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Thread: disc brakes

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    disc brakes

    Is it true that drilled and grooved discs are more likely to crack under stress ?Hi spec have that written in their website and they only recommend grooved only discs for over 300mm.So why let say audi r8 comes with grooved and drilled discs from the factory ??

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    yes they are more likely to crack

    no this will not happen on the road or ocassional track use - it's more of a concern for motorsport situations

    the added cooling benefit far outweighs the risk of cracking, that's why most performance cars have them
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    I think another point is that from a good manufacturer with racing experience,you are much less likely to have problems,and as sub39h has pointed out,in road use,you shouldn't have problems.

    I've used grooved and drilled APs before with no problems at all,on a car which really could put some heat into the brakes.

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    thanks guys for the info.Think hi spec is a well established company and do sell lots of brake kits but I told them car is only going to be used for road use and will have a much better brake set up then I eally need but they still said go for grooved only...will have to think about it as I love the looks of grooved and drilled discs.

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    just to add to this query... i actually spend a lot of time on track.... i dont recommend drilled rotors at all whether its from a reputable brand or not... eg Brembo if your application is track purposes. You will see very few dedicated track junkies use drilled rotors... cos you'll be constantly replacing them.

    I have tried all brands of drilled rotors and they just crack way to easily.... the stress it goes under track conditions... (heat and cooling cycles) will cause the rotors to crack from the drilled holes.

    Slotted/Grooved rotors are a totally different kettle of fish. I use AP Racing Slotted rotors and i've been punishing them with 10 hard core track events so far.. and they are still good as gold.

    However it should be noted... combination of pads and rotors will either make the situation worse... or actually be kinder on the rotors....
    i found pagid race pads and other pads like the Endless and Ferodos Race Pads ... were just too hard core on the Drilled rotors... but softer pads like EBC and some Hawks performance pads... were actually kinder on the rotors...

    but EBC were rubbish on track..they literally crumbled away.... there are trade offs...

    If you have no intention to track your car.. drilled rotors are perfectly fine. IF you do intend to track it..... get the best rotors you can afford.... they do make a huge difference.. i am speaking from experience... i find the AP Racing rotors much better than the Brembo Rotors. stick to two piece rotors for the pure reasons of less weight and better heat managment to put simply!

    heres a picture of my brake set up


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    Quote Originally Posted by sub39h View Post
    the added cooling benefit far outweighs the risk of cracking, that's why most performance cars have them
    drilled rotors have NOTHING to do with brake cooling none what so ever. The whole purpose of slotted and/or drilled rotors is to allow gases to escape due to intense heat build up.. and prevent glazing of the pads or rotors.

    The Slots/drilled holes also serves the purpose of "wiping" the surface of the pads... imagine if you will scraping the top layer off so that you will always get a fresh layer of pads for maximum brake bite and efficiency.

    There IS NO benefit of drilled rotors other than they look great and do allow gases to escape

    Brake Heat management is managed by the size and weight of the rotors and how much cool air you can get onto the brakes hence brake air ducts... the whole point of larger brake rotors is to act as a heat sink and draw the heat away that is generated from braking and the larger size allows the rotors to dissipate heat a lot quicker than a smaller rotor would.. as that would soak up the heat too quickly and due to its small size would not allow the rotors to dissipate heat quickly enough... where by you experience brake fade due to fluids boiling, pads cooking and everything else
    Last edited by robby_jai; 26th October 2010 at 09:45.

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    Yes I am definetly going for a 2 piece disc and ebc pads,gonna try green stuff and if not enough maybe red stuff later.car will never see the rain and it will never see the track (we dont even have one in malta !! )And also car will have a bigger kit then I actually need.Think I am going for the drilled and grooved as I am so fallen by the looks and then inspect them everytime I drive the car

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    Quote Originally Posted by qennu View Post
    thanks guys for the info.Think hi spec is a well established company and do sell lots of brake kits but I told them car is only going to be used for road use and will have a much better brake set up then I eally need but they still said go for grooved only...will have to think about it as I love the looks of grooved and drilled discs.
    Don't ever go for something just for the looks.

    That's the way to end up with Tar-Ox 10pot calipers and other daft things.



    Quote Originally Posted by qennu View Post
    Yes I am definetly going for a 2 piece disc and ebc pads,gonna try green stuff and if not enough maybe red stuff later.car will never see the rain and it will never see the track (we dont even have one in malta !! )And also car will have a bigger kit then I actually need.Think I am going for the drilled and grooved as I am so fallen by the looks and then inspect them everytime I drive the car
    I would also avoid EBC pads......I tried a set of Red Stuff against my own better judgement,having been warned previously.
    Anyway...they had initially better bite than the OEM pads but no better on sustained use or against fade,and the squealing was awful.

    If you want decent fast road or light track use pads,Ferodo DS2500 are excellent.

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    Quote Originally Posted by S3Alex View Post
    I would also avoid EBC pads......I tried a set of Red Stuff against my own better judgement,having been warned previously.
    Anyway...they had initially better bite than the OEM pads but no better on sustained use or against fade,and the squealing was awful.

    If you want decent fast road or light track use pads,Ferodo DS2500 are excellent.
    i strongly agree with this statement 1000%... EBC are not great pads and i am yet to find any one who speaks highly of them. The Ferodo DS2500 are a great street and track combo pad and they actually offer great initial bite and would take a heck of a lot to make those pads fade..

    having said that they are a bit tough on the rotors... but not overly aggressive on the rotors

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    Quote Originally Posted by robby_jai View Post
    i strongly agree with this statement 1000%... EBC are not great pads and i am yet to find any one who speaks highly of them. The Ferodo DS2500 are a great street and track combo pad and they actually offer great initial bite and would take a heck of a lot to make those pads fade..

    having said that they are a bit tough on the rotors... but not overly aggressive on the rotors
    Thanks....I was given a lot of very good advice a few yrs ago by the chap who looked after my Cosworths.

    Amongst other things,he'd run a championship winning BTCC privateer team,and competed in rallycross and Historic Grp C Racing,so he knew a thing or two about decent brakes.
    What he had to say about EBC and Tar-ox is basically unprintable,but he made the point of never letting form or looks take precedence over function,especially for braking.

    I use DS2500 pads on the VWRacing kit I have on my S3 and so far the rotors are standing up very well.

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    Quote Originally Posted by robby_jai View Post
    drilled rotors have NOTHING to do with brake cooling...
    What you basically just said in your entire post is that you need bigger brakes to act as a heat sink to cool them more effectively.

    The only way this can be true is if they have a greater surface area, which they will do if they're larger.

    Another way to increase surface area is to drill them.

    This allows you to have the cooling advantage of larger surface area but at lower unsprung weight.

    The drilled holes may give greater friction for the pads (again a byproduct of having higher surface area) and let gases escape. But to say they have nothing to with cooling is totally scientifically inaccurate. Whether they are this way by design or not is another matter. But they do help cool your brakes.
    Last edited by sub39h; 27th October 2010 at 22:48.
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    im not going to get into an argument with you online i'll just agree to disagree but you might wanna chat with a brake specialist to determine the whole purpose of drilling rotors. Yes certainly reduces weight no doubt. Definitely helps gases vent. Agree... but to say it aids in cooling i certainly dont agree.

    in my two cars setup for the track they have different combination and types of rotors, pads and calipers.. and i assure you.. the temperature variance between two rotors of the same size.. one slotted and one drilled.. the temperature difference is literally negligible. I know so because i carefully monitor brake temperatures when i go on track because a big fat VW MKV R32 hammers your brakes and the unwelcomed brake fade is a constant reminder of its weight and heat management is a major issue in the R32 brakes




    Quote Originally Posted by sub39h View Post
    What you basically just said in your entire post is that you need bigger brakes to act as a heat sink to cool them more effectively.

    The only way this can be true is if they have a greater surface area, which they will do if they're larger.

    Another way to increase surface area is to drill them.

    This allows you to have the cooling advantage of larger surface area but at lower unsprung weight.

    The drilled holes may give greater friction for the pads (again a byproduct of having higher surface area) and let gases escape. But to say they have nothing to with cooling is totally scientifically inaccurate. Whether they are this way by design or not is another matter. But they do help cool your brakes.
    Last edited by robby_jai; 28th October 2010 at 15:05.

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    try out the Pagids RS29 when your ferodos are done... they are by far the best pads i have used to date... they wipe the floor with the ferodos DS2500..

    the ferodo just dont stack up to the repeated abuses on the race track. great for the occasional sprints but not regular track thrashing!

    Quote Originally Posted by S3Alex View Post
    Thanks....I was given a lot of very good advice a few yrs ago by the chap who looked after my Cosworths.

    Amongst other things,he'd run a championship winning BTCC privateer team,and competed in rallycross and Historic Grp C Racing,so he knew a thing or two about decent brakes.
    What he had to say about EBC and Tar-ox is basically unprintable,but he made the point of never letting form or looks take precedence over function,especially for braking.

    I use DS2500 pads on the VWRacing kit I have on my S3 and so far the rotors are standing up very well.

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    Quote Originally Posted by robby_jai View Post
    try out the Pagids RS29 when your ferodos are done... they are by far the best pads i have used to date... they wipe the floor with the ferodos DS2500..

    the ferodo just dont stack up to the repeated abuses on the race track. great for the occasional sprints but not regular track thrashing!
    I may do that,depending on fitting issues.

    I had Pagids on my ex GrpN Escort Cosworth,and I have to agree...excellent pads all round.

    I haven't tried DS3000 pads but those may also be useful for track events.

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    Quote Originally Posted by robby_jai View Post
    im not going to get into an argument with you online i'll just agree to disagree but you might wanna chat with a brake specialist to determine the whole purpose of drilling rotors. Yes certainly reduces weight no doubt. Definitely helps gases vent. Agree... but to say it aids in cooling i certainly dont agree.

    in my two cars setup for the track they have different combination and types of rotors, pads and calipers.. and i assure you.. the temperature variance between two rotors of the same size.. one slotted and one drilled.. the temperature difference is literally negligible. I know so because i carefully monitor brake temperatures when i go on track because a big fat VW MKV R32 hammers your brakes and the unwelcomed brake fade is a constant reminder of its weight and heat management is a major issue in the R32 brakes
    If I may interject.

    You are actually both kind of correct. I spent a term at University researching and designing rotors for car and bike applications and my understanding is as follows. The argument for drilling the rotor is first (and arguably foremost) for cooling. The force applied by the pad (through the caliper) against the rotor generates heat by friction, as we all know this heat is detrimental to the performance of the brake and is generally referred to as "fade". Holes can be drilled through the rotor to act as vents for the heat to escape, allowing it to be drawn through the back of the rotor. This ventilation considerably reduces the temperature of the rotor, but is most noticeable under hard load scenarios e.g. track applications.

    The other reasons, but to be honest secondary reasons are to reduce gas build up (which only applies if you are using very cheap brake pads or old ones), and also the dissipation of water, although for high performance applications this is certainly not a primary design driver.

    It is also a fact that by drilling holes through a brake rotor does reduce it's load bearing ability, however again this would normally not be noticeable unless under hard load applications, or if the brake assembly was poorly designed with an "over braked" set up.
    Last edited by beanoir; 29th October 2010 at 11:30.
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    Quote Originally Posted by robby_jai View Post
    try out the Pagids RS29 when your ferodos are done... they are by far the best pads i have used to date... they wipe the floor with the ferodos DS2500..

    the ferodo just dont stack up to the repeated abuses on the race track. great for the occasional sprints but not regular track thrashing!
    do Pagid do an application for the S3 as couldn't see it?
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    Quote Originally Posted by jungleman View Post
    do Pagid do an application for the S3 as couldn't see it?
    I think we're mostly talking about aftermarket braking systems here with calipers to match,so it will depend on Pagid making pads to fit specifics like AP,Alcon and others.

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    ah fair enough... thought that may have been the case.
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