drilled and slotted brake rotor? - Page 3 - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Grand Cherokee & Commander Forums > WK Grand Cherokee & XK Commander Forum > drilled and slotted brake rotor?

End of Summer Sale, 20% OFF!2007 - 2011 Jeep JK Long Arm Lift KitsIntroducing MONSTALINER™ UV Permanent DIY Roll On Bed Line

Reply
Unread 07-24-2012, 06:59 PM   #31
Kolak
Vendor
 
Kolak's Avatar
 
Join Date: Jun 2004
Location: Phoenix, AZ
Posts: 4,880
I'm not lying to you. What would be the point of that? The SAE tested older pad formulations just for the sake of testing them.

Quote:
Originally Posted by tjkj2002 View Post
Older style pads have asbesto's that are prone to outgassing,it's the new style pads that do not so that artical could not be a few years old.It would have to be 20+ years old,if not 30+ years old due to asbesto's in brakes have been long gone which are the only pads that would see any benifit from drilled rotors.


__________________
Kolak Performance and Offroad
Member: Specialty Equipment Market Association
Telephone: 480 998-3661
kolak@aol.com or kolak@kolakperformance.com
Kolak is offline   Reply With Quote
Unread 07-24-2012, 07:04 PM   #32
Kolak
Vendor
 
Kolak's Avatar
 
Join Date: Jun 2004
Location: Phoenix, AZ
Posts: 4,880
It's clear to me, and to everyone else that has run Stillen cross-drilled rotors on their Jeeps, that you have not tried them. Otherwise you would not make an erroneous statement about pad life being compromised by the rotors causing them to "shave off."

Pad life has been exemplary with these rotors. I've been using them for well over 17 years and selling them for nearly that long. Stillen's brake division leader has a PhD in metallurgy. This is no fly-by-night organization - they sell these products because they work properly. I can't speak to other applications - I sell them for Jeeps only. I have 15 years of positive emails, large group buys and personal experience to go one. The SAE study is icing on the cake. They work, and work well.

Quote:
Originally Posted by TangoTango View Post
That is correct ... especially for a Jeep or offroad vehicle.

Slotted or the wave slot is the way to go. The drill pattern does NOT release the gasses as quickly as the slot and just tears into the pads.

Look at any of the high end race truck brakes being used. They are all slotted, not drilled.

If you want to constantly shave off your brake pads and look cool then drilled is the way to go, but for performance slotted is better.
__________________
Kolak Performance and Offroad
Member: Specialty Equipment Market Association
Telephone: 480 998-3661
kolak@aol.com or kolak@kolakperformance.com
Kolak is offline   Reply With Quote
Unread 07-24-2012, 08:59 PM   #33
tjkj2002
Registered User
2002 KJ Liberty 
 
Join Date: Dec 2009
Location: Colorado
Posts: 8,094
Quote:
Originally Posted by Kolak View Post
I'm not lying to you. What would be the point of that? The SAE tested older pad formulations just for the sake of testing them.
Well 1st testing older pads formula's that you have zero hope to even buy is pointless to prove that drilled rotors work better.Sounds like the scams Amsoil pushes by paying for tests to be rigged to show there better then the rest.So basically info that has no worth but the fact that they offer no advantage with modern pads like I already stated and there just a cosmetic factor now then an actual benificial performance part.
__________________
'02 Liberty sitting on 35" tires,HP44,RockJock60,and AtlasII t-case
tjkj2002 is offline   Reply With Quote
Unread 07-24-2012, 09:09 PM   #34
mreed21
Registered User
1999 WJ 
 
Join Date: Jun 2011
Posts: 514
I love my Stillen rotors, thanks kolak.

Sent from my DROID RAZR using JeepForum
mreed21 is offline   Reply With Quote
Unread 07-24-2012, 09:22 PM   #35
Kolak
Vendor
 
Kolak's Avatar
 
Join Date: Jun 2004
Location: Phoenix, AZ
Posts: 4,880
The SAE? A scam? Pardon my silence, but I'm speechless.

http://www.sae.org/about/general/history/

Quote:
Originally Posted by tjkj2002 View Post
Well 1st testing older pads formula's that you have zero hope to even buy is pointless to prove that drilled rotors work better.Sounds like the scams Amsoil pushes by paying for tests to be rigged to show there better then the rest.So basically info that has no worth but the fact that they offer no advantage with modern pads like I already stated and there just a cosmetic factor now then an actual benificial performance part.
__________________
Kolak Performance and Offroad
Member: Specialty Equipment Market Association
Telephone: 480 998-3661
kolak@aol.com or kolak@kolakperformance.com
Kolak is offline   Reply With Quote
Unread 07-24-2012, 10:15 PM   #36
TangoTango
Registered User
2008 WK 
 
Join Date: Oct 2011
Posts: 1,132
Stillen makes good rotors ... this is their top of the line right?

"for a street vehicle that is used offroad"

STILLEN Brake Pros now offers the Spec-T line of rotor systems, the highest level upgrade when keeping with the original equipment calipers. Available in cross-drilled AND slotted or slotted-only configurations, these upgrade systems are designed specifically for each application for the best performance with no compromise. Better stopping performance hot or cold, less weight and less fade are all requirements of the Spec-T program.

Spec-T front, 2-piece rotor assemblies feature curved-vane discs for maximum cooling and aluminum hats for weight reduction and better thermal management. High-performance hardware is used to handle all driving conditions.

Rear 2-piece assemblies also provide improved cooling with curved-vane discs. And, the factory parking brake function is retained for security and streetability.

STILLEN Spec-T -- When compromise is not an option.



TangoTango is offline   Reply With Quote
Unread 07-24-2012, 10:38 PM   #37
tjkj2002
Registered User
2002 KJ Liberty 
 
Join Date: Dec 2009
Location: Colorado
Posts: 8,094
Quote:
Originally Posted by Kolak View Post
The SAE? A scam? Pardon my silence, but I'm speechless.

http://www.sae.org/about/general/history/
QUOTE
Crossdrilling your rotors might look neat, but what is it really doing for you? Well, unless your car is using brake pads from the 40’s and 50’s, 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’. These gasses then formed a thin layer between the brake pad face and the rotor, acting as a lubricant and effectively lowering the coefficient of friction. The holes were implemented to give the gasses ‘somewhere to go’. It was an effective solution, but today’s friction materials do not exhibit the same gassing out phenomenon as the early pads.

For this reason, the holes have carried over more as a design feature than a performance feature. Contrary to popular belief they don’t lower temperatures (in fact, by removing weight from the rotor, the temperatures can actually increase a little), they create stress risers allowing 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.)

The one glaring exception here is in the rare situation where the rotors are so oversized (look at any performance motorcycle or lighter formula car) that the rotors are drilled like Swiss cheese. While the issues of stress risers and brake pad wear are still present, drilling is used to reduce the mass of the parts in spite of these concerns. Remember – nothing comes for free. If these teams switched to non-drilled rotors, they would see lower operating temperatures and longer brake pad life – at the expense of higher weight. It’s all about trade-offs.


From Stoptech:

QUOTE
Which is better, slotted or drilled rotors?

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.

That almost sounds like an excuse to use cross drilled rotors, and for your street car which probably is never driven on the track, the drilled rotors are fine, but as Stoptech states, they will crack and are not good for severe applications.

From Baer:

QUOTE
"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."

Then from Grassroots Motorsports:
QUOTE
"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?)

And then, let's check out what was said on the aforementioned Altima thread [[[ Long thread at altimas.net that was deleted by that server. it is hosted here ]]]:

QUOTE
Here is how it works. The friction between the pad and rotor is what causes you to stop. This friction converts your forward energy into heat (remember Einstein: Energy is neither created nor destroyed, it is converted). Now that heat is a bad thing. Yes it is bad for the rotors but it is a lot worse for the pads. A warped rotor will still stop the car - it will just feel like ****. Overheated pads however WILL NOT stop the car. It is here where the rotors secondary responsibility comes in. Its job now is to DISSIPATE the heat away from the pads and DISPERSE it through itself. Notice that DISSIPATE and DISPERSE are interchangeable? Once the heat is removed from the pad/surface area it is then removed. Notice where the removal falls on the list of duties? That's right - number 3. Here is the list again. Memorize it because I will be using it a lot in this post:

#1 Maintains a coefficient of friction with the pad to slow the forward inertia of the vehicle

#2 DISSIPATE the heat

#3 REMOVE the heat from the brake system

Let's look more in-depth at each step now shall we? No? Too bad assclown we are doing it anyway.

#1 Maintains a coefficient of friction with the pad to slow the forward inertia of the vehicle:
This one is pretty simple and self-explanatory. The rotor's surface is where the pads contact and generate friction to slow the vehicle down. Since it is this friction that causes the conversion of forward acceleration into deceleration (negative acceleration if you want) you ideally want as much as possible right? The more friction you have the better your stopping will be. This is reason #1 why BIGGER brakes are the best way to improve a vehicle's stopping ability. More surface area on the pad and the rotor = more friction = better stopping. Does that make sense Ace? Good. Let's move on.

#2 DISSIPATE The Heat:
Let's assume for a second that the vehicle in question is running with Hawk Blue pads on it. The brand doesn't really matter but that is what I am using as my example. They have an operating range of 400 degrees to 1100 degrees. Once they exceed that 1100 degree mark they fade from overheating. The pad material gets too soft to work effectively - glazing occurs. This means that a layer of crude glass forms on the surface of the pad. As we all know glass is very smooth and very hard. It doesn't have a very high coefficient of friction. This is bad - especially when I am coming down the back straight at VIR at 125MPH. Lucky for us the rotor has a job to do here as well. The rotor, by way of thermal tranfer DISSIPATES the heat throughout itself. This DISSIPATION lessens the amount of heat at the contact area because it is diluted throughout the whole rotor. The bigger the rotor the better here as well. The more metal it has the more metal the heat can be diluted into. Make sense? This isn't rocket science here d00d.

#3 REMOVE the heat from the brake system:
Now comes your favorite part of the process. This is what you thought DISSIPATION was. It is ok. I will allow you to be wrong. This is the step where the rotor takes the heat it DISSIPATED from the pads and gets rid of it for good. How does it do this? By radiating it to the surface - either the faces or inside the veins. It is here where cool air interacts with the hot metal to cool it off and remove the heat. Once again there is a reoccuring theme of "the bigger the better" here. The bigger the rotor, the more surface area it will have which means more contact with the cooling air surrounding it. Got it? Good.

Now let's look at why cross-drilling is a bad idea.

First - as we have already established, cross-drilling was never done to aid in cooling. Its purpose was to remove the worn away pad material so that the surfaces remained clean. As we all know this doesn't have much of a purpose nowadays.

Next - In terms of cooling: Yes - x-drilling does create more areas for air to go through but remember - this is step 3 on the list of tasks. Let's look at how this affects steps 1 and 2. The drilling of the rotor removes material from the unit. This removal means less surface area for generating surface friction as well as less material to accept the DISSIPATED heat that was generated by the friction. Now because of this I want to optimize step one and 2 since those are the immediate needs. If it takes longer for the rotor to get rid of the heat it is ok. You will have a straight at some point where you can rest the brakes and let your cooling ducts do their job. My PRIMARY concern is making sure that my car slows down at the end of the straight. This means that the rotor needs to have as much surface as possible to generate as much friction as possible and it needs to DISSIPATE the resulting heat AWAY from the pads as quick as possible so they continue to work. In both cases x-drilling does nothing to help the cause.

Now let's talk about strength - and how x-drilled rotors lack it. This one is simple. Explain again just how drilling away material/structure from a CAST product DOES NOT weaken it? Since you are obviously a man of great knowledge and experience surely you have seen what can happen to a x-drilled rotor on track right? Yes it can happen to a non-drilled rotor as well but the odds are in your favor when pimpin' bling-bling drilled y0! Since you are also an expert on thermodynamics why not explain to the group what happens to a cast iron molecule when it is overheated. I will give you a little hint - the covalence bonds weaken. These bonds are what hold the molecules together boys and girls. You do the math - it adds up to fractures.

So why don't race teams use them if they are so much better? Consistency? Hmmmm . . . no. I am gonna go with the real reason her chodeboy. It is because of several factors actually. They are as follows but in no particular order:

- Less usable surface area for generating friction
- Less material to DISSIPATE the heat away from the pads
- Less reliable and they are a safety risk because of fatigue and stress resulting from the reduced material

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. 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 cross-drilling.



Like everything else, there is advantages and disadvantages to drilling and slotting a rotor. Fortunately, technology has progressed so that we don’t have to drill or slot our rotors anymore and therefore 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, but the effect in reality is completely insignificant. Furthermore, any benefit of extra cooling is probably off set by the reduction of the rotors mass due to the drilling – which lowers the overall heat capacity of the system.

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 of this 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 have drilled rotors? Well, because people think it looks cool. The rotors on those cars fail when pushed hard as well.
__________________
'02 Liberty sitting on 35" tires,HP44,RockJock60,and AtlasII t-case
tjkj2002 is offline   Reply With Quote
Unread 07-25-2012, 01:40 AM   #38
Kolak
Vendor
 
Kolak's Avatar
 
Join Date: Jun 2004
Location: Phoenix, AZ
Posts: 4,880
Fortunately we have the Society of Automotive Engineers that proved rather conclusively that _properly_ drilled rotors improve braking performance. So that rather negates what you just posted about the cooling benefit being "insignicant" and there being no performance improvement due to the "reduction of the rotors mass."

Then there's Stillen - a dedicated bunch of people that have been making high quality drilled rotors basically forever, using only the best quality rotor blanks, proper drill patterns and radiused/chamfered holes. They don't have cracking problems as a result.

Then there's me. I've run them on my Jeeps for 15+ years and been selling them for 15+ years. Hundreds and hundreds of Jeepers on this forum alone have Stillens that they got from me. I've done several large group buys over the years and I have people that come to me from everywhere asking for them because they've heard nothing but good things.

So from my perspective - that being that I've sold a high quality product that performs as advertised, produced by a company that is dedicated to a high quality problem-free product, coupled with a decade and a half of experience, a couple thousand satisfied customers, and a really nice study from the SAE, gives me proof beyond any doubt that they are a worthwhile upgrade.
__________________
Kolak Performance and Offroad
Member: Specialty Equipment Market Association
Telephone: 480 998-3661
kolak@aol.com or kolak@kolakperformance.com
Kolak is offline   Reply With Quote
Unread 07-25-2012, 03:21 AM   #39
w1pf
Who, me?
 
w1pf's Avatar
2007 WK 
 
Join Date: Aug 2008
Location: Amherst, MA
Posts: 754
My take is that both sides of the argument have some valid points.

Stillen makes a very good product, and their products have a good history.
In the limit, a rotor that allows the pad outgassing to escape does help with pretty much any pad that you're likely to find on the street (pretty much any pad other than a pure ceramic is going to have SOME outgassing at temperature, some more so than others).

but..

WKs have relatively beefy brakes from the start (unlike, say, my '99 Durango where hard braking was a religious experience), so in Mall Rated service drilled and/or slotted rotors add only looks. Which is fine too.
__________________
2014 WK2 Overland 5.9L
2007 WK Limited 5.7L
And some past Durangos
Red WK #19, Hemi #68.. I think..
Durango Owners Club DOTY 2011
-------
"Must have been that yesterday was the day that I was born"
w1pf is offline   Reply With Quote
Unread 07-25-2012, 06:19 AM   #40
scootr29
Web Wheeler
 
scootr29's Avatar
2008 WK 
 
Join Date: Jan 2008
Location: SC
Posts: 2,700
Quote:
Originally Posted by TangoTango View Post
Stillen makes good rotors ... this is their top of the line right?

"for a street vehicle that is used offroad"

STILLEN Brake Pros now offers the Spec-T line of rotor systems, the highest level upgrade when keeping with the original equipment calipers. Available in cross-drilled AND slotted or slotted-only configurations, these upgrade systems are designed specifically for each application for the best performance with no compromise. Better stopping performance hot or cold, less weight and less fade are all requirements of the Spec-T program.

Spec-T front, 2-piece rotor assemblies feature curved-vane discs for maximum cooling and aluminum hats for weight reduction and better thermal management. High-performance hardware is used to handle all driving conditions.

Rear 2-piece assemblies also provide improved cooling with curved-vane discs. And, the factory parking brake function is retained for security and streetability.

STILLEN Spec-T -- When compromise is not an option.



Those look cool....too bad they are not available for the Grand Cherokee.
__________________
Silver WK Club Member #1
2008 CRD QT2
scootr29 is offline   Reply With Quote
Unread 07-25-2012, 06:47 AM   #41
jeffjs
Registered User
 
Join Date: Apr 2008
Posts: 131
I just bought cross drilled and slotted rotors and will be installing them shortly. They were not very expensive, and if they last as long as OEM than that's fine by me. Will report if there are any issues.

Now, people will buy what they want for their vehicle and because they spend their hard-earned money doing so, they have to do their own research before they decide on what to buy. Doesn't mean it has to work any better, just means the buyer needs to be comfortable with their purchase for their vehcile. that's all.

If you want to discuss things that may or may not have an affect on your vehcile, then let's add oiled K&N filters, CAE's, throttle body upgrades, programmers used for HP, etc. to the dicussion.

Maybe not one of these things work as advertised alone, but add them all up and maybe, just maybe there is an improvement. Do what makes you comfortable.
jeffjs is offline   Reply With Quote
Unread 07-25-2012, 10:29 AM   #42
modette
Registered User
2005 WK 
 
Join Date: May 2011
Location: Monument, CO
Posts: 455
Quote:
Originally Posted by IndyBlueWK View Post
Your right they use carbon fiber rotors and you can’t make me believe that Mercedes Benz puts them on for looks and the Z06?? ... And let me guess every single motor cycle manufacture does it to just to look cool??
Now you hit something I know, holes for motorcycle is all about saving weight. Plus unlike cages, sportbike brakes are out there int he direct wind. Cooling is NOT an issue. Rotational mass is great when a wheel is spinning at high speeds. Plus higher weight also effects turn in speed when turning a motorcycle so the higher the weight of those rotors, rims and what have you the harder it is to turn a motorcycle.

Comparing why motorcycles use drilled rotors and cages is silly and not the same.

modette is offline   Reply With Quote
Reply
Thread Tools


Suggested Threads





Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.