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Slotted/ Drilled Rotors

Discussion in '80-Series Tech' started by 92Cruiser, Apr 11, 2003.

  1. 92Cruiser

    92Cruiser

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    Planning on purchasing Slotted/ Drilled rotors from Man-A-Fre for my 92. I'm being told from 3 different brake shops that they will not turn them because those kind of rotors will snap off the cutting tip on their machine. Is this true, and if it is, where do I go?

    Thanx
     
  2. Hltoppr

    Hltoppr SILVER Star

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    92, if you wheel your junk, DON'T get the slotted and drilled rotors. Rocks can (will) get stuck in the holes. This is bad...
    and yes, I'm pretty sure the shop isn't pulling your leg on the turning. For a 1992, which isn't known to have the best brakes anyway, I think you'd be money ahead by getting good OEM rotors and pads. Also, generally, the OEM rotors will warp if they are turned. Replace the pads before you hit rivits.

    -H-
     
  3. 92Cruiser

    92Cruiser

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    -H-,


    I had the brakes done about 4 months ago and the mechanic told me the rotors would have to be replaced next time because they were getting thin. Well, one quick stop the other day and now their warped. I dont do any wheelin with this truck just mainly a DD. Thought I'd go with the slots from MAF because they are cheaper than OEM plus look cooler. Also, what do you mean by the OEM will warp if turned. My understanding is that have to be turned after being assembled to the hub.
     
  4. Hltoppr

    Hltoppr SILVER Star

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    A new rotor does not have to be turned after being installed on the hub. There is; however, a certain break in time for the new pads to properly seat onto the rotor. It's best to go easy on your new pads/rotors for a few miles.

    OEM rotors are notorious for warping once they are "turned." Turning, as you are aware, removes a small amount of material to make a smooth, fresh surface for new pads to seat onto. OEM (and I assume aftermarket) rotors don't like to have material removed for one reason or another, and the general practice is to be dilligent in replacing pads so as to not cause grooves or other gouges, and to reuse the rotors until they get thin enough from normal use and warp; then replace the rotors.

    I believe the MAF rotors are an Australian import, and I have heard nothing about their reliability or tendency to/or not to warp. When I was looking at replacing mine last November, I looked at the MAF rotors, but decided to go with OEM for the reason I previously indicated. As for aftermarket rotors, I've seen catastrophic failures where the entire outer rotor friction surface separated from the center, so that makes me stick with OEM.

    Slotted/Drilled rotors are usually used in race/high performance applications to dissipate heat caused by heavy braking. I somewhat doubt that a LC will really benefit from such an upgrade without other significant changes the the braking system are made.

    I prefer to use OEM.

    -H-
     
  5. cruiserdan

    cruiserdan SupportingVendor Emeritus Supporting Vendor Moderator

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    -H- "I prefer to use OEM"

    Well said............Is there an echo in here?

    OEM rotors for an FJ80, 43512-60050 91-92model
    list for $105.07 A smart shopper could find them for around 80 bucks.
    How much does MAF want?
     
  6. Wrench

    Wrench One Bashed Up 80

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    The mechanic is correct. I was a mechinist for 7 years and turned thousands of rotors. I can tell you that slotted rotors will snap the cutter.
    As for not turning OEM rotors. Well I had mine turned when I had my brakes done now my brakes are pulsing when I hard brake.
     
  7. Cruiserdrew

    Cruiserdrew SILVER Star

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    I have used the slotted (not drilled)rotors from DBA for the last year and have been very pleased. The stock ones warped immediately after turning at 50k. A bunch of us on the 80's list did a group buy and got them for about $75 each. I agree with the poster above. My practice has been to never turn the rotor-simply replace when they warp. I'm at that point now with my 60-the rotors have 186k miles! That OEM stuff is pretty good.
     
  8. mts

    mts

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    Unless you are completely going for looks, don't mess with drilled rotors for your LC even if you don't take it off road. &nbsp:Drilled rotors are significantly more prone to cracking/warping than blank ones.

    Drilling rotors was used to help dissapate heat/gasses on older brake pads. With improvments in pads over the last 15 years, its not an issue anymore. Porsche/Ferrari, etc still come with them on street driven cars mostly as a cosmetic issue, but also the cars they come on have "more brake than they can use" causing less stress on the rotors and the rotors they use are cast that way from the factory. Most of the ones you can buy aftermarket are drilled blank rotors.....which are complete crap in my opinion. If you want a ballpark test to be able to tell whether a rotor is "drilled" or "cast with holes" all you have to do is look at the price of the rotors. If they are anywhere close to the cost of blank rotors, they're "drilled". If they cost so much they want to make you cry, they may be "cast with holes". :eek:

    Several places that sell "drilled rotors" even go as far as to put warnings on them that they should not be used on vehicles that will be used in situations that stress the brakes (more than daily street driving, etc.).

    As far as turning a drilled rotor, it can be done, but it takes special (expensive) equipment to do it. I've never been a big fan of turning rotors anyway, especially on something as heavy as the LC.

    To agree with a couple other posters.......I'd give serious consideration to OEM rotors.

    My 1/2 cent,
    Mike
    :beer:
     
  9. yomama

    yomama

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    I have the slotted and cross drilled rotors (DBA's). I need to be able to stop that big ass boat, even though the trailer has brakes. I will not worry about turning them, if you keep the pads in check the rotors will last a hell of a long time. I have had mine on for almost a year now and no negative issues. I will say on the positive side that they improved my overall braking. The stock OEM rotors and pads were design too small for the weight of these things (stock), then you add on all this extra weight (Bull bar, winch, bigger tires, rear bumper tire carrier, second battery). I bet I have added close to 1000lb over stock curb weight. I give a thumbs up for my experience with them so far.

    Yomama
     
  10. cruiserdan

    cruiserdan SupportingVendor Emeritus Supporting Vendor Moderator

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    Yo,

    If we could drift off topic a bit, do you lannch in salt water or fresh water? How often do you inspect the rear axle?

         Regards.....Dan :beer:

    PS, just looked at your profile, scratch the salt water part.
     
  11. 92Cruiser

    92Cruiser

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    Just so I understand this correctly. If I go with OEM rotors just bolt them on and I'm done. No turning. Since my new pads have been running a couple of weeks on warped rotors do I have to replace them too? The pads are only 4 months old.
     
  12. Beowulf

    Beowulf

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    92Cruiser,
    You should not need any machining on new OEM rotors. If you are having a brake shop do the work then ask them to check the runout after installation. You can use that as a benchmark.

    I would use the old pads if saving a few bucks was important to the Cruiser fund. Your best performance will be to install new OEM 80 series pads, flush the brake fluid and replace with new DOT3/4, and put on SS brake lines.  My pedal feel was significantly improved with the last 2 (flush & new lines)  I was always bugged when switching between my wife's truck and my Cruiser because of the mushy brake pedal. Now it's nice and firm.

    For 93-97 models the OEM 100 series pads work very well.

    BTW, installing new front rotors is a little more involved than "bolt them on."   :D

    -B-
     
  13. cruiserdan

    cruiserdan SupportingVendor Emeritus Supporting Vendor Moderator

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    92,

    If your billfold can take it, you would be better served to have new pads contacting new rotors. The only thing you need to do to the rotors in the way of prep is de-grease them completely before installing the pads.............

    Regards..........Dan :beer:
     
  14. mts

    mts

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    And for even more fun, get you some speed bleeders to bleed the brake fluid on a regular basis. :G Makes it a quick, easy 1 person job.

    http://www.speedbleeder.com/

    The LC part number is SB1010. For $7 each, pretty cheap.

    Mike

    PS - No affiliation, etc, etc.
     
  15. yomama

    yomama

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    MTS,

    How many did you get? If I recall, there is also one on the leveling arm part in the rear, just wondering if you put one on there as well? I plan on getting these myself so I can put on my stainless lines that have been waiting since last year.
    I haven't put them on yet, because I know what a pain it was to bleed them with a 13yr old (Is that the phone? Ok let up, huh? Awe yes it is up). Took four tries all the way around.

    Yomama
     
  16. Beowulf

    Beowulf

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    Yomama,
    To solo bleed the brake system (complete flush with new fluid) I found a cheap ($2) bleeding system at Harbor Freight. It has some tubes and a clear plastic jar with a magnet. The tubes go down in the jar.

    Hook up the hose to the bleeder, crack it open, press pedal (put a 2x4 under the pedal to keep it from bottoming out), release, repeat. Check fluid level in master and in the jar. Fill master when needed, empty jar when needed. Watch for clear fluid flowing through the tube into the jar. Tighten bleeder and move on to the next one.

    Sequence is RR, LR, RF, LF, LSPV. (Revised 4/30)

    You will start from the farthest wheel and move to the closest, then do the LSPV last.

    You will very likely need to replace the bleeder rubber protective caps. They are a dealer item. The LSPV bleeder is larger than the individual wheel cylinder bleeders. I used about 1-1/2 qts of Valvoline synthetic brake fluid.

    Remove the 2x4 before drive testing.  :G (Yep, I forgot!)

    You will notice improved brake pedal feel with the SS brake lines. IMHO, the improvement was substantial and I was VERY pleased with the outcome.

    -B-
     
  17. mts

    mts

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    I only got 4, I forgot about the adjuster. I have not installed them yet as other projects have taken priority.....they're sitting on my work bench at home. I've used them before on other vehicles with great success though.

    Mike :beer:
     
  18. yomama

    yomama

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    Beowulf,

    Did you get that sequencing out of the book? I figured the LSPV before the rears? Usually you start at the one closest to the master cylinder and work your way to the farthest. I am at work right now where I am suppose to be....oh yea. I'll have a look in the book tonight. I have the setup you are talking about and have done it that way, but the 2x4 can't press down further after you open a valve, I have had the 2x4 fall off the pedal, just a pain and the 13yr old wasn't much better. So I like this other "speed bleeder" idea.
    One more thing...while I am at work. I have three of the stainless steel lines that came with my DBA's kit. &nbsp:Do two go in front and one in the rear? Just occurred to me...

    Yomama
     
  19. Curran

    Curran SILVER Star

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  20. Beowulf

    Beowulf

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    Yomama,

    I revised the above instructions and, as C-Dan says, I slept last night so the memory wasn't very good. You bleed farthest to closest with the LSPV last.

    There are 3 flexible brake line hoses; 2 in front, 1 in rear. See George's site for good install hints.

    I have heard that the speed bleeders are a good investment and you can get them with metric threads. However, you will need an SAE spanner to install and loosen. Use a 10mm brake line spanner to remove the old ones.

    -B-