Brakes - slotted or drilled?

[PaulPDX]

First off, I don't want this to be a pissing fest. I'd like to see a good informative discussion with good scientific substance so that anyone who has questions about the subject can make their own educated decisions.

Personally, I've heard may times about how cross drilled rotors can crack, which I think is an over-exaggerated myth... anything poorly made will break under stress. I've also heard numerous times that slotted rotors are THE only way to go.

However, if slotted rotors were indeed the only way to go then why are Porsche factory rotors cross drilled rather than slotted? This leads me to wonder if the above state ment about slotted rotors is just another over-exaggerated, over-regurgitated myth (like synthetic lube will wreck your gaskets... ridiculous).

Perhaps for track use, slotted rotors are the only way to go... but on a street car or a car that spends 80 to 100% of its life on the streets... perhaps slotted rotors aren't neccessary.

Your thoughts?

 

[jtmcinder]

Street cars don't need any slotting or drilling.

There are two reasons to slot: to let gasses that can build up between the pad and rotor to escape and to de-glaze the pad. If you are building up gasses - especially with modern pads - then you are driving way too fast for the street. Same goes for glazing.

There are three reasons to drill: the above two, plus to lighten the rotor. Again, this is serious overkill on a street car.

Drilling can be done in a way that doesn't seriously weaken the rotor. (Of course, you must start with a really good rotor.) Let's just say that the drilled rotors sold by, e.g., PowerSlot, don't meet these criteria. Those made for a Porsche do.

- Jtoby

 

[Defiant]

Originally posted by PaulPDX

However, if slotted rotors were indeed the only way to go then why are Porsche factory rotors cross drilled rather than slotted?

Well, price Porsche factory drilled rotors against some replacements on eBay. There has to be more than simple panache in that $600 per wheel difference.... build quality, perhaps?
If I were doing the swap, I'd just stick with a known name: Brembo, Wilwood, Baer, etc. Porsche quality at JC Whitney prices. For driving on the street, I don't think you could damage any of their products.

 

[PaulPDX]

I'm aware of the reasons for cross drilling and slotting. Over the years I've heard numerous individuals state that slotting is the only way to go, but when I noticed that most of the world's high performance production cars have drilled rather than slotted rotors... it made me wonder if it is yet another popular misconception that deserves to be debunked.

I've even heard some say that cross drilling is only good for looks, which is why manufacturers don't use slotted. It is humorous how so people take assumptions about certain things and pass on those ideas as if there were facts.

My personal belief is that the two formats are merely two different ways of arriving at the same goals: gas dissipation and minor weight reduction.

I'll be getting a set of Stoptechs soon. After months of pondering I decided to pass on the much cheaper Baer kit. I'm suprised that no one in the commercial DSM community has adpated the Porsche/Brembo + Ceramic rotors for our cars.

 

[jtmcinder]

Originally posted by PaulPDX
I'm suprised that no one in the commercial DSM community has adpated the Porsche/Brembo + Ceramic rotors for our cars.

I, in contrast, am not surprised at all.

DSM = doesn't spend money

Why pay big $$$ for something that really works when you can get eBay slotted and drilled rotors for $80 a corner?

- Jtoby

ps. my pedantic replies are aimed at the wider audience and should not be taken as implying a lack of knowledge in the previous poster

 

[PaulPDX]

Originally posted by jtmcinder
I, in contrast, am not surprised at all.

DSM = doesn't spend money

. So true. I've noticed the same trait too... even amongst the 2G owners. Wonder why that is... the 2G turbos aren't exactly cheap compared to other cars of the same class (price and market segment... not in terms of performance).

 

[Todd TCE]

Drilled, or drilled and slotted rotors belong on the street for appearance reasons only.

I never suggest drilled rotors on a car for track use unless it's either a drag car or the customer simply 'wants' it. Gas slots are fine for either or both. No harm, no foul. And no cracks....

 

[PaulPDX]

I contacted ST regarding the questions and thoughts I had... to my amazement both emails were answered within 5 minutes!

Here's what their general manager, Robert Lee, has to say about slotting vs cross drilling and track use:

"Slotted rotors are much more durable than drilled. Drilled rotors crack in
half the time of slotted. If you are considering going to the track I would
advise against drilled."

Then, I asked him about brake pad wear with the two rotor types...

"drilled causes more pad wear than slotted."

So... there you have it. Looks be damned. Slotted it is.

 

[Todd TCE]

You didin't seem to believe what we already told and wanted to contact the 'final word' so why did you ask in the first place? To see if we knew?

 

[Defiant]

Todd, slightly off-topic: are the slots supposed to "rake in" against rotation, or out? Brembo says "in", and that feels backward to me.

 

[Todd TCE]

Personally, I don't think or find it makes a darm bit of difference. Seen them, sold them, used them in many different ways.

I gave up on angles and went the Carroll Smith route years ago; II on the front and = on the rear... That way you get some of both directions to keep everyone happy....!

 

[talonted_one]

this too is a little off topic:

I thought dimpled and slotted rotors were a happy medium when it comes to rotors.

 

[PaulPDX]

Originally posted by Todd TCE
You didin't seem to believe what we already told and wanted to contact the 'final word' so why did you ask in the first place? To see if we knew?

Why are you taking this personally? Have I said anything to you? Have I said anything to you of personal nature?

I set out to find information. This forum isn't the only source of info. I asked the question here and elsewhere as well and was merely sharing what I found out.

Jeez, who pooped in your cereal this morning? That tone was totally uncalled for.

 

[jtmcinder]

Gee, Paul, let's think about it. You posted a question that's been asked and answered about as many times as the "how wide a tire can I wedge on my 16x6 wheels?" and got an answer from an expert who happens to build brakes for our cars for a living. But it's not until some other vendor answers your emails that you announce that you now have spoken to G*d and have some stone tablets for us to read.

- Jtoby

 

[PaulPDX]

Originally posted by jtmcinder
Gee, Paul, let's think about it. You posted a question that's been asked and answered about as many times as the "how wide a tire can I wedge on my 16x6 wheels?" and got an answer from an expert who happens to build brakes for our cars for a living. But it's not until some other vendor answers your emails that you announce that you now have spoken to G*d and have some stone tablets for us to read.

- Jtoby

Umm, no, I did not ask about tires. Read the topic and the first post, carefully.

And two, one vendor's opinion is just that: one vendor's opinion. Did I refute his opinion? No. Did I at any point say or suggest that he was wrong? No. He chimed in and I took note of it. I had asked ST the same question before Todd posted his take on the subject and did not have time to add their response until after Todd had posted. Besides, as a consumer, it doesn't hurt to ask different vendors the same question(s). Ever heard of compare and contrast? which is a vital component of analytical thinking?

Three, I started off by saying I'd like the thread to be a catch-all on the topic... which is why I shared ST's response to my questions. I did not ask ST to double check what Todd had wrote. I asked ST the question long before Todd's response.

If you don't want to read a thread on a topic that has been repeated over and over... then what's keeping you from skipping it? Do you hit yourself with a hammer and then complain to the doctor about your injuries?

Thanks for jumping on the band wagon. The ride is over.

 

[Rx3]

Well that was all very entertaining :laugh:

 

[Turbo Shogun]

Geez... So many would-be attacks...

You could almost swear this was a forum for women with DSM's.

I, too, have sensed a bit of malice floating around the forum between the "n00bs" and the more knowledgeable people. To coin a trite saying, "Can't we all just get along?"

There will always be people who are in the know, and those who aren't. It's simple charity for those who know to lend thier experience to those who don't have it...

Provided, some questions have been asked and answered numerous times, I think a bit of using the "search" function can remedy this.

So everyone, pump your brakes. (Pun intended)

 

[jtmcinder]

It's rather well-known that people are much more aggressive in email or on internet boards than they are in person. But maybe it's time to mention that the sexes are not equal in this regard. In fact, when the data from men and women are analyzed separately, the "well-known" effect to which I refer is often not significant for women.

Not that I didn't take your point.

- Jtoby

 

[Todd TCE]

Sorry Paul,

Your post came accross sounding to me, and othes, that you somehow didn't believe what we had said or that you simply needed confirmation by another person you felt had a more valid answer for you.

I'm sure we'll both get over it.

 

[Defiant]

Originally posted by Turbo Shogun
Geez... So many would-be attacks...

You could almost swear this was a forum for women with DSM's.

AND PMS.

Enough for now.

Todd, thanks for the valid information, and informed opinions as always.

We'll all be much nicer next time, but I'm closing this one before Santa sees it. He only has so much coal to go around.