MacShee98 said:
Last question: do braided-stainless lines increase braking sensitivity, feel? Do they reduce spongieness. Would they void my warranty?
I installed braided stainless steel brake hoses on my '90 coupe because I was autocrossing and the advertisement made sense. Basically the ad said that rubber hoses "bulged" on heavy braking and this made the pedal travel further (because the amount of brake fluid sent from the master cylinder increased if ever so slightly). This, so the ad claimed, produced the "sponginess". I never noticed any difference but thought, what the heck, they look cool. I'm not implying that they don't work, just that I never noticed any difference. I never even bothered to put them on my '92 coupe which had the larger diameter rotors included with the Z07 option.
I do remember that they interfered with something in the wheel-well. It might have been the wheel-speed sensor cables. The braided hoses were a little bit too short and they chaffed the cables (sorry, that was about 12 years ago). I simply put some heat-shrink tubing over them at the point of contact and replaced it periodically.
As to the warranty, my dealer never said anything, but then I never needed any serious warranty work. If they want to make a case to avoid performing warranty work I suppose *anything* that is not GM or GM-approved will give them grounds.
What I discovered was more important than hoses was the fluid used. We went autocrossing at the Dagget airport in Barstow, CA. It's in the Mojave Desert, and it was September, and it was hot. After a few runs I was negotiating a chicane at the end of a fairly long (for autocrossing) straight when the pedal went completely to the floor. It turns out what caused this was the fluid in the calipers boiling and forming bubbles. Bubbles are gas which is compressible (the fluid, for all intents and purposes, is not). The brake fade was due to putting much too much heat into the caliper for the fluid that is installed at the factory.
I flushed the brake system and refilled it with Motul 300C (buy two cans). It is designed to not boil at temperatures at or below 300 degrees centigrade (572 degrees Fahrenheit). It woked well for autocrossing. It might be overkill for normal driving, but it will not hurt. It is DOT 3 fluid.
Disc brakes work better when they are warm (the rotor expands when it gets warm decreasing the distance the pistons/pads need to travel) and what I have noticed about my Z06 is that because of the efficiency of the brake cooling ducts, the brakes stay too cool sometimes. This makes the first use after a long non-braking period less steller than the normal 3-wire-grabbing effect the system normally provides. It takes a few brake applications to get some heat into them, after which they work as you would expect. For autocrossing (Solo II), or Solo I track use, they are probably very effective. And they look cool.
Above a certain temperature the brake pad material becomes gaseous at the surface where it is in contact with the rotor. The gas causes the pad to "float" over the rotor. The effect is similar to coating the rotor with 5W-30 motor oil: it lubricates. This can be ameliorated (but not eliminated in extreme use) by switching to racing-grade pads (which squeal loudly when cold and produce prodigious amounts of caustic brake dust) or by cross-drilling the rotors. The holes let the gas escape. The problem with drilling is that it produces points where metal fatigue can begin. Cross-drilling stock rotors is not a good idea. Cars (such as some Ferrari models) are delivered with cross-drilled rotors made from steel designed to better handle stress cracking (although it can not be totally eliminated). You can purchase after-market rotors which are cross-drilled and made from the approriate grade of steel. Have a defibrillator ready when you get the invoice.
I used carbon-kevlar pads made by Porterfield Racing in Costa Mesa, CA (they were heavily into Trans-Am racing at the time and are located about a block from the Road & Track Magazine offices where you can see exotic cars being examined in the parking lot). Suprisingly, I discovered that they cost about as much as stock pads from the Chevy dealer. While autocrossing they worked wonders. They gripped extremely well. But driving back and forth to work was not so pleasant. They squealed loudly and covered the front wheels with heavy black dust after only a few miles. Even the rear brakes, which do not normally do that much work (brake bias directs more force to the heavily loaded front brakes and less to the rears because they tend to lock up easily as a result of weight transfer to the front during deceleration) generated enough dust to blacken the wheels. I didn't mind cleaning them virtually every day after work, but I discovered that they were eating the clear-coat on the wheels. Bye-bye racing pads.
There is a special paint you can buy which, when applied to the outer edges of the rotor, will change color depending on the highest temperature it is exposed to. You then compare the color to a chart which comes with the paint to determine *approximate* maximum rotor temperature. This is applied across the thickness of the rotor (along the cooling vanes), not on the area swept by the pads. You apply the paint using a small (1/8th inch) brush to create a very narrow band. You can do this many times, such as after an autocross run on a certain course, to see if changes you make to the brake system are helping to reduce temperature.
This may be more information than you wanted but it may be of use to someone else.
Ray
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