Audirings4

Cross Drilled = FAIL

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:

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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:

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"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:
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.

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.

- 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

The G Man

Thats why everyone is thinking, that Audi change their brake pad material for all the 2011 sedans, but owners here with 2011 Q5 are still complaining about brake dust. I wonder if these 2011 Audi Q5 owners just dont know how much the older Audi pad dust up or maybe Audi did not change the pad material in the 2011 Q5.

Reggie

Yes I am a huge failure

Audirings4

In more than one way.
If they make you feel better then by all means.

JohnBoyToo

Bad day on the forums....

too much angst for such a small issue...

To those comparing to previous audi's - may be a fair comparison for you, but in my 40 years of driving only one other car created as much dust as this one...

The Q5 is a FINE vehicle (in our short ownership time),
All the more reason to have high expectations for it...
but it is not a sports car and I trust that is not the target audience Audi had in mind... so why would we use sports car handling to defend the brake dust ?

The wife should have gotten gunmetal grey aftermarket rims instead of polished stainless

tridentnyc

My quote included machining. And no I wouldn't do an oil change at Jiffy Lube, not that I think there is anything wrong with it. Again, it's an oil change, I'm not replacing the engine here. Doing it myself or at Jiffy Lube is fine by me. Just because I'll be driving a "yuppie" car doesn't mean I have to act like one when it comes to doing an oil change.

I don't buy the hype when it comes to stealerships and the fear they sell.

HaveBullDogWillTravel

Jiffy lube will likely NOT use the correct oil and will NOT torque the drain plug and filter cap to the correct torque value.

I got no idea WTF that's supposed to mean. "yuppie?"...I thought that word died with the E30 BMW.

buckeyebill

Hahaha yes exactly, but I understand where he's coming from. However when you break it down, there's a Q5 for almost every segment right? StraIhht up premium all the way to maxed out prestige s-line...

The G Man

Yes exactly, and his Q5 is leased. So he doesnt care if the high school kid at Jiffy lube doesnt tighten his drain bolt right or double gasket his oil filter and he is driving down the road with oil leaking out of his engine. The car is leased, so some sucker will end end up with it after his lease is up. Also, he is probably using low octane gas on top of that.

tridentnyc

Not leased, a purchase. Since you couldn't even read a forum thread correctly I seriously doubt I'll take your "advice" on things mechanical.

Did the service guys at Audi give you the "G Man" handle? Must be because they laugh their asses off every time you come in for service and drop a grand at their dealership. One born every day.