Warping rotors theory

Discussion in '80-Series Tech' started by Gumby, Jul 6, 2005.

  1. Gumby

    Gumby Supamod Staff Member s-Moderator

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    I have two customers with pulsating brakes issues. Both have been to others before me and both have had me install new fronts and turn the rears. In both cases the pulsating returned after a few months. In the one case I just repaired the rears were warped and non turnable. Replacing the rears solved the problem again.

    I tried to figure out why I have 133K on my rotors and they are having problems after a few months. the calipers are releasing just fine. they are getting better life from their pads than I am, because I drive a lot of city miles with over size tires and heavy extra goodies, ( and a fat ass driver) . They are generally a LOT easier on their 80s than I am.

    What do they do differently than I do? I noticed when I picked up her truck today.

    i beleive the issue is caused by Chicago area weather and Toyota weird engineering.

    Anybody got a guess? :)
     
    Last edited: Jul 6, 2005
  2. hoser

    hoser SILVER Star

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    The first thing that comes to mind:

    They might drive a lot of freeway/highway miles where the brakes are nice and cool and then maybe go down a steep grade and exit an off-ramp where the temperature of the brakes raise quite rapidly and to a higher temperature than you ever see in the city. As they come to the stoplight, they maintain pressure on the hot-spot on the discs where the brake pad rests. It only takes one time to warp the rotors.

    Others have argued that discs don't really warp.
     
  3. spressomon

    spressomon glutton Moderator

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    The argument continues...do rotors get "warped", "heat distorted" or is the symptom from pad material being super heated and deposited, semi-permanently, on the rotor? Whatever the terminology I think the reason is simply too much heat in an isolated area. It seems, based upon my past experiences with other vehicles, rotor and pad composition contribute to a rotor/pad design that might be a tad too small for the weight of a given vehicle. Generally, based upon my real world experiences, going to a higher quality rotor (even cryogenically treated) with better pad material generally eliminates the problem. Grinding/surfacing rotors tends to exacperate the problem, particularly with respect to the front rotors.

    And driving style certainly plays apart as does the break in period/method for new rotors/pads. Coming to a stop after a hard and/or long stop and leaving the pads tight to the rotors isolates, instead of distributes, the built-up heat.

    My 2c.
     
  4. landtank

    landtank SILVER Star

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    By chance are they a left foot braker? Nothing like dragging the brakes around to heat them up. And I'm assuming these are at least Toyotas here and if it's the rears check that the e-brake is releasing properly. I had a rear rotor warp when I hit a little mud hole, well 3' deep. The e-brake had stuck on and that cold water did the trick.

    As for the argument, when you mount up a rotor on the lathe and it only touches the bit in one small spot, then I'd say it's warped. Seen a lot of this back when I worked in a Good Year shop.
     
  5. Gumby

    Gumby Supamod Staff Member s-Moderator

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    I don't know if I buy the whole brake deposit thing either. I've seen plenty of rotors that have a high side when put on a lathe. Whether that's deposits from the pads or distorted metal, I don't know. Either way, the culprit here is too much heat, but not due to driving style.

    landtank has the idea. Both drivers use the p-brake when they park. In Chicago, the bell crank seizes. The drivers pull the lever until they feel resistance, barely activating the shoes. Really not doing much good at all. Then the springs can't release the stuck bell crank. The rotors heat up from the friction on the inside of the rotor and warp or build up deposits or whatever.

    I never use the p-brake and have never replaced the rear rotors.


    That's my working theory anyway.
     
  6. dfmorse

    dfmorse

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    Here's another thought that might help; Proper and equal torquing on the lug nuts. Alloy wheels spec at 78ft/lbs. I set mine around 65ft/lbs with a little wd40 on the threads. Also found this interesting article:

    http://www.zeckhausen.com/bedding_in_brakes.htm

    David in Denver
     
  7. airlaird

    airlaird

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    This may help...my DBA rotors warped after 10 months. The reason? My 4" lift. I DID NOT properly do the BPV correctly. My entire truck was only using the front rotors to stop. Determine if the truck has a lift and check the BPV...there's a chance the BPV was not correctly done and the truck is only using the front brakes to stop.
    airlaird
     
  8. Arya Ebrahimi

    Arya Ebrahimi

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    I changed my front rotors and pads about 15k miles ago(in December) and they are once again warped. I blame the waterholes on my local trails because the rest of the trail is on and off the brakes heating them up, then bam, cold water...

    Ary
     
  9. Gumby

    Gumby Supamod Staff Member s-Moderator

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    One of the sets I had to change was DBAs too. In both cases I'm dealing with they are stock height.
     
  10. woody

    woody unhelpful spotter Staff Member Admin

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    I just replaced mine Monday, stock OEM rotors and 100-series pads, thru CDan....PO had machined the fronts and left rear tho (replaced right rear), so I fixed all that.

    Did the bedding process...first time I've ever done that....strange....

    lifting with OME mediums this weekend, will be adjusting the rear valve stuff....
     
  11. alia176

    alia176

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    Here's my guess: once the new pads and rotors are installed, they're not properly "bedded" in.
     
  12. PHAEDRUS

    PHAEDRUS

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    I wonder if it is a road salt issue.
    back in the late 90s chrysler had a recall on their rotors on dodge trucks and heeps. only affected the salt belt states as somehow the salt in the air or on the road lead to premature rotor warping on the veh.
    I would hope toyota used better parts but this may be a contributing factor.
    Dave
     
  13. Gumby

    Gumby Supamod Staff Member s-Moderator

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    The problem with a lot of the conjuncture is that I bed their brakes in the same as I do mine. I live in the same area. Drive in the same salt, etc. The major difference I see in my rear rotors not having the problem is the parking brake usage.
     
  14. Rich

    Rich

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    I'd suggest that when you service the rear brakes also include servicing the parking brake. Don't offer a partial job.

    I use my parking brake every time I turn off the engine. Have zero brake issues. Based on last measurment expect to get 46K miles on front pads. Haven't calculated remaining miles on rear pads. I don't live in the salt belt these days, but always used the parking brakes when I did.
     
  15. landtank

    landtank SILVER Star

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    While over torqueing the wheels and warping the rotors on Honda Accords by warehouse clubs made big news a while back, does anyone really think that would happen on an 80? Especially since you would need to warp the hub as well to have an effect on the rotor.
     
  16. Gumby

    Gumby Supamod Staff Member s-Moderator

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    In this case I can assure you the wheels were not overtorqued.

    I don't know that the parking brake can be serviced in the rust belt to assure trouble free operation throughout the life of the vehicle. I could charge them an extra few hundred dollars to replace the bellcrank assembly and I would still not be convinced that it would last another 3-4 years of trouble free operation.

    If the theory holds water and the truck I just sent out does not have reoccuring problems, then I will be sure to offer that option to people who feel the need to use their p-brake regularly.

    If they serviced it every oil change that would be different, but we are talking regular joes here, not cruiser heads. the number one problem with Toyotas that I see on a regular basis is that people just drive them until there are problems. many people buy toyotas for that reason. they come in at 100-150K with a laundry list of things that have never been touched.
     
  17. elmariachi

    elmariachi

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    FWIW, let me tell you how this happened to me twice on two of my 6 FJ-80s. The first time was in the winter of 1995 in my 1991 FJ-80 and I was en route to Virginia for Christmas. We were on the interstate in 45 degree weather and I had been running for about 2 hours at road speed, no stops whatsoever. I came sailing off the highway onto the exit ramp and slammed on my brakes. I literally felt the rotors go from smooth to warped in a matter of three seconds. They were previously fine and not one issue and instantly they got so bad that it dramatically changed the way we drove throughout the balance of the trip. I replaced them within a week of arriving home.

    Next instance was back here in Texas in my 1996 FJ-80, coming down the interstate again after a couple hours of solid running in 65 degree weather. I leaned hard on my brakes at road speed to get stopped to pick up something lying in the road. In the process of braking, I again felt the rotors go from A-OK to totally warped. It was so bad I replaced the rotors and pads the next weekend.

    In both cases my brakes were fine and well withing service specs. Based on the miles on both I would guess the rotors were original. On the second truck I tried installing aftermarket rotors and pads and they were pulsating within a month, so I went back to OEM and have never used anything but OEM since. I have also always been very careful not to heat them up like that in cold weather, but its never happened again.

    So you tell me.....was it the dramatic heat change that warped them? That's my guess.
     
  18. Land Speeder

    Land Speeder InstaH8R

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    This is all interesting as I am experiencing this same pulsating issue right now in my 91 (so no rear discs). I can feel it coming from my front Driver Side. Rotors turned and new OEM pads from a cruiser shop just 4 months ago. I've been trying to figure out why my rotors would already be warped. I mainly only do town driving with a 2" lift. Guess I'm buying new rotors shortly...
     
  19. cruiserdan

    cruiserdan SupportingVendor Emeritus Moderator

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    My rear rotors are original at 131,000 miles and I set the parking brake EVERY time I park the vehicle. No salt though.
     
  20. landtank

    landtank SILVER Star

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    I rebuilt my E (P)- brake a few years ago. The big issue is that Toyota seems to assemble them dry or with very little lubricant. I bought all new pieces which includes the pins and completely covered them in white lithium grease. I set the E-brake everytime I turn off the truck and the tension on the lever is the same as when I did them. I've done this on my old FJ60 and the wife's 4Runner with no reaccuring issue.
     
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