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Bought new black zinc-plated rotors for '00 300m

Discussion in 'LH: Large Cars, 1993-2004' started by MoPar~Man, Apr 17, 2017.

  1. MoPar~Man

    MoPar~Man Member

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    I've had brake pulsing for a while now. Rotors are maybe a year old, really cheap from Rock Auto. I also have brake-squeel problem that I tried last year to fix - tried a few different sets of pads, put lube on various surfaces, cleaned / buffed brake contact surface on arm that is part of wheel axle / knuckle.

    Took my snow tires off and put on the summer tires a couple weeks ago. I noticed that one front rotor has a "thick" spot. Running my finger across the surface it's like a raised portion of the rotor surface. Other side of rotor is flat. So this is what's causing the brake pulsing.

    Looking through ebay and seeing lots of black rotors. They say they're zinc plated, so less prone to rust. Can't find any that are plain rotors - they're either cross-drilled or slotted or both. I find a vendor selling to Canada for free shipping and I buy a pair for the front. They are drilled. I paid $55 USD, free shipping. Put them on last week. Brake pulsing is gone. I think brake squeel is gone also. Using the same pads (which are practically new). Here is what's printed on the box:

    QBP International
    OE Replacement
    Q5386
    bar code 702669000574
    Replaces AIM 5386, Ray 76722

    Just in case anyone else is looking to get new rotors.
     
  2. Tomguy

    Tomguy Well-Known Member

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    Bought a set of rotors from Advance Auto here in the US, whatever their premium line is. TRT30 is pretty much always active, 30% off orders. I bought the "PHP" rotors for my base M because physically the dimensions are identical - the PHP rotors are externally vented versus internally, for people like me who drive harder. As with every set of rotors I buy, I clean with brake cleaner, mask the braking surface off, and apply a few coats of WalMart flat black spraypaint to the rotor cap to prevent ugly corrosion. Current set has about 10k of hard driving on it and no shudder.
     
  3. MoPar~Man

    MoPar~Man Member

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    > the PHP rotors are externally vented versus internally,

    Um, what's the difference between internally vs externally vented? I thought all you had for rotor construction was either solid or vented, with vented being 2 disks with a lattice or grid or some other pattern structure between them.

    The rotors I had that I replaced (cheap set) were "vented" (ie - they were not solid) and I have a really old / pitted front set that I think are the originals and they are also vented (and this is a standard 300m, not PHP). The set I just put on ($55, drilled, zinc-plated black) are also vented.
     
  4. pt006

    pt006 Active Member

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    Mopar man; the 'thick' spot you referred to is simply a defect in the metal. We used to call them 'hard spots'. I always felt that grooves or drilling create a place for grit to get between the pads and the rotor.
     
  5. MoPar~Man

    MoPar~Man Member

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    There was a sort of chevron < > pattern or mark on the surface of one of the old rotors that seemed to mark the boundary of the thick spot on the rotor, so I suspected that this was caused by a metallurgy or forging problem with the iron. As if the iron wasn't completely mixed before it was poured or anealed. This was probably why it squeeled so much during braking. Regarding drilling the rotors - I wanted to get the zinc-plated black rotors but nobody sold them in any style other than drilled or slotted.

    Still waiting for explanation as to construction difference between internally vs externally vented rotor. Can't find any pictures on the web showing a side-by-side comparison, and can't find any mention that there even *is* such a thing.
     
  6. Tomguy

    Tomguy Well-Known Member

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    More Information for ACDELCO 18A936A (at http://www.rockauto.com/en/moreinfo.php?pk=2959149&cc=1353776&jsn=10507 )
    Externally vented. The back side is closed. The vents are on the front face of the rotor. They are visible on the first pic, which shows the front of the rotor. The third pic of the rear shows the rear is closed.

    More Information for ACDELCO 18A913A (at http://www.rockauto.com/en/moreinfo.php?pk=3864672&cc=1353776&jsn=10506 )
    Internally vented. The front side is closed. The vents are on the rear face of the rotor. They are visible on the third pic, which shows the rear of the rotor. The first pic of the front shows the front is closed.

    These are for LH cars, front rotors, otherwise identical except the venting design - internal or external. 100% cross-compatible.

    If you need better example pics I can grab ones from my Grand Cherokee OEM rotors, which are also externally vented.
     
  7. MoPar~Man

    MoPar~Man Member

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    Why on earth would you have vented rotors that are sealed/closed on the inside? The pictures you have show that they are only "half" vented. How do you get air flow through the interior separator (between the disks) when the inside face of the separator gap is sealed off? I would never buy those. I would say the aerodynamics would make them inferior from a cooling standpoint compared to rotors where the outer AND inner face of the rotor disks are vented.

    I've done a few searches for that Delco P/N and so far haven't found them being described as anything other than "vented". In other words, I haven't found them being described as either "internally" or "externally" vented. If the terms "internally vented" and "externally vented" are actually legit or real or used by the industry, I'd like to see some indication of that. A web link to something authoritative that mentions those terms would be nice.

    Edit: The wikipedia entry for Disk_Brake mentions rotor venting but does not describe any variations or sub-classifications such as "internal" or "external".
     
    #7 MoPar~Man, Apr 23, 2017
    Last edited: Apr 23, 2017
  8. Tomguy

    Tomguy Well-Known Member

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    This is not possible. I'll let you think about that one for a bit ;)
    https://www.google.com/search?q=internal+versus+external+rotor+venting&ie=utf-8&oe=utf-8
    Hell, the second link is pertinent to the LH.
    Brake rotors vented internal or external? - DodgeIntrepid.Net Forums - Dodge Intrepid, Concorde, 300m and Eagle Vision chat (at http://www.dodgeintrepid.net/18-general-discussion-second-generation/474818-brake-rotors-vented-internal-external.html )

    Edit: To help clarify, either the rotor "Hat" and the rear/interior side are cast as one piece (externally vented), or the rotor hat and the front/exterior side are cast as one piece (internally vented) and then the other braking surface is mated to it. This is as opposed to non-vented rotors, which are cast as 1 piece. If both surfaces were vented, you'd have a braking surface that doesn't attach to the rotor hat, IE: A useless paperweight.

    The only way for you to see it more clearly would be to walk into a store that stocks both PHP & non-PHP rotors local to you, and ask to compare them side by side.
     
  9. MoPar~Man

    MoPar~Man Member

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    The third photo in your first link shows what looks like a sealed interior. Or because the photo was taken from directly above, there is no way to tell if the interior is sealed. By sealed, I mean that the two rotor plates are closed (sealed) on the interior aspect of their circumference. The first photo shows that their exterior circumference is not sealed or closed. Looking again, I can't tell between photo's 2 and 3 which side (front or back) the photos are showing. I don't know if photo 2 or 3 would show an opening between the 2 rotor plates on the inside radius if the photo were taken on an angle instead of directly from above.

    Photo #4 and photo #6 (same picture?) on your second link shows that there is an opening on both the exterior and interior radius between the two rotor plates. There is no such photo showing the same view in your first link. The two links seem to show 2 different rotors (ACDELCO 18A936A vs ACDELCO 18A913A) so I don't know what to make of that.

    If the rotors you have have openings on both the interior and exterior circumference between the 2 rotor plates (as shown in photos 4 and 6) then you have vented rotors. To add the term "interior" or "exterior" to the term "vented" makes no sense. Rotors are either vented or they are not. If they are not, then the rotor is a single solid plate. If you continue to insist on using the terms "interior vented" and "exterior vented" then please show an example of those terms being used elsewhere.

    If there is such a thing as a partially-vented rotor (made from 2 plates separated by an air space formed by a structural matrix or stand-offs that is open on one circumference face but closed on the other circumference face as the photos in your first link would *seem* to indicate) then that would be the only way the terms "interior" or "exterior" could be used to describe the construction.

    Edit: Looking at the link to the dodge-intrepid forum discussion, it gives the *only* example of someone else mentioning this phenomena of "outside vs inside" venting that I have seen on all the internets. And as such, unless I see a side-by-side photo (taken from a suitable angle) that clearly shows the differences, I'm going to continue to call bogus this idea that there are 2 different types of rotor venting.

    If this concept of "inside vs outside" or "interior vs exterior" venting was real, then it would be mentioned and described on the wikipedia entry for brake rotors.
     
    #9 MoPar~Man, Apr 24, 2017
    Last edited: Apr 24, 2017
  10. Tomguy

    Tomguy Well-Known Member

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    Correct.
    Correct and correct. The first link is the PHP rotors for LH cars. The second link is the base rotors for LH cars.

    Chrysler did not use this terminology in its parts cataloging. Interior vented were base rotors, and used on all LH cars except PHP and Euro-delivered LH cars. Special Ms, Euro deliveries, and I believe the Intrepid R/T and Intrepid Police packages used the exterior venting. The catalog lists it as "Performance package".
    Examples:
    https://shop.advanceautoparts.com/p...3-P?navigationPath=L1*14921|L2*16462|L3*15696
    "Front; Performance Package; 2 Req."
    https://shop.advanceautoparts.com/p...2-P?navigationPath=L1*14921|L2*16462|L3*15696
    "Front; w/o Performance Package; 2 Req."
    Go into the store. Ask to see these two rotors. Compare them side by side. They are identical except the venting style.

    Clear here you aren't grasping what pictures and words are showing without seeing the rotors physically. I never mentioned partial venting. Both styles are fully vented.

    I proposed a solution to you. Again, Go into the store. Ask to see these two rotors. Compare them side by side. They are identical except the venting style.

    Wikipedia is a good resource, but it doesn't include every bit of detail known to mankind. Just looking @ the article it's clear that it's meant more to define what they are and not define the thousands of variations. I could add more links, his will be my last attempt: A cut-through "Schematic" showing the difference.
    More Information for CENTRIC 12063045 (at http://www.rockauto.com/en/moreinfo.php?pk=1279277&cc=1412356 ) > See pic #5, internal venting
    More Information for CENTRIC 12063048 (at http://www.rockauto.com/en/moreinfo.php?pk=1279397&cc=1412356&jsn=438 ) > See pic #5, external venting

    You are coming off as hostile here, and I don't understand why. I've presented you with facts and evidence. If seeing is believing for you, the only thing I can continue to tell you is to go into an auto parts store and compare the two rotor types for LH cars. There's nothing else I can do.
     
  11. MoPar~Man

    MoPar~Man Member

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    So now I see, comparing pic 5 with pic 5, what the difference is. And I'm trying to imagine how either one would have a performance advantage over the other one. And I would have thought that there were enough auto afficinado's / racers / gear-heads to have filled in a small detail like this on the wiki page, given that this is done for practically every other wiki topic. Did Ford or GM offer one type over another as a performance option? What do Mustangs, Camaros or Corvette's have these days? Or Charger/Challengers?

    (funny how the PHP-spec rotor is $4 cheaper than standard rotor)
     
  12. Tomguy

    Tomguy Well-Known Member

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    My Jeep came with the towing package, which includes "Heavy duty braking system" and the rotors are exterior-vented. As for what performance cars have,

    View: https://youtu.be/PDEVbTmuK6Y?t=115

    If you look here, both front and rear rotors can be seen with exterior venting, because you can see the gap for the venting. Follow my link, versus clicking play, to start @ 115 seconds in (1m55s). This is obviously Hellcats, so if they have exterior venting, you can rest assured that's superior for cooling.
     

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