I've tried researching this, but haven't found much in the way of real-world but "scientifically" valid testing. Most people seem to compare their old stock rotor with a brand new aftermarket rotor, usually replacing the brake pads at the same time, the latter often an upgraded part as well. Too many variables.

I'd really like to see someone take their stock rotor and machine it with cross-holes and/or slots (but no resurfacing). Throw it back on the vehicle (without changing the pads) and then see how it compares to the factory set-up, with respect to braking distance and heat dissipation.

If anyone knows of a YT vid like this, feel free to mention it.

Granted application and use matter substantially.
I have tried drilled and slotted and was not a fan (Hawk made in the States).
I have gone back to standard rotors.
I have whittled my Brands down to Brembo or Akebono. So far Akebono pads are still made in the states (at least in my offerings).
Brembo has moved their production to China but they still give the best performance in my opinion so I bite the bullet and have gone Brembo in my last two brake jobs.

EBC is likely the next I will try if I decide to change. They are still made in the States or the UK dependent upon product last time I checks. While they offer drilled, slotted, and dimpled I believe I will just stick with standard rotors with them as well.

quote:

Originally posted by P250UA5:

quote:

Originally posted by smlsig:
Close but not quite right. You will not find drilled rotors any any race car. Period. Most if not all race cars that are raced on road courses or endurance races have slotted rotors to aid in dissipating the gasses that “can” build up under very heavy (I.e. threshold) braking.

If I understand the OP he is asking about what to use on his trucks that will also be towing etc. We have used Cryoed Rotors for our trucks and also my Porsche race car as they will last longer than regular rotors.

The other major player is of course, the pads. Depending on how much initial “bite” you want in your brake application this will vary but which pad might be best suited for you is another discussion in its own right…

Case in point, F1 cars use solid faced rotors & they're pulling from 215 down to sub-100mph speeds

Haha that’s funny… F1 cars use custom ceramic rotors and probably cost 25-50K per corner. A little much for the OP I would think

Pad choice will make way, way more difference than whether a rotor is drilled/slotted/dimpled. If you want better braking, spend money on fancy pads, not fancy rotors.

So, drilled rotors were an attempt at increasing surface area for cooling air to pass over. They actually resulted in less surface area for the brake pad to act over, but when combined with ducting to force air into the interior of a vented rotor, they did provide more surface area for that air to pick up heat and take it away from the rotor. This had down-sides in addition to the reduced pad contact, like being more prone to cracking. Also, if you car does not have sufficient ducting forcing air through the center of the rotor, the drilled holes don't do much to help. Ducting is a double-edged sword though, because it can keep the rotors too cool during regular driving and increase pad wear by making the pads do all their work with friction rather than adhesion. See, when pads are cold they create heat through friction by rubbing against the rotor. As they get hotter, the surface of the pad melts and gets deposited on the surface of the brake rotor, and this layer acts like an adhesive, creating heat by the pad getting forcibly unglued from the surface of the rotor as it spins around. This adhesive mode of turning momentum into heat generally produces less wear than pure friction, so running your brakes too cold can make the pads wear faster.

Dimpled rotors were mainly meant to LOOK like drilled rotors without the cracking issues, but also without any heat transfer benefits either. Dimples are basically cosmetic.

Slots have some value in terms of allowing hot gasses from the center of the pad an easier route to escape under sustained, very hard braking. This is not a situation you are likely to run into, even in spirited driving on public roads. You basically need to braking at the absolute limit while doing laps on a track for this to happen. Slots actually provide slightly worse performance in normal driving because, like drilled holes or dimples, they reduce the contact area between the pad and rotor. It usually isn't enough to be noticeable without a stopwatch and controlled testing, but it is there. Of course, off-gassing can also be controlled in part with pad choice if it is a big enough issue.

So, what DOES make a difference when it comes to brake rotors? Mass is a big thing for the cast iron rotors that we use on most cars. The more mass there is in the rotor, the more heat it can absorb before overheating. Less mass can also be good if we are talking about just the center of the rotor that bolts it to the car. The fancy rotors with aluminum centers are lighter overall so they don't take as much power to spin, but still have that fat, heavy cast iron outer piece to absorb and dissipate all the heat. Speaking of mass, if you really care about braking performance, never have your rotors turned. It may save money over replacing your rotors along with your pads, but it means your rotors not only have less mass to deal with heat thanks to normal wear, but you are cutting even more mass off of the most important area to make it flat again. If you aren't having problems with rotors warping or your brakes overheating, feel free to get them turned. If you are trying to get the most out of your brakes, buy new rotors.

Some other things that can matter are the internal venting design and the thickness of the area that the pads squeeze. Unfortunately the rotor dimensions are usually pretty much fixed unless you want to replace your calipers so you may not be able to realistically get 'thicker' rotors. Also, good luck getting good data on which rotor's internal venting geometry is actually any better! If a company has made brakes for a race car (not just slapped their name on brakes some other place made) then they have at least had to worry about how to design those vents, but it is no guarantee they used any of that know-how on their consumer products. At lest your odds are better.

What about Cryo treatment? It is more of a longevity thing than a performance thing. I think the answer to whether it is worth it or not largely depends on how long you keep your cars. If you are one of those folks who will put 100k+ on a car and change the brakes more than once or twice while you own it, it might actually be worth it. If you are one of those people who buys a different car every three years, you probably won't change your brakes enough for it to matter. If you are road racing...well, you are probably eating up brakes fast enough that you can test for yourself and don't need me to tell you!

So, if rotors are, on a daily driver, not really much of a big deal when it comes to braking performance, what can you do if you want 'better' brakes? Start with pads, and a more accurate description of what you want than 'better'. Do you want immediate response? Do you want the pedal to feel less soft and squishy? Do you want brakes that fade less when they get hot from driving like a madman up in the hills? Figure out what it is you don't like or want to be better, and go from there. Semi-metallic pads often have better initial 'bite', especially when they aren't heated up. Ceramic usually deals with heat better and will fade less, but may not have the same maximum stopping force. Don't care about cold performance, but your brakes are getting so hot that you can see smoke coming from your wheel wells and smell them? Look at more of a racing-oriented pad from someplace like Hawk, Carbotech, EBC, etc. They will squeal, make tons of dust, and feel worse when they are cold, but you will be able to stop like a hero once they get hot. There are a pad compounds for weekend warriors who want to play on the weekend but drive to work the rest of the time, all the way to race pads that will make your rotors glow before they start to fade. There is an even wider variety of pad for street cars that want brakes to feel a certain way, but they aren't really trying to race them. The main things you can look for performance-wise are how grabby and immediate the pads feel, how consistent they are as they heat up, and how hot they like to be to work at their best. Most folks care about noise and brake dust as well, but it's up to you how much you care about that compared to performance, and those two things go right out the window if you move up to real race pads.

Oh, and if your brakes work just fine, but your pedal feels soft/squishy you can look at different brake lines (braided metal over PTFE tends to make the pedal feel harder than rubber lines.) Sometimes you can find different caliper guides/bushings, as well, but they are less common and usually require extra maintenance to keep them from binding compared to stock. You can always look at a total caliper replacement as well, which will often allow you to use larger rotors as well and greatly change how the brakes feel. You can also just change your brake fluid if it is old!

Sorry for the essay, but this is something I spent a decent amount of time obsessing over back when I was doing a lot of amateur racing!

- Bret

^^^This guy knows his shit.

This thread reminded me of a few things I see online, on Yootoob. Guys building engines saying "Don't do this, do this." And I often can't help but think.. I get what you're saying, but you dissemble engine all the time. May rebuild it a couple times year even. While I'm hoping to never have to do it ever again. I don't know if I should listen to what you're saying, if it really applies to "real world" stuff.

quote:

Originally posted by cas:
This thread reminded me of a few things I see online, on Yootoob. Guys building engines saying "Don't do this, do this." And I often can't help but think.. I get what you're saying, but you dissemble engine all the time. May rebuild it a couple times year even. While I'm hoping to never have to do it ever again. I don't know if I should listen to what you're saying, if it really applies to "real world" stuff.

I think what you're trying to say is one version is for track day & extreme street car driving vs everyday driver brake maintenance.
If you're in the second category, don't even consider drilled rotors and all the fancy parts stuff. Stick with stock or maybe a higher quality pad. Just don't go cheap on new rotors.

EBC solid rotors and pads are really good. I wouldn't do cross drilled at all as they warp/crack and eat the life out of pads. Slotted is good in a high performance application, like track racing, but really wear pads as well. I'd go with standard rotors or pads. I really liked my EBC ones on an expedition and they lasted, 50k miles and they still looked pretty good when I sold the vehicle. Brembo makes good stuff too.

I have drilled & slotted rotors on my Cherokee, but that's pretty much because it's what comes with the PowerStop kits and I've been very happy with their performance and longevity (no doubt b/c of pad quality).

-Rob

quote:

Originally posted by 220-9er:

I think what you're trying to say is one version is for track day & extreme street car driving vs everyday driver brake maintenance.

I was just being general, not brake related at all. Just something I think about question on taking advice from certain sources on the the net/youtube. It could just as easily be applied to shooting and guns. Info needs to be taken in context, but the people giving it may not be saying it with the same context in mind as the people reading it.