Are Brembo drilled rotors good?...>>>
01-24-2005, 02:22 PM
#13
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we used to cross drill our own rotors when I helped circle track guys...
as long as they were countersunk, they never cracked. Cross drilled rotors will run much cooler than slotted rotors will. If it is a quality rotor, I doubt you'd crack them. If you did, the company should replace them.
01-24-2005, 02:27 PM
#14
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Holes and slots can BOTH cause stress points, leading to...
cracks.
The _theory_ is they let gas escape for better braking. I've never seen a scientific test showing performance.
But if that's the case, WHY NOT JUST SLOT THE PADS? Duh. Some of them even come that way. It's not like it would make a difference which is slotted, the pads and rotor are moving relative to each other. One can picture the gas "sticking" to the pad and being release when a rotor slot comes by, OR the gas "sticking" to the rotor and being released when the slot in the pad comes by - no difference.
Do you seriously think the mass from drilling a few dozen holes makes a difference? Have you ever picked up a disc? I'd bet there's not a whit of difference between the mass removed from drilling vs. slotting and that there's more manufacturing variation between different discs than that caused by either.
The _theory_ is they let gas escape for better braking. I've never seen a scientific test showing performance.
But if that's the case, WHY NOT JUST SLOT THE PADS? Duh. Some of them even come that way. It's not like it would make a difference which is slotted, the pads and rotor are moving relative to each other. One can picture the gas "sticking" to the pad and being release when a rotor slot comes by, OR the gas "sticking" to the rotor and being released when the slot in the pad comes by - no difference.
Do you seriously think the mass from drilling a few dozen holes makes a difference? Have you ever picked up a disc? I'd bet there's not a whit of difference between the mass removed from drilling vs. slotting and that there's more manufacturing variation between different discs than that caused by either.
01-24-2005, 02:37 PM
#15
Drilled does look quite cool, I think I will miss them a bit
cross-drilled zimmermanns front rotors
<img src="http://lz7w.com/albums/zimm/IMG_3263.sized.jpg">
drilled and slotted big ECS rear rotors
<img src="http://lz7w.com/albums/ecsrear/IMG_1332.jpg">
<img src="http://lz7w.com/albums/zimm/IMG_3263.sized.jpg">
drilled and slotted big ECS rear rotors
<img src="http://lz7w.com/albums/ecsrear/IMG_1332.jpg">
01-24-2005, 03:04 PM
#16
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I bet if you put them on a scale, there would be a significant difference....
I've not picked up slotted vs drilled for the same car. But slotted M Coupe vs Drilled TT , the drilled weighed less. And I know that's not a fair comparison.
I've had pads that had a single slot down the center (up-down) and found that it tended to fill up with dust instead of relasing it. I'm not sure why, but think it may have worked better if angled.
The most likely stress points on the slotted rotors are at the edges of the disc (center and outter) where stress points for the drilled occur at each drilled location.
I speak only from my experience and from the little bit of materials engineering I remember, but I believ that drilled rotors on the track, without an adequate cooling system, is trouble waiting.
I've had pads that had a single slot down the center (up-down) and found that it tended to fill up with dust instead of relasing it. I'm not sure why, but think it may have worked better if angled.
The most likely stress points on the slotted rotors are at the edges of the disc (center and outter) where stress points for the drilled occur at each drilled location.
I speak only from my experience and from the little bit of materials engineering I remember, but I believ that drilled rotors on the track, without an adequate cooling system, is trouble waiting.
01-24-2005, 03:06 PM
#17
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Zimmerman did step up and replace them, but I've talked to others at the track...
with similar experiences.
Like I've said - just my experience and little bit of materials engineering I recall from school.
Like I've said - just my experience and little bit of materials engineering I recall from school.
01-24-2005, 03:21 PM
#18
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Define "significant..."
<center><img src="http://www.drivewerks.com/catalog/Performance/cross-rotor.gif"></center><p>
Quick calc. TT front discs are 312mm dia.
3.14 x (312/2)^2 = 76500 mm^2
Let's say 36 holes, each 5 mm in diameter = 36 x 3.14 x (5/2)^2 = 700 mm^2
So, that's about 1%, assuming a full diameter flat disc. Of course, the holes are drilled in the swept area, and there's the center which is thinner, but that center is also a significant heat sink, since it conducts heat to the hub.
So, a reasonable calculation is that cross drilled rotors remove around 1% of the mass, and likely less than 1% of the thermal mass.
I'll bet unit to unit mass varies considerably more than 1% for these castings.
And if the pad slot is filled with dust, there's not much gas blowing through there, is there?
edit:fixed math
Quick calc. TT front discs are 312mm dia.
3.14 x (312/2)^2 = 76500 mm^2
Let's say 36 holes, each 5 mm in diameter = 36 x 3.14 x (5/2)^2 = 700 mm^2
So, that's about 1%, assuming a full diameter flat disc. Of course, the holes are drilled in the swept area, and there's the center which is thinner, but that center is also a significant heat sink, since it conducts heat to the hub.
So, a reasonable calculation is that cross drilled rotors remove around 1% of the mass, and likely less than 1% of the thermal mass.
I'll bet unit to unit mass varies considerably more than 1% for these castings.
And if the pad slot is filled with dust, there's not much gas blowing through there, is there?
edit:fixed math
01-24-2005, 03:28 PM
#19
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No new toys to brag about - except for the boat.
It's just been too damn cold to have any fun on it lately. I've been doing a fair amount of work to upgrade things, but am trying to restrain the expenditures on it. Trying it the key word.
Still toying with the idea of picking up a used TT and playing with it, but need to finish getting Julie through school so we have some real fun money. I'm not a good sugar daddy.
Has Brad got the short bus running yet? I know he was getting close.
Still toying with the idea of picking up a used TT and playing with it, but need to finish getting Julie through school so we have some real fun money. I'm not a good sugar daddy.
Has Brad got the short bus running yet? I know he was getting close.