The Pros And Cons Of Different Brake Disc Designs
We all know the basic function of a disc brakes. A caliper pushes one or more pads onto the disc, causing friction and slowing the rotation of the axle it’s attached to. But while all systems operate on this general principle, the parts used for the job vary greatly.
Pad material can vary, there are many different kinds of caliper employed by both OEMs and the aftermarket, and the design of the discs can vary.
So, following on from our look at monoblock calipers, let’s examine the different kinds of brake disc:
Solid
The simplest kind of brake disc you can buy. As the name implies, these are just a solid block material. Specifically, iron. Cheap to manufacturer and cheap to buy, there’s nothing strictly wrong with them, but they won’t be as good at managing heat as the next kind of disc we’re going to look at:
Vented
Probably the most common type of disc fitted to modern cars. This design sees the two ‘faces’ of the disc spaced apart, giving room for cooling channels. These allow heat to escape, preventing the disc from getting too hot and cracking, while also increasing the life of the pads.
Originally featuring straight channels, ventilated discs have evolved through the years to improve airflow. In the image above from Brembo, you’ll see straight channels, curved channels and three different ‘pillar’ style designs.
Drilled
When a brake pad is put to heavy use, it releases gases and particles, forming a layer that prevents the pad from touching the disc as effectively - this is otherwise known as brake fade. Holes can be drilled through the disc to give the gas somewhere to escape while also reducing weight of the part, but in the process, the rotor is compromised.
A disc acts as a big heat sink, so sticking a load of holes in it means there’s less of it to dissipate heat. Plus, those holes can become stress points, potentially leading to cracking during heavy braking. In any case, modern brake pads aren’t as gassy as their predecessors, so the need for drilling has been reduced.
But still, on the road you probably won’t encounter such problems, which is why drilled discs are still a common sight on modern performance cars, where they undeniably look pretty good behind big, spangly wheels. Plus, they can be manufactured strong enough to make fracturing a rare occurrence.
Slotted/grooved
This slotted design attempts to answer the same question in a different way. Slots or grooves in the surface of the disc allow gases to escape, and there are additional benefits. The ‘scraping’ action introduced by the slots can clean the pad, and the edges of the groves increase friction, albeit at the expense of pad wear. And finally, like drilled discs, they look pretty awesome.
Groove designs vary, with one of the most distinctive being the ‘j hook’ (above) which is intended to offer the same debris and gas ejection properties while cutting down on vibrations. And if anything, they look even better.
Dimpled
Here’s option number three for letting those pesky gases escape. The surfaces are only drilled part-way through, leaving the structural integrity of the discs intact while still giving gases and debris a place to escape.
Dimples are combined with grooves on some discs, and you’ll often see drilled holes combined with slots. As to whether there’s any point other than looks, it’s hard to say.
Waved
Waved discs have been around in the motorcycle world for years, but keen to capitalise on its acquisition of Ducati, Audi began introducing the concept to some of its quicker cars a few years ago. A reduction in weight (because there’s less material) and better heat dissipation are the main advantages. As with a lot of the designs we’ve just spoken about, the looks are almost certainly a factor for these being picked by manufacturers and consumers.
Carbon ceramic
The most extreme way to approach heat management is opting for a carbon ceramic setup. A hot disc means hot pads, and that results in more gas and debris being released. So why not go for a different material than cast iron?
Carbon ceramic discs are much more resistant to heat, and are also less likely to warp or deform during heavy use, meaning they’ll usually last longer. As a bonus, they’re typically much lighter than their iron counterparts.
But there’s a reason their use still isn’t that common: cost. Carbon brakes are much more expensive to make, which means you’ll usually be charged for the privilege of optioning them on your new car. On ‘our’ old Audi RS3 longtermer for example, the carbon brakes were £4600. Plus when you replace them, you’ll be shelling out thousands to get the job done. You’ll need pads with a specific compound, and guess what - they aren’t cheap either.
Have you upgraded your brakes recently? What kind of disc did you go for, and why? If the answer is ‘it looked good’, we won’t judge! Get to the comments section and let us know.
Comments
Just changed my front discs on my car, it originally had ventilated discs which rusted badly and went with ventilated discs as well, but i can see a big difference in braking now.
My car started life with stock twin piston, and standard vented disc. Now wears a pair of 4-caliper Brembos with drilled and slotted rotors all around and ceramic pads.
The amount of times “thank god for Brembo” has been uttered makes it worth it alone. Hands down the best thing you can do to improve how your car drives and the best safety device you can equip too. Stopping now vs then can only be described as safe and controlled vs unsafe and unpredictable.
No performance car should be without performance brakes, full stop.
(See what I did there)
Stop it
https://www.youtube.com/watch?v=78wbht355R8
Perfect article, we need more of this kind
When I had my MK1 Skoda vRS. I changed the standard single piston calipers on 288mm discs to Tarox 6 pots on 312mm. Slotted disc due to it regularly going on track and pads were originally EBC yellowstuff (shockingly bad) but changed them to ds3000 for track work and a modified brembo pad from a Mercedes G wagon for the road.
Carbon Ceramics FTW
Unless carbon-carbon is involved
I have read a lot of articles and watched plenty of videos about these, and every time it seems that slatted design is the best.
Yet you barely see any slatted brake disks fitted by manufacturers. There are a few (like Aston Martin) but most go with drilled.
Surely there must be a reason other than looks (slatted disks look as cool as drilled)? Not just cost as well - you can see quite expensive supercars and even track toys (which are not concerned with looks as much) going for the drilled design. Yet every article claims drilled disks are almost pointless nowadays.
Everyone posts their brake discs so here is my rear right rusty boi
Slotted discs are quite noisy under use and depending on pad compound can wear excessively fast.
also a big point you forgot to mention is that carbon ceramic optimum performance temperature is much higher than iron rotors. It means for average street driven, it will performance worst and noisier compare to iron. But at the track, after things get heat up a little bit, carbon ceramic, then, would show its true performance.
I put new brakes on my camry that are vented, drilled, and slotted, with carbon ceramic pads. I got them in hopes that they would work better then my standard brakes which were having serious issues with fading. After getting them broken in properly I can manage a 40-0 stop quick enough to scrape the font of my car on the ground.
Not mentioned are floating discs, although shown in some pictures
Or carbon fiber, à la McLaren F1