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| RhynoCZ |
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RhynoCZ
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 Posted: 16:03 - 29 Mar 2015  Post subject: Brake pads, need help... |
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Hi, so I need a fresh set of pads for my Nissin four pot callipers, but I do not know a thing about pads, apparently. 
I had Nissin 2P253 ST and really liked them, so I decided to get the same pads, but no one sells them here. 
So, what are the alternatives? I understand there are other manufacturers, but I've got no experience here.
For instance, my local shop sells Brembo pads which has three different compounds - RC, SA, SC.
Other manufacturers use different designation of the compound on their pads, so I'm really clueless.
TL; DR I want the same performance but can't get the Nissin pads here. 
Any thoughts, experiences, suggestions... Thank you. 
https://www.bonmoto.cz/data/zbozi/original/14502.jpg
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'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor |
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| bugeye_bob |
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bugeye_bob
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Posted: 21:18 - 29 Mar 2015  Post subject: |
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your ST`s look like they were Sintered road pads,
The Brembo Compounds are SC -Sintered Track pad, SA - Sintered Road pad, RC - Road Race Pads,
So the SA seems to be like a ST.
taken from here,
https://www.biketorqueracing.co.uk/brakes/brembo-brake-pads
hth |
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| RhynoCZ |
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RhynoCZ
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| Posted: 10:00 - 30 Mar 2015 Post subject: |
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Brembo SA it is then, Thank you.
One quick question though, I'm looking at some specs and pictures and I noticed the brake compound does not cover the whole pad. This might be an unnecessary concern, but the Nissin pads where all covered and when I took them off, the compound was worn-out equally at the whole surface.
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'87 Honda XBR 500, '96 Kawasaki ZX7R P1, '90 Honda CB-1, '88 Kawasaki GPz550, MZ 150 ETZ
'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor |
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| bugeye_bob |
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bugeye_bob
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Nexus Icon
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| Val |
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Val
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| Posted: 16:56 - 30 Mar 2015 Post subject: |
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IMO Brembo are too hard. I prefer EBC Double-H Sintered Pads which work more smoothly for me.
Depends what is your definition of comfort 
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RhynoCZ
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| Ed Case |
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Ed Case
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| Posted: 20:55 - 30 Mar 2015 Post subject: |
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[quote="Val"]IMO Brembo are too hard. I prefer EBC Double-H Sintered Pads which work more smoothly for me.
Depends what is your definition of comfort [/quot
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| Pete. |
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Pete.
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| temeluchus |
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temeluchus
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| Posted: 00:00 - 31 Mar 2015 Post subject: |
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| carlosvalderr... |
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carlosvalderr...
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| carlosvalderr... |
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carlosvalderr...
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| Pete. |
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Pete.
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| Posted: 20:56 - 31 Mar 2015 Post subject: |
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| carlosvalderrama wrote: | He's right. F = mu.R
Friction force (drag at the pad), is equal to the reaction load (the pressure applied by the caliper), multiplied by the frictional coefficient, mu.
The coefficient is a function of the materials at the interface, and their mating area has, in theory, no direct effect on the value of mu.
However in the real world, temperature does affect the value of mu, so a pad the size of a 1p piece will rapidly overheat and the value of mu would fall, leading to a loss of braking force. |
Pressure, as in pounds per square inch, as in square inches of area?
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| Vincent |
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Vincent
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| Posted: 21:11 - 31 Mar 2015 Post subject: |
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| Pete. |
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Pete.
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| Posted: 21:19 - 31 Mar 2015 Post subject: |
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No it's true, friction is not proportionate to surface area, that's why they only have 10mm wide tyres in formula 1. The contact area has no effect on grip whatsoever.....in theory.......
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| c_dug |
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c_dug
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| Vincent |
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Vincent
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| Posted: 21:27 - 31 Mar 2015 Post subject: |
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How come we don't have brake pads the size of 5p coins then 
'Cos you can't exert as much force maybe? Heat dissipation?
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| carlosvalderr... |
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carlosvalderr...
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| Posted: 06:48 - 01 Apr 2015 Post subject: |
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| Pete. wrote: | No it's true, friction is not proportionate to surface area, that's why they only have 10mm wide tyres in formula 1. The contact area has no effect on grip whatsoever.....in theory....... |
Actually, even in theory tyres have more grip for a larger contact patch.
Tyre manufacturers can provide a data set called tyre load sensitivity, this is usually a curve plotting the vertical load vs the potential lateral load for a variety of camber angles.
Every compound and size of tyre will be different, but all follow a trend where the coefficient of friction drops off as the vertical load increases.
So on the same tire, a lighter vehicle could, with all things equal, corner faster.
This is mainly due to hysteresis effects in the tyre, effectively, because it's squishy.
Apologies for being off topic... The reason you don't have pads the size of a 5p is hor thermal reasons. Although you'd be able to brake with the same power output, it'd only be briefly as the low thermal mass and low surface area would mean the pad surface would overheat rapidly, dropping the coefficient of friction.
Effectively, don't worry if the pad material shape isn't exactly the same, but do ask questions if it's the size of a 5p piece.
Also, +1 for the Dunlop SP pads, I've used them and would happily have them again, decent feel, and no issues with circuit speed abuse. |
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| Pete. |
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Pete.
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| Posted: 09:37 - 01 Apr 2015 Post subject: |
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| carlosvalderrama wrote: | | Pete. wrote: | No it's true, friction is not proportionate to surface area, that's why they only have 10mm wide tyres in formula 1. The contact area has no effect on grip whatsoever.....in theory....... |
Actually, even in theory tyres have more grip for a larger contact patch.
Tyre manufacturers can provide a data set called tyre load sensitivity, this is usually a curve plotting the vertical load vs the potential lateral load for a variety of camber angles.
Every compound and size of tyre will be different, but all follow a trend where the coefficient of friction drops off as the vertical load increases.
So on the same tire, a lighter vehicle could, with all things equal, corner faster.
This is mainly due to hysteresis effects in the tyre, effectively, because it's squishy.
Apologies for being off topic... The reason you don't have pads the size of a 5p is hor thermal reasons. Although you'd be able to brake with the same power output, it'd only be briefly as the low thermal mass and low surface area would mean the pad surface would overheat rapidly, dropping the coefficient of friction.
Effectively, don't worry if the pad material shape isn't exactly the same, but do ask questions if it's the size of a 5p piece.
Also, +1 for the Dunlop SP pads, I've used them and would happily have them again, decent feel, and no issues with circuit speed abuse. |
So a 1mm square brake pad can theoretically have the same braking force as a 100mm square one which has 10,000 times the surface area, with no increase in the pressure applied?
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132.9mph off and walked away. Gear is good, gear is good, gear is very very good |
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| carlosvalderr... |
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carlosvalderr...
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| Posted: 10:26 - 01 Apr 2015 Post subject: |
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| Pete. wrote: |
So a 1mm square brake pad can theoretically have the same braking force as a 100mm square one which has 10,000 times the surface area, with no increase in the pressure applied? |
If by braking force, you mean the force generated in the direction of disc rotation acting to decelerate the machine and if we totally discount thermal effects, then yes.
No matter the pad size, the force pressing the pad to the disc is the same as the hydraulic functions of the braking system are unchanged.
Dynamic friction with stiff materials is best modelled by Coulomb theory. Coulomb is well known for his work on electrical charge, but he actualy spent more time working on architecture and mechanics.
It's from Coulomb theory as an extension of static friction theory that the formula of F=mu.R derives. As such brake pad frictional force (F) is dependent only on the force provided by the caliper pistons (R) and the coefficient of the pad/disc interface (mu).
Now, there is a proviso here. As well as temperature effects, there can be pressure effects. The linear coefficient of friction works as such because when 2 stiff surfaces are in contact, only a tiny proportion of them is actually in real contact.
If you look at the microscopic to atomic scale, even a well polished disc and pad surface will have lumps and bumps, called asperities. It's the tips of these asperities which contact the asperities on the other surface, like 2 sheets of sandpaper touching via the tips of the grains.
As load (R) is applied to the interface, it deforms and more asperities will come into contact, increasing the surface area available for generating friction (F). This is where the value of mu comes from, and why under most load conditions mu is linear. So 10% more load means 10% more contact area and 10% more friction.
However, if you had a vanishingly small contact patch, it's conceivable that you'd apply enough load to generate a surface pressure to totally bring all the surface into contact. At this point, more load won't cause any more contact and Frictional force would be at a maximum.
I've never seen this tested though, as presumably as soon as you got close to a kinetic full surface contact the thermal effects would just burn it all away.
Effectively, at the very extremes of sizes and loads, friction can go mental and do weird things, but the loads, pressures, temperatures and materials used in road level braking systems are pretty unremarkable and can be accurately simulated by coulomb theory.
tl;dr? "Yes" |
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| c_dug |
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c_dug
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| RhynoCZ |
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RhynoCZ
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| Posted: 11:05 - 01 Apr 2015 Post subject: |
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Not that it matters, but I've made up my mind and ordered the SA pads.
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'87 Honda XBR 500, '96 Kawasaki ZX7R P1, '90 Honda CB-1, '88 Kawasaki GPz550, MZ 150 ETZ
'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor |
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| carlosvalderr... |
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carlosvalderr...
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| Posted: 12:47 - 01 Apr 2015 Post subject: |
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| RhynoCZ wrote: | Not that it matters, but I've made up my mind and ordered the SA pads. |
Sorry chief, it all went a bit theoretical. Hope they work out for you though.
| c_dug wrote: |
Does that mean, to a person who isn't fluent in science, that these two objects:
(pic)
Would take the same amount of force to drag along? Is that what you're basically saying?
(Not disagreeing I'm just curious) |
Pretty much, yeah.
In the case of the image on the left, this would be on the presumption that the contacting surfaces have the same texture as on the right image.
With smooth, stiff surfaces the bulk of frictional force is generated by intramolecular and interatomic forces at the boundary, only a small amount is generated by the mechancial drag of the asperities passing over one another.
For example, two pieces of highly polished glass have a massive kinetic coefficient of friction which is almost 100% intermolecular forces.
Squishy things like tyres are different in that a lot of the frictional load comes from the texture of the road and the tyre deforming to suit.
Similarly, it's hard to drag a plastic parts box with a set of crankcases in across the garage floor because the floor is macroscopically lumpy, and the box catches on the ridges. Not much comes down to interatomic stuff then.
In reality, most interacting surfaces in daily life are not appropriate to apply just frictional laws to, heat, flexibility, inefficiencies and geometry all add an effect to the motion and can mean that what we see as friction is actually more of an effect of flexibility and roughness.
Brake pads and discs are close to ideal for Coulomb's theory. They're hard, stiff and smooth (easy tiger), and the reaction load is at pretty much exactly 90° to the motion.
If you're interested, have a quick google for Coulomb's law, you'll probably find a better worded explanation. I'm no lecturer so I'm not well practiced at explaining things. |
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Old Thread Alert!
The last post was made 10 years, 267 days ago. Instead of replying here, would creating a new thread be more useful? |
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