Brake Squeal Fix ala Genesis
03-25-2009, 01:59 PM
#1
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Brake Squeal Fix ala Genesis
Interesting technical item about the Hyundai Genesis coupe's brakes. The track models have Brembos, but with a strange twist. Apparently to stop noise this is how the stock pads are cut (top).. vs. the standard pads for the Brembos (bottom).
They said yesterday at a Las Vegas press conference that the RX-8 was one of their benchmark cars. Perhaps they listened to how many people complained about brake squeal over here. This is apparently their answer! It still begs the question "Why in the world would anyone really do this?" Ans: to sell more brake pads (and cut squeal I guess)!
Wonder if this would work in some fashion for the street driven 8s? Some pad manufacturer would need to cut them like that..... but would you buy them this way?
They said yesterday at a Las Vegas press conference that the RX-8 was one of their benchmark cars. Perhaps they listened to how many people complained about brake squeal over here. This is apparently their answer! It still begs the question "Why in the world would anyone really do this?" Ans: to sell more brake pads (and cut squeal I guess)!
Wonder if this would work in some fashion for the street driven 8s? Some pad manufacturer would need to cut them like that..... but would you buy them this way?
03-25-2009, 02:35 PM
#3
justjim
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Well I have OEM pads and they are completely silent. Its all in the installation. My track pads don't squeal either. Much ado about nothing.
Last edited by justjim; 03-25-2009 at 02:42 PM.
03-25-2009, 06:22 PM
#6
I wonder if the brembos make much difference since they use the same pad? they probably had to increase their performance compared to a std caliper by hobbling the base package.
05-07-2009, 07:59 PM
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Not to mention, the 3,470 pound Genesis Coupe stops from 60 in 111 feet, so they must not be THAT retarded after all.
Ain't science grand?
05-07-2009, 08:10 PM
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Right - of course many factors go into the performance of brakes, such as the coefficient of friction of the pad materials, their resistance to heat, etc.
But the blanket statement that less area = less power is false.
Frictional Force = Normal Force * mu, with mu being the coefficient of friction. Normal force IS a function of area, but, as area increases, normal force decrease, so in the end, the area is moot.
Obviously there are exceptions such as the extremes of either very little area, very large forces, etc.
But the blanket statement that less area = less power is false.
Frictional Force = Normal Force * mu, with mu being the coefficient of friction. Normal force IS a function of area, but, as area increases, normal force decrease, so in the end, the area is moot.
Obviously there are exceptions such as the extremes of either very little area, very large forces, etc.
05-08-2009, 06:24 AM
#11
Sydney, Australia
Right - of course many factors go into the performance of brakes, such as the coefficient of friction of the pad materials, their resistance to heat, etc.
But the blanket statement that less area = less power is false.
Frictional Force = Normal Force * mu, with mu being the coefficient of friction. Normal force IS a function of area, but, as area increases, normal force decrease, so in the end, the area is moot.
Obviously there are exceptions such as the extremes of either very little area, very large forces, etc.
But the blanket statement that less area = less power is false.
Frictional Force = Normal Force * mu, with mu being the coefficient of friction. Normal force IS a function of area, but, as area increases, normal force decrease, so in the end, the area is moot.
Obviously there are exceptions such as the extremes of either very little area, very large forces, etc.
ERRRR yeah okay... but in braking calculations there's also a ratio called swept area which is a calculation of pad side and rotor size - meaning the more area you apply a given force to, the more friction it generates because of the larger surface area, therefore the more stopping power is produced...
05-08-2009, 07:29 AM
#13
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http://www.tirerack.com/tires/tirete....jsp?techid=10
Grip - It's the contact area that counts...and the tire compound and the weight pushing down.
05-08-2009, 07:34 AM
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First, I would ask, if reducing the area reduces braking power, why does a car with 40% less brake pad surface still stop from 60 in 111'. Does that mean with normal sized pads, this car will stop from 60 in 70'? I am going to go out on a limb and say no.
Second, the swept area is more a function of the WIDTH of the pad than it is the overall pad area. Thus, if they were to make the pads narrower in the radial direction, it would greatly reduce the swept area and thus the effectiveness of the brakes.
Third, the reason wider tires have more grip than narrower tires is more complex than just wider = more contact patch = more traction. First, wider tires in general have softer compounds, which means higher coefficient of friction, which means more traction. It is also important that softer tires be wider in order for them to support the weight of the car - you simply could not make a narrow but soft tire. Also, wider tires have thicker sidewalls, which produce less roll and of course improve performance.
Now, these Genesis pads may have less fade resistance and such, they will not have less braking power.
Second, the swept area is more a function of the WIDTH of the pad than it is the overall pad area. Thus, if they were to make the pads narrower in the radial direction, it would greatly reduce the swept area and thus the effectiveness of the brakes.
Third, the reason wider tires have more grip than narrower tires is more complex than just wider = more contact patch = more traction. First, wider tires in general have softer compounds, which means higher coefficient of friction, which means more traction. It is also important that softer tires be wider in order for them to support the weight of the car - you simply could not make a narrow but soft tire. Also, wider tires have thicker sidewalls, which produce less roll and of course improve performance.
Now, these Genesis pads may have less fade resistance and such, they will not have less braking power.
05-08-2009, 07:37 AM
#15
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Also guys keep in mind one over-riding fact. Tires stop cars. Brakes stop tires.
If the Genesis half pad brake can lock up the tire, there is nothing to be gained in the braking distance dept with more pad, esp if the pad doesn't fade in the test of braking.
If the Genesis half pad brake can lock up the tire, there is nothing to be gained in the braking distance dept with more pad, esp if the pad doesn't fade in the test of braking.
05-08-2009, 08:48 AM
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i just put a set of wagner's anti-squeal pads on my car...got them at advanced auto...front and back...they're cut like that...they haven't squealed once since i installed them (about 2 weeks ago)
05-08-2009, 12:27 PM
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The comparison of the brake pad and the tire is not a valid comparison because the tire is soft and squigy and the effective coefficient of friction developed is not the same as two hard surfaces in contact with each other. The soft tire compound envelops the small imperfections in the road surface somewhat like 2 gears meshing which increases the coefficient of friction. Also a tire tread deforms in multiple dimensions under lateral and acceleration and braking loads which further complicates the shape of the contact patch. It was the final realization of this principle in the 60's that partly lead to wider tires on race cars and subsequently passenger tires. A wider tire may have a larger contact patch but it may also have a more stable contact patch which may be even more important. Sometimes you just have to think outside of the box.
Brake pad coefficient of friction is, as described above and in the formulas above by Yeahyeahyouwere, much less dependent of pad surface area because it and the rotor do not deform (much) when pressed together. The primary variable in brake pad coefficient of friction is the relationship of adherent vs abrasive coefficient of frictions and the temperature of the pad and substrate (rotor). See Brake FAQ https://www.rx8club.com/showthread.p...&highlight=faq
The comparison of swept area mentioned above by Sarras does not take into consideration the effect of rotor diameter and resulting braking torque applied to the wheel with larger rotors. Also the swept area is not referring to the pad area but the swept area of the rotor. A 2" wide pad (wide in the direction of rotor radius) that is only 1" long (long in the direction of rotor direction) will have the same swept area as a 2" by 2" pad even though the pad area is twice the size.
Before y'all criticize people ya got to get the physics straight. It takes physics to go (and stop) fast. Sometimes physicists need to actually sit in a race car (re the skinny race tires of days of yore) but more often the racers need to pay attention in physics class so they don't go off half cocked.
Brake pad coefficient of friction is, as described above and in the formulas above by Yeahyeahyouwere, much less dependent of pad surface area because it and the rotor do not deform (much) when pressed together. The primary variable in brake pad coefficient of friction is the relationship of adherent vs abrasive coefficient of frictions and the temperature of the pad and substrate (rotor). See Brake FAQ https://www.rx8club.com/showthread.p...&highlight=faq
The comparison of swept area mentioned above by Sarras does not take into consideration the effect of rotor diameter and resulting braking torque applied to the wheel with larger rotors. Also the swept area is not referring to the pad area but the swept area of the rotor. A 2" wide pad (wide in the direction of rotor radius) that is only 1" long (long in the direction of rotor direction) will have the same swept area as a 2" by 2" pad even though the pad area is twice the size.
Before y'all criticize people ya got to get the physics straight. It takes physics to go (and stop) fast. Sometimes physicists need to actually sit in a race car (re the skinny race tires of days of yore) but more often the racers need to pay attention in physics class so they don't go off half cocked.
Last edited by justjim; 05-08-2009 at 12:57 PM.
05-08-2009, 12:46 PM
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The comparison of the brake pad and the tire is not a valid comparison because the tire is soft and squigy and the coefficient of friction developed is not the same as two hard surfaces in contact with each other. The soft tire compound envelops the small imperfections in the road surface somewhat like 2 gears meshing which increases the coefficient of friction. It was the final realization of this principle in the 60's that partly lead to wider tires on race cars and subsequently passenger tires. Sometimes you just have to think outside of the box.
Brake pad coefficient of friction is, as described above and in the formulas above by Yeahyeahyouwere, much less dependent of pad surface area because it and the rotor do not deform (much) when pressed together.
The comparison of swept area mentioned above by Sarras does not take into consideration the effect of rotor diameter and braking torque applied to the wheel with larger rotors. Also the swept area is not referring to the pad area but the swept area of the rotor. A 2" wide pad (wide in the direction of rotor radius) that is only 1" long (long in the direction of rotor direction) will have the same swept area as a 2" by 2" pad even though the pad area is twice the size.
Before y'all criticize people ya got to get the physics straight. It takes physics to go (and stop) fast. Sometimes physicists need to actually sit in a race car (re the skinny race tires of days of yore) but more often the racers need to pay attention in physics class.
Brake pad coefficient of friction is, as described above and in the formulas above by Yeahyeahyouwere, much less dependent of pad surface area because it and the rotor do not deform (much) when pressed together.
The comparison of swept area mentioned above by Sarras does not take into consideration the effect of rotor diameter and braking torque applied to the wheel with larger rotors. Also the swept area is not referring to the pad area but the swept area of the rotor. A 2" wide pad (wide in the direction of rotor radius) that is only 1" long (long in the direction of rotor direction) will have the same swept area as a 2" by 2" pad even though the pad area is twice the size.
Before y'all criticize people ya got to get the physics straight. It takes physics to go (and stop) fast. Sometimes physicists need to actually sit in a race car (re the skinny race tires of days of yore) but more often the racers need to pay attention in physics class.
05-08-2009, 12:54 PM
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This is false, the coefficent of friction is a constant parameter, the only way to change it is to change the material its constructed of. The reason for wider tires is due to them being constructed of softer rubber with a much higher friction coefficient. But to compensate for the tangential forces (weight, downforce, etc) the tire must be wider. Also wider tires wear out slower than narrow, but the measure width of a tire does not = its friction.
Also wider tires do no always have softer compounds although they do have different construction to deal with the width.
Last edited by justjim; 05-08-2009 at 01:01 PM.
05-08-2009, 01:20 PM
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I beg to disagree. There is some truth to what you say but wider tires of equal rubber compound do indeed make stickier tires which is why we like wider tires on performance cars. You are right that the coeffcient of friciton of a tires rubber does not change with width but the "stickage" (edited above to effective coefficient) does because the "stickage" is dependent on multiple variables and not just the coefficient of friction of the the particular rubber compound on the tarmac. Tire construction is all about keeping the footprint as large and stable as possible under differing conditions such as acceleration, deceleration and lateral cornering loads. Because tires do deform in complex and multiple ways they do not perform like steel train wheels on a railroad track.
Also wider tires do no always have softer compounds although they do have different construction to deal with the width.
Also wider tires do no always have softer compounds although they do have different construction to deal with the width.
As for contact area you are correct, a larger contact area is better, but not because of friction, because of chance. You have a better chance of your current coefficient of friction touching the ground, but if more of the tire touches the ground it does not mean you have more friction because you'll be applying less weight to each section of contact (think about laying on a single needle, then think about laying on a thousand needles, which would pierce deeper into you? The reason 1000 needles will not pierce is because you're dividing your weight by 1000 instead of 1, with your skin acting as the coefficient of friction.)
The reason you'll spin out in a turn is due to you breaking your coefficient of friction on your tires, not the amount of tire touching the ground. I gave the same explanation when grading papers
.
Last edited by dillsrotary; 05-08-2009 at 01:23 PM.
05-08-2009, 01:31 PM
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Third, the reason wider tires have more grip than narrower tires is more complex than just wider = more contact patch = more traction. First, wider tires in general have softer compounds, which means higher coefficient of friction, which means more traction. It is also important that softer tires be wider in order for them to support the weight of the car - you simply could not make a narrow but soft tire. Also, wider tires have thicker sidewalls, which produce less roll and of course improve performance.
I'm sorry, it's times like these that make me LOVE science and my Theoretical and Applied Mechanics degree
05-08-2009, 01:42 PM
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Though you are close, i'm going to disagree. You agree that width does not matter when mention the friction of a material. The reason width is larger is due to the softer material, a narrow soft tire with a great coefficient of friction cannot support the weight of the car, but the wider tire spreads the weight equaling, instead of a small area.
As for contact area you are correct, a larger contact area is better, but not because of friction, because of chance. You have a better chance of your current coefficient of friction touching the ground, but if more of the tire touches the ground it does not mean you have more friction because you'll be applying less weight to each section of contact (think about laying on a single needle, then think about laying on a thousand needles, which would pierce deeper into you? The reason 1000 needles will not pierce is because you're dividing your weight by 1000 instead of 1, with your skin acting as the coefficient of friction.)
The reason you'll spin out in a turn is due to you breaking your coefficient of friction on your tires, not the amount of tire touching the ground. I gave the same explanation when grading papers.
As for contact area you are correct, a larger contact area is better, but not because of friction, because of chance. You have a better chance of your current coefficient of friction touching the ground, but if more of the tire touches the ground it does not mean you have more friction because you'll be applying less weight to each section of contact (think about laying on a single needle, then think about laying on a thousand needles, which would pierce deeper into you? The reason 1000 needles will not pierce is because you're dividing your weight by 1000 instead of 1, with your skin acting as the coefficient of friction.)
The reason you'll spin out in a turn is due to you breaking your coefficient of friction on your tires, not the amount of tire touching the ground. I gave the same explanation when grading papers
.Last edited by justjim; 05-08-2009 at 02:11 PM.
05-08-2009, 01:49 PM
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I brought up this subject to explain that the friction of brake pads should not be compared to the fricition of tires as they are fundamentally different in several ways. I think that dillsrotorary and I agree on enough that that point is valid. I think we are beginning to get off topic so I am going to suggest we start a new thread where we can continue this, as there are a few points of disagreement left and it is possible I might learn something. See https://www.rx8club.com/showthread.p...18#post3010918
And I am interested in hearing what else you have to say Jim, this is a great discussion.
