4RUNR

Anybody ever did that to cool the rotors better? Given that I don't drive anywhere where they would serve their purpose it seems like it could be beneficial.

Cebby

Mine has a little scoop on it to duct the air to the rotor. Without it, I think they might get hotter than it does now. Just my . 02

Unhappy99

Although not on a 4Runner, I have removed brake shields on a track car and it dropped temps 50 to 100F. To me, there isn't much of a reason to do it on a 4Runner. The only time I've had the fronts hot enough to boil fluid is when the 4600lb trailer's brakes went out, and I doubt having a bit of extra cooling would have helped.

Riding the brakes will boil them. Hi temp brake fluid like ATE SuperBlue, Motul 600 or Ford HD does help, but the real solution is learning not to overheat them. Flushing fluid once every two years also helps significantly as brake fluid is hydroscopic and boiling point drops fast as it absorbs water from the atmosphere.

4RUNR

My major concern is the warping of the rotor. When driven down hill or even slightly spirited driving the rotors warm up enough to warp slightly, when they cool down they are fine again.

Unhappy99

This is just another example of fine Toyota build quality. Per TSB BR007-00, 99 4Runners have improperly hardened rotors. If you're on the rotors which shipped from the factory, they're bad. Good news is that cheapo $40 rotors fix the problem. And no, turning a soft rotor doesn't work.
TSB Link

p.s. How's your fuel gauge?

4RUNR

To be honest, the shaking problem is almost non-existent when driving normally, and the rotors from what I gathered in the other thread only wore down 0.002" from factory in 85k miles and no grooves at all, very even wear.

If they were cooled better and not shaking at all Toyota might of made an everlasting rotor. At that rate they should last about 2 million miles

What is the defect? They are so soft that the material is re-deposited back to the pad?

(The fuel gauge flawless so far (knock on wood))

Unhappy99

Rotors are made of cast iron and then hardened by special heating and cooling cycles. When done properly, the entire swept area is the same hardness. When done wrong, then some areas are harder than others. As they heat up the softer areas expand more than the harder ones. The rotors surface warps and you feel vibrations under braking.

At about 35K miles, I could feel mine warp when heated but seemed ok when cool. By 45K, they vibrated all the time. They made it through Toyota's warranty period and no more, which appears to be the design goal. And yes, only a few thousandths of wear with no grooving. They're simply made bad and should be replaced.