Best pad/rotor combo for F-body
07-13-2011, 03:50 PM
#61
The OEMs do it mostly for bling and because it is expected by their buyers... Porsche offers them so they have to put them on the Z06, etc. Not to mention that a lot of high end cars are running carbon brakes, not iron disks nowadays. It is somewhat speculative admittedly because they typically aren't going to release any proprietary testing and engineering data and what we get for information form them is much more heavily influenced by marketing then engineering.
Be that as it may, I wouldn't say that the opponents of C/D rotors are the only ones that are making some statements that aren't exactly true. Especially the old SAE paper business... the only semi-decent one I am aware of was from GM. It is available if you buy it from the SAE or are a member. However, it isn't like it proved anything once and for all as it didn't have the strongest experimental model. In any case, I don't know that I would say that it was proved on the basis of one paper. I have looked around for more of them, which are also probably hidden, or more likely the manufacturers have real data that is proprietary that we are not seeing... At any rate, if you happened to have a rotor constructed the same way as in the GM paper and used semi-metallic pads then you might see a cooling benefit of 20% at high speed (160kph). However, that system also had hotter rear rotor temps at low speed. System 2 which is more analogous to a performance car did benefit 12% at 140kph. The system with organic pads (3) was worse all around with drilled disks. Which begs the question of pad material and braking mechanism as drilled or slotted will help improve abrasive force at the expense of adhesive. They did also note that disk mass was pretty similar, only .2kg different at most, or about 5% for each set.
If we are also taking the GM paper as brake gospel, then they determined there was in fact no improvement in wet performance for a drilled disk, and that thermal fatigue life of drilled rotors is up to 50% shorter than blanks, and that pad life is 50% less under heavy use and 25-30% worse under typical street use.
And as far as the Z06, if GM cared about brake cooling and performance as opposed to bling and being cheap that car would have a left and right directionally vaned front disk and not one part put on the other side backwards.
I do agree that race-cars aren't necessarily analogous to street cars, especially considering that they are running huge multi-piece disks that are very thick and designed for long narrowish pads. They are probably also running very high temp pad compounds and need the slots to abrade the pads for extra bite until the pads get to temperature.
Be that as it may, I wouldn't say that the opponents of C/D rotors are the only ones that are making some statements that aren't exactly true. Especially the old SAE paper business... the only semi-decent one I am aware of was from GM. It is available if you buy it from the SAE or are a member. However, it isn't like it proved anything once and for all as it didn't have the strongest experimental model. In any case, I don't know that I would say that it was proved on the basis of one paper. I have looked around for more of them, which are also probably hidden, or more likely the manufacturers have real data that is proprietary that we are not seeing... At any rate, if you happened to have a rotor constructed the same way as in the GM paper and used semi-metallic pads then you might see a cooling benefit of 20% at high speed (160kph). However, that system also had hotter rear rotor temps at low speed. System 2 which is more analogous to a performance car did benefit 12% at 140kph. The system with organic pads (3) was worse all around with drilled disks. Which begs the question of pad material and braking mechanism as drilled or slotted will help improve abrasive force at the expense of adhesive. They did also note that disk mass was pretty similar, only .2kg different at most, or about 5% for each set.
If we are also taking the GM paper as brake gospel, then they determined there was in fact no improvement in wet performance for a drilled disk, and that thermal fatigue life of drilled rotors is up to 50% shorter than blanks, and that pad life is 50% less under heavy use and 25-30% worse under typical street use.
And as far as the Z06, if GM cared about brake cooling and performance as opposed to bling and being cheap that car would have a left and right directionally vaned front disk and not one part put on the other side backwards.
I do agree that race-cars aren't necessarily analogous to street cars, especially considering that they are running huge multi-piece disks that are very thick and designed for long narrowish pads. They are probably also running very high temp pad compounds and need the slots to abrade the pads for extra bite until the pads get to temperature.
