Brake setup...Here's what I want to do...
09-30-1999, 03:32 AM
#12
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If anyone can explain...
how cross drilling helps cool brake rotors, please let me know.
I've examined this from every angle I can think of, and engineering principles do not support this claim. It's a myth (IMHO) propogated by the sellers of cross drilled rotors! Best as I can determine:
1) Cross drilling helps relieve gases which generate between pad and rotor under SEVERE braking conditions.
2) Slotting also helps relieve these gases (to less an extent) and helps maintain a "clean" pad surface (cheese grater effect).
3) To improve cooling, increase the amount of air flowing over the rotor, increase the heat transfer area (by internally venting and/or increasing the rotor diameter/thickness).
4) Increasing the mass of the rotor (making it thicker and/or larger) increases its heat capacity (the amount of heat it can absorb for a given temperature rise).
Cross drilling acts against no 4 as it reduces rotor mass.
Please, racing people, tell me If I'm all wet here!
I've examined this from every angle I can think of, and engineering principles do not support this claim. It's a myth (IMHO) propogated by the sellers of cross drilled rotors! Best as I can determine:
1) Cross drilling helps relieve gases which generate between pad and rotor under SEVERE braking conditions.
2) Slotting also helps relieve these gases (to less an extent) and helps maintain a "clean" pad surface (cheese grater effect).
3) To improve cooling, increase the amount of air flowing over the rotor, increase the heat transfer area (by internally venting and/or increasing the rotor diameter/thickness).
4) Increasing the mass of the rotor (making it thicker and/or larger) increases its heat capacity (the amount of heat it can absorb for a given temperature rise).
Cross drilling acts against no 4 as it reduces rotor mass.
Please, racing people, tell me If I'm all wet here!
09-30-1999, 08:46 AM
#14
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A couple reasons
That gas is VERY hot, the quicker that it is vented the less heat it can transfer to the rotor.
Less contact area for the pads to transfer heat to the rotor.
Less mass to cool off between braking sessions.
The less the rotor weighs, the less effort the brakes put out
The pad extrudes into the holes under hard braking, kind of like a tire gripping the road by forming around the roughness of the asphalt. Slotted rotors are not good for this.
.
Remember that braking for one turn does not overheat ANY properly sized rotor. It is the repeated braking, and the issue is how fast can you cool off the rotors between corners? If the rotor weighs less, then it will be a little hotter after braking. However, that heat is quickly dissapated because the temp is so much more than ambient. Therefore, with the more effective cooling and lower mass, drilled rotors have less heat energy in them AND are at a lower temp by the next turn.
Todd W
Less contact area for the pads to transfer heat to the rotor.
Less mass to cool off between braking sessions.
The less the rotor weighs, the less effort the brakes put out
The pad extrudes into the holes under hard braking, kind of like a tire gripping the road by forming around the roughness of the asphalt. Slotted rotors are not good for this.
.
Remember that braking for one turn does not overheat ANY properly sized rotor. It is the repeated braking, and the issue is how fast can you cool off the rotors between corners? If the rotor weighs less, then it will be a little hotter after braking. However, that heat is quickly dissapated because the temp is so much more than ambient. Therefore, with the more effective cooling and lower mass, drilled rotors have less heat energy in them AND are at a lower temp by the next turn.
Todd W
09-30-1999, 08:49 AM
#15
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Mine didn't do it all summer, but now they have started to again.
It might be dependent on the pads you run. My drilled Brembos were pretty quiet all summer, but now that it is colder there is a slight roar at low speeds if the brakes aren't warm yet. You still wouldn't hear it over the stereo, but I don't have one in the coupe
Tell me more about these Zimmerman rotors, are they German? Name suggests so!
Todd W
Tell me more about these Zimmerman rotors, are they German? Name suggests so!
Todd W
09-30-1999, 09:26 AM
#16
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Yes, but...
So far, every cross drilled rotor I've seen on a track car & even some "street only" ones (driven hard) has had cracks. No thanks. I'll take a vented, heavier-duty rotor that can dissipate heat effectively.
I think that these cross drilled rotors may look cool but to me, true performance and long-term durability is more important.
-C.
I think that these cross drilled rotors may look cool but to me, true performance and long-term durability is more important.
-C.
09-30-1999, 10:31 AM
#17
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I said that somewhere at the beginning of this thread
I got off track talking about drilled rotors. I only have drilled because they were cheap used off another car. I think my Powerslot rotors are warped, but I just need better rotors (slotted or not).
How was RA?
Todd W
How was RA?
Todd W
09-30-1999, 01:12 PM
#18
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Great...
I'll post about R.A. when I get home from work tonight. There were a few people who post on A4.org at the event, so I'm surprised no one else has written anything yet.
Anyway, I'll give my take on it later tonight.
-Cathleen
P.S. - I was so wrapped up in stuff and busy that I didn't take ANY pictures! I bought 8 rolls of film and didn't take a one!
We did get some professional pics at the track, though. Those are to be used on the website, however, so I can't post them (the guy who took them gets the credit and such).
Anyway, I'll give my take on it later tonight.
-Cathleen
P.S. - I was so wrapped up in stuff and busy that I didn't take ANY pictures! I bought 8 rolls of film and didn't take a one!
We did get some professional pics at the track, though. Those are to be used on the website, however, so I can't post them (the guy who took them gets the credit and such).
09-30-1999, 01:56 PM
#19
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Congratulations Cathleen...
Two years in a row as top A4 at the concours event. Personally, I think the weather is why you didn't take many pictures...two days of cold steady rain isn't fun for photo shoots. However, it sure made the track time interesting!
10-01-1999, 03:03 AM
#20
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Well...
That gas is VERY hot, the quicker that it is vented the less heat it can transfer to the rotor.
Less contact area for the pads to transfer heat to the rotor.
Less mass to cool off between braking sessions.
The less the rotor weighs, the less effort the brakes put out
The pad extrudes into the holes under hard braking, kind of like a tire gripping the road by forming around the roughness of the asphalt. Slotted rotors are not good for this.
.
Remember that braking for one turn does not overheat ANY properly sized rotor. It is the repeated braking, and the issue is how fast can you cool off the rotors between corners? If the rotor weighs less, then it will be a little hotter after braking. However, that heat is quickly dissapated because the temp is so much more than ambient. Therefore, with the more effective cooling and lower mass, drilled rotors have less heat energy in them AND are at a lower temp by the next turn.
Less contact area for the pads to transfer heat to the rotor.
Less mass to cool off between braking sessions.
The less the rotor weighs, the less effort the brakes put out
The pad extrudes into the holes under hard braking, kind of like a tire gripping the road by forming around the roughness of the asphalt. Slotted rotors are not good for this.
.
Remember that braking for one turn does not overheat ANY properly sized rotor. It is the repeated braking, and the issue is how fast can you cool off the rotors between corners? If the rotor weighs less, then it will be a little hotter after braking. However, that heat is quickly dissapated because the temp is so much more than ambient. Therefore, with the more effective cooling and lower mass, drilled rotors have less heat energy in them AND are at a lower temp by the next turn.