No one mention brakes fading like they tend to do when stopping quickly from high speed. Does anyone know what process causes braked to fade? And, slotting and drilling help, but it is not to get rid of heat. So, class, what causes fade and how do slots and holes help?
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an alternative browser.
You should upgrade or use an alternative browser.
Directional brake rotor slots, does it matter?
- Thread starter Auto-Union
- Start date
- Status
- Not open for further replies.
- Joined
- Jun 2, 2003
- Messages
- 23,591
Hot brake pads start gassing out, which reduces friction. Slots and holes allow the gasses to escape, thus reducing brake fading.
As usual in most braking component threads, there's a wealth of misinformation here, so I'll try to clear some things up.
First off, as AcuraTech mentioned, it will be of great benefit to
READ THIS THREAD: http://theoildrop.server101.com/forums/s...part=1&vc=1
Now
a) The direction of the slots on a brake rotor don't really matter. What really matters is if the rotors have directional vanes (the internal vanes in a vented rotor). If the rotor is directionally vaned, the rotor must be mounted so the slanted vanes at the top of the rotor when mounted slant towards the back of the car.
The reason for this is that directionally vaned rotors function like an impeller in a turbocharger or hairdryer. The centrifugal force when it spins throws air outwards (while sucking air in from the center). The curved/slanted vanes aids this. If the vanes are oriented backwards, they will try to scoop air in at the edges interfering with the flow of air.
If you look at enough different companies with directionally vaned slotted rotors, you will find that some companies will have the slots going one way, whilst others have them going the other way and some companies even have slots on one rotor that go both ways. It doesn't matter. All that matters is making sure the vanes in a directionally vaned rotor are oriented correctly.
Most lower class vented rotors though, are NOT directionally vaned (lower class meaning components NOT on Porsches etc.). If you look at the vanes in the vented rotors, they are completely radial and don't slant or curve in any particular direction. In that case, mount the slots whichever way you like the look. It doesn't really matter.
Now with all that out of the way I'll explain some of the physics in how they are 'commonly' oriented. On the left side of the car, the slots at the top of the rotor should look like this \.
The reasoning behind this is that when the leading edge of the slot is at the outer most edge of the rotor, the slot imparts a small force on the brake pad directed towards the center of the rotor/hub. Likewise, if the slots are oriented the other way, there is a small force imparted outwards. In reality, the force s small enough that as I mentioned above, some manufacturers don't really care so they have the slots machined so that on the left side of the car, they would face / on the top with the leading edge of the slot being nearest the hub.
If you were concerned about the small inward/outward force, then let me clairfy it simply in this manner. When you replace your brake pads, you remove the spring clip on the back/outside of the caliper and slide the pads outwards. You cannot remove the pads by sliding them inwards towards the center of the rotor, hub. There is a solid piece at either end of the caliper that hold the tabs/ears on the pads. would you rather have the small force acting inwards against these solid pieces or ouotwards on the spring clips? Once again, in real life, the force isn't large enough to matter.
NOW as far as brake fade goes, these days, there are generally to types of brake fade. Both are a result of exceeding your braking systems thermal capacity in one way or another or more specifically, exceeding the thermal capacity of one of the components in your braking system.
1) Fluid fade also known as boilover. This is when your braking system generates enough heat to boil the fluid in your brake calipers entraining air bubbles in the system. Usually, the effort of your foot on the brake pedal is translated directly to movement of the pistons in the brake calipers (since fluids are relatively incompressible), squeezing the brake pads against the rotors and slowing the vehicle. When you have air bubbles in the system, the range of movement in depressing the brake pedal is now taken up in compressing the air bubbles entrained in the fluid.
Solution for this is to flush your old brake fluid. Brake fluids have dry and wet boiling points. some of you might be thinking, "Huh, what's this about dry and wet? It's a fluid,.... shouldn't it be wet?". Well, glycol ethers (DOT 3, 4, 5.1 etc) are hygroscopic. They absorb moisture (an intentional feature). The dry boiling point is for fresh fluid which has absorbed no moisture and the lower 'wet' boiling point is after they have absorbed a certain parcentage of moisture.
If you're getting fluid fade, you'll have the characteristic 'mushy' pedal. Sometimes on roadcourses, fluid fade can allow the pedal to go all the way to the floor with little to no deceleration. If you encounter this, pump your brakes to build pressure. flush the fluid and try using a fluid with a higher boiling point.
2) The other kind of brake fade is known as pad fade. This happens when your brakes get so hot they exceed the MOT (Maximum Operating Tempeature) of the brake pads. The surface of the pads will liquefy and you lose braking performance. You can differentiate this from fluid fade in that the pedal feels firm but the car isn't slowing down. The solution is to get better brake pads (with a higher MOT).
Both probllems can also be relieved (usually for racers) by increasing the cooling ability of the brake system by fabricating your own cooling ducts to the brakes.
These 2 are the only real examples of brake 'fade'. where the braking performance 'fades' from use/abuse. Well, with the exception of one more type called 'green fade'.
Green fade only happens with brand new pads. All pad compounds are held together with some kind of binder (some type of resin). On new brake pads, it helps to bed-in the pads to the rotors and to burn off the excess binder. During bed-in (usually done with a series of about 8-10 slowdowns from ~60mph to ~10-15mph WITHOUT stopping), it's possible for the 3rd, 4th and 5th slowdowns to roll much further (with less deceleration) even though you're pressing on the brake pedal just as hard because the binders are boiling off and leaching from the pad reducing the pad's friction. The 7th through the 10th slowdowns will generally elicit much harder deceleration than the first few as the pads bed-in and the binders finish boiling off. Some folks avoid green fade by cooking their pads in a barbecue grill for a while, boiling off the excess binder.
Max
First off, as AcuraTech mentioned, it will be of great benefit to
READ THIS THREAD: http://theoildrop.server101.com/forums/s...part=1&vc=1
Now
a) The direction of the slots on a brake rotor don't really matter. What really matters is if the rotors have directional vanes (the internal vanes in a vented rotor). If the rotor is directionally vaned, the rotor must be mounted so the slanted vanes at the top of the rotor when mounted slant towards the back of the car.
The reason for this is that directionally vaned rotors function like an impeller in a turbocharger or hairdryer. The centrifugal force when it spins throws air outwards (while sucking air in from the center). The curved/slanted vanes aids this. If the vanes are oriented backwards, they will try to scoop air in at the edges interfering with the flow of air.
If you look at enough different companies with directionally vaned slotted rotors, you will find that some companies will have the slots going one way, whilst others have them going the other way and some companies even have slots on one rotor that go both ways. It doesn't matter. All that matters is making sure the vanes in a directionally vaned rotor are oriented correctly.
Most lower class vented rotors though, are NOT directionally vaned (lower class meaning components NOT on Porsches etc.). If you look at the vanes in the vented rotors, they are completely radial and don't slant or curve in any particular direction. In that case, mount the slots whichever way you like the look. It doesn't really matter.
Now with all that out of the way I'll explain some of the physics in how they are 'commonly' oriented. On the left side of the car, the slots at the top of the rotor should look like this \.
The reasoning behind this is that when the leading edge of the slot is at the outer most edge of the rotor, the slot imparts a small force on the brake pad directed towards the center of the rotor/hub. Likewise, if the slots are oriented the other way, there is a small force imparted outwards. In reality, the force s small enough that as I mentioned above, some manufacturers don't really care so they have the slots machined so that on the left side of the car, they would face / on the top with the leading edge of the slot being nearest the hub.
If you were concerned about the small inward/outward force, then let me clairfy it simply in this manner. When you replace your brake pads, you remove the spring clip on the back/outside of the caliper and slide the pads outwards. You cannot remove the pads by sliding them inwards towards the center of the rotor, hub. There is a solid piece at either end of the caliper that hold the tabs/ears on the pads. would you rather have the small force acting inwards against these solid pieces or ouotwards on the spring clips? Once again, in real life, the force isn't large enough to matter.
NOW as far as brake fade goes, these days, there are generally to types of brake fade. Both are a result of exceeding your braking systems thermal capacity in one way or another or more specifically, exceeding the thermal capacity of one of the components in your braking system.
1) Fluid fade also known as boilover. This is when your braking system generates enough heat to boil the fluid in your brake calipers entraining air bubbles in the system. Usually, the effort of your foot on the brake pedal is translated directly to movement of the pistons in the brake calipers (since fluids are relatively incompressible), squeezing the brake pads against the rotors and slowing the vehicle. When you have air bubbles in the system, the range of movement in depressing the brake pedal is now taken up in compressing the air bubbles entrained in the fluid.
Solution for this is to flush your old brake fluid. Brake fluids have dry and wet boiling points. some of you might be thinking, "Huh, what's this about dry and wet? It's a fluid,.... shouldn't it be wet?". Well, glycol ethers (DOT 3, 4, 5.1 etc) are hygroscopic. They absorb moisture (an intentional feature). The dry boiling point is for fresh fluid which has absorbed no moisture and the lower 'wet' boiling point is after they have absorbed a certain parcentage of moisture.
If you're getting fluid fade, you'll have the characteristic 'mushy' pedal. Sometimes on roadcourses, fluid fade can allow the pedal to go all the way to the floor with little to no deceleration. If you encounter this, pump your brakes to build pressure. flush the fluid and try using a fluid with a higher boiling point.
2) The other kind of brake fade is known as pad fade. This happens when your brakes get so hot they exceed the MOT (Maximum Operating Tempeature) of the brake pads. The surface of the pads will liquefy and you lose braking performance. You can differentiate this from fluid fade in that the pedal feels firm but the car isn't slowing down. The solution is to get better brake pads (with a higher MOT).
Both probllems can also be relieved (usually for racers) by increasing the cooling ability of the brake system by fabricating your own cooling ducts to the brakes.
These 2 are the only real examples of brake 'fade'. where the braking performance 'fades' from use/abuse. Well, with the exception of one more type called 'green fade'.
Green fade only happens with brand new pads. All pad compounds are held together with some kind of binder (some type of resin). On new brake pads, it helps to bed-in the pads to the rotors and to burn off the excess binder. During bed-in (usually done with a series of about 8-10 slowdowns from ~60mph to ~10-15mph WITHOUT stopping), it's possible for the 3rd, 4th and 5th slowdowns to roll much further (with less deceleration) even though you're pressing on the brake pedal just as hard because the binders are boiling off and leaching from the pad reducing the pad's friction. The 7th through the 10th slowdowns will generally elicit much harder deceleration than the first few as the pads bed-in and the binders finish boiling off. Some folks avoid green fade by cooking their pads in a barbecue grill for a while, boiling off the excess binder.
Max
Auto-Union
Thread starter
My original question was about slot direction, and only that. As far as what exact rotors I buy, best for the money seems logical. These were $100 rotors for $50. I advocate plain rotors of good quality, but am willing got sieze the opportunity to upgrade of something better at the same/similar price. As far as price, let's take what they charge OTC at AT's place of employment as a starting point. What's that, about $80ea?
- Joined
- Jun 2, 2003
- Messages
- 23,591
Why don't you got with ATE elliptically slotted, vented rotors? They are non-directional and less costly than comparable slotted or drilled rotors. They offer very good performance for the price ($63 per front rotor for my Audi) and the slots also function as a disc wear indicator (at least for my '96). These rotors are noticeably superior to the smooth, vented OEM ATE rotors.
Or does ATE not make rotors for the CRV?
Or does ATE not make rotors for the CRV?
I ran into the same thing that porcupine mentions with Brembo slotted rotors, the instructions that came with them clearly indicated that they were to be installed backward from what I see on most cars that I have seen.
The instructions showed the slots contacting the pad at the OUTSIDE edge of the rotor first, then to the inside.
I figured that Brembo knows more than I do, and installed them that way.
Of course, I have steel wheels with hub caps, so looks did not matter.
The instructions showed the slots contacting the pad at the OUTSIDE edge of the rotor first, then to the inside.
I figured that Brembo knows more than I do, and installed them that way.
Of course, I have steel wheels with hub caps, so looks did not matter.
Auto-Union
Thread starter
Ok guys. I actually had PowerSlots when the first came out on my Coupe GT. That car can warp rotors and did with them. Plain Brembros on now, after about 50k they are still fine. I con't really care about slots or XD, but am looking for quality good enough to woprk with the ceramic pads that are *specified* for this application. Probally I will re-use the current ones.
- Status
- Not open for further replies.
Similar threads
- Replies
- 8
- Views
- 340
- Replies
- 27
- Views
- 706
- Replies
- 24
- Views
- 8K
- Replies
- 53
- Views
- 3K