Cross Drilled, Slotted, and plain old Vented rotor under the 'advanced' microscope...
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Joined: Jul 2000
Posts: 520
From: MD
Originally posted by teamsleep13
What do u think about aluminum rotors?
What do u think about aluminum rotors?
Really, I think that the best thing for increasing braking performance on a road course would be either working on better cooling (there are cool ceramic coatings out there that allow for better heat dissipation, I’d like to try coating the inside of rotors with that stuff) and pad compounds more that work well over greater heat ranges.
In the long run, if you make any real advantages you loose your big, sexy brakes, but you gain functionality and possibly go back to the more classic 60’s/70’s Trans Am style stance…
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From: Upstate NY
Originally posted by teamsleep13
What do u think about aluminum rotors?
Hunter
What do u think about aluminum rotors?
Hunter
As a friction surface it wears rapidly, even on a 1/8 inch thick hard-coated bicycle application.
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From: MD
Originally posted by OldSStroker
Aluminum loses 75% of it's strength by about 400F, and melts at temps below the glowing cast iron working temps.
As a friction surface it wears rapidly, even on a 1/8 inch thick hard-coated bicycle application.
Aluminum loses 75% of it's strength by about 400F, and melts at temps below the glowing cast iron working temps.
As a friction surface it wears rapidly, even on a 1/8 inch thick hard-coated bicycle application.
There are some grades that would still be close to strong enough slightly above that, but they all melt at around 1100* (before they get glowing hot) and would fall appart well befor that.
For that matter, I assumed that he meant aluminum with some sort of a steel liner for the friction surface (no idea how you'd attach them and account for the expansion differences). A pure hardcoated aluminum piece would never last long enough for street use, even if you got around the temp issue...
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From: looking for a flow bench so Brook and I can race
Originally posted by OldSStroker
I haven't seen it on Baer's site. Do you have a pic or link?
I'm very skeptical.
I haven't seen it on Baer's site. Do you have a pic or link?
I'm very skeptical.
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Posts: 209
Originally posted by WS6 TA
This seems to be an awfully fluff filled thread for advanced tech… forgive me if I repeat something that someone already said, it was painful enough reading that I only skimmed most of it.
In a nutshell:
- cross drilled rotors are a hold back to the 60’s. Back then pads would outgas as you used them and rotors were cross drilled to allow a path for these gasses to escape so the pads would stay in contact with the rotor surface. Pad compounds have gotten much better and out gassing is no longer an issue. There is NO reason why a car with modern pad compounds and a steel or iron rotor should be cross drilled. They do nothing for cooling. They do little for weight reduction, and the hard/drilled edges are stress risers which create a location for cracks to start.
- Slotted rotors are really designed for rally and similar applications. The slots do not cool, they do not lighten or anything else. They clean contaminants from the pad surface so when you apply the brakes right after driving through a mud puddle you actually have brakes. They’re sort of a combination scraper and groove to flow crap away from the pad surface (think aquatread tires). BTW, if they are not properly designed they become a great source of stress risers and cracks. For 99% of us, slotted rotors will do nothing but cause our pads to wear faster and decrease the life of the rotor.
- Larger rotors are not used for more stopping power. Any rotor that can lock the brakes can exert more torque then the tires can apply to the ground (in other words, all the stopping power that the chassis could use), in most cases, this would be a very small rotor. What bigger rotors do is act as a bigger heat sink. They have more mass, more thermal inertia so that if you apply the same amount of heat to them they do not get as hot (stopping converts the kinetic energy of the car to heat). The idea is that if you can control the range of temperatures that the rotors can possibly see to a smaller range you will have an easier time designing pads that will give consistent braking performance. If it wasn’t for heat then the best design would be the smallest rotor that you can generate enough torque to lock the wheels, these things are heavy, and remember that rotating mass is like adding 4x the stationary mass to the car WRT to the necessary force you must generate to accelerate (decelerate) the car. For street use, almost no one needs larger brakes, they just need pads that better suit their driving style.
- Most drilled and slotted rotors are sold for their appearance… it’s a ricer mod. People associate it with high performance brakes. The super high end Porsche stuff is the only exception that I know of. Their “crossdrilled” are actually cast (with a taper and chamfer) in ceramic composite rotors that are meant to work with a special pad. They’ve discontinued and redesigned them at lest 2x that I know of because they did not work correctly or wouldn’t live.
- Another effort that a lot of experimenting in this field is going in is better heat dissipation. If you can dissipate more heat you can run a smaller rotor with the same results. One of the ‘cooler’ (sorry) things that I’ve seen are rotors with lots of little cones cast into the finned vented area to increase surface area and better dissipate heat.
And then my real pet peeve… if you can run smaller rotors you can run smaller diameter, lighter wheels and tires
This seems to be an awfully fluff filled thread for advanced tech… forgive me if I repeat something that someone already said, it was painful enough reading that I only skimmed most of it.
In a nutshell:
- cross drilled rotors are a hold back to the 60’s. Back then pads would outgas as you used them and rotors were cross drilled to allow a path for these gasses to escape so the pads would stay in contact with the rotor surface. Pad compounds have gotten much better and out gassing is no longer an issue. There is NO reason why a car with modern pad compounds and a steel or iron rotor should be cross drilled. They do nothing for cooling. They do little for weight reduction, and the hard/drilled edges are stress risers which create a location for cracks to start.
- Slotted rotors are really designed for rally and similar applications. The slots do not cool, they do not lighten or anything else. They clean contaminants from the pad surface so when you apply the brakes right after driving through a mud puddle you actually have brakes. They’re sort of a combination scraper and groove to flow crap away from the pad surface (think aquatread tires). BTW, if they are not properly designed they become a great source of stress risers and cracks. For 99% of us, slotted rotors will do nothing but cause our pads to wear faster and decrease the life of the rotor.
- Larger rotors are not used for more stopping power. Any rotor that can lock the brakes can exert more torque then the tires can apply to the ground (in other words, all the stopping power that the chassis could use), in most cases, this would be a very small rotor. What bigger rotors do is act as a bigger heat sink. They have more mass, more thermal inertia so that if you apply the same amount of heat to them they do not get as hot (stopping converts the kinetic energy of the car to heat). The idea is that if you can control the range of temperatures that the rotors can possibly see to a smaller range you will have an easier time designing pads that will give consistent braking performance. If it wasn’t for heat then the best design would be the smallest rotor that you can generate enough torque to lock the wheels, these things are heavy, and remember that rotating mass is like adding 4x the stationary mass to the car WRT to the necessary force you must generate to accelerate (decelerate) the car. For street use, almost no one needs larger brakes, they just need pads that better suit their driving style.
- Most drilled and slotted rotors are sold for their appearance… it’s a ricer mod. People associate it with high performance brakes. The super high end Porsche stuff is the only exception that I know of. Their “crossdrilled” are actually cast (with a taper and chamfer) in ceramic composite rotors that are meant to work with a special pad. They’ve discontinued and redesigned them at lest 2x that I know of because they did not work correctly or wouldn’t live.
- Another effort that a lot of experimenting in this field is going in is better heat dissipation. If you can dissipate more heat you can run a smaller rotor with the same results. One of the ‘cooler’ (sorry) things that I’ve seen are rotors with lots of little cones cast into the finned vented area to increase surface area and better dissipate heat.
And then my real pet peeve… if you can run smaller rotors you can run smaller diameter, lighter wheels and tires
2. Slotted rotors mostly help to shed water. Mud tends to stick in the slots, and increase rotor wear. They help with pad outgassing slightly, but noting compared to cross-drilling.
3. Comparing autos and motorcycles is apples and oranges. Almost all motocycles have thier front rotors exposed to fresh air, not buried inside a wheel or behind bodywork. Therfor, a solid rotor on a motorcycle is still "vented". Some of the bigger heavier bikes, such as the Goldwing, use a true vented rotor on the rear wheel, as the wheel is shrouded by the bodywork and luggage.
4. Most performance bikes come with drilled rotors, because they really do work better than solid rotors. The one situation where a solid rotors outperforms a drilled rotor is in very muddy offroad situations. The drilled holes will fill with mud, and wear the pads and rotor dow very quickly.
5. One of the latest technologys with motorcycle rotors is the wave rotor. A solid rotor, but with a wave pattern on the I.D. and O.D. The pads extends beyound portions of the rotor, and provide gas venting, while also preventing mud build-up and excessive wear like drilled rotors.
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From: looking for a flow bench so Brook and I can race
Originally posted by PGR
1. Brake pad technology has improved quite a bit since the 60's, however they still outgas to some extent. Everytime a pad heats up then cools down, it outgasses, then absorbs air. Agreed, they do little for cooling, or weight reduction. They are typically thicker that flat rotors, and when properly designed, can be just as strong.
1. Brake pad technology has improved quite a bit since the 60's, however they still outgas to some extent. Everytime a pad heats up then cools down, it outgasses, then absorbs air. Agreed, they do little for cooling, or weight reduction. They are typically thicker that flat rotors, and when properly designed, can be just as strong.
1. outgas is so minimal, its negligable
2. when the rotor gets thicker, it gets heavier.
we figured about 1/32 of an inch thicker MORE than makes up for the holes from a cross drilling.
so in concultion, the are heavier, weaker and stop slower
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Joined: Dec 1998
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Originally posted by treyZ28
1. outgas is so minimal, its negligable
2. when the rotor gets thicker, it gets heavier.
we figured about 1/32 of an inch thicker MORE than makes up for the holes from a cross drilling.
so in concultion, the are heavier, weaker and stop slower
1. outgas is so minimal, its negligable
2. when the rotor gets thicker, it gets heavier.
we figured about 1/32 of an inch thicker MORE than makes up for the holes from a cross drilling.
so in concultion, the are heavier, weaker and stop slower
So, the cross drilled rotor is actually lighter, and stops quicker.
Unlike most car rotors, these are stamped steel, not cast iron. Cast iron is very brittle compared to steel, so the idea that cross drilling makes them weaker really isn't a significant issue for motorcycles with steel rotors.
I've also swapped solid rotors onto my dirtbike for winter riding, and they don't break worth a damn compared to the drilled rotors - except in mud.
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Joined: Jul 2000
Posts: 520
From: MD
Bikes and cars are in no way a valid comparison. In a lot of cases with cars we're talking 7x the weight with less then 2x the rotor area and probably more then 10x the heat added to the rotor.
you're in a completely different catiegory with what you can get away with.
you're in a completely different catiegory with what you can get away with.
Last edited by WS6 TA; May 7, 2003 at 05:42 PM.
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From: looking for a flow bench so Brook and I can race
Originally posted by PGR
Well, I have two 1100 streetbikes. Both have nearly identical brake systems - 300mm dia x 5mm thick dual front rotors. One bike is cross-drilled, the other is slotted. They are both running identical brake pads. The bike with the cross-drilled rotors will easily outbrake the other, even though the bike weighs 100 lbs more!
So, the cross drilled rotor is actually lighter, and stops quicker.
Unlike most car rotors, these are stamped steel, not cast iron. Cast iron is very brittle compared to steel, so the idea that cross drilling makes them weaker really isn't a significant issue for motorcycles with steel rotors.
I've also swapped solid rotors onto my dirtbike for winter riding, and they don't break worth a damn compared to the drilled rotors - except in mud.
Well, I have two 1100 streetbikes. Both have nearly identical brake systems - 300mm dia x 5mm thick dual front rotors. One bike is cross-drilled, the other is slotted. They are both running identical brake pads. The bike with the cross-drilled rotors will easily outbrake the other, even though the bike weighs 100 lbs more!
So, the cross drilled rotor is actually lighter, and stops quicker.
Unlike most car rotors, these are stamped steel, not cast iron. Cast iron is very brittle compared to steel, so the idea that cross drilling makes them weaker really isn't a significant issue for motorcycles with steel rotors.
I've also swapped solid rotors onto my dirtbike for winter riding, and they don't break worth a damn compared to the drilled rotors - except in mud.
but none of it applys to cars
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Joined: May 2002
Posts: 199
From: Seattle Area
Now now boys, play nice.
On the aluminum rotors, ya I can see why, wouldn't want melted rotors dripping on my nice wheels.
I was lookin around the net for carbon rotors, and found those, but found even better, carbon ceramic rotors they are using on GT2's and 3's and the Enzo. These are a blend of ceramic material with carbon fiber, which allows really good braking performance throughout all the heat ranges, solving the crappy braking carbon rotors have while they are cold. Also, the rotors have immense heat withstanding because of the ceramic material. This is all great, but my fav part is that they can be super light! Like 20-40lbs off each rotor depending on size.
Now since they have much better heat withstanding abilities, instead of having huge 14 inch rotors wouldn't 10 or 11 inch rotors do? One problem is that they tend to heat the caliper up alot and consequently the brake fluid, but monobloc aluminum calipers, and titanium pistons should dissapte heat well enough, and if not brake fluid recirulators installed at the calipers should help this.
And once u plop down the 2-4 grand a rotor, they will last you 200,000 plus miles!!! And if ya sell ur car, just take ur rotors wiht you.
Hunter
On the aluminum rotors, ya I can see why, wouldn't want melted rotors dripping on my nice wheels.
I was lookin around the net for carbon rotors, and found those, but found even better, carbon ceramic rotors they are using on GT2's and 3's and the Enzo. These are a blend of ceramic material with carbon fiber, which allows really good braking performance throughout all the heat ranges, solving the crappy braking carbon rotors have while they are cold. Also, the rotors have immense heat withstanding because of the ceramic material. This is all great, but my fav part is that they can be super light! Like 20-40lbs off each rotor depending on size.
Now since they have much better heat withstanding abilities, instead of having huge 14 inch rotors wouldn't 10 or 11 inch rotors do? One problem is that they tend to heat the caliper up alot and consequently the brake fluid, but monobloc aluminum calipers, and titanium pistons should dissapte heat well enough, and if not brake fluid recirulators installed at the calipers should help this.
And once u plop down the 2-4 grand a rotor, they will last you 200,000 plus miles!!! And if ya sell ur car, just take ur rotors wiht you.
Hunter
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Joined: Jul 2000
Posts: 520
From: MD
Initial thoughts: light weight and heat tolerance doesn’t do you any good if it can’t dissipate the heat faster. AAMOF, the lack of ‘thermal inertia’ will just result in everything getting hotter faster. Aluminum rotors/titanium calipers will conduct heat much better, conduct it straight into the brake fluid, boiling it.
Materials that withstand the higher temperatures are great (almost) as long as you can build everything out of it. The reason I say almost is that even if everything in the system will withstand higher heat and work well, you’ve still got the problem that most pad compounds only work over a relatively narrow range, so great, they work well when you get them glowing hot, but it’s going to suck when you roll out of your driveway and the brakes don’t work till you run a few hot laps.
Remember, you’ll have to apply the same technology to your wheels and their coatings also, even some current high performance street and track pads designed to work at relatively low temps will destroy the finish on most wheels.
Materials that withstand the higher temperatures are great (almost) as long as you can build everything out of it. The reason I say almost is that even if everything in the system will withstand higher heat and work well, you’ve still got the problem that most pad compounds only work over a relatively narrow range, so great, they work well when you get them glowing hot, but it’s going to suck when you roll out of your driveway and the brakes don’t work till you run a few hot laps.
Remember, you’ll have to apply the same technology to your wheels and their coatings also, even some current high performance street and track pads designed to work at relatively low temps will destroy the finish on most wheels.
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From: Michigan's left coast
Originally posted by treyZ28
Also, I talked to him about your theory of how thicker cross drilled rotors crack easier. he said that although he never designed or tested one, he was VERY confident thicker was better.
Looking through his "rotor thickness vs cracking" test, the results are clear as glass. Thicker is MUCH MUCH stronger!
Also, I talked to him about your theory of how thicker cross drilled rotors crack easier. he said that although he never designed or tested one, he was VERY confident thicker was better.
Looking through his "rotor thickness vs cracking" test, the results are clear as glass. Thicker is MUCH MUCH stronger!
Sorry that I brought bikes into the conversation - my intent was simply to point out that they're significantly different than cars and get that out of the way early on. It's probably worth noting that while most bikes have drilled rotors, the vented OEM rotors on my Yamaha Vmax were NOT drilled. My guess is that the boys from Iwata know a thing or two about this topic