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View Full Version : drilled vs. slotted...or maybe both?



Evomaniac
06-18-2008, 02:55 AM
alright...heres the deal...im planning on getting some new rotors but can't decide whether to get drilled, slotted, or drilled and slotted rotors...im currently using my ep as a daily driver but i will soon put it on the track as well just for kicks...so if you all had this option, what will you all choose to replace your rotors? drilled, slotted, or drilled and slotted?

Chazwick05
06-18-2008, 03:12 AM
alright...heres the deal...im planning on getting some new rotors but can't decide whether to get drilled, slotted, or drilled and slotted rotors...im currently using my ep as a daily driver but i will soon put it on the track as well just for kicks...so if you all had this option, what will you all choose to replace your rotors? drilled, slotted, or drilled and slotted?

i upgraded my rotos to oem size brembo slotted with hawk hps pads. it's inexpensive and awesome for a dd!

Evomaniac
06-18-2008, 03:24 AM
but dont your pads wear out faster with slotted rotors?

Evomaniac
06-18-2008, 03:24 AM
and how much was it for the rotors and pads?

ep3moschini
06-18-2008, 04:55 AM
Brembo Blanks FTW!

T_Virus
06-18-2008, 07:29 AM
Brembo blanks are really good but too bad they only make the front's and not the rears for our car...

Lucid Moments
06-18-2008, 07:31 AM
There is no point in upgrading your rotors unless your stock ones are worn to the point of needing replacement anyway. Even then stock replacements are your best option.

If you want something that looks cool then you can go with slotted but understand that it doesn't improve performance. Drilled rotors actually can decrease performance so those are an absolute no go.

T-MacK
06-18-2008, 07:33 AM
Brembo blanks are good....So are KVR slotted rotors.
Not a big fan of the cross drilled rotors. Had a set crack on me when I was circuit racing my EF back in the day, not to mention how many people I've known that hvae had this happen.

ShadySi
06-18-2008, 07:44 AM
I just got brembo blanks and hawks pads.. installing this weekend. I had a fun little wobble in the front of my car.. I was assuming it was because my rotors are warped.. Either way.. I think @ 80K miles.. they should probably be replaced :mrolleyes:

I think that if you don't get oem replacements (which you should) then just get slotted.

dichotomous
06-18-2008, 08:24 AM
are there any rotors that rust less than a standard rotor? I got the brembo blanks and with about 500mi on them there is plenty of surface rust on the hat portion and the edges

shadowmd
06-18-2008, 09:23 AM
i have the powerslot big rotor kit. love'em and no rust after 8months and a maryland (salty) winter

jimmyjames
06-18-2008, 09:25 AM
There is no point in upgrading your rotors unless your stock ones are worn to the point of needing replacement anyway. Even then stock replacements are your best option.

If you want something that looks cool then you can go with slotted but understand that it doesn't improve performance. Drilled rotors actually can decrease performance so those are an absolute no go.

Word.
110,000 miles and my stock rotors and pads are still fine.
I had warped rotors on my CL-S and replaced them with Rotora slotted rotors.
drilled/slotted rotors are kind of ricey on something that isn't being raced.

RHCP0801
06-18-2008, 09:25 AM
powerslots dont rust at all

Evomaniac
06-18-2008, 04:00 PM
ok...then i'll just consider to get some oem blank brembos..or ill just get my stock ones resurfaced...im at 70,000 miles right now...but ill definitely get the hawk hps pads...how much was it for the brembo blanks? is it all four or just front two?...

dichotomous
06-19-2008, 07:06 AM
ok...then i'll just consider to get some oem blank brembos..or ill just get my stock ones resurfaced...im at 70,000 miles right now...but ill definitely get the hawk hps pads...how much was it for the brembo blanks? is it all four or just front two?...

got mine at tire rack for $40 each, just fronts

HondaFreak
06-19-2008, 09:43 AM
There is no point in upgrading your rotors unless your stock ones are worn to the point of needing replacement anyway. Even then stock replacements are your best option.

If you want something that looks cool then you can go with slotted but understand that it doesn't improve performance. Drilled rotors actually can decrease performance so those are an absolute no go.

I actually disagree a bit here. :rapture:
I installed Powerslot slotted rotors specifically for the track and they made a big difference over stock. I used Hawk blue's with my slotted rotors and braking was improved over stock compounds and rotors.
Powerslots at the track (http://www.k-series.com/forum/showthread.php?t=14576)
^^^^
There's a little review of how slotted rotors worked at the track.
The short of it is, these will work, but not for long depending on what pad compound the OP uses. Drilled rotors IMO are just bling. Heat stress fractures are inevitable at the track and those holes are going to prolly fracture fast. My slotted rotors lasted 5.33 track hours and they were DESTROYED. For track a BBK is inevitable unless you like buying front rotors 2 or 3 times a year. My ¢.02 from my track experience's.

Christian

Lucid Moments
06-19-2008, 10:34 AM
I actually disagree a bit here. :rapture:
I installed Powerslot slotted rotors specifically for the track and they made a big difference over stock. I used Hawk blue's with my slotted rotors and braking was improved over stock compounds and rotors.
Powerslots at the track (http://www.k-series.com/forum/showthread.php?t=14576)
^^^^
There's a little review of how slotted rotors worked at the track.
The short of it is, these will work, but not for long depending on what pad compound the OP uses. Drilled rotors IMO are just bling. Heat stress fractures are inevitable at the track and those holes are going to prolly fracture fast. My slotted rotors lasted 5.33 track hours and they were DESTROYED. For track a BBK is inevitable unless you like buying front rotors 2 or 3 times a year. My ¢.02 from my track experience's.

Christian


Did you ever use the Hawk Blues with the stock rotors? Different brake pads would make a huge difference so that I'm not sure you could tell the difference in the rotors.

Evomaniac
06-19-2008, 10:34 AM
thanks...ima order some brembo blanks in a bit...i got the pads and ss brake lines...

zzfinaldropzz
06-19-2008, 10:37 AM
i just got my set of 4 drill & slotted and pads for $200 from 88 Rotors..... Lifetime warranty.. :)

HondaFreak
06-19-2008, 11:10 AM
Did you ever use the Hawk Blues with the stock rotors? Different brake pads would make a huge difference so that I'm not sure you could tell the difference in the rotors.

True, the rotors could have made no difference at all. Although there's that little problem with gas build-up between the pad and rotor. Since I have ABS it's not a big worry if I have to slam the brakes.
No sir, my OEM Rotors had seen 1 trackday and started to heat stress fracture. I had them turned, however they had to take off twice as much as normal. I would think the Hawk blues wouldn't treat the OEM rotors any better as far as longevity.

Christian

Lucid Moments
06-19-2008, 11:29 AM
i just got my set of 4 drill & slotted and pads for $200 from 88 Rotors..... Lifetime warranty.. :)

We've gone beyond actually answering your question now and are just having fun arguing about the benefits of slotted or whatever rotors.:mbiggrin: If you spend any time on here you will notice that we do that kind of thing a lot.:mangel:


True, the rotors could have made no difference at all. Although there's that little problem with gas build-up between the pad and rotor. Since I have ABS it's not a big worry if I have to slam the brakes.
No sir, my OEM Rotors had seen 1 trackday and started to heat stress fracture. I had them turned, however they had to take off twice as much as normal. I would think the Hawk blues wouldn't treat the OEM rotors any better as far as longevity.

Christian

Modern pad materials don't outgass much from what I have read. That is mostly left over worry from the olden days.:tape:

Also, how long had you been running your stock rotors on the street before you took them to the track? I suspect that they had already seen some significant use. Even if they hadn't though the difference is going to be in the material of the rotors, and not in whether they have slots or not. So the Brembo blanks may be just as good a material as the powerslots.

HondaFreak
06-19-2008, 12:16 PM
We've gone beyond actually answering your question now and are just having fun arguing about the benefits of slotted or whatever rotors.:mbiggrin: If you spend any time on here you will notice that we do that kind of thing a lot.:mangel:



Modern pad materials don't outgass much from what I have read. That is mostly left over worry from the olden days.:tape:

Also, how long had you been running your stock rotors on the street before you took them to the track? I suspect that they had already seen some significant use. Even if they hadn't though the difference is going to be in the material of the rotors, and not in whether they have slots or not. So the Brembo blanks may be just as good a material as the powerslots.

The OEM rotors had 10K on them before I went to the track. As far as life of an OEM rotor goes, me thinks those rotors were still infants. I know little about the gas release of modern pads, you could be 100% correct about the gas releasing being insignificant. But then that would mean 95% of after-market manufacturers are selling snake oil in the form of slotted and drilled rotors, or they are not doing their homework to find out if slotted or drilled rotors actually are needed. Refer to these rotors being BLING!
I replaced my rear OEM rotors with a Fastbrakes 10.9" rear kit, and I am waiting on a StopTech 13" front kit. Then we'll see what's what as far as good performance ANDDDD longevity. Which is important at the track.

Christian

Lucid Moments
06-19-2008, 03:25 PM
The OEM rotors had 10K on them before I went to the track. As far as life of an OEM rotor goes, me thinks those rotors were still infants. I know little about the gas release of modern pads, you could be 100% correct about the gas releasing being insignificant. But then that would mean 95% of after-market manufacturers are selling snake oil in the form of slotted and drilled rotors, or they are not doing their homework to find out if slotted or drilled rotors actually are needed. Refer to these rotors being BLING!

They are absolutely Bling. And I'm sure the manufacturers know it, but they make what sells and a lot of people buy bling.


I replaced my rear OEM rotors with a Fastbrakes 10.9" rear kit, and I am waiting on a StopTech 13" front kit. Then we'll see what's what as far as good performance ANDDDD longevity. Which is important at the track.

Christian

Why a big rear brake? If anything with improved front brakes you want less rear brakes. I run the Wilwood fronts with their Polymatrix B pads and have found adequate brake bias by running Hawk HP+ rear brake pads. I've been through a bunch of front brakes and there is still a ton of meat left on the same set of rear pads.

With better brakes on the front end you will transfer more weight to the front so they do still more of the work. If you don't decease the rear braking then you will lock your rear wheels up.

bmyers4321
06-19-2008, 03:31 PM
you guys buying the brembo blanks why dont you just get the Honda rotors they are made by brembo.

v1c10us
06-19-2008, 07:00 PM
fact: drilled rotors decrease surface area, thus decreasing friction, and when chamfered incorrectly are prone to heat fractures.
fact: slotted rotors do have less surface area, but it is negligible and the cooling effect that reduces your brake fade will outweigh the decrease in friction
fact: slotted rotors keep pad wear even

I have slotted on the rear and blanks on the front with SS brake lines and I recently replaced my HAWK HPS pads with Endless Super Street S-Sport pads and the difference is amazing, they are multiple times better than the HAWK HPS pads, although their is more brake dust.

Lucid Moments
06-19-2008, 07:21 PM
fact: drilled rotors decrease surface area, thus decreasing friction, and when chamfered incorrectly are prone to heat fractures.
fact: slotted rotors do have less surface area, but it is negligible and the cooling effect that reduces your brake fade will outweigh the decrease in friction
fact: slotted rotors keep pad wear even

I have slotted on the rear and blanks on the front with SS brake lines and I recently replaced my HAWK HPS pads with Endless Super Street S-Sport pads and the difference is amazing, they are multiple times better than the HAWK HPS pads, although their is more brake dust.

I'll agree with your comments about the drilled rotors with one exception. The real loss from cross drilling has nothing to do with surface area, but the cross drilling does reduce the rotor mass which reduces its heat capacity.

On the slotted rotors I disagree almost catagorically. Cooling from slots? Not likely. I don't see any way the slots aid in cooling. You are again confusing the loss in surface area and the loss in mass, but I'll agree that the loss in mass is negligable.

SiRCivic03
06-19-2008, 08:42 PM
EP3s that aren't race cars don't need cold air intakes. EP3s that aren't race cars don't need 2.5-3" exhausts. EP3s that aren't race cars probably don't need slotted brake rotors. My point here is that people do these modifications to their cars anyways. There has to be some science behind the use of slotted ("vented" or whatever) rotors, why else would so many true race cars use them in competition? I don't know...I don't want to sound stupid i just wanted to say that I'll be purchasing a set of power slot OEM sized front rotors just for peace of mind while auto crossing and for the very few track days I will go on this year. Will it help while I'm daily driving? probably not. Will it help when i'm pushing my car when I'm at a competitive or non competitive high performance driving event and instill some piece at mind? definately yes. just my two cents

HondaFreak
06-20-2008, 08:22 AM
I'll agree with your comments about the drilled rotors with one exception. The real loss from cross drilling has nothing to do with surface area, but the cross drilling does reduce the rotor mass which reduces its heat capacity.

On the slotted rotors I disagree almost catagorically. Cooling from slots? Not likely. I don't see any way the slots aid in cooling. You are again confusing the loss in surface area and the loss in mass, but I'll agree that the loss in mass is negligable.

Cooling.....did I insinuate cooling. Sorry if I did, no I was referring to gas release. No drill or slot is for cooling, just gas release. DOH!
But as you mentioned if gas release on modern brake compounds is insignificant, then so should the slots and drills. No gas release means no need for a spot for it to escape.

Christian

dichotomous
06-20-2008, 09:31 AM
drilled rotors will be lighter, which wont help with braking all that much, but will help with acceleration and turning. I have not seen a current sportbike without drilled brake rotors..... but the race bikes use carbon solid (and sometimes slotted) rotors, showing that drilled is both bling and weight

v1c10us
06-20-2008, 01:26 PM
you guys buying the brembo blanks why dont you just get the Honda rotors they are made by brembo.

thats like saying, hey you guys buying aftermarket clutches, why dont you just buy the honda clutch, its made by exedy!
or, hey you guys buying the enkei rpf-10's, why dont you just buy ap1 wheels, their made by enkei!

v1c10us
06-20-2008, 01:28 PM
I'll agree with your comments about the drilled rotors with one exception. The real loss from cross drilling has nothing to do with surface area, but the cross drilling does reduce the rotor mass which reduces its heat capacity.

On the slotted rotors I disagree almost catagorically. Cooling from slots? Not likely. I don't see any way the slots aid in cooling. You are again confusing the loss in surface area and the loss in mass, but I'll agree that the loss in mass is negligable.

I specifically said that the loss of surface area decreases the amount of friction.
If a brake pad touches a 2 square inches of rotor it will have a certain coefficient of friction, if .5 square inches of that part of the rotor are holes that the brake pad cannot mate with there will be a loss of friction.

the rotor mass has a negligible effect on its heat capacity, the real issue is the chamfering, by having a hole in your rotor you have a very sharp point all the way around the hole that will cool and heat much faster than the rest of the rotor, this causes the metal to become brittle and heat fractures occur.
the only form of drilling that is acceptable is with a full radius chamfer in which the edges of the hole are 90 degree curves, instead of a point, this eliminates those stress points, and eliminates the cracking problem, but the problem is still that with a vented rotor, the point between the 2 faces inside the rotor cannot be chamfered like this and will still run into the same issues.

edit:
http://www.sp-performance.com/images/Strait_hole.GIF
http://www.sp-performance.com/images/Counter_hole.GIF
http://www.sp-performance.com/images/Radius_hole.GIF
http://www.sp-performance.com/images/Sinusoid_curve.GIF
the problem is ^that right there on a vented rotor there is a gap in the 2 faces, this area cannot be chamfered and will be at even more risk, because it is heated and cooled even better than the outside, thus still allowing the problem.
The last one is ideal, but only a few companys make that, and it has an even greater decrease in surface area due to the gradient required on the curve
I dont really have a scientific reason for why the slots cool your rotors, but Im fairly sure it has something to do with air getting in them.

dichotomous
06-20-2008, 01:40 PM
I specifically said that the loss of surface area decreases the amount of friction.
If a brake pad touches a 2 square inches of rotor it will have a certain coefficient of friction, if .5 square inches of that part of the rotor are holes that the brake pad cannot mate with there will be a loss of friction.
edit: im just kinda amazed that you could disagree with surface area having anything to do with friction, have you ever noticed that wider tires give you more traction because there is more surface area? or that a bald or slick tire will grip better because there is more surface area? Cut big holes in your brakes and everytime your brakes hit that part you'll discover that they stop gripping.. it would be just like abs! (stupidest fucking invention ever, we're supposed to drive the car, the car isn't supposed to drive us)

you are wrong, the friction coefficient doesnt rely on area whatsover, check out the formulas if you like. things like adhesion may, which is why wider tires grip more, they have things going on other than friction. but you wont loose friction by having less area. the holes can also help sweep the pads cleaner similar to a slotted rotor, but mainly its to help with weight I think, used to be because of outgassing of pads but thats not been a problem for a while

irrational
06-20-2008, 02:01 PM
Slotted and drilled are commonly seen to "cool" when they are in fact designed to vent gases to the best of my knowledge. If anything other than blanks I would consider dimpled over drilled due to strength concerns of going through the rotor surface. I had dimpled and slotted rotors from EBC on my CRX and they made a HUGE difference. Was thinking of going with the same on my EP but the car is much heavier and my decision is being influenced from the previous comments of this thread.

v1c10us
06-20-2008, 02:21 PM
you are wrong, the friction coefficient doesnt rely on area whatsover, check out the formulas if you like. things like adhesion may, which is why wider tires grip more, they have things going on other than friction. but you wont loose friction by having less area. the holes can also help sweep the pads cleaner similar to a slotted rotor, but mainly its to help with weight I think, used to be because of outgassing of pads but thats not been a problem for a while

lol.. alright wise ass, yes you're correct, the coefficient of friction doesnt rely on the area, but it is a factor based on a specific area.
sure; 2 small pieces of sand paper rubbing together may have the same coefficient of friction, but that is because the factor is based on a specific amount of that sandpaper, factor in the entire piece and the bigger it is, the more friction you will encounter entirely.
Its the same amount per square centimeter or whatever you wanna measure it in, but if there are more centimeters, there will be more resistance.
you will lose(not loose) friction by having less area, and i cant believe you would argue that, if size didn't have anything to do with it we would all drive around on bicycle tires

Zzyzx
06-20-2008, 02:21 PM
Lets see....

To Quote this article http://www.teamscr.com/rotors.html by James Walker, Jr. of scR motorsports


Crossdrilling

Crossdrilling your rotors might look neat, but what is it really doing for you? Well, unless your car is using brake pads from the 40’s and 50’s, not a whole lot. Rotors were first ‘drilled’ because early brake pad materials gave off gasses when heated to racing temperatures – a process known as ‘gassing out’. These gasses then formed a thin layer between the brake pad face and the rotor, acting as a lubricant and effectively lowering the coefficient of friction. The holes were implemented to give the gasses ‘somewhere to go’. It was an effective solution, but today’s friction materials do not exhibit the same gassing out phenomenon as the early pads.

For this reason, the holes have carried over more as a design feature than a performance feature. Contrary to popular belief they don’t lower temperatures (in fact, by removing weight from the rotor, the temperatures can actually increase a little), they create stress risers allowing the rotor to crack sooner, and make a mess of brake pads – sort of like a cheese grater rubbing against them at every stop. (Want more evidence? Look at NASCAR or F1. You would think that if drilling holes in the rotor was the hot ticket, these teams would be doing it.)

The one glaring exception here is in the rare situation where the rotors are so oversized (look at any performance motorcycle or lighter formula car) that the rotors are drilled like Swiss cheese. While the issues of stress risers and brake pad wear are still present, drilling is used to reduce the mass of the parts in spite of these concerns. Remember – nothing comes for free. If these teams switched to non-drilled rotors, they would see lower operating temperatures and longer brake pad life – at the expense of higher weight. It’s all about trade-offs.

Slotting

Slotting rotors, on the other hand, might be a consideration if your sanctioning body allows for it. Cutting thin slots across the face of the rotor can actually help to clean the face of the brake pads over time, helping to reduce the ‘glazing’ often found during high-speed use which can lower the coefficient of friction. While there may still be a small concern over creating stress risers in the face of the rotor, if the slots are shallow and cut properly, the trade-off appears to be worth the risk. (Have you looked at a NASCAR rotor lately?)

other tech articles.. I suggest reading the one on brake systems.
http://www.teamscr.com/techarticles.html

Zzyzx
06-20-2008, 02:30 PM
lol.. alright wise ass, yes you're correct, the coefficient of friction doesnt rely on the area, but it is a factor based on a specific area.
sure; 2 small pieces of sand paper rubbing together may have the same coefficient of friction, but that is because the factor is based on a specific amount of that sandpaper, factor in the entire piece and the bigger it is, the more friction you will encounter entirely.
Its the same amount per square centimeter or whatever you wanna measure it in, but if there are more centimeters, there will be more resistance.
you will lose(not loose) friction by having less area, and i cant believe you would argue that, if size didn't have anything to do with it we would all drive around on bicycle tires

Friction relies on two things.

1. Pressure
and
2. the coefficient of friction between the two objects.

So,
Although a larger area of contact between two surfaces would create a larger source of frictional forces, it also reduces the pressure between the two surfaces for a given force holding them together. Since pressure equals force divided by the area of contact, it works out that the increase in friction generating area is exactly offset by the reduction in pressure; the resulting frictional forces, then, are dependent only on the frictional coefficient of the materials and the FORCE holding them together.

If you were to increase the force as you increased the area to keep PRESSURE the same, then increasing the area WOULD increase the frictional force between the two surfaces.
Answered by: Paul Walorski, B.A. Physics
(the above was Quoted from here) (http://www.physlink.com/education/askexperts/ae140.cfm)


Regarding the tire issue, as above friction is dependent on pressure & the coefficient of friction between the tire & ground. So, increasing the width of that tire does not increase traction in and of its self. The increase in traction comes with how the tires compound reacts to pressure. See, as weight is applied to a tire the amount of "grip" increases. But... the tires coefficient of friction Decreases.

So, as weight is applied traction increases at a decreasing rate. Meaning there will be a point where the amount of traction applied to every square cm of tire contact patch will exceed the traction output of that compound, and the tire starts to slip.

To counter act that, you start with a larger contact area, so Every square cm of tire is initially holding less weight then the narrow tire, and therefore the tire can hold more weight / generate more traction.


Can we say Physics for the win?

MugsyTheGr8
06-20-2008, 02:36 PM
lol.. alright wise ass, yes you're correct, the coefficient of friction doesnt rely on the area, but it is a factor based on a specific area.
sure; 2 small pieces of sand paper rubbing together may have the same coefficient of friction, but that is because the factor is based on a specific amount of that sandpaper, factor in the entire piece and the bigger it is, the more friction you will encounter entirely.
Its the same amount per square centimeter or whatever you wanna measure it in, but if there are more centimeters, there will be more resistance.
you will lose(not loose) friction by having less area, and i cant believe you would argue that, if size didn't have anything to do with it we would all drive around on bicycle tires

he said that tire don't rely solely on friction. from what i understand, there is also a molecular bond going on between the pavement and the tire. im not going to pretend i understand it all, but that's why a wider tire is better as long as the vehicle is heavy enough to compress it.

as for friction. it is not dependent on area. its dependent on the force applied.

MugsyTheGr8
06-20-2008, 02:38 PM
Friction relies on two things.



Regarding the tire issue, as above friction is dependent on pressure & the coefficient of friction between the tire & ground. So, increasing the width of that tire does not increase traction in and of its self. The increase in traction comes with how the tires compound reacts to pressure. See, as weight is applied to a tire the amount of "grip" increases. But... the tires coefficient of friction Decreases.

So, as weight is applied traction increases at a decreasing rate. Meaning there will be a point where the amount of traction applied to every square cm of tire contact patch will exceed the traction output of that compound, and the tire starts to slip.

To counter act that, you start with a larger contact area, so Every square cm of tire is initially holding less weight then the narrow tire, and therefore the tire can hold more weight / generate more traction.


Can we say Physics for the win?
i just read that chapter in tune to win. good stuff.

Zzyzx
06-20-2008, 02:41 PM
i just read that chapter in tune to win. good stuff.

Good book.

Its amazing how all the other pieces of the tuning picture fall in to place once you see how tires actually generate traction.

you understand why weight transfer is bad, You understand why bigger brakes don't stop the car faster...

MugsyTheGr8
06-20-2008, 02:43 PM
Good book.

Its amazing how all the other pieces of the tuning picture fall in to place once you see how tires actually generate traction.

definitely. i've learned so much from it and it has made me realize whats most important when building/tuning a vehicle for performance.

bmyers4321
06-20-2008, 02:43 PM
thats like saying, hey you guys buying aftermarket clutches, why dont you just buy the honda clutch, its made by exedy!
or, hey you guys buying the enkei rpf-10's, why dont you just buy ap1 wheels, their made by enkei!
not really. my reason for saying it is that honda uses the brembo blanks for there cars so what is the purpose of buying them online and having to wait when you can go get them at the dealer. if they dont have it they can most likely have it for you the next day. the only reason i could see buying them online is if they were cheaper. there is a difference between what you said(quoted) and what i am saying. yes aftermarket clutches will be better than stock depending on what you get same with wheels. but brake rotors, well im think i made my point.

v1c10us
06-20-2008, 03:13 PM
Friction relies on two things.

1. Pressure
and
2. the coefficient of friction between the two objects.

So,

Regarding the tire issue, as above friction is dependent on pressure & the coefficient of friction between the tire & ground. So, increasing the width of that tire does not increase traction in and of its self. The increase in traction comes with how the tires compound reacts to pressure. See, as weight is applied to a tire the amount of "grip" increases. But... the tires coefficient of friction Decreases.

So, as weight is applied traction increases at a decreasing rate. Meaning there will be a point where the amount of traction applied to every square cm of tire contact patch will exceed the traction output of that compound, and the tire starts to slip.

To counter act that, you start with a larger contact area, so Every square cm of tire is initially holding less weight then the narrow tire, and therefore the tire can hold more weight / generate more traction.


Can we say Physics for the win?


holy fuck.
yes that article is all true but you need to re read it.
what you wrote was so full of careless errors I couldn't even make heads or tails of what you said.


Meaning there will be a point where the amount of traction applied to every square cm of tire contact patch will exceed the traction output of that compound, and the tire starts to slip.
increasing the traction applied will exceed the traction of the tire and the tire will lose traction? wtf is that shit.
Increasing the pressure applied to the mating surfaces will reduce the friction causing the tire to lose traction, I believe you meant..

His article made sense and I agree with it. although i do not agree with your interpretation of it.

I will address what you wrote in order..
the coefficient of friction between the tire and the ground doesnt exsist, each object has its own coefficient of friction. I believe you are having a hard time differing the coefficient of friction and friction, much as many people don't understand the difference between drag and the coefficient of drag.
increasing the width of the tire DOES increase the traction in and of itself.
you have a greater surface area, thus there is less pressure, allowing you to apply more pressure before losing traction.
the tires coefficient will never decrease based on pressure, the friction shared between the road and tire increases with pressure until the increase is too negligible to counteract the pressure, and then the tire slips.
as i said, you have friction and coefficient of friction confused.

as for the rotors thing; and after this point you guys can blab on all you want.
you bolded this in physics guy's article


If you were to increase the force as you increased the area to keep PRESSURE the same, then increasing the area WOULD increase the frictional force between the two surfaces. yet you failed to accept it.
If you increase the force(how hard you brake) while increasing the area(rotor size) you will increase frictional forces...
What we can learn from this is that if you increase the force as you decrease the area you will LOSE frictional force..
So if you're braking equally hard, the rotor with less area will have less friction.
If you make your rotor have more area, you can brake harder.
Fact

Zzyzx
06-20-2008, 03:24 PM
you're really grasping for straws here.

v1c10us
06-20-2008, 04:05 PM
you're really grasping for straws here.

mhmm..
fine then, just ignore everything I wrote and just read this part



Quote:
If you were to increase the force as you increased the area to keep PRESSURE the same, then increasing the area WOULD increase the frictional force between the two surfaces.
yet you failed to accept it.
If you increase the force(how hard you brake) while increasing the area(rotor size) you will increase frictional forces...
What we can learn from this is that if you increase the force as you decrease the area you will LOSE frictional force..
So if you're braking equally hard, the rotor with less area will have less friction.
If you make your rotor have more area, you can brake harder.
Fact.

your article proved it, I already knew it, and you're just refusing to accept it because it would require you to admit that you didn't understand what you were writing to begin with.

Zzyzx
06-20-2008, 04:39 PM
mhmm..
fine then, just ignore everything I wrote and just read this part



Quote:
If you were to increase the force as you increased the area to keep PRESSURE the same, then increasing the area WOULD increase the frictional force between the two surfaces.
yet you failed to accept it.
If you increase the force(how hard you brake) while increasing the area(rotor size) you will increase frictional forces...
What we can learn from this is that if you increase the force as you decrease the area you will LOSE frictional force..
So if you're braking equally hard, the rotor with less area will have less friction.
If you make your rotor have more area, you can brake harder.
Fact.

your article proved it, I already knew it, and you're just refusing to accept it because it would require you to admit that you didn't understand what you were writing to begin with.

Way to obfuscate your previous opinions.

You said,

I specifically said that the loss of surface area decreases the amount of friction.
If a brake pad touches a 2 square inches of rotor it will have a certain coefficient of friction, if .5 square inches of that part of the rotor are holes that the brake pad cannot mate with there will be a loss of friction.

and now that you have information otherwise your argument changes? nice maneuvering.


If you increase the force(how hard you brake) while increasing the area(rotor size) you will increase frictional forces...

since we are talking specifically about rotor size/surface area in this thread, where is this magical increase in pressure coming form that you couldn't also apply to the rotor with less surface area? Are you assuming in your argument that we'd also be changing caliper clamp load output? Or are you hoping that we wouldn't realize that you can push just as hard on the brake pedal and have the same clamping load at the caliper with a drilled/slotted rotor as a blank?

Remember, since pressure equals force divided by the area of contact, (P=F/A)and since the Force is constant because there were no changes in the brake system besides rotor surface area... Increasing said surface area is just going to reduce the pressure on every square cm of pad/rotor. Which brings us back to surface area not mattering, just pressure and the coefficient of friction of the items in question.

v1c10us
06-21-2008, 12:54 AM
lol..
I stand by everything I said with one backpedal for the sake of the argument.
The caliper is not changing, nothing is changing other than the area of the 2 mating surfaces and the dispersion of pressure, that has been clear the entire time.
Forget the point of increasing surface area to increase friction, we'll just pretend that Rsx-s brake swaps are completely pointless(and dont say anything about the caliper, its still 1 piston and the brake booster is still the same, aint a damn ounce more pressure being applied, just dispersed over more AREA!)
I dont care what you say or how the fuck you say it and i'm sick of trying to get through to you here.
The fact remains that if you take a brick the size of a sugar cube and put a brick ontop of it and slide it across a surface laterally, it will be easier to slide than a brick sized brick with a sugar cube sized brick on top if it..
The fact also remains that when you have bigger tires there is more friction and your gas mileage will decrease.
The fact remains that if you take one finger and slide it across a book and then take your entire hand and slide it across a book you will feel more resistance.
The fact remains that if you provide the same amount of pressure on on a smaller surface area the friction will decrease, the pressure per unit increases, and this increase decreases the amount of friction shared by the two surfaces.
i'll repeat it bolder and bigger, just for you.
If you apply the same amount of pressure on a smaller surface area the friction decreases, the pressure per unit increases because it has less area to disperse over and this increase in pressure causes a decrease in friction, as you said, and as your article said. Now stop arguing a mute point.
and if you honestly believe what you're saying then go drill half inch holes in your rotors and drive around, i promise you, when you apply the brakes you wont even feel them let go when the pads hits the big empty spot =]


edit: me saying if you increase the pressure while increasing the surface area was me quoting your article; your article said
If you were to increase the force as you increased the area to keep PRESSURE the same, then increasing the area WOULD increase the frictional force between the two surfaces.

Zzyzx
06-21-2008, 05:35 PM
your original argument was that friction was subject to surface area, where it is clearly not (as shown in the sentence you quote). You seem to be confusing where this increase in pressure is coming form. as with out increasing the clamping force of the caliper, as you increase surface area, Pressure would decrease. (pressure equals force divided by the area of contact) the force coming from the caliper squeezing the pad against the rotors surface. I.e. as you increase pad/rotor contact, Pressure decreases.


the simplest response


- on a macroscopic level, surface area has no significant effect on friction. Only the force pushing 2 surfaces together and their materials (listed as their coefficient of friction against each other) matter. For instance, a 100 lbs block of steel will slide with the same difficulty no matter how you change its surface area in contact with the ground. This is because decreasing the surface area decreases the area that covalent bonding between the block and the ground (decreases friction), but it increases the force-per-area that supports the weight (increases friction), and the two friction methods cancel each other out.

So, that brick you talked about... doesn't matter how large or small of a contact patch it has. its still going to take the same amount of energy to get moving.

So you can keep believing that a larger pad & rotor some how magically increases the amount of brake power they can produce. Physics states other wise.

Now there are other factors that can be useful in generating more brake torque. For one, a larger rotor requires you to move the caliper farther from the center of rotation, which increases the mechanical advantage the caliper has on the rotor. (increasing brake torque output). But as physics states (seriously look it up) Just increasing pad/rotor interface size with out moving the caliper yields no significant difference in brake torque output.

As far as brake swaps I never said they were pointless, they just dont do what you think they do.... Think about it, you change the caliper(different pressure output per pedal input)... and move that caliper farther away from the center of rotation (greater amount of Torque multiplication).

The only advantage increasing the pad/rotor interface would give you would be a reduction in temperature across the pad's surface. as each square cm of pad would be under less pressure then the smaller pad.... and therefor less heat will be generated per cm2.

dofu2
06-21-2008, 05:50 PM
So, that brick you talked about... doesn't matter how large or small of a contact patch it has. its still going to take the same amount of energy to get moving.

A bit off the main topic of the thread, but would this apply to stickier substances like tires too? Hypermilers like to fill their tires up to the max so they can get as small of a contact patch of tire to the ground as possible because they claim it'll help move or keep the car moving with less power. But this article you just quoted is saying that contact patch size does not matter...

Lucid Moments
06-21-2008, 06:40 PM
There is more stuff going on with tires too though. Sidewall flex for one. I know that I've seen somewhere in this thread information regarding how the coefficient of friction on tire compounds grows at a decreasing rate as pressure is increased.

Zzyzx
06-21-2008, 06:55 PM
A bit off the main topic of the thread, but would this apply to stickier substances like tires too? Hypermilers like to fill their tires up to the max so they can get as small of a contact patch of tire to the ground as possible because they claim it'll help move or keep the car moving with less power. But this article you just quoted is saying that contact patch size does not matter...

Your looking at rolling resistance, different forces to overcome.
http://en.wikipedia.org/wiki/Rolling_friction




Woo... tons of articles on google..
http://wiki.answers.com/Q/Does_friction_force_depends_on_surface_area_direct ly_or_indirectly
http://zebu.uoregon.edu/1999/ph161/friction.html (pictures as well)
a reply form the DOE http://www.newton.dep.anl.gov/askasci/phy99/phy99449.htm

meetthenewguy
06-21-2008, 07:17 PM
I went with power slot crypos with hawk pads and ss lines and flush with DOT 4 while I was at it, what a difference! installed myself in about 4 hours with a buddy and some beer cost about 600

v1c10us
06-21-2008, 10:24 PM
fair enough, I still have a few points i disagree on but I'm through arguing.
tires however are a completely different subject, rolling friction and sliding friction are very different things, although they are both forms of kinetic friction forces act on them differently.
edit: you said quite a few times that an increase in pressure causes a decrease in friction, so under that principle would you not say that by removing area of the rotor, you are increasing the pressure and thus decreasing friction =\

Zzyzx
06-21-2008, 11:29 PM
you said quite a few times that an increase in pressure causes a decrease in friction
could you quote that, because i dont recall having ever said that, aside with tires. and you are dealing with the properties of rubber in that instance.

v1c10us
06-22-2008, 12:42 AM
I suppose you never said it
I called my physics professor this morning over all this mess and he informed me as to where I was making my error.
The issue is that friction gives off so much energy as heat(and at this point he started on a tirade about how innefficient brakes are on a car and how we should be ussing eddy currents)the energy given off from friction is dependent on the distance the object was sliding against. The longer(or in my feeble mind, i assumed this meant the amount of area) the path the object takes, the more slowly it loses its energy provided it used the same amount of force as a shorter path.. he said it more complex and it made sense when he said it, but basically what I took from it is that the entire reason a bigger rotor works better is because its spinning in a circle, thus making it a longer path of travel, meaning that less energy is wasted under the same amount of force or something =\
so you lose less energy to heat, Im going to give up on this whole thing because he made me more confused, but I guess I can understand it as this. if you slide an icecube across one inch of table you expended all of the force over a shorter distance, so it lost more energy to heat than if you had moved it a longer distance....that also sounded much better in my head and i will give up now..

dofu2
06-22-2008, 03:57 AM
Your looking at rolling resistance, different forces to overcome.
OK, thanks.