What did you do to the G today?
#8821
08-20-2018, 10:26 PM
Registered User
#8822
08-20-2018, 10:31 PM
Neato! Anything for a reasonable price isn't gonna work FWIW. I just prefer blanks or Slots only. If you had brake noise it was your pad choice or high frequency vibration from lack of lubrication/shims typically, IME.
Thanks for your reply about the info, I learned something today.
Thanks for your reply about the info, I learned something today.
#8823
08-21-2018, 06:51 AM
Join Date: Mar 2009
Location: By the sea, Tx
Posts: 18,299
Received 1,487 Likes
on
1,222 Posts
G35 sedan w/ too much money in mods
#8825
08-21-2018, 11:58 AM
EDIT: Turns out Hall S already said this above in post #8822 c:
FYI - Rotors that come 'drilled' from the factory (IE Porsche) are not drilled, the holes are actually included in the casting molds. Drilling any cast iron after it cools will introduce stress risers due to the crystal structure (Face Center Cubic) of the metal at lower temperatures. This is fine on most applications, but as you put the iron through extreme heat cycles, the thermal expansion will cause micro-cracks to form, which are propagated when they reach these stress risers.
Introducing the cavities/holes in the casting process ensures the iron will flow (again due to crystal structure, but BodyCC this time) around the cavities and cool into that shape without any anomalies in the crystal structures.
Source: i make brakes
FYI - Rotors that come 'drilled' from the factory (IE Porsche) are not drilled, the holes are actually included in the casting molds. Drilling any cast iron after it cools will introduce stress risers due to the crystal structure (Face Center Cubic) of the metal at lower temperatures. This is fine on most applications, but as you put the iron through extreme heat cycles, the thermal expansion will cause micro-cracks to form, which are propagated when they reach these stress risers.
Introducing the cavities/holes in the casting process ensures the iron will flow (again due to crystal structure, but BodyCC this time) around the cavities and cool into that shape without any anomalies in the crystal structures.
Source: i make brakes
#8827
08-21-2018, 12:25 PM
EDIT: Turns out Hall S already said this above in post #8822 c:
FYI - Rotors that come 'drilled' from the factory (IE Porsche) are not drilled, the holes are actually included in the casting molds. Drilling any cast iron after it cools will introduce stress risers due to the crystal structure (Face Center Cubic) of the metal at lower temperatures. This is fine on most applications, but as you put the iron through extreme heat cycles, the thermal expansion will cause micro-cracks to form, which are propagated when they reach these stress risers.
Introducing the cavities/holes in the casting process ensures the iron will flow (again due to crystal structure, but BodyCC this time) around the cavities and cool into that shape without any anomalies in the crystal structures.
Source: i make brakes
FYI - Rotors that come 'drilled' from the factory (IE Porsche) are not drilled, the holes are actually included in the casting molds. Drilling any cast iron after it cools will introduce stress risers due to the crystal structure (Face Center Cubic) of the metal at lower temperatures. This is fine on most applications, but as you put the iron through extreme heat cycles, the thermal expansion will cause micro-cracks to form, which are propagated when they reach these stress risers.
Introducing the cavities/holes in the casting process ensures the iron will flow (again due to crystal structure, but BodyCC this time) around the cavities and cool into that shape without any anomalies in the crystal structures.
Source: i make brakes
#8828
08-21-2018, 12:57 PM
Originally Posted by g356sp
EDIT: Turns out Hall S already said this above in post #8822 c:
FYI - Rotors that come 'drilled' from the factory (IE Porsche) are not drilled, the holes are actually included in the casting molds. Drilling any cast iron after it cools will introduce stress risers due to the crystal structure (Face Center Cubic) of the metal at lower temperatures. This is fine on most applications, but as you put the iron through extreme heat cycles, the thermal expansion will cause micro-cracks to form, which are propagated when they reach these stress risers.
Introducing the cavities/holes in the casting process ensures the iron will flow (again due to crystal structure, but BodyCC this time) around the cavities and cool into that shape without any anomalies in the crystal structures.
Source: i make brakes
FYI - Rotors that come 'drilled' from the factory (IE Porsche) are not drilled, the holes are actually included in the casting molds. Drilling any cast iron after it cools will introduce stress risers due to the crystal structure (Face Center Cubic) of the metal at lower temperatures. This is fine on most applications, but as you put the iron through extreme heat cycles, the thermal expansion will cause micro-cracks to form, which are propagated when they reach these stress risers.
Introducing the cavities/holes in the casting process ensures the iron will flow (again due to crystal structure, but BodyCC this time) around the cavities and cool into that shape without any anomalies in the crystal structures.
Source: i make brakes
#8829
08-21-2018, 01:00 PM
I see the stop tech ones have the chamfered and casting holes, so those are the ones to buy on a budget in a hurry.
Thanks for teaching me something today! I now know what to look for more.
What's interesting is no motorcycle ones have ever had a "leading edge" like you guys mention here and they work just fine. Example in below picture. It is a two piece rotor held by bobbins though.
Thanks for teaching me something today! I now know what to look for more.
What's interesting is no motorcycle ones have ever had a "leading edge" like you guys mention here and they work just fine. Example in below picture. It is a two piece rotor held by bobbins though.
#8830
08-21-2018, 02:11 PM
Registered User
A couple ways to possibly identify if the holes were cast in or machined (drilled) later... Look at the inside walls of the holes. If they're 'rough' (use the vanes on the inside of the rotors (of front rotors) for comparison), they're cast. If they're smooth or shiny, they've been machined. Then again, some may cast in holes and then drill them out larger although that seems pretty silly and unnecessary. The precision of the size of these holes isn't that critical.
You can't use the 'edge' of the holes as a sure sign either. If you look at onevq35de's last example, notice how the curved section blends into the horizontal and vertical edges (tangency) ? Depending on the pattern (mold), it could look like that at first but the rotor face gets machined so you'll lose part of that blend. You'd be back to a sharp edge ! Now I'm wondering, even with cast-in holes, do they at least spot-face them during machining ?#s3gt_translate_tooltip_mini { display: none !important; }
You can't use the 'edge' of the holes as a sure sign either. If you look at onevq35de's last example, notice how the curved section blends into the horizontal and vertical edges (tangency) ? Depending on the pattern (mold), it could look like that at first but the rotor face gets machined so you'll lose part of that blend. You'd be back to a sharp edge ! Now I'm wondering, even with cast-in holes, do they at least spot-face them during machining ?#s3gt_translate_tooltip_mini { display: none !important; }
#8831
08-21-2018, 03:42 PM
[QUOTE=Urbanengineer;7147557]I see the stop tech ones have the chamfered and casting holes, so those are the ones to buy on a budget in a hurry.
Nope. Stop Tech drills'em too. Just called. I sense that most aftermarket rotors are going to be drilled. Perhaps even some of the higher end oem's as well.
Nope. Stop Tech drills'em too. Just called. I sense that most aftermarket rotors are going to be drilled. Perhaps even some of the higher end oem's as well.
#8832
08-21-2018, 03:44 PM
A couple ways to possibly identify if the holes were cast in or machined (drilled) later... Look at the inside walls of the holes. If they're 'rough' (use the vanes on the inside of the rotors (of front rotors) for comparison), they're cast. If they're smooth or shiny, they've been machined. Then again, some may cast in holes and then drill them out larger although that seems pretty silly and unnecessary. The precision of the size of these holes isn't that critical.
You can't use the 'edge' of the holes as a sure sign either. If you look at onevq35de's last example, notice how the curved section blends into the horizontal and vertical edges (tangency) ? Depending on the pattern (mold), it could look like that at first but the rotor face gets machined so you'll lose part of that blend. You'd be back to a sharp edge ! Now I'm wondering, even with cast-in holes, do they at least spot-face them during machining ?#s3gt_translate_tooltip_mini { display: none !important; }
You can't use the 'edge' of the holes as a sure sign either. If you look at onevq35de's last example, notice how the curved section blends into the horizontal and vertical edges (tangency) ? Depending on the pattern (mold), it could look like that at first but the rotor face gets machined so you'll lose part of that blend. You'd be back to a sharp edge ! Now I'm wondering, even with cast-in holes, do they at least spot-face them during machining ?#s3gt_translate_tooltip_mini { display: none !important; }
#8833
08-21-2018, 04:38 PM
#8834
08-21-2018, 05:17 PM
#8835
08-21-2018, 06:01 PM
As far as I know, Zimmerman is the only company that includes the holes in the casting. The SOLE purpose of the holes is to reduce the weight of the rotor - pads use to need holes/slots for off-gassing, but pad binding materials have come a long way since the days of asbestos, and no longer off-gas in large enough quantities for the pads to need any relief.
The benefit of slotting the face of the rotors is that the sharp edge of the slots will artificially increase the initial torque of the pads, which aids in pedal feel, especially on the street. This will also help inexperienced track drivers in terms of pedal feel, but experienced track rats are already mashing the pedal deep into the brake zone on high torque race pads, so it doesn't make much difference there. Where the slots will make a difference regardless of skill level is in the release characteristics of the pad. The orientation of the slots will help separate the pad from the disc, which aids in pedal modulation once you're already on the brakes and reduces pad drag. This is where directional rotors come into play (along with cooling vanes, but not so much on OE rotors), if your rotors are slotted but don't have a 'left' and 'right' such that the slots are facing the same direction on both sides of the car, then they are probably just for show.
On a slightly related side note, when people complain about pad rollback, its typically a problem with worn suspension components or wheel bearings (usually found on older cars), not a problem with the brakes. Installing rollback springs in your calipers is a band-aid for unrelated suspension issues.
The benefit of slotting the face of the rotors is that the sharp edge of the slots will artificially increase the initial torque of the pads, which aids in pedal feel, especially on the street. This will also help inexperienced track drivers in terms of pedal feel, but experienced track rats are already mashing the pedal deep into the brake zone on high torque race pads, so it doesn't make much difference there. Where the slots will make a difference regardless of skill level is in the release characteristics of the pad. The orientation of the slots will help separate the pad from the disc, which aids in pedal modulation once you're already on the brakes and reduces pad drag. This is where directional rotors come into play (along with cooling vanes, but not so much on OE rotors), if your rotors are slotted but don't have a 'left' and 'right' such that the slots are facing the same direction on both sides of the car, then they are probably just for show.
On a slightly related side note, when people complain about pad rollback, its typically a problem with worn suspension components or wheel bearings (usually found on older cars), not a problem with the brakes. Installing rollback springs in your calipers is a band-aid for unrelated suspension issues.