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to cross drill or no cross drill (rotors) 900

posted by  Chrix on  Mon Mar 31 08:49 CST 2003
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I need to replace the front rotors on my 91 940GLE. I checked out FCP Groton and Im torn between the Zimmerman solid vented discs and the Zimmerman crossed drilled. Since the cost difference is minimal, my main concerns would be longevity of the rotors and pads and if crossed drilled rotors provides a shorter stopping distance vs solid vented discs. So what do you guys think?
Almost forgot, what about Textar vs Mintex or PBR pads?

Thanks in advance,
Chris








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    to cross drill or no cross drill (rotors) 900

    posted by  invar on  Mon Mar 31 14:53 CST 2003
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    no reason to get cross drilled rotors if your current rotors aren't cross drilled and are perfectly acceptable. you're not going to reduce braking distance unless your braking distance has been adversely affected from brake fade caused by heat.

    you will, however, find that the cross drilled ones are more susceptible to warping and cracking.

    besides, any one who's serious about competition and is worried about their brakes would have a brake cooling duct installed. run some hoses from the front where the air rushes in, and have it piped towards your rotors/calipers. simple.
    --
    Kenric Tam
    1990 Volvo 740 base sedan (B230F)
    My Volvo 'Project'








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    to cross drill or no cross drill (rotors) 900

    posted by  Token Ring Man on  Mon Mar 31 11:15 CST 2003
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    Personally speaking, I'd drill holes in the backing plate. This will allow cooling air to get into the center of the brake area and move through the brake cooling slots.

    Backing Plate Slots
    --
    Warren Bain - '99 V70GLT G-Valve > 70K mi, '96 965 >110Kmi Wifemobile near Manassas Va.. Check the 700/900 FAQ via the 'features' pull down menu.








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    to cross drill or no cross drill (rotors) 900

    posted by  the kick inside on  Mon Mar 31 10:29 CST 2003
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    hmm, first off im no expert, second of this is an ill educted opinion...but i always thought the idea of cross drilled discs was to do with cooling...i.e. off-setting brake fade...

    now call me a wuss, but unless your in competition if your getting your bricks brakes hot enough for that...u seriously need to slow down...

    the only people who I know who run that sort of kit use it for competition - and they dont care about pad life (or disc life - or engine lie much come to that) and anyway most of them are using ablative technologies now anyway,...








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      to cross drill or no cross drill (rotors) 900

      uid 42's pic
      posted by  Shatz on  Tue Apr 1 00:14 CST 2003
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      I also know nothng about drilled rotors, but I think your term, "ablative", captures my expectations perfectly. It may cool rotors quickly to prevent fade, but my goal would be to never put myself in that situation. If you think about the action of the rotor against the pad that has leading edges all over its surface, I think it would act like an inefficient grinding wheel against the pad.








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        to cross drill or no cross drill (rotors) 900

        posted by  the kick inside on  Wed Apr 2 09:33 CST 2003
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        last visit: Thu May 17 09:58 CST 2007
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        hmmm, ablative technology (limited understanding her, just talking to a couple of people who run competition cars) is nothignto do with cross drilling, essentialy we are talking hi-tech here, basically the disc wears away withe the pads and is designed to do so, basically more friction, they use some very fancy materials (like carbon fibre and ceramics)..not to be found on road cars as they have very short life spans and are mucho expensive - by short i mean in the 100's of miles for a disc...








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    to cross drill or no cross drill (rotors) 900

    posted by  Aye Roll on  Mon Mar 31 09:28 CST 2003
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    I think cross-drilling is bogus science, but it does look cool.
    In my opinion, it accelerates pad wear, and can contribute to rotor warping since it removes some material. These rotors don't need any help warping.
    I don't think there's a significant difference in stopping distance. The crossdrilled rotors might help prevent brake fade after long downhills or multiple hard stops due to better ventilation.

    A better prevetative measure would be to replace the 4 cone bushings- worn bushings seem to contribute to rotor warp.

    I have had good luck with both Mintex and PBR pads. However I don't own a 940 so I can't be sure they're equally good.
    --
    Rob Bareiss, New London CT ::: "Roterande Fläkt Och Drivremmar!"








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      to cross drill or no cross drill (rotors) 900

      posted by  Pilicer on  Mon Mar 31 10:58 CST 2003
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      What is a cone bushing?
      Thanks,
      Bill








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        to cross drill or no cross drill (rotors) 900

        posted by  Aye Roll on  Mon Mar 31 20:40 CST 2003
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        last visit: Tue Oct 14 21:08 CST 2014
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        Part number 5 on this diagram:
        http://www.fcpgroton.com/volvo700900ftsuspension.htm

        Its also called a strut rod bushing. They're cone shaped, hence the name. When they wear they allow fore-aft movement of the control arm, resulting in shakes, clunks, and warped rotors.
        You have 4 of them and should replace them if they've never been changed.
        --
        Rob Bareiss, New London CT ::: "Roterande Fläkt Och Drivremmar!"







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