Ford Mustang Forum banner
Status
Not open for further replies.
1 - 20 of 59 Posts

·
Registered
Joined
·
189 Posts
Discussion Starter · #1 ·
So, I had been having vibration from my brakes that I thought was due to warped rotors(it turns out the the idea of rotors warping before cracking is mostly a myth, my research seemed to indicate that most "warped" behavior is actually due to uneven deposits of brake pad material on the rotors caused by high stress heavy braking, which causes the rotor thickness to vary, and thus produce symptoms that people associate with warping). Anyways, I then started to do some research into cross-drilled and slotted rotors. I found some disturbing information.

In the short, crossdrilled rotors where originally used to address a problem caused by brake pad compounds from the 40's and 50's, a problem which has long since been fixed. Today, crossdrilling rotors only serves to make a rotor look cooler and to create stress concentrations that can lead to rotor failure.

Here is a good article I found summarizing the opinions held by most highly knowledgeable people in this area : Signal to Noise - cross-drilled rotors

Here are some of the quotes from that article to give you an idea what it says:
AP Racing:
"Grooves improve 'cleaning' of the pad surfaces and result in a more consistent brake performance. Grooved discs have a longer life than cross-drilled discs."

Baer:
"What are the benefits to Crossdrilling, Slotting, and Zinc-Washing my rotors? In years past, crossdrilling and/or Slotting the rotor for racing purposes was beneficial by providing a way to expel the gasses created when the bonding agents employed to manufacture the pads...However, with today's race pad technology, 'outgassing' is no longer much of a concern...Slotted surfaces are what Baer recommends for track only use. Slotted only rotors are offered as an option for any of Baer's offerings."

Darrick Dong; Director of Motorsports at Performance Friction: "Anyone that tells you that drilling makes the disc run cooler is smoking crack."

Waren Gilliand:
(Warren Gilliland is a well-known brake engineer in the racing industry and has more than 32 years experience in custom designing brake systems ...he became the main source for improving the brake systems on a variety of different race vehicles from midgets to NASCAR Winston Cup cars.) "If you cross drill one of these vented rotors, you are creating a stress riser that will encourage the rotor to crack right through the hole. Many of the rotors available in the aftermarket are nothing more than inexpensive offshore manufactured stock replacement rotors, cross drilled to appeal to the performance market. They are not performance rotors and will have a corresponding high failure rate"

Grassroots Motorsports:
"Crossdrilling your rotors might look neat, but what is it really doing for you? Well, unless your car is using brake pads from the '40s and 50s, not a whole lot. Rotors were first drilled because early brake pad materials gave off gasses when heated to racing temperatures, a process known as "gassing out." ...It was an effective solution, but today's friction materials do not exhibit the some gassing out phenomenon as the early pads. Contrary to popular belief, they don't lower temperatures. (In fact, by removing weight from the rotor, they can actually cause temperatures to increase a little.) These holes create stress risers that allow the rotor to crack sooner, and make a mess of brake pads--sort of like a cheese grater rubbing against them at every stop. Want more evidence? Look at NASCAR or F1. You would think that if drilling holes in the rotor was the hot ticket, these teams would be doing it...Slotting rotors, on the other hand, might be a consideration if your sanctioning body allows for it. Cutting thin slots across the face of the rotor can actually help to clean the face of the brake pads over time, helping to reduce the glazing often found during high-speed use which can lower the coefficient of friction. While there may still be a small concern over creating stress risers in the face of the rotor, if the slots are shallow and cut properly, the trade-off appears to be worth the risk. (Have you looked at a NASCAR rotor lately?)

Power Slot:
"At one time the conventional wisdom in racing circles was to cross-drill brake rotors to aid cooling and eliminate the gas emitted by brake pads. However, today's elite teams in open wheel, Indy and Trans Am racing are moving away from crack prone, cross-drilled brake rotors in favor of rotors modified with a fatigue resistant slotting process."

Stop Tech:
"StopTech provides rotors slotted, drilled or plain. For most performance applications slotted is the preferred choice. Slotting helps wipe away debris from between the pad and rotor as well as increasing the "bite" characteristics of the pad. A drilled rotor provides the same type of benefit, but is more susceptible to cracking under severe usage. Many customers prefer the look of a drilled rotor and for street and occasional light duty track use they will work fine. For more severe applications, we recommend slotted rotors." (Note that even though Stop Tech sells both drilled and slotted rotors they do not recommend drilled rotors for severe applications.)

Wilwood:
Q: Why are some rotors drilled or slotted?
A: Rotors are drilled to reduce rotating weight, an issue near and dear to racers searching for ways to minimize unsprung weight. Drilling diminishes a rotor's durability and cooling capacity."

On the other hand, it appears that slotted rotors do not noticeably diminish rotor strength and provide the benefit of sweeping the brake pads and expelling water from the braking surface. I think I'm going to go with a set of slotted rotors for my replacements.

On another note, I am slightly disturbed by the fact that I had to search so hard for this information. I feel like this should be common knowledge that is mentioned to anyone who discusses buying crossdrilled rotors, which i definitely did not see while looking through some of the archived threads.

Here is a thread about a person who had a set of crossdrilled rotors fail BECAUSE of the crossdrilling.R1concepts Drilled And Slotted Rotor Failure - MyMonte.com - A 1995 to 2007 Chevy Monte Carlo Community Scary thing is they where rotors that have recieved good reviews on nearly all of the automotive forums that I found where they are common upgrades.

If you dont touch the brakes and like to look cool with inferior parts that most people will think give you some advantage, then crossdrilled rotors may be for you. But if you value functionality and realistic gain over looking cool and you like to push your brakes pretty hard, stay away from crossdrilled rotors.
 

·
Registered
Joined
·
189 Posts
Discussion Starter · #3 ·
Good research... Never cared for drilled rotors. Much prefer slotted or dimpled.
Yah, I had also been looking at sloted&dimpled rotors. At least the dimples dont provide a straight through hole, and thus I'm sure they dont weaken the rotors as much as crossdrilled. But it seems like dimpled rotors could only be advantageous by addressing the "outgassing" problem that was solved with new brake pad compounds 40 years ago. Sure, they provide another edge to sweep the brake pad surface, but in this respect, they could only sweep a small portion of the pad surface. So therefore they are less effective at that one benifit than are slots. And the fact is that when you remove material from the face of the rotor you are removing material which contacts the brake pads and creates drag while absorbing heat. You effectively lower the friction area of the rotors and reduce the amount material in the rotors which can absorb heat, thus causing the heat from braking to be concentrated in a smaller area than it would be with solid or just slotted rotors. Sure, slots could cause some of the same things, but they provide a noticeable improvement in initial bite and wet weather performance. Dimpling AND slotting just increases these side effects without increasing the gains. Then again, they DO look nifty. I personally think only things that are functional can ever REALLY look good. And THATS why I dont have a stick on hood scoop from walmart on my car. :laugh:
 

·
Registered
Joined
·
398 Posts
I've had my Rotorpros drilled & slotted rotors on my '05 stang for over 70k miles and they are still great. No warping, no cracking and they stop just fine.

I really think it depends on the quality of the rotor and that they are broken in properly after installing them from my experience.
 

·
Registered
Joined
·
2,250 Posts
Today, crossdrilling rotors only serves to make a rotor look cooler and to create stress concentrations that can lead to rotor failure.
Scam? Strong language...

So one of two reasons brake manufacturers make crossdrilled rotors today is to increase chance of failure? That conclusion doesn't hold water.
 

·
Registered
Joined
·
189 Posts
Discussion Starter · #7 ·
Scam? Strong language...

So one of two reasons brake manufacturers make crossdrilled rotors today is to increase chance of failure? That conclusion doesn't hold water.
No. The reason they make them is so that people will pay more for a product that only has material removed. A large part of the consumer base THINKS they have an effect, and so they will pay more for a product that takes almost very little cost to produce over solid or slotted rotors.
dysan said:
I've had my Rotorpros drilled & slotted rotors on my '05 stang for over 70k miles and they are still great. No warping, no cracking and they stop just fine.

I really think it depends on the quality of the rotor and that they are broken in properly after installing them from my experience.
No, i dont mean to say they WILL always fail, or that every brand will, its just that there is absolutely no evidence whatsoever that they provide any kind of benefit, yet there is definently evidence that crossdrilled rotors are not as strong as slotted or even dimpled rotors, and there are a ton of cases where this has led to failure.
And by the way, nearly every single review of R1 concepts rotors states flawless performance, yet in my hour or two of research I found atleast two examples of catastrophic failure. Yet still, the reviews that say they work excellent outweigh the negative reviews 100 to 1. But does that mean that crossdrilled rotors are no more likely to fail that slotted or dimpled rotors? No. The fact is they where designed to solve a problem that no longer exists. Everyone who is extremely into automotive design (think rally, formula one, and nascar engineers to name a few) believes that they have no benifit, or at the very best have a benifit that is far outweighed by the cost. There is a reason you can find slotted but not crossdrilled rotors on rally cars.
 

·
Registered
Joined
·
1,260 Posts
i like when people say "tons of cases" without really documenting anything,

the fact is i agree with you, why are they more if they are only removing material.. "its has to be made with precision holes and what not" meh, arguable
 

·
Registered
Joined
·
2,003 Posts
It's like jeans with the holes already in them....you pay more for less material. :laugh:
 

·
Registered
Joined
·
189 Posts
Discussion Starter · #10 ·
i like when people say "tons of cases" without really documenting anything,

the fact is i agree with you, why are they more if they are only removing material.. "its has to be made with precision holes and what not" meh, arguable
Im sorry, I did provide one pretty vivid example of failure, unfortunately I had already closed out the other one when I posted. Still though, if you read through that forum post I put a link to about the person who had his crossdrilled R1Concepts rotors fail, you will see atleast 4 other people talk about having similar severe cracking issues, though most where caught before the point of complete failure.

More than anything, it just bothers me that so many people believe this to be a legitimate upgrade, when they are simply a more inefficient method of achieving what slotting does, while at the same time greatly reducing rotor strength. Its a misconception based on outdated information. More than a few reputable brake systems companies admit that the only advantage to be had from crossdrilled rotors is decreasing unsprung weight.

Personaly I push my car pretty extreme in most situations, getting to the maximum possible speed and thus requiring the absolute maximum braking. I warped(or caused uneven brake deposits due to high rotor and pad temperatures, im not sure which) the stock rotors after having the car two weeks, and the car only had 10k miles and the rotors LOOK perfect. I have no doubt that if i bought some of the less expensive crossdrilled rotors there would be a decent chance of failure. And worst of all, if I didnt do all the research I did, I probably would have bought R1Concepts or BrakePerformance rotors believing the four or five great testimonials I ran across right away.

/end rant

Anyways, I am a mechanical engineering student specializing in automotive race design, so I may very well have Function over Form as a much higher priority than most, and thus I am far more bothered by what i found out than most people probably would be...

It's like jeans with the holes already in them....you pay more for less material. :laugh:
Hahahaha, Exactly! .
 

·
Registered
Joined
·
2,250 Posts
Anyways, I am a mechanical engineering student specializing in automotive race design, so I may very well have Function over Form as a much higher priority than most, and thus I am far more bothered by what i found out than most people probably would be....
There's lots of engineers, fabricators, designers, racers, etc on this site.

If you're so bothered by what you "found" write to Chevy and the Corvette engineering team since every Z06 and Grand Sport vette has cross-drilled rotors :bigthumbsup

or maybe they put them on just for looks?
 

·
Registered
Joined
·
189 Posts
Discussion Starter · #12 ·
If you're so bothered by what you "found" write to Chevy and the Corvette engineering team since every Z06 and Grand Sport vette has cross-drilled rotors :bigthumbsup

or maybe they put them on just for looks?
Actually, yah. Why are their fake air intake ducts on the Honda S2000? Why are there fake brake cooling ducts in front of the rear wheel wells on the Mustang GT/CS? Why does the Dodge Challenger R/T have a fake carbon fiber stripe on its hood? Why do the lexus IS-F and quite a few different Porsches have fake quad exhaust tips? Because they LOOK like they make things go fast, so consumers will pay more. :bigthumbsup

Dont trust me, trust Wilwood. If you go to their Q&A page( http://www.wilwood.com/TechTip/TechFaqs.aspx#RT ) they say pretty clearly that with the testing and analysis they have done (and they are one of the best companies in the brake system business), they have found that the only advantage is the cleaning action best accomplished by slotting. They sell cross drilled rotors because many want them for, in their words, "their pure aesthetic value." They go on to say "A drilled rotor provides the same type of benefit(referring to the sweeping advantage of slotted rotors), but is more susceptible to cracking under severe usage; however, for street and occasional light duty track use, they will work fine. For more severe applications, we recommend slotted rotors." In essence, if you want nifty looking rotors and dont expect to heavily abuse your brakes, crossdrilled should be fine. But if you want functionality and the ability to stress your brakes to the extreme without worrying about durability, then slotted is the only real choice.
 

·
Registered
Joined
·
1,627 Posts
On another note, I am slightly disturbed by the fact that I had to search so hard for this information. I feel like this should be common knowledge that is mentioned to anyone who discusses buying crossdrilled rotors, which i definitely did not see while looking through some of the archived threads.
It's common knowledge among those that put their brakes to heavy autocross or roadracing use.

I always tell people to stay away from crossdrilled brakes except for maybe just light street use.

A lot of mods people get are for the "cool" factor, so forum discussions aren't always the best source for technical research.

How many time have you seen people posting about wanting big cams, and the first thing they say is for the bad ass sound?
 

·
Registered
Joined
·
189 Posts
Discussion Starter · #14 ·
A lot of mods people get are for the "cool" factor, so forum discussions aren't always the best source for technical research.

How many time have you seen people posting about wanting big cams, and the first thing they say is for the bad ass sound?
I guess thats what bothers me. I normally just shake my head at those doing mods solely for the "cool" factor, but in this case, that obsession with looking cool has resulted in the knowledge that purely asethetic advantage of crossdrilled rotors generally comes with greatly decreased durability and strength which can result in catastrophic being largely lost, or at the very least uncommon. Many people could be putting themselves at risk to making a mistake that could cause massive failure and expensive property damage without even realizing that the perceived performance "benefit" is all myth and illusion.
 

·
Registered
Joined
·
516 Posts
Thank you, I learned something here and am now a smarter person :smartass:
 

·
Registered
Joined
·
711 Posts
Ok guys lets get something straight here.
1) This is not a scam
2) The general public are morons
3) What people think works well/looks good is accepted
4) Wisdom is knowledge
5) Most of us (males) all like holes :D

Given the above it is natural for a guy to look for a rotor with holes and slo(u)ts in it. You are not going to see absolutely any difference between any of the configurations unless you are severly driving your car. Whether it be on the track, on the street, or through the woods to grandmas house.... Your breaks are the only thing between you and sanity. For standard applications or slight modification the OEM rotors are great. If you want a little more stopping power for the track; get some slotted rotors to dissipate some of the dust/heat. If you have 1000+ hp and are driving warp-speed to Jupiter then I would reccomend upgrading your brake package to something a little more stout then some fancy looking pieces of iron rubbin' on some ceramic bricks... :hihi:
 

·
Registered
Joined
·
711 Posts
That's funny! :laugh:
Hey man, we all gain some of those brain-nerve-thingies from somewhere....I like the neurons I have...what about u??
 

·
Registered
Joined
·
2,250 Posts
Hey man, we all gain some of those brain-nerve-thingies from somewhere....I like the neurons I have...what about u??
When ModularMuscle finished saying he learned something from reading this thread, he used the smartass :)smartass:) smilie, which I found amusing...if that's what you're referring to?
 

·
Registered
Joined
·
766 Posts
Practical experience......When I was doing Time Trials with a 93GT that had the 13" cobra brake mod, I started out using drilled rotors. They lasted 2 sessions on the track....Cracks between the holes. I then swithched to grooved rotors. They were fine except I used up expensive brake pads very fast. I looked at the AI and AIX cars that were running in NASA and they all had regular rotors. If you look at the race pads you should be using on the track they already have a groove in the middle for out gassing. I swithched to regular rotors and had no problems with them or the pads. This stuff is expensive and anything that works and lasts a longer time is the way to go IMO.
If you drive on the street only, it does not matter and enjoy whatever you want to use.
I have the Brembos on my 05 that I open track and use the stock rotors with DTC60 Hawk pads when I rip and tear. That combo works well for me
 
1 - 20 of 59 Posts
Status
Not open for further replies.
Top