. I understand there is a train of thought about brake dust, but the
gains are marginal at best mostly i believe it is cosmetic.
</personal opinion>

cross drilling
If you are still having HEAT problems as the temp increases on the braking
surface in MOST cases the coeffiecient of friction DECREASES significantly
meaning that you have LESS braking power on the same surface area. So if you can't or
don't want to increase the braking surface area your choice is to increase
the heat dissapation surface area in hopes of keeping the same coeffient
of friction on a slightly decreased surface area. that is where the trade
off occurs. at low temperatures the braking force is smaller than before,
but at high temp the braking force drops off at a lower rate than it was
before the X-drilling. Once again unless you are racing / braking very
hard alot X-drilled are for cosmetic reasons.

The best step for stopping brake fade it to move to a vented rotor system
that is LARGER that what you had before. This is why my motorcycle has
dual solid (weight) cross drilled rotors that are approximately 1/2 th
radius of the front wheel. larger calipers w. more pistons server to
disperse the heat and provide a greater braking surface area. so the heat
per unit area is smaller.


Having experinced brake fade to failure on a mountain in a car and later
on a motorcycle, I tend to overbuild my brake systems. other problems that
you may get when upgrading your brake system. if you
have performance mismatches you may actually EXPLODE a brake pad under
heavy braking. Been there done that, yes on the street, coming down a
mountain. and as some on the list will probably agree stock systems tend
to let you know they are begining to fail and you should back off, a
highly modified brake system will give little warning and go from great
pedal to the floor in a _VERY_ short period of time.

Brian (ranting)
87 16v RIP  (had X-drilled)
85 Cabby dead tranny (vented rotors)
82 Cabby 16v Xdrilled in the front debating the 16v rotors for the rear
81S dunno dont care
91 VFR750F dual Xdrilled in the front, Xdrilled rear, SS lines, Huge front
fork springs, heavy front fork oil, sticky ass tires, fat rider.

On Mon, 10 Sep 2001, Scott F. Williams wrote:

> Marc wrote:
> > This is why you have vented rotors for any
> > serious braking setup. And if you are really serious,
> > the you have them drilled. Drilled rotors are not
> > necessary for street setup though,
>
> I say if you are really serious then you install better brake pads and or
> upsize the rotors/calipers/master cylinder. Drilling holes decreases the
> amount of brake surface and really isn't a great idea unless you've got
> brake mass to spare.
>
> Btw, I've got drilled rotors on just the back of my Scirocco for bias
> reasons. That is, I expect the front of my car to provide a greater portion
> of the stopping force. The holes in the rotors ensure that my pads clamp
> down on just air and voila!
>
> YMMV...
> --
> Scott F. Williams
> NJ Scirocco nut
> Golf GTI 16v rallycar
> Mazda 323 GTX turbo assault vehicle
>
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> http://www.usrallyteam.com
>
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