Are these brakes a good deal?
05-08-2012, 03:47 PM
#161
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tyler omfg i lost it over here. 
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Undying Dreams (05-08-2012)
05-08-2012, 03:49 PM
#162
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I can't wait till we're done arguing. dub, when are you going to quit?
05-08-2012, 03:52 PM
#164
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Wow. It may have gotten somewhat off topic but that is uncalled for.
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Undying Dreams (05-08-2012)
05-08-2012, 03:54 PM
#166
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uh oh...i'd delete that link OP or you'll get banned.
05-08-2012, 03:54 PM
#167
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Yeah, it got really off-topic. All I needed to know, is if they were a good deal or not. Then we get this whole debate on whether or not drilled is good or not, and vr6vdub vs. everyone else, it was all unnecessary.
05-08-2012, 03:55 PM
#169
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Thank you 2 for commenting, I am not clicking on that link now. lol
05-08-2012, 03:57 PM
#170
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05-08-2012, 04:00 PM
#171
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Majofo (05-08-2012)
05-08-2012, 05:03 PM
#174
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05-08-2012, 05:09 PM
#175
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05-08-2012, 05:17 PM
#176
There are many claims as to the benefits of drilled vs slotted rotors on stopping power. This guide is intended to provide some facts about drilled and slotted rotors. As a member of the SAE (Society of Automotive Engineers), I was pleased to see a paper "The Effect of Rotor Crossdrilling on Brake Performance" by two GM engineers published in 2006. They examined three vehicle platforms with cross-drilled rotors vs standard rotors to measure convection cooling capability, fade characteristics, wet braking, pedal feel and lining wear. The result is summarized as follows:
- For the sports sedan, the coefficient of friction was 21% higher for drilled rotors than standard front rotors at 340F and higher using 15 brake snubs at 62mph. The track simulated 124 mph fade test showed 37% better brake output for drilled rotors. The drilled rotor brake temperature was about 150 degrees cooler.
- For the performance car, the coefficient of friction was significantly higher for drilled rotors especially at high temperature.
- Wet braking at high pedal pressure was the same for drilled or standard rotors. Wet braking is not significantly improved by drilled rotors.
- Pedal force was much more consistent with drilled rotors over the brake temperature range. That is, to stop at the same deceleration rate, the driver does not need to modulate pedal pressure based on different brake temperatures. This reduces driver fatigue and improves brake response.
Here is good synopsis of the study that highlights some things Brakemotive conveniently glossed over.
----------------------------------------------------
I recently came across this SAE technical paper co-authored by two brake engineers at GM - The Effect of Rotor Crossdrilling on Brake Performance http://www.sae.org/technical/papers/2006-01-0691
Basically, it looks like they didn't necessarily set out to do a full performance comparison, but incidental to their testing on three brake systems they found they had enough data to write it up as a paper.
It'll cost you $14 do download a copy, but it's well worth it if you are interested in the subject. Hopefully at least some of you are willing to give it a read and start a discussion about it. Below are my thoughts to kick it off.
First off, the surprising conclusion is that drilling the rotors actually does increase the rate of cooling for a given a rotor, by up to about 20% in one case. Unfortunately however, that gain comes with some very serious drawbacks, including the possibility that your rotors may actually run hotter despite of it.
I believe one of the most significant considerations in interpreting the paper's data is that they used semi-metallic brake pads for all the testing. From what I've read, these typically have a max operating temp rating of about 500~550 deg C. Secondly, I understand that the primary functional mechanism of this type of pad is abrasion rather than adhesion. By contrast, the higher temp rated race type pads are more biased towards an adhesive mechanism relying upon a transfer layer of material deposited on the rotor.
Where this comes in to play is in interpreting the test data that shows higher apparent friction and deceleration gain for the plain rotor at low temp, the cross-drilled rotor at higher temp, and generally greater temperature fade stability for the cross-drilled. At low temp, the greater surface area of the plain rotor is the dominant performance factor, as one would expect. At higher temps however, the breakdown of the pad is the dominant consideration and the cheese grater effect of the cross-drilled rotors helps to compensate for this by providing increased mechanical friction.
If however, this test were to be repeated with a higher temp rated adhesive type race pad, I'd expect the results to be exactly the opposite. That is at lower temps where you would expect the race pad to perform poorly, the cross-drilled rotors would provide an abrasive mechanism and increased performance. But at higher temps, not only would the lesser surface area of the cross-drilled rotor become the dominant consideration, but the abrasive mechanism of the holes would inhibit proper formation of the transfer layer.
Another interesting aspect of the paper is the radical base performance difference between the three brake systems used in the test. "System 3" appears to be an overall poor performer in comparison with the other 2 systems. In the case of System 3, the cross drilling appears to be a pure bling change, as it is rather consistently outperformed by the plain rotors, despite their being smaller in overall diameter. System 1 was a better performer, but quite unbalanced. Almost all the work on this system was being done by the front rotors. System 2 looks to be the best of the lot, and consequently showed the least radical performance deviations between the plain and cross-drilled rotors.
I believe the base performance difference between System 1 and System 2 helps in interpreting the results showing increased cooling efficiency with the cross-drilled rotors. On System 1, tests at 50kph, 100kph, and 160kph, showed an increase of cooling values (hA) of 8.8%, 12.1%, and 20.1% on the front and -3.2%, 1.9%, and 8.5% on the rear. For System 2, the values at 50kph, 110kph, and 140kph are 7.8%, 10.4%, and 12.1% for the front and 4.1%, 7.7%, and 13.4% rear. The other key piece of data is the raw hA numbers. At 160kph, the average hA for the front rotors of System 1 is 19.26 for the plain rotors and 23.13 for the cross-drilled. By comparison, the System 2 values at 140kph are 23.35 for the plain rotors and 26.18 for the drilled. The conclusion I draw from this is that while cross-drilling does improve the cooling rate, the degree of benefit is inversely proportional to the size of the rotor. From a pure cooling rate consideration, the plain rotors of System 2 outperform the cross-drilled rotors of System 1. In practical terms, using cross-drilled rotors would seem to make the most sense only after you have run out of options for increasing the rotor diameter.
Pad wear on cross-drilled rotors was also shown to be up to up to 50% greater under hard use, and about 25~30% greater under street use. What was not explicitly tested was the effect of this increased wear on temperature. As I understand it, the thinner the pad, the higher the pad temp. My suspicion is that at some point, the diminished heat capacity of the pad due to wear more than offsets the gain in cooling capacity of the cross-drilled rotors. I further suspect that this may be the operating mechanism behind many of the catastrophic failures of cross-drilled rotors at the track. Basically, they will start off strong, but the accelerated rate of pad wear soon drives the rotor into an overheated condition.
Some of the other data and conclusions from the paper on cross-drilled rotors:
There is no practical difference in wet weather performance.
Pad outgassing is not factor
Thermal fatigue life is significantly shorter for cross-drilled rotors. In the case of poorly balanced and possibly under-sized System 1, by as much as 50%.
Last edited by vr6vdub; 05-08-2012 at 05:22 PM.
05-08-2012, 05:22 PM
#177
^Off topic, but thanks again for the power-steering whine fix DIY Majofo. Yesterday I was getting my car inspected at a gas station and some girl rolled up in a TL saying that during cold starts her car sounded like it was gonna blow up. Lucky for her I bought a spare one and it was in my trunk.
Put the new o-ring in for her, and this morning she called and said that she owed me lunch for fixing her car. I responded with: Lunch < Blumpkin while eating a BLT with buttered syrup waffles as bread
Put the new o-ring in for her, and this morning she called and said that she owed me lunch for fixing her car. I responded with: Lunch < Blumpkin while eating a BLT with buttered syrup waffles as bread
Last edited by Abe_Froman; 05-08-2012 at 05:28 PM.
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05-09-2012, 01:50 PM
#179
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05-09-2012, 01:53 PM
#180
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why is this still going on?
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Mrtastygoody (05-09-2012)
05-09-2012, 01:53 PM
#181
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^LOL!
At first I was about to come in here and be like "REALLY? REALLY KIDS?"
Then I laughed and it was ok.
At first I was about to come in here and be like "REALLY? REALLY KIDS?"
Then I laughed and it was ok.
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05-09-2012, 02:58 PM
#183
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05-09-2012, 03:01 PM
#184
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I saw he commented and was like "Oh God" but to my surprise it was that and I got a good laugh. Everything went better than expected 
lol
lol
05-09-2012, 03:32 PM
#186
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