Drilled vs. Slotted vs. Plain Brake Discs and pad wear

05.28.2013

I had someone on the Corvette forum ask about drilled vs. slotted vs. plain brake discs, and which ones are the toughest on pads. I threw together a summary of the merits of each:

Generally speaking, the more leading edges you have on the face pattern of the disc, the more places the pads have to 'grab' the disc face, and the more pad wear they will cause. It's a tradeoff...more leading edges= more bite, less leading edges= less pad bite.

So in order of pad wear, from the most pad wear to least pad wear, it would look something like this:

Drilled discs
Slotted discs with lots of leading edges ( X pattern, J Hook, etc.)
Slotted discs with straight slots
Plain face discs (without any slots or drill holes)

That said, we're talking about a modest increase in pad wear as we move up the ladder from the bottom. In other words, I wouldn't expect a drilled disc to wear a pad twice as fast as a plain face disc. It's really tough to attach a number or order of magnitude to it, so I'm not going to make anything up and pretend it's fact.

The hierarchy above holds true for noise as well. The more aggressive drill or slot patterns will create more scraping or whirring noises than a plain-faced disc. However, drilled discs are generally not the best performance option, as they are more prone to cracking. They look good, but stick with some form of slot pattern if you plan to run them hard.

Summary:
Drilled- looks good on the street but highest NVH, not recommended for track use due to a propensity to crack.

Slotted discs with lots of leading edges- Good on street, and best for track. Offer high pad bite with reasonable amount of noise and NVH on street. A carefully executed design such as the AP Racing J Hook distributes heat evenly throughout the disc and helps prevent disc cracking and uneven pad deposits.

Slotted discs with straight slots- Slightly less noise on street vs. an aggressive slot pattern, but also a little less pad bite. Slots that go to the outer edge of disc are bad because they create stress risers/cracks. Also, standard straight slot patterns tend to cause temperature gradients (hot spots around the slots and cool spots in between them on disc face), which can contribute to cracks and or pad deposits/judder.

Plain face discs (without any slots or drill holes)-
Lowest NVH for street use, but less pad bite on track vs. any of the slotted discs. More even heat distribution than a straight slot disc, and less prone to uneven pad deposits/judder.

Choosing which type is best for you is all about tradeoffs and what your goals are with your car.


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