Rear Rotor Issue...

[97C28O]

I've had this issue for a long time and finally wanted to get some opinions on it...

I changed my rear rotors and pads about 4 years ago. Originally had Balo Rear Rotors and PBR Deluxe pads. The new brakes would squeal/ whine/ high pitch every time the brakes were applied (Yes, greased pins and also anti squeal paste added to pad plates and contact points to caliper) Saw rear passenger rotor appeared to be "glazed" and assumed it caused the brake noises... Switched out the rotor to Centric Plain rotors and noise was still present, the wearing on the rear passenger rotor still looked odd after months of driving. Decided to try new brake pads (maybe the "bite" didn't work well with PBR) so I purchased Akebono Euros. Noise disappears for few weeks, but the rotor looked the ask after MANY MORE MONTHS.

I decided to leave it alone and see what happens if time progress, NOTHING! Still the same noise to date, same rotor looks the same (doesn't wear like normal)

Yes, all brake bedding procedures were done (I've done a fair share of brake jobs), Rotor changes/ Pad changes involved scuffing up the surfaces due to material continent ion with new products.

[202brabus]

Stop riding your brakes

I've had this issue for a long time and finally wanted to get some opinions on it...

I changed my rear rotors and pads about 4 years ago. Originally had Balo Rear Rotors and PBR Deluxe pads. The new brakes would squeal/ whine/ high pitch every time the brakes were applied (Yes, greased pins and also anti squeal paste added to pad plates and contact points to caliper) Saw rear passenger rotor appeared to be "glazed" and assumed it caused the brake noises... Switched out the rotor to Centric Plain rotors and noise was still present, the wearing on the rear passenger rotor still looked odd after months of driving. Decided to try new brake pads (maybe the "bite" didn't work well with PBR) so I purchased Akebono Euros. Noise disappears for few weeks, but the rotor looked the ask after MANY MORE MONTHS.

I decided to leave it alone and see what happens if time progress, NOTHING! Still the same noise to date, same rotor looks the same (doesn't wear like normal)

Yes, all brake bedding procedures were done (I've done a fair share of brake jobs), Rotor changes/ Pad changes involved scuffing up the surfaces due to material continent ion with new products.

[97C28O]

stop posting useless tips.

[Chisel86]

I'm wondering if you have a sticky piston. Maybe a caliper rebuild or exchange is in order?

[Edwin28]

have you open the caliper and check if the piston come out all the way? Have you bleed it?

[97C28O]

I'm wondering if you have a sticky piston. Maybe a caliper rebuild or exchange is in order?

I'm hoping not to go to that extreme. I had tried a product that you spray onto the rotors (silver metallic) and the rotors are getting scuffed by the pad. Question is if there is enough pressure on the pads? I'll try bleeding them soon.

have you open the caliper and check if the piston come out all the way? Have you bleed it?

I had the caliper off the rotor and pads and depressed the brakes and piston operates fine, did that couple times with a piston retracting tool.

[Vetruck]

Yes, all brake bedding procedures were done (I've done a fair share of brake jobs), Rotor changes/ Pad changes involved scuffing up the surfaces due to material continent ion with new products.

Each time you put new rotors on, can you explain to me exactly how you did the brake bedding? This is critical info. I am an assumption looking at the pic, but please explain your bedding procedure.

[Vetruck]

Since no reply from the OP? I will continue with critical info so others will be informed what went wrong here and how to avoid this type of problem in future brake jobs.

What I see in the pictures the OP posted is a "hot spotted" rotor. This is very common and can be 100% prevented when you are armed with proper understanding and information.

The OP listed right away that he installed new rotors and performed the proper bedding procedures- this unfortunately for him is WRONG to do.
Why?
New rotors need to be "Seasoned" first before any bedding process can be done to them. Seasoning a new rotor can take up to 5 or 6 days. Yes, 5 or 6 days!!! THis is why most back yard mechanics as well as so called professionals and racers make this critical mistake and "cook" their brand new rotors by using them too hard too soon trying to bed them in.

Bedding and seasoning are two entirely different things. Seasoning needs to be done first, otherwise you will destroy a new rotor trying to bed a pad. Rotors are generally made of Iron. When a rotor is cast new, this iron will flow into place in the casting and it will leave void areas of imperfections in the metal casting. The iron has to be "normalized" in a sense that the metal needs to be gradually re-heated and the iron will change properties and flow the molecules into stronger bonds and fill voids from high heat casting and rapid cooling. The best way this is usually described is the same effect you see when pouring hot liquid over ice- the ice cracks and has voids. A new rotor needs the metal to be conditioned to accept heat properly....I will say that again- The new rotor needs the metal to be conditioned to accept heat properly!

You can and should condition brand new rotors with brand new pads. It will seem like the same procedure as bedding pads, BUT IT IS NOT. This is where many make mistakes and ruin the surface of the rotors. If a rotor is not "conditioned" with the metal brought slowly to temp and normalized to molecules to fill voids, the rotor can "hotspot" certain ares of the face. What a hot spot is? it is where the iron metal has rapidly breeched temperature of 1100* and as a result the iron has chemically changed properties forming what is known as Crystaline. Once in the crystaline state, that portion of rotor will not accept heat.

What causes a new iron rotor to form crystaline spots so easily? it is from #1 the voids in molecules from casting, and #2 the oils and such used on the face of the rotor to machine them.

When you install new rotors, you have to have patience and allow for the proper time span to not rely on the car for two days, and then drive it very cautiously for another 3-4 days trying to baby it at all times to NOT put any excessive heat into them at all. This allows for the new rotors to slightlky and gradually heat up, and then "COMPLETELY COOL DOWN" (I like to let mine sit overnight after a 10 minute drive completely babying it and just letting the pads warm the rotors from just the installed contact that they ride against eachother even when the brake pedal is not applied. Use a few stops as possible (best to drive down a back road very slow and avoid stops- I know, this is hard to find? Just drive around you neighborhood letting the car idle at 5-10 mph and lightly pedal it as you corner or slow to avoid kids, cars, pedestrians etc. A few very slow laps around works- THEN LET THE CAR SET OVERNIGHT) What I do to make this easier on the first heat cycle is I simply bake my new rotors in the oven twice before I install them on the car/truck. I place them in the cold oven racks (all of them at once if your oven is large enough) and then turn the oven on and bring them up to 400*. Once this temp is reached I turn the oven off and let them cool. The next day I repeat this and I bake them at 400* for an hour(this gets them actually to 400* internally this time), and then let them cool entirely. I then install them and do the "around the block" procedure, and for a 3rd time I let them completely cool. I do this 3 times in one day over about 12 hours. The new rotors are now heat cycled and the iron has normalized- they are now ready for the "bedding" procedure to bed the brake pad material onto the rotor surface.

Now is where you follow pad bedding procedures and do several harder (but not locking up) slow downs from 45-15mph 4times, then drive around slowly letting cool. The pads will/may smeel a little and feel like a little fading occurred. In about 10 mins of slow driving trying a little as possible to use braking (again baby the car). What you are doing is tranfering some pad material to the rotors and letting it cool evenly onto the rotor surface. once cooled a little with normal driving you now do it again a little higher speed from about 60 down to 15mph (NEVER STOP THE CAR!!! IF you have to then stop shot and let the car creap forward a little letting the rotors turn under the pad surface not to rest on one section)., Do this 3-4 times and then drive around again and let the material cool evenly on the rotor surface back to normal driving temps using the rake pedal as little as you can. YOU NOW LET THE CAR SIT OVERNIGHT AND COMPLETELY COOL THE ROTORS.

For the next 3 days use of the car---> DRIVE IT NORMAL like you are driving a limo with clients in the back....PERIOD. Do not try and "TEST" your new brakes. You are still actually aiding in the rotor "seasoning" as well as in the pad bedding process. After this is all done? Go hammer them. You want to put about at least 100miles on them before you hammer on them with spirited driving- I try and put about 300 on mine just for safe measure. Al the while I will take opportunity to do more bedding and cooling one an hour lets say when I see the road and traffic is conducive to this during these 3 days.

Dean

ps- heat cycling is basically getting heat into metal and letting it completely cool. The more you do this, the stronger the metal becomes.

This is also the reason why racers use old engine blocks and machine them. New engine blocks are not as strong. Old blocks have often been heat cycled with daily use thousands of times.

[Chisel86]

Vetruck, is this a reason why new performance rotors can feel "warped" after only a year with regular use?

[Vetruck]

Vetruck, is this a reason why new performance rotors can feel "warped" after only a year with regular use?

Yes this is usually the problem. What a "warped rotor" actually is is simply brake pad build up on a section of the rotor surface. it can be caused by two things. 1) by having a hot spot on the rotor as described above. The rotor iron becomes hard in sections and does not absorb heat. I had to re look up the terms and I have it incorrect above in my novel. I listed it as crystalline when it is in fact Cementite. When poured into a cast like mold, Iron has a crystalline type formation. These molecules form with voids so the crystals in iron can be reformed to tighter bonds. The change with rapid heat I was describing is where the iron breeches a certain threshold and permanently changed properties into what is called Iron Cementite- These are the hot spots. They do not dissipate heat like the rest of the brake surface, so brake pads will deposit more build up on the rotor surface in this/these areas and have a pulsating feel over time. The rotor needs to be turned on a lathe to remove the pad material build up. Unfortunately, once a rotor is overheated, the Cementite area will never go away.
2) the second way this happens is by heating up brakes in very hard use (like on a race track) and then stopping on them without them cooling down first. Stopping on hot brake pads will clamp a pad on one section of the rotor surface and will create pad transfer of material that will lead to it rubbing more then other portions and causeing even more buildup over time. EBC Greenstuff pads are notorious for this- they require a lot of cool down time (an extra lap or two of slow driving after spirited laps are finished prior to bring the car to a dead stop. Something like a hard canyon run wand then coming to a stop will do this if the brakes are hot- like coming aggressively out of the mountains and then stopping at a traffic light at the bottom. Always stop back a little and let the car roll a foot or two- every few seconds- if space will allow for this. It helps prevent brake "warp"

[Vetruck]

This becomes a habit as you gain racing experience. It is a mandatory part of cool down after a run. You will note @ 11:25 of this video I instinctively put the car into reverse a few feet to move the rotors in the pad sections to distribute heat as I had to stop. (Hopefully the video starts at 11:25) I had already completed a cool down lap, came to a stop for a few seconds, then backed it up a little to get the pads onto another section of rotor face.
https://youtu.be/ru7zpv4R2Tg?t=11m25s

[Denlasoul]

Vetruck, can you shed some light on cross-drilled and/or slotted rotors? Popular internet belief is that slotted rotors by itself is better that cross-drilled bc the slots aid in cleanng the pads. Also can you comment on how cross-drilled rotors are made? Again, popular internet belief has two methods: 1) rotors are cast with the holes and 2) solid rotors are drilled after they are cast. The popular belief is that drilling a solid rotor weakens it.

[Vetruck]

Vetruck, can you shed some light on cross-drilled and/or slotted rotors? Popular internet belief is that slotted rotors by itself is better that cross-drilled bc the slots aid in cleanng the pads. Also can you comment on how cross-drilled rotors are made? Again, popular internet belief has two methods: 1) rotors are cast with the holes and 2) solid rotors are drilled after they are cast. The popular belief is that drilling a solid rotor weakens it.

I have a very simple statement that will lead you to answer your own question.

Which is stronger, forged pistons, or cast pistons?

Don't believe car forum banter.

[Vetruck]

The same principle applies to forged billet wheels compared to cast wheels. One is generally 3-4 times more expensive for the sole reason it is much stronger and more precise/better made.

I am on my phone trying to text type. Ill get into this later when on a keyboard.

[Vetruck]

I am home now on a keyboard- So here goes a novel...lol.

I have heard of Cast rotors before like with the Dodge neon I race, But they are very cheap quality stuff. Cast holes would still need to be cleaned up with machine work, as well as the rotor itself would be very weak and susceptible to cracking. Cast metal is not as dense in the granular flow with poured into a mold. From what I know cast hole rotors are very rare. When a company states "cross drilled" it is just that - drilled with a CNC machine. The drills are put into the center of the cooling vane passages of the rotor vents so they actually function for off gassing and cooling. Do they work? hell yes. I challenge anyone to tell me why then Porsche for instance sells there up scale cars with drilled rotors if it is for looks only? More on this later in this post!!! Ferrari ALSO makes drilled rotors in their high end carbon fiber rotors-why? off gassing of brake pad friction- makes for better pad contact.

As for cross drilled vs Slotted rotors? yes slotted rotors clean of the pad surface- great for a dirt bike or a dirt circle track car application where YES it actually gets dirt on the rotors. This is not for cleaning off pad glazing. Slotted rotors aid in cooling the pad and off gassing, but has been proven that drilled works better. The MAIN DRAWBACK to slotted rotors is they make the brake pad wear out probably twice as fast (My own personal experience) The howl- sometimes kind of a cool sound when coming down hard on the binders with curved slot rotors, but really no improvement over drilled rotors. Dimpled rotors proved to be best of all three for strength (But again- More on this later on the actual use of drilled rotors the "correct way"). Most manufacturers do it simply because people by them for looks. It is common to see "drilled and slotted rotors" options. I even built a set once with them only because the rotor choice was plenty large and light- AND- the only rotor that size that fit my agenda.(Otherwise I would have used just drilled rotors)

Now when drilled rotors crack.....

They are not properly engineered for the application. Someone is generally taking an OEM rotor, drilling holes in it- upping the price and selling it to average joe. This is simply taking away rotor mass on what generally already is too small a rotor for performance applications. (I.E.- taking lets say my front C220 rotor off and just drilling holes into it and putting it back onto the car. It will hurt my performance ...UNLESS...in the rare occasion it is matched to a higher friction coefficient pad that will gas on a solid rotor and needs a drilled face for better initial bite- I will name one great pad of such use- Stillen Metal Matrix pads. They shine with drilled rotors- only a little above average without them)

The other problem is how they are drilled. They really need to be done on a curved vane rotor. A lot of cheapie companies take straight vane OEM rotors and drill them. These rotors are light weight to begin with, and they are now taking off more material in a vane section that is not that heavy duty to begin with. They also do not chamfer the holes which will lead to stress- especially when heated. Even if the holes are slightly chamfered, one the rotor wears and is turned once, the chamfers are gone and the rotor will have 90* stress points on each hole and not dissipate the heat evenly into the bore of each hole. It heats much more rapidly in concentrated areas. Cracks will generally occurs based on all the combined factors on a cheapie rotor. You want more education on rotor heavy-duty properties when speaking of cooling vanes? Do an internet search and read about straight vane rotors vs curved vane rotors. Rotors are not all equal by the faintest definition of that comparison- Huge difference in quality and heat acceptance properties.

I will post this for now, and move to the next post for addition info on how to properly use a drilled rotor....

[Vetruck]

I will start off with a visual example. This is a radical package I built on my old 3rd gen Camaro (ex wife got in a divorce years ago- it was her car I built for her to grocery get and take my kid around town as a taxi) This car , as with pretty much every car I own, handles extremely well (Emphasis on "EXTREMELY"). I built her a sleeper car that would pretty much clean ass on anything around taking corners. The brakes happened out of necessity for safety to bring the car down quickly from speed since it moved so much faster around corners, onramps etc then pretty much anything on the street- this car is well known in the Camaro/Firebird world. It pulled an amazing lateral 1.07g's and 60-0 in 102ft. A stock IROC Camaro performance package did that same test in Road and Track magazine when new back in the day and had .87g's and 147ft 60-0 on the same size tires I ran!!!!


OK, with all that said, I will now get into the importance of building a performance brake package and why drilled holes are so beneficial.

It is all about weight savings. You want to gain rotation leverage, but not gain in unsprung weight, not gain in rotation weight. Rotational weight will slow a car down in acceleration, AND it will not allow you to slow down as quickly under braking conditions if the mass is greater with inertia.

When you take lets say a 12" rotor and a 13" rotor (both mounted with the same caliper- so take that out of the equation) the 13" rotor will have more surface leverage area to slow the car. It is further from the fulcrum point of rotation. BUT...the 13" rotor is heavier then the 12" rotor. So what you gain in leverage force, you loose somewhat in rotation mass and unsprung weight increase because of weight. Taking a 12" rotor and drilling it will take away mass and hurt cooling properties of the rotor because it is now smaller in material mass- so that could and usually will fade a prake because it runs higher heat ranges.

So here's what you do, you step UP to a 13" rotor but with drilled surfaces. You can make a 13" as light as a 12", BUT with increase leverage and increased coiling surface because the open voids of the drilled holes act like a heat sink when compared to a solid surface rotor.

Let me now show you that same brake setup next to what I took off the car OEM size. it had the original (on right) 10.5"x 1.0" rotors and single piston Iron calipers, and I built custom myself (one of a kind still to this day, and not duplicated by anyone) a 6piston 13.06"x 1.25" brake setup that fit "underneath a factory 16x8" IROC wheel". This package, even though it is so massive compared to the OEM setup, was actually 4 LBS!!!!! lighter weight each side of the car. That is HUGE!!!! When you deal with unsprung weight, it is the golden ticket to making a car handle well. It is less weight to thrust upward over a road imperfection and less weight to unsettle the chassis. It makes the car maintain contact with the road better when lighter, as well as makes for better comfort inside the car. Most average cars have a ride ratio of 2:1-3:1 range. a Cadillac is know for a higher ride ratio of more like 3.5:1-4:1 range, but is done NOT by reducing unsprung weight for performace- but by increasing sprung weight for comfort. Reducing unsprung weight is EXPENSIVE to do. Cars like Ferrari's' Lambo's etc try to get ride ratios of 5:1 range. With a 2500lb car- this means the suspension and wheels weight only 500 of those 2500 lbs. Most cars like my old camaro weight 3500 lbs (mine was 3100 with extensive mods) so at a 3:1 ride ratio that means about 2000lbs chassis, and 1000 lbs suspension. Drop the chassis weight with fiberglass hoods, aluminum heads etc? and the ride ratio gets worse, not better. The suspension needs to drop in weight more so. 8 lbs of unsprung weight is equivalent to 40 lbs of sprung weight. I dropped 68 lbs off that car's unsprung weight- while adding performance like this radial brake setup.

[John Jones Jr.]

Cheers Vetruck for your very detailed posts. That seems like excellent info and very interesting comments too.

So, a question for you. Without fitting larger calipers what's the best way to improve braking performance for fast road use? I've been thinking of using a 'performance' pad of some type, different rotors (slotted, drilled etc) and ducting cool air to the rotors from the from the front. Really, Vetruck I'm just looking best valve for buck but improvements none the less. Any ideas?

[Denlasoul]

Dean, thanks for the information! This stuff is exactly what I was looking to find. Now it is on the site and (hopefully) people can reference it.

Thinking I may need to rethink my brake set up....

[Chisel86]

Yes this is usually the problem. What a "warped rotor" actually is is simply brake pad build up on a section of the rotor surface. it can be caused by two things. 1) by having a hot spot on the rotor as described above. The rotor iron becomes hard in sections and does not absorb heat. I had to re look up the terms and I have it incorrect above in my novel. I listed it as crystalline when it is in fact Cementite. When poured into a cast like mold, Iron has a crystalline type formation. These molecules form with voids so the crystals in iron can be reformed to tighter bonds. The change with rapid heat I was describing is where the iron breeches a certain threshold and permanently changed properties into what is called Iron Cementite- These are the hot spots. They do not dissipate heat like the rest of the brake surface, so brake pads will deposit more build up on the rotor surface in this/these areas and have a pulsating feel over time. The rotor needs to be turned on a lathe to remove the pad material build up. Unfortunately, once a rotor is overheated, the Cementite area will never go away.
2) the second way this happens is by heating up brakes in very hard use (like on a race track) and then stopping on them without them cooling down first. Stopping on hot brake pads will clamp a pad on one section of the rotor surface and will create pad transfer of material that will lead to it rubbing more then other portions and causeing even more buildup over time. EBC Greenstuff pads are notorious for this- they require a lot of cool down time (an extra lap or two of slow driving after spirited laps are finished prior to bring the car to a dead stop. Something like a hard canyon run wand then coming to a stop will do this if the brakes are hot- like coming aggressively out of the mountains and then stopping at a traffic light at the bottom. Always stop back a little and let the car roll a foot or two- every few seconds- if space will allow for this. It helps prevent brake "warp"

I'm just curious then, would you be able to possibly remedy this by heat cycling a used rotor in the oven? Because I have drilled Centric PowerStop rotors that pulsate after only a year, and they have never seen a track, nor have I done any full hard stops...

[Vetruck]

Cheers Vetruck for your very detailed posts. That seems like excellent info and very interesting comments too.

So, a question for you. Without fitting larger calipers what's the best way to improve braking performance for fast road use? I've been thinking of using a 'performance' pad of some type, different rotors (slotted, drilled etc) and ducting cool air to the rotors from the from the front. Really, Vetruck I'm just looking best valve for buck but improvements none the less. Any ideas?

Basically the same as I did on mine. just added some Porterfield R4S pads. here is the info on them from Porterfield. Ask for racers discount- they will give it if you just simply say you are in a sanctioned racing organization like SCCA, etc.

http://porterfield-brakes.com/images...6_02_45_30.pdf

The only pad I like better for street use is Stillen metal matrix pads, but I recommend them with drilled rotors to get a better initial bite and overall feel. I did not use Stillen pads on my car because they only offer my fronts (no rear application for my year car '94). The R4-S pads are a very close second and are actually better on a non-drilled OEM rotor.

[Vetruck]

I'm just curious then, would you be able to possibly remedy this by heat cycling a used rotor in the oven? Because I have drilled Centric PowerStop rotors that pulsate after only a year, and they have never seen a track, nor have I done any full hard stops...

If the rotors are use, they already heat cycled. Just driving them around the block will bring them up a few hundred degrees. What type of pads are you running?

I will say something that will not make you happy, but I am all about facts here- Powerstop rotors are one of those cheapie companies I discussed in an earlier post. They are Chinese crap- not the best of metal used in them. You are far better off going to a Napa ultra premium rotor or a Brembo OEM replacement- both are excellent quality and on par with factory Mercedes quality. Those powerstops are crap blanks use and them drilled removing even more mass making them inferior quality for heat control. This is why you will always get pad transfer buildup on them when you get a little harder on the brakes doing aggressive driving. Get used to having to turn them at least once a year if not more often as they age and more material is trued off them.

And to Den- Thank you, I just try to always leave personal opinion out and factual opinion in when based on people making purchase decisions. best bang for the buck is just good simple OEM quality rotors and R4-S pads.

And now if you want personal opinion? I listed a few years ago that Ceika brakes site. Trent (Dearlove) had some pretty awesome looking setups made for his car a while back. it is an option I pondered, but this car I have is no rocketship and I decided the OEM setup I have is good enough for what I would ever do with this car. I bought it more for luxury/prestige for the girlfriend to drive. I always have my eye out for another W202 if I spot one. Would be nice to build myself one a little quicker and in Black. Kind of a his and hers cars in that garage insted of my old Suga Caddy I beat to death saving my other cars. it would be cute with hers' white (the 94 Brabus) and mine black because frankly I am white and she is black- Would be funny to have the opposite in daily drivers. anyways, if I do, I will definitely be looking into lighter weight Ceika packages for it.

back to China an quality control.....Don't trust them. Anyone remember the story a few years back about the pet food company in China that was exporting dog food to the U.S.? Research found out that those bastards were right next to a wood factory and were putting Melamine Dust particles left over from the mill next door into the pet food and mixing it up to make it weigh more/mass--all for profit. That kind of crap goes on all the time over there. https://en.wikipedia.org/wiki/2007_pet_food_recalls

[John Jones Jr.]

http://porterfield-brakes.com/images...6_02_45_30.pdf

The only pad I like better for street use is Stillen metal matrix pads, but I recommend them with drilled rotors to get a better initial bite and overall feel.

Top man, thanks again.

[Chisel86]

If the rotors are use, they already heat cycled. Just driving them around the block will bring them up a few hundred degrees. What type of pads are you running?

I will say something that will not make you happy, but I am all about facts here- Powerstop rotors are one of those cheapie companies I discussed in an earlier post. They are Chinese crap- not the best of metal used in them. You are far better off going to a Napa ultra premium rotor or a Brembo OEM replacement- both are excellent quality and on par with factory Mercedes quality. Those powerstops are crap blanks use and them drilled removing even more mass making them inferior quality for heat control. This is why you will always get pad transfer buildup on them when you get a little harder on the brakes doing aggressive driving. Get used to having to turn them at least once a year if not more often as they age and more material is trued off them.

Yeah I was afraid of that. It's interesting though because these are already oversize for my application (calipers and rotors from C55) and they still do that? Makes me hate to think how bad they'd have been if they were the stock smaller size. The pads are Centric Posi-quiet metallic. Thanks.

[Vetruck]

Ive used a lot of brake pads in my day, never those tough. Wat always worries me about brake pads is these companies that do this Pre-burnishing or what this company is calling "Scorching" of their new rake pads to reduce resin and aid in break in. I have not see a good quality brake pad company ever do this. Only companies with poor friction so called performace pads like Hawks, PerformanceFriction, EBC, and Powerstop. Of those 4, I have used three of them and the Hawks are best (if you want to use the term best lightly) of the bunch. THe HPS pads are a decent cost and are pretty much equivalent to using a simple organic brake pad but with longer wear properties- not a performance pad at all in my book. As I stated above, EBC pads are notorious for pad buildup/transfer- they are the worst of the 3 of 4 above listed.

What I would watch out for when looking for a brake pad? Is charts like this: They have those blue graph charts comparing all 3 types of "THEIR" brake pads, but absolutely no reference to real world performance friction levels like a #: 0.41 coefficient for example. They state the friction levels remain consistent with temps- but where is the proof? Here is their charts:
http://www.centricparts.com/products/posiquiet

I personally feel it is a company just determined to get rid of the noise issues they have had with the materials they are using from the get go. Brake pad compounds and blends are somewhat guarded secrets. They also need to be changed in mixtures based on the vehicles weight. Most companies have a one for all pad and this is why problems with noise etc occur.

Now take a company like Wilwood- here is a normal racing pad (and street pad) spec charts showing heat range and friction levels.
http://www.wilwood.com/BrakePads/BrakePadsApp.aspx

Even Wilwood has notoriously had issues with street pad compounds. They are noisy. I have not used any Wilwood pads in about 10 years now other than full race pads (H compounds for short rack stints, B compound for long duration race use). Wilwood street pads were so bad (Ive used them all) I finally took some old pads to Porterfield and had them scrap off the Wilwood T compound and make a set of R4-S pads for my setup I showed above. (They now stock those at Porterfield for the Wilwood calipers).

[Vetruck]

Yeah I was afraid of that. It's interesting though because these are already oversize for my application (calipers and rotors from C55) and they still do that? Makes me hate to think how bad they'd have been if they were the stock smaller size. The pads are Centric Posi-quiet metallic. Thanks.

have them turned, and try some different pads. Hawks HPS are not bad (good bang for buck for daily street use), but I would still recommend using the R4-S

Porterfield R4-S pads for a 2005 C55 are part # AP847.1 (Fronts) / AP603 (rears)