Installing Slotted Rotors and Ceramic Brake Pads
Rotors: Blank vs Cross Drilled vs Slotted and Warping Automotive Thinker - Discussing apologise, free wifi codes and passwords you finer points of automobiles There is more misinformation about cross drilled rotors than anything else I can think of on a car.
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.
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.
Many people and advertisements claim that cross drilling helps the rotor cool.
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.
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 drilled rotors vs drilled and slotted 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.
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?
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.
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.
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.
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.
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.
But either way, the initial bite tends to be better in the wet.
Some rotors have many hotel and seven casino silver 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 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.
When the pad is overheated, it can leave large visible deposits on the rotors surface.
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.
I have updated this post to reflect this information.
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.
Will aftermarket ceramic pads help keep the build up down, or is OEM the way to go?
So unfortunately, the problem is with the iron itself in typical car rotors and not the pads.
Unless you are driving very hard to the point of fading your brakes, good pads and rotors should not develop vibrations for a very long time… it does seem to happen eventually though.
I free username and generator 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.
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.
Its heat capacity will drop by almost 1%.
That is equivalent to 0.
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.
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.
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.
Drilling actually reduces the surface area and mass of the rotor.
Slotting increases the surface area of the rotor but reduces its mass.
Dan, I believe you are missing please click for source many other factors.
Now prove to me that cross drilling rotors has a significant effect on cooling.
Those holes must help, right?
Because race cars have cross drilling.
Hmmm… It also states that in the Martinsville race drivers apply thier brakes every 8 seconds for five hundred laps.
But yeah, NASCAR uses slotted rotors.
But wait, they give no benefit, just look cool and no race cars use them.
Slotting see more seem popular these days with race teams that maintain iron rotors, but what exactly are they saying the slots do?
I would like to see an objective number on the improvement over a blank rotor.
Remember, this is suppose to be a science, and scientific things are measurable.
Best wishes Hi Steve, I was a member of SAE when I was in college.
I would like to know what pads were used for his tests and also what car was used.
I would like to know if during his test, the rotor had a OEM style heat shield behind it which usually blocks the intake of click rotor.
This should effect the results of his crossdrill tests which I feel are very incomplete.
Furthermore, he is confusing and not at all definitive on the relationship of crossdrilling and cooling.
He says it increases the cooling and heat transfer ability of the rotor, but this raises the question: does the rotor also get hotter than a blank rotor?
Heat transfer works both ways… He also has a picture of a drilled hole being blocked with brake debris which would suggest no flow through the holes at all.
Another question I have is: On monticello casino and raceway expansions car with ducts running directly to the center of the rotor, do cross drilled holes still act as an intake or is air now being expelled through the holes?
Hole pattern: Interleaved I think everyone could agree that this would be a lot better.
On the topic of glazing: Glazing is associated with overheating a given pad compound.
Under normal operating conditions, a pad does not glaze.
Clearly, as I and many of my readers have experienced, pushing a street pad hard will lead to glazing.
But if a race pad is used and never overheated, will glazing be an issue?
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?
Drilled rotors do nothing other than look cool.
They have no effect on squeaking.
There can be a few reasons for squeaky brakes, like caliper issues.
But most likely its the pads you are using.
If your rotors are still good, get them resurfaced and try a different pad.
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.
Thank you, Mark Slotted and drilled rotors will do nothing to cure this issue.
Is this happening to all your rotors or just one?
If its just one, that would sound like a stuck caliper.
If all, sounds like you are really hard on the brakes.
If you just are hard on them, then I would look for a different pad.
Dont get anything ceramic.
This leads me to believe it is warped rotors… and I never turn a rotor.
I did some research and BrakeBest rotors seem to be manufactured by Terms conditions freedom 251 correct me if this is wrong.
Is this a decent rotor to purchase?
Do you have a specific brand you would recommend?
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?
The only high temp option would be to move into a race pad, and those are kinda annoying on the street so they are not really a good idea.
You might want to experiment with different pads.
I just got Hawk PC Performance Ceramic pads and I have been impressed with them on my street car.
In fact, this is the first ceramic pad that has ever impressed me.
If you find that only 1 rotor is having this problem, I would check for a stuck caliper.
It happens even on new cars.
Hub caps can also restrict, or enhance air-flow over rims, depending on their design, helping to dissipate that heat, or contain it.
Tire Rims They surely do, but for a single piece rotor the type found on typically every carI have wondered if the cooling effect they have negatively effects the rotors.
The issue is that the center of the rotor already heats and cools at a different rate than the surface that the pads touch.
The cooling effect of the wheel most likely makes these temperature differentials greater, putting more stress into the rotor.
This is an issue because its not uncommon for rotors to crack from all this stress, even if they are not cross-drilled.
Hello John, and others.
I feel NASCAR is for the racing flunkies, and for the real race car drivers, to get ready for retirement.
So I guess Talking about braking from a sport that actually uses the brakes is somehow not relevant?
What works best multiple times…I would hate to round that 100th turn with no brakes.
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.
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.
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:.
Hardly worth the issues noted above.
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.
You should probably read my post before commenting.
I already explained why car companies put them on street cars.
I also said that i was not aware of any professional races teams that run drilled rotors.
So please show me these race teams that are running them.
Also, as far as slotting, I said I was not clear on its benefits.
Slotting does not weaken the rotor like drilling does and may provide some benefit in clearing the rotor surface from debris.
Furthermore, I doubt you are telling me the whole story with your experience.
All this BS about how rotors transfer heat and deform but not a single mention of metallurgy.
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.
Then run them on identical cars under similar conditions.
On another note, where can I read the SAE articles without paying through the nose?
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.
My performance was primarily due to the very high temp pads.
Some of these different alloys are also claimed to have preferable heat transfer properties but my opinion thats probably mostly marketing spin also.
Brake rotors are NOT made of steel.
F1 rotors are not drilled because they use carbon ceramic rotors which require a lot of heat to adventure game on python optimally, these rotors are designed to hold on to heat rather than dissipate them.
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.
Good on me eh?
While this thread has been fun to read, the road tells the real story.
I am heading back to high quality blanks with The best ceramics I can find.
click at this page change 100% of the fluid every time I do the brakes.
consider, comfort inn and suites casino tampa fl have 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 appreciatedMr.
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.
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!
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.
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.
Am I best off replacing pads, rotors, or both?
Back ones only or front too?
John Milmont — very well written article, found it via Google after researching plain or slotted rotors on eBay.
The pulsing is coming from the rotors — what you should be interest in is how it got that way.
There is a few reasons why this happens, but it does happen naturally over time.
Over time, rotors rust especially if you live in an area with snow and salt and they always rust at a different rate under the pad area.
This creates an uneven surface which you feel as pulsing.
This is probably the most common reason for pulsing in everyday cars.
Because you want to save money, I would start by replacing the front rotors and pads first.
Then, see how the car is after that.
If its still happening, then do the rears.
Its always a good idea to do the brake fluid too since its probably been in there since the car was new.
What you will be hearing is the sound of the cracks forming….
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?
The damage probably occurs immediately after a braking events when airflow at speed cools the rotors far more rapidly than stationary convection.
So, You do not recommend Ceramic pads, or cross drilled rotors?
This brake upgrade stopped the car hot and cold much shorter distance than original.
I am a true believer in ceramic pads.
I have run many rallyes with this setup and had no problems from the braking system.
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.
I agree with 99% of what you have said… but I just have one last question… Its the simpler question….
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 Darshan, I dont think the issue is your rotors, its drilled rotors vs drilled and slotted likely the pads.
I have found that a lot of pads from local parts stores are pretty crappy and tend to create pulsing brakes quickly.
I have had them on my car for I think 3 years now and they are still very smooth.
The PC compound from hawk is one of their newer compounds.
I was not impressed with their HPS pad which they have had for a long time.
I was actually so disappointed in those i took them off my car and sent them back.
Historically, Hawk compounds have not been very good, but it looks like these new pads are changing that.
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.
Anybody know dr jekyll and mr hyde slot 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.
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.
It sounds like one or more of your calipers are seized.
Sadly, this tends to happen a lot with slider type calipers, the kind that are on your VUE.
Not only will the rotors need to be replaced, but the adventure game on python will need to be serviced.
Whats most likely happening is that the seized caliper is causing the pads to drag an inappropriate amount causing too much heat buildup.
The overheating causes the problems described in the article… Solid article.
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?
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 do not care if the brake life will be short because of cracks if they ever happenbut 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.
Drilled, Slotted & Vented Brake Rotors - What's Best?
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.
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