exploding brake pads! Re: What's the straight dope on SS brake lines?(long tech response)

[Gary Huff <scirocco86@home.com>]

Speaking of exploding brake pads, my A4 1.8T decided to lose about 1/2 of a pad on the passenger side rear wheel on vacation -- whoops. What a shitty VW flaw, one day 1/2 pad left, next day it's gone and im on the backing plate. It was my birthday, so I ordered cross drilled front & rear rotors, Mintex C-tech pads, stainless lines, and super blue fluid for it. WTF not, it needs a new rear rotor now, and the front pads don't seem to wear, they've chewed through 1/2 the rotor already though! Weird. Those of you with A4 Golf/Jettas, keep an eye on your brakes. I drive the shit out of this car, so I guess I should expect this to happen. 	-ghuff

On Mon, Sep 10, 2001 at 08:51:35PM -0400, Brian McGarvey wrote:
> 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
> >
> > Check out our rally team's website!
> > http://www.usrallyteam.com
> >
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