6

I just replaced all four corners pads and rotors with the Power Stop Economy kit off Rock Auto and I'm having horrible shaking while braking at highway speeds. All slide pins have been re-greased and appear to have been in good order. On a hunch I replaced the front slide pin boots and it's still shaking. I'm contemplating re-jacking the car and replacing the slide pin boots on the rears, but I'm just not sure that the issue is the slide pins. Any idea on further troubleshooting before I just drop it off at the local mechanic?

Thanks in advance!

  • Are you properly torquing the lug nuts once you're done? And it's not the ABS system acting up, right? – JPhi1618 Apr 25 '16 at 18:06
  • I am familiar with "torquing to spec," but do not usually bust out the torque wrench for the lug nuts. I usually use a 24-V impact drill to torque those suckers on. Haven't had an issue yet. I can try that to see if that fixes it... Also, definitely not the ABS. – mcwagner Apr 25 '16 at 18:34
  • You'll probably find that the rotors are warped when you do a run out test on them. Caliper pins would cause uneven wear if seized or over greased. – Ben Apr 25 '16 at 21:33
  • Well, reading that does not a great feeling make. They weren't sized and had a good amount of "squish" upon inspection. I might just wait to post results from the mechanic when I bring it in. I've just about had it with this car. – mcwagner Apr 25 '16 at 21:57
  • Sized = seized. I'm an idiot. – mcwagner Apr 26 '16 at 7:54
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The brake shake has to be from either warped rotors or irregular grabbing of the pads on the rotors.

Warping:

  • You said you just put on new rotors, right? Really new ones? Its possible that one of the new rotors isn't square to its mounting. I would think you'd be able to see this with a dial indicator.

  • Are you sure the flat inner surface of the rotors is smooth to the wheel hub? A small rock stuck in there could be the culprit. Alternatively, if the inner diameter of the new rotors was too small to the hub, then there would be an interference, and the rotor wouldn't seat home. You would not really know. If its close you can try the play-doh test. Take a small ball of Playdoh modeling clay ($0.50 at Walmart) place it in a location where the rotor should touch the hub, push the hub on, remove it and see how flat the playdoh got squeezed? Playdoh is awesome for testing clearances between parts you can't normally see.

Differential Braking:

  • It's possible the shake comes from grossly differential braking at each of the corners. I thought for your car the cross corners are linked (one brake circuit for Left Front, Right Rear, the other for Right Front, Left Rear) Possible to bleed the brakes at each of the corners again? Start with the furthest wheel cylinder and bleed it. Then the next closest, etc. If you had an air bubble in the wrong place that wouldn't be good.

  • Are you sure the shoes are free to move in their holders? A stuck disk shoe wouldn't be good. Possible you got one wonky to its retaining spring?

  • Additionally, how did you compress the wheel cylinders before you installed the new shoes? Did you use an unbalanced C-Clamp to a zillion foot pounds of torque? Its possible you scored or jammed the piston inside the wheel cylinder, so that wheel doesn't get appropriate braking force. (You can use a C-clamp and scrap wood to balance the loads but you have to go way slow and gentle.)

  • Additionally, depending on the design, rear wheel discs can be problematic depending on the how they interface to the parking brake. I remember older Nissan's having a terrible time with this. The parking brake self adjuster would get jammed up and create terrible havoc in the brake system.

  • One other thought. If you somehow spilled excess lubricant on one of the brake pads that might make things go wonko. Generally this will burn off after a while, but not necessarily. I don't know how this would propagate to the car during braking but it wouldn't be good.

Idea for a quick test... find a quiet street with no traffic. Drive the car with long slow apply of brakes. You want to generate a little bit of heat. Then stop the car, turn it off, jump out and test the temperature of all eight surfaces of the brake rotors (carefully) with your fingers. Do they all feel equally warm? If one surface feels cold I'd start the investigation there.

  • Now these seam plausible. For cylinder compression I used a brake tool applied cautiously, as usual. I'm thinking it's differential braking. I'll start with your specified tests. Thanks for the post! – mcwagner Apr 26 '16 at 8:02
  • If you don't want to put your fingers on the rotors you can use one of those infrared thermometers to measure the temperatures. Touching the rotors would put your fingers in danger of burns and it would put your finger oils on the rotor. If you use the infrared thermometer, be sure to get close to get an accurate reading. The farther you are, the more chances for error. – cdunn Apr 26 '16 at 15:24
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When putting the tires back onto the car after replacing the rotors and pads, you need to torque the nuts to the proper specification. If you don't, and or if you don't use a star pattern to torque down the lug nuts, you can warp the rotor.

Do you have, or can you borrow a dial indicator? With that and a magnetic base you can measure the run out on your brand new rotors. If they are out of spec, you may have damaged them by over torquing the lug nuts.

Also, was there any debris on the hub that got between the rotor hat and the face of the hub? If anything is trapped in there it will push the rotor off axis and that can cause a shimmy as well. To find any of these problems you need to measure the run out with a dial indicator.

And at the end of the day, always torque your lug nuts to spec. Over torquing can and does cause exactly this problem.

  • If anything, the impact drill under torqued them. Ran the torque wrench over the lug nuts and most of them needed a 1/4 - 1/2 turn. So maybe not that. I do always use a star pattern to re-attach, so no worries there. I'll see about borrowing a dial indicator. Thing is: I've done dozens of brake changes on European cars with NONE of these issues. I thought for sure that the Japanese vehicle would be a snap... – mcwagner Apr 25 '16 at 21:12
  • Might just be the debris between the rotor hat and the wheel hub. Any kind of rust, sand, dirt, anything could cause that rotor to have way to much run out. The stuck pad was a good catch by @zipzit. Glad it wasn't a torque issue. – cdunn Apr 26 '16 at 15:21

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