4 x 4 300zx brakes

[Guest andrewH4integra]

Forgive me if this has been addressed here before I am new to the board. With that said I have been road-racing for years in my Acura Integra H4/ITA car and I am moving back into the 240Z for some nastalgia runs this weekend @VIR. I have the 300zx Vented rotors with the 4x4 calipers on the front with Carbotech Xp1108 brake pads, drums in the rear. The last couple of times I have had the car out I have had a lot of trouble with glazing the rotors. Pad material is being left on the rotors and it makes the breaking very unsettling like terrbily warped rotors. I just had the rotors resurfaced and I am hoping for better results this weekend. What causes this too much heat? too soft a pad (these are race compound pads)?? not enough heat?

[alexideways]

Did you go through the BEDDING procedure properly???

 

As contrary to most people's beliefs, when we say WARPED discs, it doesn't really mean that the discs are crooked, what happens is that the discs builds some hot spots and these spots wear down faster than the cooler spots and thus makes the pedal pulse, since the discs get thinner on those spots.

 

If you went trough the bedding procedure properly, you SHOULD have pad material that stays on the disc, it's called the transfer layer.

 

Brakes work in two ways, the most obvious and what most people think of when they think about how brakes work, is called ABRASIVE friction which is, as the name implies, produced by the pad material dragging on the disc's surface, this happens only before the brakes get to temperature.

 

The second way they work (if the bedding procedure has been followed cautiously) is called ADHESIVE friction, this happens when the brakes get hot enough. The disc spins, the pads make contact, heat builds up, the pad material starts to melt and STICKS to the TRANSFER LAYER and, as the discs continues to spin, it breaks the bond, stick, break, stick, break... which slows the car down.

 

If, while you're bedding the brakes, you happen to stop the car completely while the brakes are boiling hot, the pad will stick to the disc and leave a thick spot of material, which will make the brakes feel like you have warped discs every time the "thick" spot goes between the discs and pads.

 

If you have racing compound and you didn't bed the pads properly, first, before the brakes get hot enough to work under adhesive friction, they are so abrasive, that they'll just heat away at your discs and once they get hot enough, the abrasion will only get worst on those hot spots and the pads will also leave material only on the hottest spots, which will result in an undriveable car.

 

At the end of a race season, if you bedded your pads properly, it's not rare to see discs that are thicker than they were when new, due to all the material transfer.

 

This is also the reason why racing pads are no good on the street, cause they never get hot enough to work under the adhesive friction mode and they just grind away at your discs without offering the braking performance you were expecting.

 

This is also the reason why sports cars usually have rear drums for e-brakes, cause if you park a car with hot brakes and then set the e-brake, well you just glued your pads to the discs.

 

Hope it helped.

[Guest andrewH4integra]

Thanks for the reply, I dont think the bedding is the issue. I have bedded tons of pads with the integra and never had a problem. This has happened with more than one set of pads on this car. Basically since I started taking the car to the track the brakes have been an issue.