What Kind of Rotors Should I Get?
Updated June 26, 2007
You Don't need Drilled or Slotted Rotors for a Hummer.
While I'll agree to a certain point, here's some quotes from many known
brake engineers and brake manufacturers in regards to slotting vs. drilled
vs. normal.
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Darrick Dong; Director of Motorsports at Performance Friction: "Anyone that
tells you that drilling makes the disc run cooler is smoking crack."
Power Slot: "At one time the conventional wisdom in racing circles was to
cross-drill brake rotors to aid cooling and eliminate the gas emitted by
brake pads. However, today's elite teams in open wheel, Indy and Trans Am
racing are moving away from crack prone, cross-drilled brake rotors in favor
of rotors modified with a fatigue resistant slotting process."
Stop Tech: "StopTech provides rotors slotted, drilled or plain. For most
performance applications slotted is the preferred choice. Slotting helps
wipe away debris from between the pad and rotor as well as increasing the
"bite" characteristics of the pad. A drilled rotor provides the same type of
benefit, but is more susceptible to cracking under severe usage. Many
customers prefer the look of a drilled rotor and for street and occasional
light duty track use they will work fine. For more severe applications, we
recommend slotted rotors." (Note that even though Stop Tech sells both
drilled and slotted rotors they do not recommend drilled rotors for severe
applications.)
Wilwood: "Q: Why are some rotors drilled or slotted?
A: Rotors are drilled to reduce rotating weight, an issue near and dear to
racers searching for ways to minimize unsprung weight. Drilling diminishes a
rotor's durability and cooling capacity."
From Waren Gilliand: (Warren Gilliland is a well-known brake engineer in the
racing industry and has more than 32 years experience in custom designing
brake systems ...he became the main source for improving the brake systems
on a variety of different race vehicles from midgets to Nascar Winston Cup
cars.) "If you cross drill one of these vented rotors, you are creating a
stress riser that will encourage the rotor to crack right through the hole.
Many of the rotors available in the aftermarket are nothing more than
inexpensive offshore manufactured stock replacement rotors, cross drilled to
appeal to the performance market. They are not performance rotors and will
have a corresponding high failure rate"
From Baer: "What are the benefits to Crossdrilling, Slotting, and
Zinc-Washing my rotors?
In years past, crossdrilling and/or Slotting the rotor for racing purposes
was beneficial by providing a way to expel the gasses created when the
bonding agents employed to manufacture the pads...However, with today's race
pad technology, 'outgassing' is no longer much of a concern...Slotted
surfaces are what Baer recommends for track only use. Slotted only rotors
are offered as an option for any of Baer's offerings."
Grassroots Motorsports: "Crossdrilling your rotors might look neat, but what
is it really doing for you? Well, unless your car is using brake pads from
the '40s and 50s, not a whole lot. Rotors were first drilled because early
brake pad materials gave off gasses when heated to racing temperatures, a
process known as "gassing out." ...It was an effective solution, but today's
friction materials do not exhibit the some gassing out phenomenon as the
early pads. Contrary to popular belief, they don't lower temperatures. (In
fact, by removing weight from the rotor, they can actually cause
temperatures to increase a little.) These holes create stress risers that
allow the rotor to crack sooner, and make a mess of brake pads--sort of like
a cheese grater rubbing against them at every stop. Want more evidence? Look
at NASCAR or F1. You would think that if drilling holes in the rotor was the
hot ticket, these teams would be doing it...Slotting rotors, on the other
hand, might be a consideration if your sanctioning body allows for it.
Cutting thin slots across the face of the rotor can actually help to clean
the face of the brake pads over time, helping to reduce the glazing often
found during high-speed use which can lower the coefficient of friction.
While there may still be a small concern over creating stress risers in the
face of the rotor, if the slots are shallow and cut properly, the trade-off
appears to be worth the risk. (Have you looked at a NASCAR rotor lately?)
AP Racing: "Grooves improve 'cleaning' of the pad surfaces and result in a
more consistent brake performance. Grooved discs have a longer life than
cross-drilled discs."
