Contour Enthusiasts Group Archives Forums Modifications Brakes Slotted Rotors - Revisted

Please read this entire thread as it addresses common misconceptions! And again be sure to read the FAQ
-Andy

The only thing i have heard bad about the slotted rotors is that they eat the pads just a tad bit faster, but they do help in performance. Is there any truth to this? I doing my front and rear brakes and want to upgrade it to have good street performance. Im going to be running Hawk HPS pads with whatever i go with.

From what I hear they don't help much/at all for street performance and they will eat up pads.

What Kremit said. They are not as problematic as the Cross-drilled rotors, and they actually do have a performance benefit under some circumstances.

But they do cause your pads to wear faster, and they are not optimum, performance-wise, for anything but the most extreme, high speed, repeated-hard-braking situations. Hence, you probably don't "need" them.

Mod Edit: There are many misconceptions in the statement below, see Silver Snake's explanation further down.


All the slots are for are for additional cooling (more air flow & surface area) and will only benefit you in an instance where you're using your brakes a lot such as a track event, auto-x, racing, et cetera. For a daily driven car they're a waste and overkill IMHO. As the other posters mentioned they'll wear the pads quicker than standard rotors, will typically warp easier since they're not quite as sturdy, and can potentially crack near the slots too thus making them not as structurally sound (although not nearly as likely compared to cross-drilled ones). They do look kinda good though so if that's what you're going for then I suppose they can be worth it then. Just my $.02

Good stuff, thanks for the info everyone. Im just going to go with brembo blanks.

Can't go wrong with Brembo's (damn this sounds like bimbo's)

Originally posted by JohnnyBravo:

---

All the slots are for are for additional cooling (more air flow & surface area) and will only benefit you in an instance where you're using your brakes a lot.....

---

Actually, slots are not for cooling, airflow or surface area. Slotted discs are used to clean the pad or "wiping the fire-band" as its called in the industry. The slots sole purpose is to clean the top layer of the pad, and prevent glazing of the friction material surface. By maintaining a clean even surface, friction level or mu can be kept more consistent from stop to stop.

Originally posted by airman1:

---

Slots are there to help remove the fumes and brake pad vapor occuring after hard braking, thus helping in cooling of the pads not rotors/discs/...

---

No they are not. Please see above. Fumes are no longer an issue with modern brakes (last 20yrs), as pad out-gassing doesn't occur due to new manufacturing techniques and materials.

Originally posted by airman1:

---

Will slotted rotors crack easier than non-slotted ones? Maybe...

---

Yes. Always.

Originally posted by airman1:

---

Drilled rotors, regarding cracking, are acctually safer that non drilled because crack would stop at the hole and would not spread, while non-drilled rotors if they crack, it's over.

---

This just isn't correct. There are too many factors at play. I can show you drilled rotors that show crack propagation twice as big as solid rotors. It has to do with rotor design, cheek thickness, venting design, etc. There are too many factors at play to simply say "X rotor is better because its drilled"

Originally posted by airman1:

---

Rotors are drilled for weight savings and looks alone, there is no heat benefits in drilloing of the rotors.

---

Wrong. Appearance plays a major factor in rotor cross-drilling, that much is true. However, for automotive use (not motorcycle) weight is never a factor. The weight savings from a drilled rotor is insignificant. Its done for appearance and slight performance gains. If the rotor is thermally sized properly (i.e., it has enough thermal mass), x-drilled holes allow for slightly quicker cooling (at a loss of thermal mass). However, they will crack quicker than an identical solid faced disc. The performance gains are slight, and not one that will be noticed by even the most discriminating street driver.

Originally posted by airman1:

---

There is one concern with drilled rotors. Moisture, and water dropplets can accumulate in those holes and eventually end up under pads, thus creating a problem.

---

Actually, testing performed by both Brembo and Porsche has shown that x-driled rotors offer improved perfomrance in wet effectiveness. In simple terms, it gives moisrture and water vapor a place to go, instead of forming a boundary layer under the pad.


Not trying to be a jerk, just trying to "correct the tech".

Good info, Snake.

Any time.