Latest thinking on rotors and pads??
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Suspension, Brakes and Tires Discussion, Latest thinking on rotors and pads?? in Item Specific Cadillac Discussion; ...
  1. #1
    Rob Benham is offline Cadillac Owners Fanatic
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    Latest thinking on rotors and pads??

    1994 Seville SLS

    Hi again. I fitted rear rotors a year or so ago, and paid for ones with lifetime warranty. The fronts however, I had skimmed on a Hunter machine at a local tire shop. As soon as I saw the cutting tool I realised that all was not well. I simply do not believe that discs should be cut...grinding is the only process that I would approve of in other applications of this type. Still, it was Hobsonís choice.

    Sure enough, after a few weeks, the brakes are shaking the car really badly. The guy from the shop says that it must be the rear brakes, cos the steering wheel is not vibrating rotationally.

    I doubt this, but now Iím trapped between suppliers. Jacking the fronts then the backs and turning the wheel by hand with the brakes partly on, does not show any sign of variation of grip during rotation.

    I have read hereĖa long time agoĖthat rotors do not really warp...they just get pad chemicals ingrained into the metal. I donít really want to get into that argument, but Iím at a loss at the moment.

    If I replace the pads, and it is still bad, could I then put rotors on and bed the same pads in again. Or would they be too warn to the old contours?

    Is there any way to clean the rotors. I also read on the same thread that one should not use emery paper/cloth.

    I have searched, but what is the latest thinking on mid priced rotors and pads. Iím getting mixed reaction to ceramic V green. I no longer want to drive hard...so a mid performance product is good.

    I have heard Warner mentioned as being part of another groupe. Thanks for any info? RB

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  3. #2
    RKunz2's Avatar
    RKunz2 is offline Cadillac Owners Member
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    Red face Re: Latest thinking on rotors and pads??

    Rob,

    I'm no expert, but I've talked with several people that would consider themselves to be, including a GM Tech. Regardless of what GM or Ford publicly tells you, none of them recommend cutting, grinding, or anything else on late model rotors (even though that's the first thing the dealerships do).

    Replacement, period. On badly warped or hot spotted (same difference from what I can see) rotors, you shouldn't do anything but get them off the car and start over with a good OE replacement. From what I understand, run-out on these rotors can also be a contributing factor to that all too famous shake, shiver, or whatever you want to call it on the Sevilles at 62-70 mph on the freeway. But, what do I know, I'm just a driver...

  4. #3
    Rob Benham is offline Cadillac Owners Fanatic
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    Re: Latest thinking on rotors and pads??

    I have spent the most frustrating day chasing round for a good quality rotor.

    After some research, I decided to go for Raybestos cos of the claim that it was well balanced.

    Itís a long, long story why I think Caddys need a well balanced rotor as well as the wheel.

    Looking at their web site was not a good experience. Where can I get one locally? NOTHING. Just a list of service shops. If someone else was going to do it I wouldnít need the info...yellow pages would suffice.

    Go shopping on site: load of meaningless names for rotors...no prices, etc.

    Talk to us. $1.75 a minute.......yea right. Prima donnaish $%^@$%^

    When a web site is that bad, it puts you off the product.

  5. #4
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    Krashed989 is offline Cadillac Owners Connoisseur
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    Re: Latest thinking on rotors and pads??

    Ok, the best thing I would recommend you to do is take the car to someplace where they can check the "Run-out" on the rotors. It is a very simple thing to do, I'm not sure about pricing though. The run-out is basically how warped each rotor is. There is an allowance but the most I have seen was 10 thousanths of an inch (they should have a book or computer program telling them what the allowance is on your car). If they do that, I can guarantee you that they will find which rotor is warped if any. Also have them check the bearings. Bad bearings can cause warped rotors. Also hard braking can cause hot spots which physically change the composition of the metal in your brakes, making spots on them tempered and that makes them wear down unevenly causing the same sensation as warped rotors.

    I personally don't like any pads or rotors that say lifetime warranty. If they don't wear down that means that there isn't very much friction, and if there isn't much friction that means less braking power. I also don't like the lifetime warranty pads because they eat rotors like crazy.

    When you get new rotors installed make sure they test the run-out first thing. I have gotten new rotors before that were already warped so I had to put them on the lathe before I even got a chance to use them.

  6. #5
    RKunz2's Avatar
    RKunz2 is offline Cadillac Owners Member
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    Talking Re: Latest thinking on rotors and pads??

    Quote Originally Posted by Rob Benham
    Looking at their web site was not a good experience. Where can I get one locally? NOTHING. Just a list of service shops. If someone else was going to do it I wouldnít need the info...yellow pages would suffice.

    Rob,

    Funny thing, I can swear there's a Raybestos factory location in either Westlake Village or Agoura Hills, CA. Their building (and logo) are visible from the 101 freeway on the right side as you go towards the San Fernando Valley (L.A.).

    Unfortunately, I can't find any listing for them at all...strange. I did pull up a Raybestos Brake Parts, Inc. in Corona, CA, but again, no phone number listing.

    Best bet would be to go to a retailer, or find something on the web, I guess.

    How'd you get the information about Raybestos being the most well-balanced rotor? I'm interested because these damn cars are so sensitive to rotational forces it's silly.

  7. #6
    Rob Benham is offline Cadillac Owners Fanatic
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    Re: Latest thinking on rotors and pads??

    You make some valid points K989.

    RK2 I'll look in that area on the web as well thanks

    The fact is that imports do not seem to need the rotors skimming anywhere near as much, and I have to say that I donít believe in this procedure because the surface of discs become very hard in a way that you could liken to case hardening. To cut this off is a loss.

    People say that the pad will not "see" so much surface area with undulations in the surface. Well this is true for a new pad, but when it is worn in there is actually more total surface.

    As mentioned, a long time ago on this forum, a very experienced engineer made the argument that discs to not warp...yet the testing seems to belie this. Could it be that the impregnation of the pad and road dirt into the disc actually sculp away some of the metal? Again I do not know, but it would seem strange that so many people would continue to believe warping to be the case if it were not true.

    On the balance issue. I have taken extreme care to get (Michelin) tires with no discernable run-out. One dealer worked with me on this, and it took 17 goes...yes seventeen...to get a perfectly round tire on the wheel. This included 8 rejected tires, the rest removing and reseating attempts. Iím glad to say that the tires that were brutalized during this process were not the ones I ended up with.

    I have come to the conclusion, that if there is any flutter, the suspension will interpret this as part of itís process...and harden the ride. This then makes things worse ad infinitum.

    I am rarely totally happy with the ride, though sometimes, just for a few miles, it will be utterly smooth. I think this might be because a start on a smooth road, may not kick-start the above process. I just donít know.

    Getting back to the point of rotor balance. If my wheels are so carefully balanced, there has to be something just not perfect. The only other thing I can think that would have the mass, is the rotor. (Iím fairly sure the bearing are okay) Though the much smaller diameter would mean that it would have to be very poorly made indeed, so when I saw the claim of good balance on the Raybestos web site, it was a positive plus mark.

    I have been delayed by getting to a Nappa store and finding that they sell rotors under (I think )the United name. They assure me that they are made by Raybestos but could not say if the balance was as good. So Iím no further forward. The saga will continue tomorrow.

  8. #7
    RKunz2's Avatar
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    Arrow Re: Latest thinking on rotors and pads??

    Rob,

    Talked with my newphew couple nights ago (he's actually my supplier).

    I couldn't remember what pad we used....well, you guessed it, it's a Raybestos pad. Raybestos Ceramic Gold or something like that. Anyway, the pads are awesome, perform very well with little to no brake dust, squeal, or noise.

    My rotors are not Raybestos and I think they've warped again because the dealer had the wheels off the car a couple months ago (which is when I noticed the shake). Unfortunately, dealer techs are known for "slamming" lugs on with the gun and not paying too close attention to lug torque specs. Previously, America's Tire has been the only one to touch the wheels for rotation/balance, etc., and I use them because they ALWAYS hand torque the lugs.

    Anyway from what I understand, Raybestos is the only mfg. that actually balances their rotors after machining. Their machining process is also a little different than most, but ultimately it creates a very high quality piece. That's also reflective in their pricing because Raybestos rotors are about triple of what the other ones go for.

    That's what I hear anyway.

  9. #8
    air1ren is offline Cadillac Owners Member
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    Re: Latest thinking on rotors and pads??

    My 97 STS had a bad vibration that seemed to come from the rear brakes. Pads no help. Put cheap new rotors on the back and it is smooth as can be...

  10. #9
    Rob Benham is offline Cadillac Owners Fanatic
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    Re: Latest thinking on rotors and pads??

    I gave up on Raybestos simply because of the difficulty of getting any within 12 hours. First I called Wagner tech, and they assured me that they machine the premium disc very accurately.

    Good enough, itís an old car and perhaps I was being too fussy, but I have had hot kit back home and always set high standards on brakes and tires.

    When I put the first rotor on, I felt the need to check it...so I gently bolted it up and ran the engine. Fortunately I had left the pads in so that the Traction system did not pop the piston.

    The lateral accuracy was okay, but the run-out was about 2mm. I tried the other new disc on the same side, it was just the same. Has to be the hub all along I thought. But then I put the old disc back on. The run-out on that was negligible. I just could not believe it.

    How could I know if it was the whole surface bobbing or just the edge?

    I phoned Wagner again.

    They doubted the possibility of such error, and after a long conversation it was agreed that I would take them back to OíRielyís, and put them on the cutter just to spin them.

    The run-out was there. To cut a l-s-short, I went to another branch in the hope of getting a pair from another batch. The first one on the car was perfect. The second not quite so good but better than the originals by far. By now I realised that I was really expecting too much of a mass produced disc. It is cut on a CNC machine, and the lateral accuracy is supposed to be a small part of a thouí..... but in the real world...............

    The more I learn about these massive discs, the more I believe that the manufacturers here need to make a substantial change in the materials used in this product. And I mean on the ordinary car, not specialist vehicles. After all, isnít it the aim of designers to keep the unsprung weight down?

    There should be NO need to resurface a disc due to warping...ever. At least that should be the aim, so that in the real world, the few that are rouge, get replaced...gratis.

    Well, thatís how I feel after a 40 min job takes all day!

    Rant mode OFF.

  11. #10
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    Re: Latest thinking on rotors and pads??

    Try marking one of the lug bolts and the corresponding lug hole on the rotor, then check the run-out and mark where on the rotor and the hub the run out peaks. Then take the rotor off and put it on in a different position. Then check the run out again, if the run out peaks at the same spot on the hub and not the rotor you know its the hub, and vise versa. The best machine i can think of for you is an on-car-brake-lathe. It resets the run-out to 0 every time.

    Have you seen the future disk brake?... It has the same rotor as cars have now but the caliper covers the whole thing and one pad is a whole disk itself. They do not warp because the whole surface is being used at the same time when you brake instead of just that little spot. the pads are expensive but they last more than three times as long as the smaller ones again because of its greater suface area. I forget where I saw it though, I think it was a discovery channel show, lol.

  12. #11
    Rob Benham is offline Cadillac Owners Fanatic
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    Re: Latest thinking on rotors and pads??

    I wish I had thought of that...Great idea. But still, the second set seem to be very smooth in rotation as well as laterally. No pedal pulse at the moment.

    Itís interesting to hear of these new brakes. They have used multi layer full circle disks on some large aircraft for many years. Many of the big old jets used to rely on braking far more than reverse thrust. After a landing the crew would be expected to get the parking brake off as soon as the chocks were in.

    For this reason, I intend to creep just a tad at traffic lights etc., when the discs are very hot. Hopefully the material will not be etched into the metal if it is not pressed on very hard for several moments.

    Huh! Didnít know font sizes would be transferred from the WPssr


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