Drilled or slotted rotors still relevant?
- Thread starter J. A. Rizzo
- Start date
- Status
Originally Posted By: BuickGN
This screen hurts my eyes staring at it for too long.
TN film panel?
Originally Posted By: BuickGN
I'll post a summary tomorrow. Anyone know what I can and can't post? I signed the license agreement and I'm not going to violate it but I think a brief summary in my own words would be ok, right? Is anyone even interested before I go to the trouble?
No idea what you can and can't post. Could you post the agreement for us to help you interpret it?
I am definitely interested in hearing more about this.
This screen hurts my eyes staring at it for too long.
TN film panel?
Originally Posted By: BuickGN
I'll post a summary tomorrow. Anyone know what I can and can't post? I signed the license agreement and I'm not going to violate it but I think a brief summary in my own words would be ok, right? Is anyone even interested before I go to the trouble?
No idea what you can and can't post. Could you post the agreement for us to help you interpret it?
I am definitely interested in hearing more about this.
Well, here's a vague overview...
Tests were performed on 4 different braking systems each run with crossdrilled rotors and with blanks. Same pads for each system.
Tests were performed at both the track and on the dyno.
In the wet, at low braking effort, the crossdrilled rotors had significantly more bite (over 50%). At higher effort, the blanks and crossdrilled rotors were much closer. This was thought to be the hydrodynamic wedge having more of an effect with less clamping pressure.
Drilled rotors improved front rotor cooling with higher speeds showing larger improvements. It's very significant but I'm afraid to post the number. Improved cooling was seen at every speed.
Rear rotor cooling was interesting. On one system with high airflow to the rotor, smaller rotors, and many drilled holes, saw higher temps at low speeds, a wash at moderate speeds and it was not until higher speeds there was a temperature reduction. On the model with the larger rotors and less airflow temperature decreses were seen everywhere with drilled rotors.
Apparent friction started higher with the blank rotors with a starting temp of 100C and quickly fell as temps rose.
Apparent friction started lower with the drilled rotors but remained almost flat to 400C resulting in significantly less pedal effort once hot than the blank rotors.
Brake pad temperatures were significantly lower with drilled rotors.
Glazing the pads was almost a non issue with the drilled rotors.
Pad wear under normal temps was very close but as temps rose the pads wore much quicker with the drilled rotors. Pad wear was more even with drilled rotors.
Drilled rotors recovered quicker.
Drilled rotors showed more of an advantage in vehicles with lower airflow to the rotors.
Some of the cracking at the holes was found to be a factor of the design of the hat area causing stress and not heat alone.
Hot Roughness (Hot Judder) was non-existant with the drilled rotors. My TL suffered from this very badly with the stock brakes. As soon as they picked up any kind of temperature they felt like they were warped. It happened at a lower and lower temperature as time went on. This was said to be the rotor distorting unevenly during heat cycles and resulting in high spots that catch brake pad material which only gets worse over time.
The cons of course are a shorter thermal fatigue life, quicker pad wear at high temps, and a whirring noise under heavy braking.
I know it's vague but I think I covered all of the large points. This thing was 28 pages long, lots of neat details.
Tests were performed on 4 different braking systems each run with crossdrilled rotors and with blanks. Same pads for each system.
Tests were performed at both the track and on the dyno.
In the wet, at low braking effort, the crossdrilled rotors had significantly more bite (over 50%). At higher effort, the blanks and crossdrilled rotors were much closer. This was thought to be the hydrodynamic wedge having more of an effect with less clamping pressure.
Drilled rotors improved front rotor cooling with higher speeds showing larger improvements. It's very significant but I'm afraid to post the number. Improved cooling was seen at every speed.
Rear rotor cooling was interesting. On one system with high airflow to the rotor, smaller rotors, and many drilled holes, saw higher temps at low speeds, a wash at moderate speeds and it was not until higher speeds there was a temperature reduction. On the model with the larger rotors and less airflow temperature decreses were seen everywhere with drilled rotors.
Apparent friction started higher with the blank rotors with a starting temp of 100C and quickly fell as temps rose.
Apparent friction started lower with the drilled rotors but remained almost flat to 400C resulting in significantly less pedal effort once hot than the blank rotors.
Brake pad temperatures were significantly lower with drilled rotors.
Glazing the pads was almost a non issue with the drilled rotors.
Pad wear under normal temps was very close but as temps rose the pads wore much quicker with the drilled rotors. Pad wear was more even with drilled rotors.
Drilled rotors recovered quicker.
Drilled rotors showed more of an advantage in vehicles with lower airflow to the rotors.
Some of the cracking at the holes was found to be a factor of the design of the hat area causing stress and not heat alone.
Hot Roughness (Hot Judder) was non-existant with the drilled rotors. My TL suffered from this very badly with the stock brakes. As soon as they picked up any kind of temperature they felt like they were warped. It happened at a lower and lower temperature as time went on. This was said to be the rotor distorting unevenly during heat cycles and resulting in high spots that catch brake pad material which only gets worse over time.
The cons of course are a shorter thermal fatigue life, quicker pad wear at high temps, and a whirring noise under heavy braking.
I know it's vague but I think I covered all of the large points. This thing was 28 pages long, lots of neat details.
Last edited:
That's an interesting document for sure, but only relevant to similar setups.
I can tell you from personal experience on large trucks that drilling and slotting only worsened our overheating problems. Losing mass from a heat sink is never a good idea.
I think what the data really illustrates is that there are nearly infinite variables in braking systems!
I can tell you from personal experience on large trucks that drilling and slotting only worsened our overheating problems. Losing mass from a heat sink is never a good idea.
I think what the data really illustrates is that there are nearly infinite variables in braking systems!
Originally Posted By: SteveSRT8
That's an interesting document for sure, but only relevant to similar setups.
I can tell you from personal experience on large trucks that drilling and slotting only worsened our overheating problems. Losing mass from a heat sink is never a good idea.
I think what the data really illustrates is that there are nearly infinite variables in braking systems!
The article focused on cars. 4 different setups in fact. In every one of them crossdrilling showed cooler rotor and pad temps. Losing mass in exchange for more surface area is not a bad idea. Case in point, the 13" rotors on my TL weigh the same as my stock 11.8" yet somehow I can't get the 13" anywhere close to fading while it was easy with the stock rotors. If mass was always the most important thing in brakes, why not have a 10lb 5" rotor on everything?
That's an interesting document for sure, but only relevant to similar setups.
I can tell you from personal experience on large trucks that drilling and slotting only worsened our overheating problems. Losing mass from a heat sink is never a good idea.
I think what the data really illustrates is that there are nearly infinite variables in braking systems!
The article focused on cars. 4 different setups in fact. In every one of them crossdrilling showed cooler rotor and pad temps. Losing mass in exchange for more surface area is not a bad idea. Case in point, the 13" rotors on my TL weigh the same as my stock 11.8" yet somehow I can't get the 13" anywhere close to fading while it was easy with the stock rotors. If mass was always the most important thing in brakes, why not have a 10lb 5" rotor on everything?
Can't answer that question.
But as a fleet owner I can tell you that on 9000 pound plus Savana 3500 vans driven in city traffic a drilled and slotted MEGA expensive rotor ran way HOTTER than a stocker with the same pads.
We went through dozens of pad and rotor combos for these trucks up till they went to 4 wheel discs with multi pot calipers in around 2002 or so. Absolutely verified with digital infrared thermometer.
This does not in any way relate to your tech article. Just my actual real world experience on the street with several trucks.
But as a fleet owner I can tell you that on 9000 pound plus Savana 3500 vans driven in city traffic a drilled and slotted MEGA expensive rotor ran way HOTTER than a stocker with the same pads.
We went through dozens of pad and rotor combos for these trucks up till they went to 4 wheel discs with multi pot calipers in around 2002 or so. Absolutely verified with digital infrared thermometer.
This does not in any way relate to your tech article. Just my actual real world experience on the street with several trucks.
Originally Posted By: SteveSRT8
Can't answer that question.
But as a fleet owner I can tell you that on 9000 pound plus Savana 3500 vans driven in city traffic a drilled and slotted MEGA expensive rotor ran way HOTTER than a stocker with the same pads.
We went through dozens of pad and rotor combos for these trucks up till they went to 4 wheel discs with multi pot calipers in around 2002 or so. Absolutely verified with digital infrared thermometer.
This does not in any way relate to your tech article. Just my actual real world experience on the street with several trucks.
That actually makes sense even in the context of the article.
It showed that in some situations, primarily low vehicle speed with lots of drilled holes for the size of the rotor, crossdrilling could raise temps. As rotor speeds increased, it evened out and then showed an advantage.
One other thing the article pointed out was as rotor temps got into the "hot" range crossdrilling ate the pads much more quickly.
Can't answer that question.
But as a fleet owner I can tell you that on 9000 pound plus Savana 3500 vans driven in city traffic a drilled and slotted MEGA expensive rotor ran way HOTTER than a stocker with the same pads.
We went through dozens of pad and rotor combos for these trucks up till they went to 4 wheel discs with multi pot calipers in around 2002 or so. Absolutely verified with digital infrared thermometer.
This does not in any way relate to your tech article. Just my actual real world experience on the street with several trucks.
That actually makes sense even in the context of the article.
It showed that in some situations, primarily low vehicle speed with lots of drilled holes for the size of the rotor, crossdrilling could raise temps. As rotor speeds increased, it evened out and then showed an advantage.
One other thing the article pointed out was as rotor temps got into the "hot" range crossdrilling ate the pads much more quickly.
I agree.
I have one vehicle that runs 4 pot Brembos with a slotted factory rotor and I am certain that there is a negative effect on pad wear.
I have one vehicle that runs 4 pot Brembos with a slotted factory rotor and I am certain that there is a negative effect on pad wear.
- Status