Got new crossdrilled rotors in mail
08-17-2002, 08:57 AM
#31
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Kinda makes you wonder who the expert is, eh.
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08-17-2002, 10:44 AM
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From what little I think I know about the subject, the holes help vent gasses that out-gas from the surface of the pads when they're hot. Otherwise, the gas acts as a 'lubricant' layer between pad & rotor, reducing the coefficient of friction between them. Slots do pretty much the same.
"Drilled" is bad, "cast-in" is good from the standpoint of cracking. Drilled holes have a sharp-cornered transition from flat rotor surface to hole, which acts as a stress raiser. Cast holes tend to be naturally radiused, and resist fatigue cracking from heat cycles & mechanical stress better.
All this is, of course, worth at least as much as you paid for it.
Jim, armchair expert...
"Drilled" is bad, "cast-in" is good from the standpoint of cracking. Drilled holes have a sharp-cornered transition from flat rotor surface to hole, which acts as a stress raiser. Cast holes tend to be naturally radiused, and resist fatigue cracking from heat cycles & mechanical stress better.
All this is, of course, worth at least as much as you paid for it.
Jim, armchair expert...
08-17-2002, 10:49 AM
#33
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[quote]Originally posted by jim968:
<strong>From what little I think I know about the subject, the holes help vent gasses that out-gas from the surface of the pads when they're hot. Otherwise, the gas acts as a 'lubricant' layer between pad & rotor, reducing the coefficient of friction between them. Slots do pretty much the same.
"Drilled" is bad, "cast-in" is good from the standpoint of cracking. Drilled holes have a sharp-cornered transition from flat rotor surface to hole, which acts as a stress raiser. Cast holes tend to be naturally radiused, and resist fatigue cracking from heat cycles & mechanical stress better.
All this is, of course, worth at least as much as you paid for it.
Jim, armchair expert...</strong><hr></blockquote>
From what I recall of the aforementioned Altima thread, the gas thing hasn't been an issue since the 60s, because of new brake pad technology. And since you want more mass in your rotors to absorb and dissipate more heat from the pads, any loss, through holes (drilled or cast) or slots, is a bad thing. They even showed a picture of a GT2 rotor (maybe it was a 996TT) that had all these little cracks around the cast holes. It convinced me. But I might be remembering the rest wrong.
<strong>From what little I think I know about the subject, the holes help vent gasses that out-gas from the surface of the pads when they're hot. Otherwise, the gas acts as a 'lubricant' layer between pad & rotor, reducing the coefficient of friction between them. Slots do pretty much the same.
"Drilled" is bad, "cast-in" is good from the standpoint of cracking. Drilled holes have a sharp-cornered transition from flat rotor surface to hole, which acts as a stress raiser. Cast holes tend to be naturally radiused, and resist fatigue cracking from heat cycles & mechanical stress better.
All this is, of course, worth at least as much as you paid for it.
Jim, armchair expert...</strong><hr></blockquote>
From what I recall of the aforementioned Altima thread, the gas thing hasn't been an issue since the 60s, because of new brake pad technology. And since you want more mass in your rotors to absorb and dissipate more heat from the pads, any loss, through holes (drilled or cast) or slots, is a bad thing. They even showed a picture of a GT2 rotor (maybe it was a 996TT) that had all these little cracks around the cast holes. It convinced me. But I might be remembering the rest wrong.
08-17-2002, 12:31 PM
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[quote]"Drilled" is bad, "cast-in" is good from the standpoint of cracking. Drilled holes have a sharp-cornered transition from flat rotor surface to hole, which acts as a stress raiser. Cast holes tend to be naturally radiused, and resist fatigue cracking from heat cycles & mechanical stress better.[/QB]<hr></blockquote>
The zimmerman rotors I got are crossdrilled however they have done a really nice job on the friction surface to radius the holes. Looks kind of like counter sinking then polished.
The zimmerman rotors I got are crossdrilled however they have done a really nice job on the friction surface to radius the holes. Looks kind of like counter sinking then polished.
08-17-2002, 12:37 PM
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[quote]Originally posted by Skwerl:
<strong>And since you want more mass in your rotors to absorb and dissipate more heat from the pads, any loss, through holes (drilled or cast) or slots, is a bad thing.</strong><hr></blockquote>
What I was told is that decreasing surface friction area with holes actually increases surface area to disapate heat. There is more surface area inside the walls of the holes than would be if you did not drill them at all. Probably makes the rotor weaker but maybe runs cooler and definately looks cooler. Even if they are weaker at 195 a set I will just treat them as disposable, consumable product.
<strong>And since you want more mass in your rotors to absorb and dissipate more heat from the pads, any loss, through holes (drilled or cast) or slots, is a bad thing.</strong><hr></blockquote>
What I was told is that decreasing surface friction area with holes actually increases surface area to disapate heat. There is more surface area inside the walls of the holes than would be if you did not drill them at all. Probably makes the rotor weaker but maybe runs cooler and definately looks cooler. Even if they are weaker at 195 a set I will just treat them as disposable, consumable product.
08-17-2002, 05:46 PM
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This is a really good thread. I just got done installing new rear rotors on my 951 yesterday. They said "made in germany" so I figured they would be durable. After the installation I washed the car and my nice shiny rotors almost immediately began to rust all over the hub. Today they came right back off and got scrubbed down well with some steel wool, cleaned with brake cleaner and got shot with a few coats of Plasti-Kote "aluminum" engine paint ($3.99) on the non-friction surfaces. I used Skip's advice on the cardboard template for use in masking. Worked well and the color is perfect. My new fronts ordered from Paragon last week will also get this treatment.
08-17-2002, 09:15 PM
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[quote]Originally posted by Logan5:
<strong>
Even if they are weaker at 195 a set I will just treat them as disposable, consumable product.</strong><hr></blockquote>
195/set where?
<strong>
Even if they are weaker at 195 a set I will just treat them as disposable, consumable product.</strong><hr></blockquote>
195/set where?
08-18-2002, 12:23 AM
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[quote]Originally posted by Dan Gallagher:
<strong>
195/set where?</strong><hr></blockquote>
Actually Dan... it was 149.00 dollars + 20 for shipping. Plus I bought two new sets of Wagner Pads. It was like 195 for everything.
Ebay.
Here is the auction I won, you can contact them or look at their other auctions. They are a reputable shop in Long Island NY so you could probably just go over there and buy them and save on the shipping. That is funny <img src="graemlins/roflmao.gif" border="0" alt="[hiha]" /> that I am a California boy telling you where to buy stuff in your town on the other side of the country.
<a href="http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=1847500072&rd=1" target="_blank">Rotor Auction</a> <img src="graemlins/roflmao.gif" border="0" alt="[hiha]" />
<strong>
195/set where?</strong><hr></blockquote>
Actually Dan... it was 149.00 dollars + 20 for shipping. Plus I bought two new sets of Wagner Pads. It was like 195 for everything.
Ebay.
Here is the auction I won, you can contact them or look at their other auctions. They are a reputable shop in Long Island NY so you could probably just go over there and buy them and save on the shipping. That is funny <img src="graemlins/roflmao.gif" border="0" alt="[hiha]" /> that I am a California boy telling you where to buy stuff in your town on the other side of the country.
<a href="http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=1847500072&rd=1" target="_blank">Rotor Auction</a> <img src="graemlins/roflmao.gif" border="0" alt="[hiha]" />
08-18-2002, 12:27 AM
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yea, actually i talked to those people once before, they only have the front rotors right? i wanted to get the rear too but they only place i see them is performanceproducts or tweeks (which is like $150 each) i thoughrt maybe you knew a place that had front & rear