Who's right, who's wrong? (X-Drilled rotors...)
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Joined: Dec 1999
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From: Behind a workbench, repairing FC Electronics.
Who's right, who's wrong? (X-Drilled rotors...)
I've seen lots of cars with cross drilled rotors, some of them aren't exactly rice...
Some of the guilty parties are here...
However I saw this before, and it popped up recently as I was looking at a few things:
I've also never seen a stock brake rotor that's cross drilled, not even on Porsches and such.
So, who's right and who's wrong...
Also, the same article reccomends removing the backing plate... What are the consequences of removing this plate? Why did the Mazda engineers decide to put it there?
Some of the guilty parties are here...
However I saw this before, and it popped up recently as I was looking at a few things:
Originally posted at www.MazSpeed.com - http://www.mazspeed.com/brakecooling.htm
Cross drilling is only useful for solid brake rotors, not for vented brake rotors. It is a habit left over from the '60s, from the days before there were vented brake rotors. One of the most severe braking applications is trying to slow down a 3400 pound NASCAR stock car, and they do not use cross drilled rotors. They use huge vented rotors, and on tracks where they use their brakes the hardest, like Martinsville and Richmond, they use several air ducts to feed the center of the rotors with cool air. They do not cross drill their rotors because it does not help their brakes work better.
Cross drilling is only useful for solid brake rotors, not for vented brake rotors. It is a habit left over from the '60s, from the days before there were vented brake rotors. One of the most severe braking applications is trying to slow down a 3400 pound NASCAR stock car, and they do not use cross drilled rotors. They use huge vented rotors, and on tracks where they use their brakes the hardest, like Martinsville and Richmond, they use several air ducts to feed the center of the rotors with cool air. They do not cross drill their rotors because it does not help their brakes work better.
So, who's right and who's wrong...
Also, the same article reccomends removing the backing plate... What are the consequences of removing this plate? Why did the Mazda engineers decide to put it there?
84SE-EGI helpy-helperton
Joined: Oct 2002
Posts: 3,591
Likes: 549
From: Phoenix, AZ
Well, speaking for the crowd that did all the research and decided to get them anyway; my response is that there are several car manufacturers that go out of their way to install vented AND cross-drilled brake rotors on their top of the line cars, and their names are synonymous with quality and performance; AMG-Mercedes, Porsche, and BMW all offer cross-drilled and vented rotors on their performance oriented cars. That's enough for me, particularly since I DON'T have the ducting of a racecar to get fresh, ram air into the centers of my vented (front and rear) brake rotors (84SE).
I went with KVR rotors which are cross-drilled in alignment with the internal 'vanes' of the stock rotors to preserve structural integrity. This results in an inconsistent drill pattern but doesn't sacrifice the disk strength. Also of note is that I live in AZ where outside air temps often reach or exceed 115deg F in the summertime here, requiring a lot of performance out of brake pads and rotors since there just isn't much cooling capacity in very hot air environments. Add to that the heating from road surfaces, and you're talking anywhere from 130-140deg F at brake height. It would take a lot of airflow to cool rotors used hard in this environment.
Back to the point, however; the backing plates were designed by Mazda to prevent decreased brake performance due to SPLASH hazards, along with helping to direct airflow within the rotor and wheel when it's rotating. Anytime you allow any water to get on the rotors, you risk a single-wheel that won't stop as smoothly as the others, which could cause a slide or spin. These also serve as dust covers to try and keep your disks as clean as possible. I still have my dust covers, front and rear, and don't see much purpose in removing them.
I think that you should proceed with a 'project' mentality and approach the upgrade of your braking system from a very planned angle. When I got to the point of making a decision on $500 worth of cross-drilled rotors, I'd already invested $150 in stainless brake lines (soft lines), and $100 in a new Master Cylinder, $50 in front and rear caliper rebuild kits, and $80 in HAWK HP+ brake pads to get every conceivable edge in braking performance. The rotors came last, and this was due to having already upgraded the other parts that matter MORE in terms of overall brake utility.
Start with the more common things which will net better performance for less money, unless you're out for the looks, alone. Looks are a valid point, however, since we all want to drive cars that look nice. HTH,
I went with KVR rotors which are cross-drilled in alignment with the internal 'vanes' of the stock rotors to preserve structural integrity. This results in an inconsistent drill pattern but doesn't sacrifice the disk strength. Also of note is that I live in AZ where outside air temps often reach or exceed 115deg F in the summertime here, requiring a lot of performance out of brake pads and rotors since there just isn't much cooling capacity in very hot air environments. Add to that the heating from road surfaces, and you're talking anywhere from 130-140deg F at brake height. It would take a lot of airflow to cool rotors used hard in this environment.
Back to the point, however; the backing plates were designed by Mazda to prevent decreased brake performance due to SPLASH hazards, along with helping to direct airflow within the rotor and wheel when it's rotating. Anytime you allow any water to get on the rotors, you risk a single-wheel that won't stop as smoothly as the others, which could cause a slide or spin. These also serve as dust covers to try and keep your disks as clean as possible. I still have my dust covers, front and rear, and don't see much purpose in removing them.
I think that you should proceed with a 'project' mentality and approach the upgrade of your braking system from a very planned angle. When I got to the point of making a decision on $500 worth of cross-drilled rotors, I'd already invested $150 in stainless brake lines (soft lines), and $100 in a new Master Cylinder, $50 in front and rear caliper rebuild kits, and $80 in HAWK HP+ brake pads to get every conceivable edge in braking performance. The rotors came last, and this was due to having already upgraded the other parts that matter MORE in terms of overall brake utility.
Start with the more common things which will net better performance for less money, unless you're out for the looks, alone. Looks are a valid point, however, since we all want to drive cars that look nice. HTH,
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