Suspension Brakes Slotted or Plain Rotors / Vendor Frustration

Discussion in 'Tuning and Performance' started by RonsMinnie, Jan 29, 2011.

  1. RonsMinnie

    RonsMinnie New Member
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    A couple of months ago I went one track session too many on my front brake pads and messed up my rotors. So I called a respected vendor and tried to order the identical slotted rotors that I was using. The vendor said he did not stock the slotted rotors and the plain rotors where what I needed, and the the "slotted thing" was old technology.

    Now just after four track session these new rotors are starting to show heavy signs of "ribbing or scoring". When I asked some track rat friends for there thoughts they said maybe pads but slotted rotors prevents this condition. I did not think pads where the issue as I had installed new Wilwood PolyMatrix "B" pad with the new plain rotors.

    A few "google searches" later I found this article on this EBC Brakes web site: EBC Brakes | Rotor quality and bedding in new rotors article ( I have copied it below).

    Rotor surface finishes such as slots - what do they really do... Plain rotors cost less and rotors without slots are less money to buy for sure but can exhibit some problems.
    Firstly the phenomenon known as rotor galling or brake rotor ribbing or rotor scoring happens everyday with the world being full of fairly soft cast iron rotors. The better the pad the more likely a plain (not slotted) rotor will suffer rotor ribbing. The picture below shows a typical normal rotor that is suffering from rotor ribbing.

    [​IMG]

    You don’t throw this rotor away, it is not ideal but it is not a safety issue either, you just have to live with this condition unless you want to upgrade to a slotted brake rotor. Slotted rotors have a major benefit in smoothing the brake pad gently as it wears through its useful life, the slots do NOT cheese grate the pads away surprisingly enough and lifetimes can actually be BETTER on a brake pads used against slotted rotors than one used on plain brake rotors because the pad runs cooler and more efficiently.
    This is what a slotted rotor looks like after 10,000 miles using the same pads as the plain rotor in the illustration above.


    [​IMG]


    The key benefit then of a slotted rotor, is smooth and parallel brake pad and brake rotor wear. EBC make a drilled and slotted rotor with its GD series and these work very well on heavier and faster cars and are a big favourite with light truck users.
    EBC does not like the aftermarket idea to cross drill rotors, these can crack, if you want to see this for yourself click here.

    A search of Wilwood web site revealed thoughts that where less direct, but they do say,

    " For most performance applications, slotted is the preferred choice."
    This quote is from: Wilwood High-Performance Disc Brakes - Frequently Asked Questions (FAQs)

    I am especially concerned with this condition as I need to swap back and forth from track to street pads and when it is time for new pads they will not bed in easily.

    So the question is the EBC article correct or is the respected vendor point of view the most current?
     
  2. Way Motor Works

    Way Motor Works New Member

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    Post some pics of your rotors the B pads may be too hard for you. May not be in operating temp range for you and need a softer pad.
    This is what we found with our track cars:
    When I used drilled rotors, and we just cracked them.
    When I used slotted rotors, lasted longer before cracking, but wore through the pads faster.
    When I used drilled and slotted I cracked them much faster, pad wear was little better than slotted only, but rotors wore out much faster.
    When I used plain face rotors they lasted the longest. Would still crack after a couple track events, but not the first day like the drilled. Also the quality of rotor also effected how long they lasted. The directional vains made them last longer than the straight vain.
    In 2006 I ran a set of plain face rotors for the entire season, and they are actually still my emergency set in case I need em in a hurry.
    In 2007 I went through 3 sets of various rotors cause they were out of the plain face rotors.

    Also did you drive to the track with the B's on the car? how far was it if you did?
     
  3. Rixter

    Rixter Well-Known Member

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    What about for street driving, is slotted (and drilled) going to make any improvement as far as stopping?
     
  4. RonsMinnie

    RonsMinnie New Member
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    #4 RonsMinnie, Jan 31, 2011
    Last edited: Jan 31, 2011
    I do not think so. Stopping distance is much more do with tires & traction than brakes. Once they are locked up, the brakes have done all they can do.

    Better brakes have more to do with repeatability and longevity than stopping distance. The job of brakes is to take kinetic energy and turn it into heat. Most brake mods help dissipate the heat that is created, which improves the ability to stop over and over again.
     
  5. Rixter

    Rixter Well-Known Member

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    Larger rotors should help improve braking as well. Its too bad the larger 316mm JCW rotors can't be added to stock MCS brakes. I'll bet there'd be a market for that if anybody ever came out with an adaptor for mounting the stock calipers on larger rotors. Way ;)?
     
  6. ScottinBend

    ScottinBend Space Cowboy
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    Larger rotors simply give you more rotor mass to help with heat dissipation.
     
  7. Rixter

    Rixter Well-Known Member

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    That's interesting because on our mountain bikes, if we switch from 6" to 8" rotors, even without changing calipers or any other brake components you gain about 30% additional stopping power. I think the stock rotors are 294mm and the JCW are 316mm, so not a dramatic difference.
     
  8. goaljnky

    goaljnky New Member

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    Not only is the brake surface ratio increase is smaller, I think you also need to take under consideration the weight that is being stopped.

    In the bike example with are talking about 33% increase in brakes to stop about 210 lbs (30 lbs bike, 180lbs human).

    The car is 7% increase to stop 2800+/- lbs? You are hardly gonna see any difference that can be measured consistently. Maybe 3-5 feet from 60mph?
     
  9. Rixter

    Rixter Well-Known Member

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    Good point! :Thumbsup:
     
  10. andyroo

    andyroo New Member
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    Good point, but again, you're almost always tire limited rather than stopping power limited when it comes to stopping distances. Yes you do get a little more stopping power with a larger rotor all else equal, but there are many reviews of crappy poorly thought out big brake kits where stopping distances INCREASE because of too much front stopping power screwing up the bias. :)

    And I agree with Way on the blank/slotted/drilled thing. No reason to do drilled, slotted are functionally fine, blank last longest if the pad is right. The fancy PFC dimples or AP Racing j-hooks are nicest (and prettiest).

    - Andrew
     
  11. Nitrominis

    Nitrominis Banned

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    How about slotted and or drilled rotors look good on a street car?
    They both will result in heat dissipation, removing gas, water etc. as reported over their historical use and technical information available?

    Larger diameter disc's if the brake bias is correct will give improve braking performance. I personally did not notice anything with the larger disc and factory caliper on the rear?
    The front are so over kill I had to get use to stopping all over again. The term stop on a dime applies to my front. Please don't ask how they do on a track... my mini really is about street performance and looks not track! But I am sure that the Mustang calipers and very large diameter disc I use would be more than capable of good track performance.
     
  12. Redbeard

    Redbeard JCW: because fast is fun!
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    Interesting. I'm getting ready to play the brake swap game on the MINI. I'm getting close to needing to relpace the front rotors and I was considering getting the slotted rotors and a new set of EBC pads to bed-in on them. Now I am debating the slotted versus solid...
     
  13. goaljnky

    goaljnky New Member

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    My M came with drilled front and back. Probably BMW M guys not knowing what they're doing again.
     
  14. minimark

    minimark Well-Known Member

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    If racing and your trying to get that last little bit, then really good slotted/drilled disc are worth the money. But for the weekend warrior, a fellow with a lot of track and racing experience recommended the inexpensive Centric rotors (street&track rated) for track days. Been running them ever sense with zero problems and they stop very good...they also don't kill my wallet if I strap a very aggressive brake pad to them and wear them out pretty quick. 2 cents

    PS: We now have them on all our cars too. ;)
     
  15. Nitrominis

    Nitrominis Banned

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    well now talk about getting something simple to confusing in 60 seconds?? Now I don't know what to believe??

    This is from Flash-Offroad:
    What Kind of Rotors Should I Get?

    What Kind of Rotors Should I Get?


    You Don't need Drilled or Slotted Rotors for a Hummer.

    While I'll agree to a certain point, here's some quotes from many known brake engineers and brake manufacturers in regards to slotting vs. drilled vs. normal.
    -----------
    Darrick Dong; Director of Motorsports at Performance Friction: "Anyone that
    tells you that drilling makes the disc run cooler is smoking crack."

    Power Slot: "At one time the conventional wisdom in racing circles was to cross-drill brake rotors to aid cooling and eliminate the gas emitted by brake pads. However, today's elite teams in open wheel, Indy and Trans Am racing are moving away from crack prone, cross-drilled brake rotors in favor of rotors modified with a fatigue resistant slotting process."

    Stop Tech: "StopTech provides rotors slotted, drilled or plain. For most performance applications slotted is the preferred choice. Slotting helps wipe away debris from between the pad and rotor as well as increasing the "bite" characteristics of the pad. A drilled rotor provides the same type of benefit, but is more susceptible to cracking under severe usage. Many customers prefer the look of a drilled rotor and for street and occasional light duty track use they will work fine. For more severe applications, we recommend slotted rotors." (Note that even though Stop Tech sells both drilled and slotted rotors they do not recommend drilled rotors for severe applications.)

    Wilwood: "Q: Why are some rotors drilled or slotted?
    A: Rotors are drilled to reduce rotating weight, an issue near and dear to racers searching for ways to minimize unsprung weight. Drilling diminishes a rotor's durability and cooling capacity."

    From Waren Gilliand: (Warren Gilliland is a well-known brake engineer in the racing industry and has more than 32 years experience in custom designing brake systems ...he became the main source for improving the brake systems on a variety of different race vehicles from midgets to Nascar Winston Cup cars.) "If you cross drill one of these vented rotors, you are creating a stress riser that will encourage the rotor to crack right through the hole. Many of the rotors available in the aftermarket are nothing more than inexpensive offshore manufactured stock replacement rotors, cross drilled to appeal to the performance market. They are not performance rotors and will have a corresponding high failure rate"


    From Baer: "What are the benefits to Crossdrilling, Slotting, and Zinc-Washing my rotors? In years past, crossdrilling and/or Slotting the rotor for racing purposes was beneficial by providing a way to expel the gasses created when the bonding agents employed to manufacture the pads...However, with today's race pad technology, 'outgassing' is no longer much of a concern...Slotted surfaces are what Baer recommends for track only use. Slotted only rotors are offered as an option for any of Baer's offerings."

    Grassroots Motorsports: "Crossdrilling your rotors might look neat, but what is it really doing for you? Well, unless your car is using brake pads from the '40s and 50s, 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." ...It was an effective solution, but today's friction materials do not exhibit the some gassing out phenomenon as the early pads. Contrary to popular belief, they don't lower temperatures. (In fact, by removing weight from the rotor, they can actually cause
    temperatures to increase a little.) These holes create stress risers that allow 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...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?)

    AP Racing: "Grooves improve 'cleaning' of the pad surfaces and result in a more consistent brake performance. Grooved discs have a longer life than cross-drilled discs."
     
  16. Jason Montague

    Jason Montague New Member
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    :cornut:Not trying to sharp shoot here but, increasing the diameter of the rotor would increase the mechanical advantage. The LEVER is being lengthened and therefore less effort is required to stop rotation. Correct me if I'm wrong Engineer Guys. Increased rotor diameter equals decreased stopping time even with no increase in brake pad surface area.:Thumbsup:

    Jason
     
  17. ScottinBend

    ScottinBend Space Cowboy
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    Stopping distance is directly related to the tires, not to rotor diameter. Simply being able to lessen the power needed to stop the rotation doesn't mean the distance will be affected.

    Question.....can you lock up the rear brakes by pulling on the parking brake handle while going 50mph? Yes, and those are some rather small rotors. As has been debated over and over again, larger brake components simply give you more consistent braking over time. The pad material will have some effect on braking, but again you would still be able to lock up the tires way before you can bring the car to a stop.
     
  18. andyroo

    andyroo New Member
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    Properly designed big brake kits with larger rotors will have correctly sized pistons so that bias is not screwd up. You can increase rotor size safely with a well designed kit. :)

    - Andrew
     
  19. andyroo

    andyroo New Member
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    #19 andyroo, Feb 10, 2011
    Last edited: Feb 10, 2011
    Check out BMW racecars then....they don't usually use drilled rotors. But drilled is fine for a street car if you really want that look.

    Slotted is fine for the track and a lot of track cars use them. Don't ask about ceramic brakes as they blow my mind :lol:

    As Nitro said, increased rotor diameter (all else being equal) does mean more braking force, but not necessarily shorter stopping distances. Even if it feels like you're braking "harder" with the front dropping down and you're thrown forward in your seat, it doesn't matter if the tires can't handle it. They only have so much grip. Some of the best braking cars i've been in do not have a lot of front bias....you can almost feel the car "squat" under braking.

    - Andrew
     
  20. goaljnky

    goaljnky New Member

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    I know, I know. I'm just stocking the fires a bit. Drilled are are fine for taking the family to dinner, or the dog to the park.
     

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