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Rotors

Discussion in 'Wheels / Suspension / Tires / Brakes' started by utn, Oct 6, 2004.

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  1. utn

    utn Member

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    I own a 1989 Honda CRX DX and I wish to modify my brakes a little bit. My first question is.

    1. Is it possible to drill your own rotors with the use of a drill press?

    The only reason I could see this not working would be an uneven surface after drilling, or possibly metal shavings left in between the rotor. How could you re-finish or resurface the rotor afterwards?

    Also, how easy is it to swap out the rear drums on the DX with rotors?


    Thanks,
    Scott
     
  2. Loco Honkey

    Loco Honkey Banned

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    Don't ever do this. Your rotors will crack. Here's some good reading for you on brakes, how they work, and cross drilled rotors...

    Here is how it works. The friction between the pad and rotor is what causes you to stop. This friction converts your forward energy into heat (remember: Energy is neither created nor destroyed, it is converted). Now that heat is a bad thing. Yes it is bad for the rotors but it is a lot worse for the pads. A warped rotor will still stop the car - it will just feel like shit. Overheated pads however WILL NOT stop the car. It is here where the rotors secondary responsibility comes in. Its job now is to DISSIPATE the heat away from the pads and DISPERSE it through itself. Notice that DISSIPATE and DISPERSE are interchangeable? Once the heat is removed from the pad/surface area it is then removed. Notice where the removal falls on the list of duties? That's right - number 3. Here is the list again. Memorize it because I will be using it a lot in this post:

    #1 Maintains a coefficient of friction with the pad to slow the forward inertia of the vehicle

    #2 DISSIPATE the heat

    #3 REMOVE the heat from the brake system

    Let's look more in-depth at each step now shall we? No? Too bad, assclown, we are doing it anyway.

    #1 Maintains a coefficient of friction with the pad to slow the forward inertia of the vehicle:
    This one is pretty simple and self-explanatory. The rotor's surface is where the pads contact and generate friction to slow the vehicle down. Since it is this friction that causes the conversion of forward acceleration into deceleration (negative acceleration if you want) you ideally want as much as possible right? The more friction you have the better your stopping will be. This is reason #1 why BIGGER brakes are the best way to improve a vehicle's stopping ability. More surface area on the pad and the rotor = more friction = better stopping.

    #2 DISSIPATE The Heat:
    Let's assume for a second that the vehicle in question is running with Hawk Blue pads on it. The brand doesn't really matter but that is what I am using as my example. They have an operating range of 400 degrees to 1100 degrees. Once they exceed that 1100 degree mark they fade from overheating. The pad material gets too soft to work effectively - glazing occurs. This means that a layer of crude glass forms on the surface of the pad. As we all know glass is very smooth and very hard. It doesn't have a very high coefficient of friction. This is bad - especially when you're coming down the back straight at VIR at 125MPH. Lucky for us the rotor has a job to do here as well. The rotor, by way of thermal tranfer, DISSIPATES the heat throughout itself. This DISSIPATION lessens the amount of heat at the contact area because it is diluted throughout the whole rotor. The bigger the rotor the better here as well. The more metal it has the more metal the heat can be diluted into.

    #3 REMOVE the heat from the brake system:
    Now comes the step where the rotor takes the heat it DISSIPATED from the pads and gets rid of it for good. How does it do this? By radiating it to the surface - either the faces or inside the vanes. It is here where cool air interacts with the hot metal to cool it off and remove the heat. Once again there is a reoccuring theme of "the bigger the better" here. The bigger the rotor, the more surface area it will have which means more contact with the cooling air surrounding it.

    Now let's look at why cross-drilling is a bad idea.

    First - as we have already established, cross-drilling was never done to aid in cooling. Its purpose was to remove the worn away pad material so that the surfaces remained clean. As we all know this doesn't have much of a purpose nowadays.

    Next - In terms of cooling: Yes - x-drilling does create more areas for air to go through, but remember - this is step 3 on the list of tasks. Let's look at how this affects steps 1 and 2. The drilling of the rotor removes material from the unit. This removal means less surface area for generating surface friction as well as less material to accept the DISSIPATED heat that was generated by the friction. Now because of this I want to optimize step one and 2 since those are the immediate needs. If it takes longer for the rotor to get rid of the heat it is ok. You will have a straight at some point where you can rest the brakes and let your cooling ducts do their job. My PRIMARY concern is making sure that my car slows down at the end of the straight. This means that the rotor needs to have as much surface as possible to generate as much friction as possible and it needs to DISSIPATE the resulting heat AWAY from the pads as quick as possible so they continue to work. In both cases x-drilling does nothing to help the cause.

    Now let's talk about strength - and how x-drilled rotors lack it. This one is simple. What happens to a cast iron molecule when it is overheated? I will give you a little hint - the covalence bonds weaken. These bonds are what hold the molecules together. You do the math - it adds up to fractures.

    So why don't race teams use them if they are so much better? Consistency? Hmmmm . . . no. I am gonna go with the real reason here. It is because of several factors actually. They are as follows but in no particular order:

    - Less usable surface area for generating friction
    - Less material to DISSIPATE the heat away from the pads
    - Less reliable and they are a safety risk because of fatigue and stress resulting from the reduced material

    And what are the benefits? Removal of particulate matter and enhanced heat removal. I gotta tell ya - it is a tough choice but I think I am going to stick with the safe, reliable, effective-for-my-stopping needs solution.
     
  3. Loco Honkey

    Loco Honkey Banned

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    Also, Scott, what is the purpose for modifying your brakes? Do you actually want to stop faster, or do you just want the drilled look? Also, what is your reason for swapping the drums to disc?
     
  4. Slammed90Lude

    Slammed90Lude Senior Member

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  5. GSRCRXsi

    GSRCRXsi Super Moderator Moderator VIP

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    ji didnt write that article, lol.
     
  6. utn

    utn Member

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    Thats what I call a good article (Not that it matters where it came from). Thanks for sharing it with me. The main reason I wanted to drill my rotors is, I thought it would aid in cooling my brakes, because the way I saw it, more surface area would cool the brakes even with less mass from the holes, they're going to last longer because theyre cooler (including pads). I also like the look of drilled rotors, my DX has slotted rotors in front, now it seems like flat rotors would be better i.e. more friction. Now I plan to get some new rims to support some larger rotors in front and back (hopefully). The main reason I want rotors in back is, to me drums look cheap, rotors are nice and shiny and look better to me, there isnt a huge empty space in the rear wheel with rotors (unless they're tiny). Rotors have better stoping power too.

    Thanks again for the article. B)
     
  7. Loco Honkey

    Loco Honkey Banned

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    Sounds to me like you're buying brakes for the wrong reasons. Just keep your brakes stock and get some fake rotor simulators.
     
  8. Loco Honkey

    Loco Honkey Banned

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    Sure didn't, but the guy that did is a dousche and doesn't deserve recognition.
     
  9. CRX-YEM

    CRX-YEM Super Moderator Moderator VIP

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    Getting a larger diameter slotted rotor for the front isn't a bad idea. as far as the slots reducing surface area they are so small that the los in friction is negligible.
    Keeping in mind that 70% of the stopping power is done by your front brakes.

    As far as putting disc's in the rear, well your drums actually have far more surface area, the only problem with drums breaks is their less effective cooling of the brake shoes.
     
  10. cycloneb18c3

    cycloneb18c3 Senior Member

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    that article should be pinned in the brake/suspension section, its good stuff.
     
  11. Gumbo

    Gumbo Junior Member

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    slotted rotors actually serve a purpose, aside from looks, in that the slots are there to vent the gas that builds up between the pad and the rotor when the pad heats up, if the gas isn't released, it can have detrimental effect on your braking performance. If there's gas between the pad and the rotor, obviosly there isn't going to be pad to rotor contact, therefore less friction.
     
  12. Loco Honkey

    Loco Honkey Banned

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    No, actually, you're wrong. That's what drilling was for. Back in the '50s, when friction material was organic, and would actually produce a gas. Now, with the metallic, semimetallic, and ceramic pads, there's no more outgassing. What slotted rotors are really for are to prevent glazing, as they shave the pad constantly. This is fine if you happen to have fifty year old pads, or are using the wrong pads for the temps you're getting the brakes up to. There is no advantage to having slotted rotors, period.
     
  13. Cashizslick

    Cashizslick !i!i!i!i!i!i!i!i!i!i!i!

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    Honestly, i figured as much. I bought my Powerslot rotors because my stock ones were warped to hell, and i wanted something that looked halfway decent/sexier than brembo blanks.
     
  14. ahedau

    ahedau Senior Member

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    then why is it that NASCAR, F1 & the WRC sport drilled rotors? If they have no advantage these fellas wouldn't spend the money to use them.

    In my real world experience brembo slotted/drilled rotors HAVE been an improvement.

    I tried some 60-0 tests with OEM fluid, OEM rotors & ceramic pads. After only 3 test I had to stop due to fade.

    Same pads, OEM fluid & Brembo slotted/drlled rotors.. took over 6 tests before they faded

    Next I completly drained each brake and then put in Valvoline Syntech fluid. This time over 10 60-0 tests before the brakes faded slowly. I never really lost confidence.

    Tomorrow I add smurf-jiz for another round of tests and then the HP+ pads when they get here.

    this is based on straight line 60-0 tests in an EG civic and the biggest dif was good hi-temp fluid. your results may vary. :shrug:
     
  15. Gumbo

    Gumbo Junior Member

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    Thanks Ji, I stand corrected, I was just repeating what they taught us at tech, I guess the old guys are a bit backwards
     
  16. Loco Honkey

    Loco Honkey Banned

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    I dunno. Why don't you email them and ask them, instead of us all speculating as to why we think they use them...?
     
  17. Loco Honkey

    Loco Honkey Banned

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    No worres. I've done the same. It's inda hard when you're fed bad information...
     
  18. K2e2vin

    K2e2vin Senior Member

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    i thought f1 had carbon fiber rotors that are slotted or blank?

    the only advantage i see in drilled rotors is reduced rotational inertia...
     
  19. cycloneb18c3

    cycloneb18c3 Senior Member

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    nascars and wrc cars have them cause their pads get glazed over trying to slow a car thats doing 200mph, and the drilled holes scrape the glazing off so they can stop. same with slotted. They are a waste of money unless your doing 200mph, and they'll do nothing but eat pads away(and waste your time and money replacing them.
    just get blanks they work fine for any car running on the street.
     
  20. 94RedSiGal

    94RedSiGal Senior Member

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    Agreed. But ONLY if the original writer is credited.
     
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