Rotors: Blank vs Cross Drilled vs Slotted and Warping

There is more misinformation about cross drilled rotors than anything else I can think of on a car. The general consensus seems to be that drilled and slotted rotors offer better performance than “blank” rotors. This is simply not the case.

At one point in time race cars did have cross drilled rotors, and this is probably where the idea that they offer increased performance came from. But if you look at any serious professional race car today, I would be shocked if you found any cross-drilling.

Like everything else, there are advantages and disadvantages to drilling and slotting a rotor. Fortunately, technology has progressed so that there is no longer a need to cross dill rotors and therefore, we don’t have to deal with its disadvantages.

The reason why rotors were drilled in the first place was to relieve the gas that was created when the pad material started to breakdown (burn). Since modern pads don’t gas off any significant amount, this is simply not a concern.

Many people and advertisements claim that cross drilling helps the rotor cool. I’m sure those little holes do help the rotor cool in some regard (possibly not measurable), but the effect in reality is completely insignificant. Furthermore, any benefit of extra cooling is most likely off set by the reduction of the rotors mass due to the drilling which lowers the overall heat capacity of the rotor.

So now that you know that there is no benefit to running a cross drilled rotor, we are left with a major disadvantage. What all of those little holes do is create stress risers and a surface that’s unevenly heated and cooled. The result is that the rotor becomes very easy to crack and makes a catastrophic failure much more likely. The worst situation is when a crack forms and connects between multiple holes – much like a connect-the-dot puzzle. This can lead to a large piece of the rotor breaking free which I can assure you is not good at all.

So why do all those high dollar cars like Ferrari, Lamborghini and Porsche have drilled rotors? Well, because people think it looks cool. The rotors on those cars fail when pushed hard as well, and the professional race teams that run these cars replace them with non-drilled rotors. In my experience, cross-drilled rotors just don’t last as long as a blank rotor. If you ever go to the track and find someone pushing a car hard that has cross-drilled rotors, put your ear near one of his wheels and listen carefully when he gets back to the paddock. You will hear small metallic pings and pops as the rotor cools unevenly. What you will be hearing is the sound of the cracks forming….

So what about slotting?

Slotting serves the same purpose as drilling but doesn’t weaken the rotor as much. Slotting is also advertised to “wipe” the surface of the pad preventing glazing. I don’t know how much of this is true or how much of an effect this has, but  the real world result of this is that your pads don’t last as long. Typically, if you glaze your pads, you have already surpassed the heat range of the material and the pad will most likely have “melted” onto the rotor surface creating an uneven transfer layer. I don’t see how slotting is going to prevent this.

So what really happens when the rotor is “warped”?

When you’re on the brakes and there’s a pulsing sensation or vibration, we typical call this situation warped rotors. Surprisingly, I have placed a dial indicator on so-called warped rotors to find that they have no run-out what-so-ever, and also, on new rotors that have run-out but don’t produce any pulsing.

What does happen is that the layer of pad material on the rotor surface builds up unevenly, and also, the metallurgy of the rotor can change states. The layer of pad material on the rotors surface, if unevenly distributed, will create hot spots. If these spots get hot enough, it can form cementite in the rotors metal – a rough iron carbide formation that creates a lot of friction, but is terrible at dissipating heat. The cementite formation can get so bad and cause so much friction that even when you are off the brake pedal completely, because your pads are always in contact with the rotor ever so slightly, it can create a vibration when driving normally. I have even mistaken this vibration as my tires being out of balance.

Uneven transfer layer buildup and cementite is what produces “warped” rotors, not run-out or distortion. Cementite is a problem with iron rotors, rotors made of other materials like carbon do not suffer from this problem.

Vibrating can also be caused by a crack in the rotors surface. If you have a vibration that only appears during hard or extended braking, it may be a crack. The reason for this is that the cracks opens up when the rotor is hot and closes when it’s cold. You may never even know that there is a crack if you never build heat in the system…

Let me digress a little bit – There is surely some uneven dimensional change (warping) to the rotor if you have a localized hot spot. But this seems to be only temporary and when the rotor cools, it returns to its normal flat state. I suppose you could drive through a puddle with very hot brakes and cause a permanent measurable change, but it must be rare.

If I have my rotors resurfaced, will that fix the problem?

In my experiences, no. When I have had my rotors resurfaced, it only cured the vibrations temporarily. Within a few months, they return even if I haven’t been doing any hard driving. So what gives? Most likely, parts of my rotors had turned to cementite and it was thick enough where resurfacing did not remove it all. Even if there was a small area left after resurfacing, that one spot will create a hot spot which will grow in fairly short order.

Food for thought:

  • So actually there is one benefit to cross-drilling and slotting but I didn’t want to mention it since it’s also insignificant – that benefit is in wet weather. It turns out that drilling and slotting either give a place for water to evacuate like the tread on a tire, or allows steam to gas through kind of like what drilling was intended for. I don’t know what really happens, maybe both. But either way, the initial bite tends to be better in the wet.
  • Many people have such strong convictions about rotor warping that they wont believe anything I say in this post. I dare those people to put an indicator on a ‘warped’ rotor and actually find the distortion in the rotors surface. Rotors do tend to have run-out even when new, but you would never know it as long as the run-out is in tolerance; so, don’t mistake some run-out for warping when the rotor had it from the day it was installed and when the pulsations in the brake pedal only started recently. Also, don’t let some fool mechanic cut your brand-new rotors to ‘straighten them out’ or to get rid of the in-tolerance run-out, this will just shorten the rotors life.
  • In general, cutting rotors is only a band-aid.
  • There is different levels of cross-drilling. Some rotors have many more holes per inch than others. The ones with a high density of holes suffer more than ones like the rotor at the top of the page. The results are the same when pushed hard.
  • On the street, drilled rotors are ok, but can create noise. The thing that kills drilled rotors is fast heating and cooling cycles over a wide temperature range. This is why no one uses them on race cars.
  • The transfer layer on the rotors surface is typically invisible in all but extreme cases. When the pad is overheated, it can leave large visible deposits on the rotors surface.
  • Rotors with curved vanes are significantly more efficient than those with straight vanes.
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75 Comments to "Rotors: Blank vs Cross Drilled vs Slotted and Warping"

  1. jim's Gravatar jim
    November 7, 2012 - 8:33 pm | Permalink

    i have cross drilled and slotted rotars. To there credit I have some things to say; Although logically the physics side about what you said concerning heat dissapation and so forth makes sense i have some food for thought. My front right calliper locked. I drove for 3 days on the high way upto 85 MPH or more with out knowing my brake was locked. On the 3rd day my car started vibrating. After all the excruciating heat abuse that the rotar was put through for 3 days my mechanic put the rotar though a test and it was completly unharmed. I only needed new pads and callipers. My (extremley suprized and knowledgable mechanic said) if it were any other rotar it would have been toast.

  2. David's Gravatar David
    September 16, 2013 - 11:05 pm | Permalink

    My car has had the rotors resurfaced 2 times, and I still get a shake while breaking. It seems like light breaking is the worse at highway speeds. Now I’m looking at getting new rotors and pads, you’re description says to use carbon based rotors to slow the cementite build up. Will aftermarket ceramic pads help keep the build up down, or is OEM the way to go?

  3. Howard Wiseman's Gravatar Howard Wiseman
    December 9, 2013 - 4:12 pm | Permalink

    No luck here with resurfaced rotors. I think the metal has lost its temper.

  4. Dan's Gravatar Dan
    March 5, 2014 - 7:24 pm | Permalink

    I am not sure if you know much about heat transfer or energy. If you are worried about your rotors getting too hot under braking, having crossed drilled rotors WILL help cool your rotors. Heat Capacity is the amount of energy it will take to raise a material by 1 Kelvin or J / Kg*K. The heat capacity of air is ~1000 J/ Kg*K depending on humidity while most metals are much less than that. For instance solid Iron ~100 J/KgK. If you have 10000 Joules of energy then it will increase a Kg of air by 10 Kelvin. While for the same amount of Iron it will go up 100 Kelvin! Saying crossed drilled and slotted rotors give no benefits to cooling is completely wrong! In general increasing surface area will help in cooling. Please do some research before posting, you are trying to discredit all the engineers building sports cars. #imtalkingaboutscience

    • Kevin's Gravatar Kevin
      April 24, 2014 - 9:36 pm | Permalink

      Dan, you seem to be confusing specific heat capacity with volumetric heat capacity. Let’s imagine that a solid iron rotor has 1% of its material removed by drilling. Its heat capacity will drop by almost 1%. The density of iron is very roughly 8 g/cm**3, whereas air’s density at sea level is around 1.2 Kg/m**3. That is equivalent to 0.0012 g/cm**3, or less than 1/6000th of the density of iron. Given your argument that air’s specific heat capacity (energy needed to heat a unit mass) is 10x that of iron, then the air in the holes will have 10/6000 or 1/600 of the heat capacity of the iron that used to fill them (its volumetric heat capacity is very low). Obviously the contribution of the air to the rotor’s heat capacity will be negligible and far less than what the removed iron used to contribute. The heat capacity of the rotor will effectively drop in proportion to the amount of material removed, but since so little material is removed this will not be noticeable.

      Of course, in the real world it is not a stagnant mass of air or iron that cools a hot rotor. Instead it is largely the constant replenishment of the air around the rotor with relatively cool ambient air (that, and radiation (ie, glowing) if the rotor is really hot). Even at low speeds, huge amounts of air are flowing around the rotor and carrying off heat. Providing a larger cooling area by drilling certainly *could* improve the rotor’s cooling, though predicting how much would be very hard to do analytically as the air in this region would be very turbulent. If the air is so turbulent that there is little net flow through the holes, then the extra surface area will not help much as the air inside will just get hot. My main point, though, is that air is significant because it’s always in fresh supply, not because a Kg of air can hold more heat than a Kg of iron.

      Incidentally, one of the best ways to reduce rotor temperatures is not to drill them, but to install brake ducts. If you read instructions for bedding track or racing pads, they will often advise you to cover up brake ducts, but they will not advise a longer or higher-speed bedding process for drilled rotors versus solid. That suggests that either the manufacturers have overlooked drilling, or they consider it less effective than ducting.

    • Steve's Gravatar Steve
      January 3, 2015 - 3:57 am | Permalink

      Drilling actually reduces the surface area and mass of the rotor. Slotting increases the surface area of the rotor but reduces its mass.

      • Rad's Gravatar Rad
        January 30, 2015 - 2:45 pm | Permalink

        Steve you may want to review your post as it doesn’t make sense

  5. jared's Gravatar jared
    June 7, 2014 - 10:53 pm | Permalink

    So, I just read an article on espn’s web site that states that the system that brembo developed after months and months of research starting with finite element analysis and moving to computational fluid dynamics followed by more advanced and rigorous tests for all the NASCAR teams they have their systems on, have slotted rotors. Hmmm… It also states that in the Martinsville race drivers apply thier brakes every 8 seconds for five hundred laps. Two turns x 500 laps = 1,000 applications per race where the rotors reach 1200 degrees with only 8 seconds to cool off. Pretty demanding. But yeah, NASCAR uses slotted rotors. But wait, they give no benefit, just look cool and no race cars use them. …………

  6. Dave's Gravatar Dave
    June 15, 2014 - 12:56 am | Permalink

    I would have to disagree with your statement that rotors rarely warp. I have put a dial indicator on numerous rotors in my shop and found them to be warped. I have a 2001 Silverado (bought new) that has warped every set of rotors that I put on it… from OEM, to cheap Advance Auto, to expensive drilled/slotted. The drilled/slotted actually lasted a few years prior to warping, suggesting that it is heat related and they do help dissipate heat better. The original rotors warped within the 1st year. If you haven’t seen rotor warpage with a dial indicator then you haven’t checked many. I once had a new set on a Ford truck that pulsated immediately and were out .005″ out of the box. Drilled rotors do have less surface are, so there probably is a slight reduction in braking performance, but in my case the increased reliability is worth the tradeoff. I got on here because they are warped again and I’m trying to find a good brand that will not warp at all. I have my doubts. I just think they were not designed to be heavy/large enough for the vehicle’s size.

  7. Steve Waclo's Gravatar Steve Waclo
    June 24, 2014 - 3:02 am | Permalink

    Hello all,

    There’s an outfit called the Society of Automotive Engineers (SAE) and here is a comprehensive report they did on this topic:

    http://home.wavecable.com/~vtucker/A4/rotors.pdf

    Wish I could cut through the 28 pages and provide some profound insight, but I’m afraid you will just need to read it yourself.

    Best wishes

  8. Laura's Gravatar Laura
    October 6, 2014 - 5:03 pm | Permalink

    I have stock pads and rotors on 2012 Accord sedan. I had the brajes checked when I started to hear noises. My mechanic said that the pads had started to crystalize, and rotors were”wharped”. He recommended replacing with drilled or slotted rotors. I did some mountain driving this summer. Would this make any sense?

  9. Kumar's Gravatar Kumar
    October 14, 2014 - 2:09 pm | Permalink

    Hello John and others,

    So for everyday driving on a sedan with squeaking noise and vibrations when breaking: do you recommend replacing stock blank rotors rather than fancy drilled or slotted rotors? Also, what if we just resurface and change break pads? I understood that just resurfacing is not 100% solving the problem, but seem like a cheaper alternative. But is it worth it?

  10. MD Putnam's Gravatar MD Putnam
    October 20, 2014 - 11:45 am | Permalink

    A more comprehensive SAE paper on drilled rotor performance:
    http://papers.sae.org/2006-01-0691/

  11. November 26, 2014 - 9:07 pm | Permalink

    Ive turned hundreds or rotors, Ives seen plenty of warp, and that that this guy don’t know crap about it period !

  12. Mark's Gravatar Mark
    June 1, 2015 - 4:02 pm | Permalink

    I have a Lexus LX-570, my rotors have gotten warped and discolored on multiple occasions and were replaced with factory rotors. Now after the end of my warranty period I took the car to Midas for brakes and rotors. The initial ones they used lasted less than 3 months. To fix the problem they are suggesting slotted and drilled rotors and carbon pads. Any other suggestions?

  13. Mark's Gravatar Mark
    June 1, 2015 - 4:03 pm | Permalink

    Hello John and everyone else,

    I have a Lexus LX-570, my rotors have gotten warped and discolored on multiple occasions and were replaced with factory rotors. Now after the end of my warranty period I took the car to Midas for brakes and rotors. The initial ones they used lasted less than 3 months. To fix the problem they are suggesting slotted and drilled rotors and carbon pads. Any other suggestions?

    Thank you,

    Mark

  14. Wes's Gravatar Wes
    August 13, 2015 - 7:49 pm | Permalink

    Hello John and Everyone,

    This post still seems to be alive so here’s my question. I have a 2010 Mazda CX-9 Touring, and I’ve recently noticed a shimmy in the steering wheel. The issue doesn’t occur under 65mph, but the faster I drive and harder I brake, the more the steering wheels vibrates (most noticeably coming down steep hills at faster speeds). This leads me to believe it is warped rotors… and I never turn a rotor. Always replace as I just don’t think it’s worth the money.

    Here’s my question… I’ve been looking at blanks at my local O’Reilly and they offer their “BrakeBest” rotors. $80 for a pair. Where OEM from factory will be $120 each. I did some research and BrakeBest rotors seem to be manufactured by Bosch (correct me if this is wrong). Is this a decent rotor to purchase? Have you heard of anything good/bad on this brand? Do you have a specific brand you would recommend?

    Thanks,
    Wes

  15. Dean Dupre's Gravatar Dean Dupre
    August 28, 2015 - 12:07 pm | Permalink

    Hi there,
    I have a 2014 Cadillac CTS-V, the front discs ‘warped’ after less than 12000 miles of driving. However, the car is an automatic, and ambient temperature here in Abu Dhabi is generally over 45°C. The discs were skimmed, but the problem has recurred after only covering another 3000 miles.
    The general driving conditions are free-flowing motorways, with the odd few miles in city traffic.
    Should the pad compound be changed to reflect the high ambient temperature?

    Many thanks
    Dean Dupre

  16. Josh's Gravatar Josh
    October 27, 2015 - 3:39 am | Permalink

    Hello John, and others. I’d like to say that I agree 100% with what you’ve said here. I don’t have an SAE certification, or an automotive degree if that even exists, but I do have real world experience. I brake hard, and I’ve used slotted, drilled, slotted and drilled and I’ve noticed that if there is a difference in performance from the fancy rotors versus blanks than it’s either negligible, or so insignificant that it’s not noticeable. With all the physics jargon thrown out on this post I’ll say that the best way to prove something is to go out and test it, not throw numbers, equations, and scientific lingo around. But on a lighter note, I’m still grinning about the argument brought up about NASCAR using slotted rotors during a race. I’m grinning because I didn’t realize NASCAR was racing. I wouldn’t call driving in a counter clockwise circle for hours a motor sport. I feel NASCAR is for the racing flunkies, and for the real race car drivers, to get ready for retirement.

    • Artofkicking's Gravatar Artofkicking
      March 29, 2017 - 10:41 am | Permalink

      So I guess Talking about braking from a sport that actually uses the brakes is somehow not relevant? Seriously if you’re saying drag racing counts where you only use your brakes once (often with a parachute back-up) I feel like the point is missed.

      What works best multiple times…I would hate to round that 100th turn with no brakes. lol

      • CSN's Gravatar CSN
        May 22, 2017 - 1:44 pm | Permalink

        I used to work in NASCAR, as an aerodynamicist. It is absolutely racing, and while all racing formulae are to some degree contrived I’d agree that circle-track racing is more contrived than most. That said, just like drag racing, the talent is finding and staying on the edge of the envelope on any given day. (And in all the other aspects on and off the track of course.)

        As for this nonsense: “the best way to prove something is to go out and test it, not throw numbers, equations, and scientific lingo around”, insomuch as it merits a response: neither on their own are sufficient. Science is broadly a rigorous method of not fooling yourself, and you are always the easiest person to fool. Practical experience is a critical part of doing good science. “Jargon”, when used properly, is a necessary way of being precise and concise to avoid ambiguity.

  17. Andy's Gravatar Andy
    November 16, 2015 - 3:00 pm | Permalink

    Cross drilling rotors is done to reduce their mass – See Newton’s Second law of physics.

    It is the same thing as putting lighter rims and tyres on your car or lightening your flywheel – rotational mass stores inertia, removing rotational mass frees up torque at the expense or power stored in inertia.

    Reducing the weight of the spinning components of your drive line will increase your acceleration as less torque will be required to accelerate, so the torque your engine produces (your power band) will be larger. The downside will be your fuel millage – without the stored energy of the extra inertia, your car will slow down faster when coasting.

    It is this last point that makes lightening your rotors with holes seem like the smart thing to do. However, reducing rotational mass elsewhere and having more contact pad surface on the brakes usually yields better results with out the issues already mentioned.

    Rotational mass has a ration of anywhere between 7:1 – 11:1 over static mass depending on who knows what…

    So, for the sake of argument, lets say that cross drilling removes a quarter of a pound from each rotor:

    .25 x 4 x11 = 11lbs of weight from the car. Hardly worth the issues noted above.

  18. Kevin the Engineer's Gravatar Kevin the Engineer
    November 20, 2015 - 5:33 pm | Permalink

    John Milmont,
    If drilled and/or slotted rotors are worthless ,why do car companies, race teams ect still defy all your “uhmmm wisdom”?
    The only thing that ever stopped a vehicle of mine from warping the front rotors, that came with horribly undersized front brakes was, powerstop replacements (drilled and slotted). schools out.

  19. IngyHere's Gravatar IngyHere
    January 10, 2016 - 12:51 pm | Permalink

    Wow. All this BS about how rotors transfer heat and deform but not a single mention of metallurgy. Steel is not Fe and it’s not Al, either. I understand rotors are made in certain grades of steel, but not all steel is the same and manufacturing process plus blend has a lot to do with product performance. I’ve had rotors made overseas that “warped” in three weeks whereas the same item made under better manufacturing standards lasted indefinitely. A true applied test would take identical rotors from the same batch, same manufacturer, same foundry and apply cross drilling and/or slotting to the same rotors. Then run them on identical cars under similar conditions.

    On another note, where can I read the SAE articles without paying through the nose?

    • Reuben's Gravatar Reuben
      January 17, 2017 - 8:59 am | Permalink

      Yes, I think this is an often overlooked aspect.

      The issue is that people have factory or other cheaper rotors and they warp or crack or whatever and then someone tells them to buy fancy slotted rotors, which turn out to be much better and then they come to the conclusion that the slots must be the only difference and therefore the slots are the key.

      What they are forgetting is that they likely just purchased rotors of an overall higher quality in terms of materials and manufacturing and that’s what’s making the difference.

      I used to be on the slotted bandwagon until I realised how good heavy duty plain rotors were and did some more thorough and realistic thinking about how likely it is that the slots and/or holes would be a noticeable benefit.

      I’ve done track days where I had factory calipers with high end plain rotors and pads and a number of other people (with the same model car and similar power) had fancy Brembo calipers and slotted and/or drilled rotors and mid level pads and I could out brake them all day. i could out brake them all day with practically zero fade.

      My performance was primarily due to the very high temp pads. high performance pads are tougher on rotors so you need higher quality rotors, which like you say, are often slightly different alloys than cheaper rotors. Some of these different alloys are also claimed to have preferable heat transfer properties but my opinion thats probably mostly marketing spin also.

      Next to pad choice and the overall mass and hardness of the rotors, slotting or drilling a rotor would have such a negligible difference in performance ether way that I could never justify the additional cost let alone justify any potential reduction of the structural integrity of the rotors or any increase in wear on my brake pads (good pads aren’t cheap).

    • Ryan's Gravatar Ryan
      April 4, 2018 - 10:22 pm | Permalink

      Steel? Are you kidding? Brake rotors are NOT made of steel. They’re made of grey iron, G3000 to G4000 usually. That’s why they need to be coated in order to prevent rust. Cross-drilled rotors are superior to blank rotors in bite, brake fade, and lower temperatures across a certain range, as proved in the SAE paper “The Effect of Rotor Crossdrilling on Brake Performance 2006-01-0691”. F1 rotors are not drilled because they use carbon ceramic rotors which require a lot of heat to function optimally, these rotors are designed to hold on to heat rather than dissipate them. Look at images of F1 brake rotors and you’ll see the even the vanes are much smaller than your standard Civic ventilated rotors.

      In street applications, cross-drilled rotors are superior. In racing applications, it depends on ruleset, as they are subject to certain rotor diameter and weight. Most of the times, maximum heatsinking is preferred over more heat dissipation, so blank or slotted rotors are the safer choice. In touring races, cross-drilled rotors are used often as braking points are followed by high speed straights, which makes greater use of airflow through the brake rotor.

  20. Dave W's Gravatar Dave W
    March 26, 2016 - 9:18 pm | Permalink

    So, I drive an ’08 Lexus GS350. I drive it the way I believe it was meant to be driven which means I had to have the transmission & AWD transfer case replaced at exactly 100K. Good on me eh? I’ve been through several sets of brakes including rotors. While this thread has been fun to read, the road tells the real story. I went from factory blanks to slotted only and then to slotted & drilled. I am heading back to high quality blanks with The best ceramics I can find. I change 100% of the fluid every time I do the brakes. Interesting that just today as I was disassembling the RR wheel to replace the bearing assembly and I found my rotor looks precisely like the image above which was a bit of a shock. Applied physics lessons aside (but truly appreciated), Mr. Milmont is correct.

  21. Bill's Gravatar Bill
    April 10, 2016 - 11:47 pm | Permalink

    I have read some different articles on this. There was a question in a post about the purpose of slotted rotors. My finding showed the purpose was to release gasses produced by the brakes. By releasing this gas the pads bite on the rotor instead if this cushion of air. They also help in wet conditions to allow water to push out again giving the pads a better surface to bite on.
    As far as my two sense. Ad far as drilling a rotor in rages to heat. I don’t believe the question is surface area dissipating heat. From my own experience the holes rather give the heat a place to go. In other words as the heat builds in rotors the heat has the holes as vents. Now I have no scientific proof of this however I did talk to some experts in the auto industry and that’s what the conversation was. Again these are opinions I heard as I am no expert. As far as that picture of the rotor on top of page I would guess it would be cracked. It looked like someone stood on the brakes for hour on that to the point it wore the rotor to no end. So regardless of being drilled that rotor went thru hell. Thanks

  22. Kareem Forbes's Gravatar Kareem Forbes
    May 26, 2016 - 5:42 pm | Permalink

    Hi, this is a great article. I replaced my 2006 Lexus IS 250 front pads and rotors with EBC grey iron rotors (slotted but not drilled) and with ceramic pads(EBC red stuff). This was probably in around 2009. The biggest advantage I found is that there was a great reduction in dust created by the ceramic pads compared to the factory pads and rotors, and pad lifespan. A few years into them I noticed vibration while braking from highway speeds. This past spring 2016 I noticed that the car now vibrates above 60km/hr and at 100km/hr the rearview mirror is blurry, so I guess it’s finally time to change them. The pads I was told still have 50% wear on them but the rotors sound to have warped as you say. Well can’t say I didn’t get my money’s worth. Thanks.

  23. Kareem Forbes's Gravatar Kareem Forbes
    May 26, 2016 - 5:43 pm | Permalink

    Hi, this is definitely a great article. I replaced my 2006 Lexus IS 250 front pads and rotors with EBC grey iron rotors (slotted but not drilled) and with ceramic pads(EBC red stuff). This was probably in around 2009. The biggest advantage I found is that there was a great reduction in dust created by the ceramic pads compared to the factory pads and rotors, and pad lifespan. A few years into them I noticed vibration while braking from highway speeds. This past spring 2016 I noticed that the car now vibrates above 60km/hr and at 100km/hr the rearview mirror is blurry, so I guess it’s finally time to change them. The pads I was told still have 50% wear on them but the rotors sound to have warped as you say. Well can’t say I didn’t get my money’s worth. Thanks.

  24. Jim Grace's Gravatar Jim Grace
    July 2, 2016 - 11:28 pm | Permalink

    I have a 96 Mustang GT road car slightly modified. I will choose slotted based on this article. The only goal is to have the best brakes possible in an emergency situation. The choice I have from the supplier is stock, slotted or cross drilled.

  25. Pips's Gravatar Pips
    July 9, 2016 - 7:00 am | Permalink

    I drive a Jaguar XKR in the UK. I have vented cross drilled rotors. All the holes are full of pad debris. They look cool on the Jag but as all the holes are blocked I fail to see what positive affect the holes could have son cooling. The amount of metal rom moved by the wholes relative to the complete rotor is tiny. Weight saving or change to heat capacity must be minimum.
    The rotors and pads are worn and need replacing but I will be replacing them with quality but blank (solid) rotors.

  26. Pips's Gravatar Pips
    July 9, 2016 - 7:04 am | Permalink

    I drive a Jaguar XKR in the UK. I have vented cross drilled rotors. All the holes are full of pad debris. They look cool on the Jag but as all the holes are blocked I fail to see what positive affect the holes could have on cooling. The amount of metal removed by the holes relative to the complete rotor is tiny. Weight saving or change to heat capacity must be minimum.
    The rotors and pads are worn and need replacing but I will be replacing them with quality but blank (solid) rotors.

  27. Pips's Gravatar Pips
    July 9, 2016 - 7:05 am | Permalink

    I drive a Jaguar XKR in the UK. I have vented cross drilled rotors. All the holes are full of pad debris. They look cool on the Jag but as all the holes are blocked I fail to see what positive affect the holes could have on cooling. The amount of metal removed by the holes relative to the complete rotor is tiny. Weight saving or change to heat capacity must be minimum.
    The rotors and pads are worn and need replacing but I will be replacing them with quality but blank (solid) rotors. I will report back if unitive a difference.

  28. Roland's Gravatar Roland
    August 3, 2016 - 8:35 pm | Permalink

    I drive a 2011 Altima SR…six speed and fun to drive. Are the OEM rotors cut thinner as I was only able to get two resurfacing turns done in 77k miles!
    Planning to replace them with OEM but Nissan wants $130 each for front rotors and $99 for pads. I work in Austin TX and do a great deal of stop and go driving…also drive our 80 mph toll road often so driving good distances at 85 mph is not uncommon.

  29. Roland's Gravatar Roland
    August 3, 2016 - 8:46 pm | Permalink

    I drive a 2011 Altima SR…six speed and fun to drive. Are the OEM rotors cut thinner as I was only able to get two resurfacing turns done in 77k miles!
    Planning to replace them with OEM but Nissan wants $130 each for front rotors and $99 for pads. I work in Austin TX and do a great deal of stop and go driving…also drive our 80 mph toll road often so driving good distances at 85 mph is not uncommon. Had issue trying to post and hoping it works this time.

  30. Roland's Gravatar Roland
    August 3, 2016 - 8:48 pm | Permalink

    ….any suggestions on good OEM quality or better replacement kits?

  31. Haider's Gravatar Haider
    November 28, 2016 - 6:22 pm | Permalink

    An excellent read.
    I think most forget that: drilling/slotting/ducting aside, it’s critical to choose correct and good quality materials appropriate for the application.
    As far as the average driver can take their daily on the road in terms of brake abuse: the single biggest difference in performance will be from pads. Also, putting our egos aside: we’re not race drivers, so our perception of brake performance is inadequate at best.

  32. Dave's Gravatar Dave
    January 29, 2017 - 8:21 pm | Permalink

    I just changed the front rotors only on a Volvo XC90. Rotor were factory blanks and I replaced them with “cheap” drilled slotted eBay specials. Old rotors mic’ed good but were “warped”. Brake thumping is gone now and the pedal weight when stopping is dramatically reduce (even my wife noticed and is thrilled). I could care less about the “science” behind them just very happy with the results.

  33. Simon's Gravatar Simon
    April 8, 2017 - 12:03 am | Permalink

    I drive a 2010 Peugeot 207 CC (don’t laugh, it’s a lot of fun for a small car) but under braking I get a huge amount of pulsing, almost like the ABS is kicking in except slower, plus uneven grab at different speeds under the same brake pressure. I’ve just watched a Youtube vide of someone replacing rotors and pads and it looks like it’s within my skill set (after buying a few more tools), but money’s tight and I need to shop carefully. Am I best off replacing pads, rotors, or both? Back ones only or front too? I don’t drive over 120kph so performance parts aren’t an issue, but I do a stop-start round-trip commute of 60km daily.

    @John Milmont – very well written article, found it via Google after researching plain or slotted rotors on eBay. Thanks!

  34. CSN's Gravatar CSN
    May 22, 2017 - 1:51 pm | Permalink

    Great article but I have to take issue with this:

    “You will hear small metallic pings and pops as the rotor cools unevenly. What you will be hearing is the sound of the cracks forming….”

    Pings and pops come from many parts that are differentially heated and cooled. My solid-rotored E63 M6 was pinging like crazy after coming back from a hard drive recently. Do heat-induced cracks even happen all at once, or grow slowly over time without a sound? I’m not sure, but you can hardly assess damage from normal heat pings. The damage probably occurs immediately after a braking events when airflow at speed cools the rotors far more rapidly than stationary convection.

  35. Jon's Gravatar Jon
    May 23, 2017 - 5:49 pm | Permalink

    So, You do not recommend Ceramic pads, or cross drilled rotors? I replaced my factoy brakes with cross drilled and EBC Red ceramic pads. Broke them in proper( Most people don’t know how to properly break in or “seat” pads) did all this 5 years ago, never had a crack. This brake upgrade stopped the car hot and cold much shorter distance than original. just now replacing w slotted / cross drilled and new ceramic pads. I am a true believer in ceramic pads. I have run many rallyes with this setup and had no problems from the braking system. https://ebcbrakes.com/product/redstuff-brake-pads/
    356 hp 08 jetta 2.5 turbo.

  36. Jon's Gravatar Jon
    May 23, 2017 - 5:50 pm | Permalink

    So, You do not recommend Ceramic pads, or cross drilled rotors? I replaced my factoy brakes with cross drilled and EBC Red ceramic pads. Broke them in proper( Most people don’t know how to properly break in or “seat” pads) did all this 5 years ago, never had a crack. This brake upgrade stopped the car hot and cold much shorter distance than original. just now replacing w slotted / cross drilled and new ceramic pads. I am a true believer in ceramic pads. I have run many rallyes with this setup and had no problems from the braking system.
    356 hp 08 jetta 2.5 turbo.

  37. Jake B's Gravatar Jake B
    June 20, 2017 - 7:15 am | Permalink

    Ferritic Nitro-Carburizing Brake Rotors are on my 2014 Malibu and I can honestly say that with they have not warped whatsoever and I have 65000 miles on them.

    https://www.acdelcotechconnect.com/pdf/MarApr_2012_TechCONNECT_R1.pdf

  38. Jake B.'s Gravatar Jake B.
    June 20, 2017 - 7:24 am | Permalink

    Y’all need to Google “Ferritic Nitro-Carburizing (FNC) Brake Rotors” … I can’t post the ACDelcoConnect PDF file because this site thinks its advertising or spam, but the Google result will have that at the top. They came with my 2014 Chevrolet Malibu and I can honestly say that with 65K miles I have completely smooth brakes with no warping or vibration. It’s amazing. OTOH, my wife’s Town & Country minivan, even with the Mopar rotors and brake pads only last 25K miles.

  39. Jake B.'s Gravatar Jake B.
    June 20, 2017 - 7:25 am | Permalink

    Y’all need to Google “Ferritic Nitro-Carburizing (FNC) Brake Rotors” … They came with my 2014 Chevrolet Malibu and I can honestly say that with 65K miles I have completely smooth brakes with no warping or vibration. It’s amazing. OTOH, my wife’s Town & Country minivan, even with the Mopar rotors and brake pads only last 25K miles.

    https://www.acdelcotechconnect.com/pdf/MarApr_2012_TechCONNECT_R1.pdf

  40. Jake B's Gravatar Jake B
    June 20, 2017 - 7:26 am | Permalink

    Y’all need to Google “Ferritic Nitro-Carburizing (FNC) Brake Rotors” … They came with my 2014 Chevrolet Malibu and I can honestly say that with 65K miles I have completely smooth brakes with no warping or vibration. It’s amazing. OTOH, my wife’s Town & Country minivan, even with the Mopar rotors and brake pads only last 25K miles.

    https://www.acdelcotechconnect.com/pdf/MarApr_2012_TechCONNECT_R1.pdf

  41. Dan's Gravatar Dan
    November 19, 2017 - 3:18 pm | Permalink

    You are defensive and lazy. Use goggle and do do the work yourself you may learn something in the process. You are not an engineer, we have explained the facts to you, but we can not understand them for you, that is called learning.

  42. Fred Ernst's Gravatar Fred Ernst
    February 12, 2018 - 3:48 am | Permalink

    I would disagree with the statement that round holes in rotors are “stress risers”. They are usually associated with sharp inside corners (like the inside corners of the slots in rotors). If you punched square holes in the rotor, each inside corner would be a stress riser. If you had a rod that suddenly went from 1″ dia to 1/2″ dia, that step would be a stress riser. That is why you would change dia. gradually (taper). So, I don’t think a round hole would be a stress riser in a rotor. By the way, I drive a BMW. It came with blank rotors from the factory (no holes), and I replace them with OEM blank rotors.

  43. Darshan Murphy's Gravatar Darshan Murphy
    March 27, 2018 - 1:03 pm | Permalink

    John M,

    I am an engineer, and I know or understand 99% of what has been discussed… This is the best write up on the issued of enhanced rotors and warping I have read so far. Kuddos! I agree with 99% of what you have said… but I just have one last question… Its the simpler question….. Since my 76 Nova and my 72 Cutless, I have not owned an American Car that doesn’t suffer from “warped” rotor syndrome!! Horrible! And ever since I have been on a crusade to find the holy grail of rotors.. No luck yet, and no expertise that is consistent as to what to do or what to buy… Thus the simple question for you: What is the best rotor (type or Brand or both) to buy? And what is the latest on your Hawk ceramic pads? My 2014 Impala needs rotors and pads in the next month. If you can help that would be great

    (Oh by the way everyone, anyone can get a paper or report to say anything they want!! So just because it has SAE on it, or came from their library does not mean it has any validity! And any report or paper that fails to list assumptions and all variable values, and follows the general scientific method, fails on the first word!! (John has it right) Only Peer reviewed material carries any amount of respect and validity)

    • May 22, 2018 - 11:13 am | Permalink

      SP Drilled , are on my W-body and all pluses NO VIBES 75kmi little pad wear too.

  44. Robert's Gravatar Robert
    May 29, 2018 - 2:40 am | Permalink

    Very educational exchanges. I chased down more opinions on rotors and have decided on plain ones, and on Centrics, based on your recommendations and Amazon reviews. I also have been chasing down prices. Amazon’s parts finder for my 2002 Base RSX SUCKS! and gave me the wrong part number for the front Centric rotors and a $53.54 price each. So far, carid.com has the best deal at $27.29 each. Amazon had a price of $73.43 for the front Hawk PC pads, also based on your recommendations. So far, various websites have them at prices of $36, 40, 44, 44, and $69. One concern, however, is that the four cheapest sets are from websites ending in “.top” and “.xyz”. Wikipedia lists the .top domain as apparently legit, but another source talks about scams on that domain. I suppose I’m protected through my credit card company or Paypal, whichever they accept, but I’m hesitating a bit. Anybody know anything about those domains or any other strange ones? This has been an all-day project, and I thank you for pointing me in the (hopefully) right directions.

  45. Dustin s rigsby's Gravatar Dustin s rigsby
    June 16, 2018 - 9:58 am | Permalink

    why does every street bike have drilled slotted rotors then

  46. Dave Newman's Gravatar Dave Newman
    August 1, 2018 - 7:09 am | Permalink

    I have a 07 saturn vue replace front brakes an rotors about 3,000 miles ago. When the car is cold and driving slow brakes are fine; but on the highway, it feels like the rotors are warped. Can i get away with just up grading the pads .

  47. Cole Thomas's Gravatar Cole Thomas
    December 14, 2018 - 3:15 am | Permalink

    Solid article. Driving a 2015 Jetta TDI with solid rear discs, been dying to get ventilated as I have at least a 40/60 brake dispersion front/rear – sometimes swear its 30/70, dust builds first on rear. Point, I have 23k on all 4 rotors/pads, solid OE spec etc. Solid rotors in back have dark even line in middle of contact patch- 1/2 inch polished inner and outer portion of contact. My rotors are one time use parts (found that out the hard way). Would my issue solely be on the pad side of things and try replacing only the pads, or is this a heat issue and try to avoid this with a slotted solid disc with performance ceramic pads?

  48. Dan D's Gravatar Dan D
    December 17, 2018 - 12:39 pm | Permalink

    This is a very interesting conversation. I would like to add something that seems it was not mentioned and that is leased vehicles. I have leased for decades, all Lexus. Since the second gen Lexus IS, I have had them. And every 15K miles or so (about half way of the lease) I have to replace the front brakes (and maybe the pads on the back). I live in Miami FL where it is hot most of the year but then it can rain at any time and water is very cold from that rain. I understand very well the pros and cons for each option when it comes to rotors and pads, but I find that for a lease vehicle, since I don’t have to worry about it for more than three or four years, that I am better replacing the stock rotors for a set of either crossed-drilled or the combination of crossed-drilled and slotted. Why? Because in my case, the replacement will last me for one and a half to two years before I return the vehicle and get a new one and in my experience, those work best for the rain and they do avoid warping when it is very hot, I have been driving for an hour or so (brakes are burning hot) and it starts to rain “cats and dogs” out of nowhere, flooding streets in a matter of 10 to 15 minutes. I do not care if the brake life will be short because of cracks (if they ever happen), but I do care about being able to brake in such wet situations, and crossed-drilled are the best. I do buy good quality from good brands, not the top of the line (no need) but not cheap ones either. All the physics, math, real life testing and opinions are good to read and understand, but when it comes down to reality, each case is different, and in my case, all the cons for those type of brakes are irrelevant as most likely, will not affect me and I will be getting a new vehicle before anything noticeable could happen to the brakes. Cheers.

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