there is no doubt about the cooling power of a cross drilled rotor. but we all know they seem to crack on us.

i have heard that CAST cross drilled rotor is less likely to crack because it is "made" with the holes in them. rather than the forged which many i know have cracked on them.

i hear baer makes cast rotors and was wondering if there are any other companies out there that do the same. does anyone have these rotors?

tony

 

It's not so much how the holes got there or how they were made (cast or drilled) but the fact that they are there that causes the stress risers and subsequent failures. Search the archives and FAQ. Although the subject hasnt been discussed much lately, it has been beaten to death in the archives...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">there is no doubt about the cooling power of a cross drilled rotor.</TD></TR></TABLE>

I agree. There is no doubt there is no additional cooling power what-so-ever. But at least they cost more, wear out pads faster, and crack quicker. Good stuff

 

cooling is nice but i'd rather have more heat capacity from a "blank" rotor. cooling is what vents and brake ducting is for

 

And from What I've read in Porsche forums awhile back when I was curious about cross drilling and slotting, Even Brembo does NOT Cast cross drilled holes into their Rotors.

From what I remember there wasn't Anyone that actually cast cross drilled rotors for regular automobile applications, they are All drilled After the cast process. I remember reading this from a Brembo Engineer/Porsche specialist of it being too difficult, time consuming and expensive to be considered even by Brembo.

 

I was under the impression that Porsche casts the holes in their rotors.

The advantage of casting the holes in rather than drilling is that it doesnt leave open endgrains in the edges of the metal, which would cause cracks to develop more quickly.

Still, even with the holes cast instead of drilled, they will crack sooner than a blank rotor. All rotors crack eventually with enough heat and stress - even blank ones - but those rotors with holes and slots are more susceptible and they will typically fail sooner.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 1GreyTeg &raquo;</TD></TR><TR><TD CLASS="quote">And from What I've read in Porsche forums awhile back when I was curious about cross drilling and slotting, Even Brembo does NOT Cast cross drilled holes into their Rotors.

From what I remember there wasn't Anyone that actually cast cross drilled rotors for regular automobile applications, they are All drilled After the cast process. I remember reading this from a Brembo Engineer/Porsche specialist of it being too difficult, time consuming and expensive to be considered even by Brembo.</TD></TR></TABLE>

Yeah I remember now, somewhat vaguely. He said something about how he would love to see the mold for a such a casting. Actually if you think about it, a rotor with cast holes does sound kinda crazy from a manufacturing perspective...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jsi &raquo;</TD></TR><TR><TD CLASS="quote">

Yeah I remember now, somewhat vaguely. He said something about how he would love to see the mold for a such a casting. Actually if you think about it, a rotor with cast holes does sound kinda crazy from a manufacturing perspective...</TD></TR></TABLE>
Yeah it does seem like it would be a waste to spend as many resources as it would take to cast holes into a rotor. They are a wear item, after all . . .

 

The holes were to release gas greated by the brakes. A gas that is no longer a problem due to current brake manufacturing processes.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Grumpy &raquo;</TD></TR><TR><TD CLASS="quote">The holes were to release gas greated by the brakes. A gas that is no longer a problem due to current brake manufacturing processes.</TD></TR></TABLE>
Yep.

Some of the Porsche drivers have claimed that the holed-rotors are helpful in wet conditions nowadays though - something about evacuating water from the rotor surface, rather than the gasses they were originally intended for decades ago.

 

the holes in porsche's bl1ng ceramic brakes are not drilled. i cant remember whether their ceramic brake rotors are sintered but i konw the holes are not a product of processing after they are manufactured.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Maengelito &raquo;</TD></TR><TR><TD CLASS="quote">the holes in porsche's bl1ng ceramic brakes are not drilled.</TD></TR></TABLE>

This is correct.

Even the ferrari/porsche/etc rotors that come as OE equipment are not cast with the holes, it is an added process. If the rotors were cast that way, they crack on the initial cooling in production, among other issues created in producing them this way (mold release, etc).

 

I don't think casting holes into brake rotors isn't a good idea either. Incorporating "pillars" into the mold (the only way to get holes into a casting unless you postprocess them ie drilling) means that the metal flows around the pillars and must "reconnect" on the other side, which causes irregularities. These irregularities (deformations, whatever) cause the thermal/stress riser problems when the rotor has to do its job.

Edit: .RJ beat me to it.

 

Hmm. I don't think I've ever seen carbon/carbon rotors with holes...

K

 

Don't the Ferrari Enzo carbon rotors have holes?

 

The Porsche Carrera GT did not have drilled rotors. Never seen an Enzo, though.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GSpeedR &raquo;</TD></TR><TR><TD CLASS="quote">The Porsche Carrera GT did not have drilled rotors. Never seen an Enzo, though. </TD></TR></TABLE>

They look drilled to me...

and the enzo has drilled too:

 

On this topic:

Would slotted be better? Or does modifying a rotors design affect it's structural integrity all together? Does this mean Stock OEM style rotors are better? I would like to know. Thanks in advance.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by InfamousDC2FI &raquo;</TD></TR><TR><TD CLASS="quote">On this topic:

Would slotted be better? Or does modifying a rotors design affect it's structural integrity all together? Does this mean Stock OEM style rotors are better? I would like to know. Thanks in advance.
</TD></TR></TABLE>
It is generally accepted that blank rotors are the safest to use because it typically takes longer for them to develop significant cracks under high stress conditions.

All rotors will eventually crack given enough heat and stress, but "modified" rotors will usually do so more quickly, for obvious reasons.

Besides, blank rotors are cheaper and don't wear down the pads as quickly. Rotors are a wear item; their main function is as a heat sink, and a hard, durable surface for the pads to contact - there's no reason to spend extra on fancy rotors that don't make any real difference. From what I have read here, it seems that many of the drivers will just buy an inexpensive set of blank rotors from AutoZone, and throw them out after one or two race weekends.

 

If you want cooler rotors then make some darn ducts to get some cooler air back there to them. MUCH cheaper and better way of going about it than cross drilled rotors IMO.

Also, if it's a street car your rotors are not getting too hot anyway.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 577HondaPrelude &raquo;</TD></TR><TR><TD CLASS="quote">
Also, if it's a street car your rotors are not getting too hot anyway.</TD></TR></TABLE>

Very true.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Targa250R &raquo;</TD></TR><TR><TD CLASS="quote">
It is generally accepted that blank rotors are the safest to use because it typically takes longer for them to develop significant cracks under high stress conditions.

All rotors will eventually crack given enough heat and stress, but "modified" rotors will usually do so more quickly, for obvious reasons.

Besides, blank rotors are cheaper and don't wear down the pads as quickly. Rotors are a wear item; their main function is as a heat sink, and a hard, durable surface for the pads to contact - there's no reason to spend extra on fancy rotors that don't make any real difference. From what I have read here, it seems that many of the drivers will just buy an inexpensive set of blank rotors from AutoZone, and throw them out after one or two race weekends.</TD></TR></TABLE>

Thanks for a excellent reply

So on the subject of talking about braking performance, we have come to a semi-conclusion that blank rotors (OEM, autozone etc...) are more ethical for reliablility and budget reasons.

So in terms of improving your braking performance, are "big-brake" conversions (the ones that are suppose to make a difference in braking ability) wear with simular lifespans as the structurally weak rotors as described aboved?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 577HondaPrelude &raquo;</TD></TR><TR><TD CLASS="quote">If you want cooler rotors then make some darn ducts to get some cooler air back there to them. MUCH cheaper and better way of going about it than cross drilled rotors IMO.

Also, if it's a street car your rotors are not getting too hot anyway.</TD></TR></TABLE>

my car is also a track car, not only a daily driver. so i guess going cross drilled isnt worth it. slotted or blanks seems to be the preferred rotor on this board. ill probably do the same

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 577HondaPrelude &raquo;</TD></TR><TR><TD CLASS="quote">Also, if it's a street car your rotors are not getting too hot anyway.</TD></TR></TABLE>

They are for the BLING factor, yo!!!

I have to admit, I got the cross-drilled rotors for the very same reason. But after 2 pairs of cracked rotors (plus the fact that my pads didn't last too long), I will no longer get cross-drilled or slotted rotors. Blank is the way to go!!!

 

a good set of solid rotors, great pads, great brake fluid, and good cooling methods is the ideal way to go.

 

for informational purposes:

http://content2.us.porsche.com...ypccb


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote"> This remarkable technology features a lightweight ceramic disc with involute cooling channels and a specially developed composite pad. Each disc is formed from a specially treated carbon fiber compound, which is then silicated in a high-vacuum process at nearly 3,100 °F (1,700 °C).

Cross-drilled and internally vented for optimum dispersal of moisture and heat </TD></TR></TABLE>