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Discussion Starter · #1 ·
I have a 2014 ATS, luxury. A few months ago it needed front brakes, so I went to Auto Zone, bought pads and rotors, slapped em on, went on with my life. Not long after, I'd say 6 weeks, the front developed a pretty substantial vibration only when braking. Normal driving was great, but braking felt like a bad rotor, or rotors. I let it go for a short time then pulled them off and had the rotors swapped under warranty. New rotors, problem gone.

A few weeks later, problem starts to show back up. WTF. 2 sets of bad rotors? Not likely, but.....problem is back. I said ok, Eff these rotors, bought another set from another source. Put them on, problem gone. Yeah, screw auto zone and their crappy rotors.

A few weeks later....boom. It's back. Ok, something is wrong. Car needed tires by now so I had a good set of Michelins put on, no improvement. This car has a bad wheel bearing, tie rod, something. Jack it up, front end is tight. Tight tight. No noise as you drive, no vibrations while driving, just braking. And it's getting worse. Caliper? So I pull the caliper off, press the pistons in, they move effortlessly. Not stuck at all. Hmmmm.....not the caliper. I put it back together with the caliper pistons back all the way, and spin the wheel. Spins nice about 3/4 of the way around, then hits a dead spot. So bad rotor, wheel bearing, something in the rotation.

Next day I jack it up, put an indicator on the hub, no run out. WTF. It was really cold so I packed it in for the day. Last night I jack it up and pull the rotors and swap sides. Problem goes from driver side to the passenger. And, its almost gone. I drove 2 miles, vibration is far less. Ok, bad rotor, got to be. I drove it again later last night, about 2 more miles, vibration is just as bad.

I call the dealer to price calipers, rotors, etc. Dude says man, your caliper isn't bad if the pistons move freely. Agreed. But whats killing rotors? Says maybe I need a pin kit. I said well I did have an issue getting the pins out when I did the pads last. He said maybe the pad is sticking or not retracting or something. Ok price a set for me. $96. Jesus, it's 2 pins and a clip. Ok whatever, I'm used to paying more for parts on this car. He says maybe I need a control arm, or bushings. Hows that killing rotors? I don't see it.


Anyone got any thoughts? I try not to be a parts changer. I want to troubleshoot down to the problem before I throw 10 new parts at it. I'm starting to be at a loss here.
 

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Check the lateral runout of the rotor surface with the brakes assembled. Use washers or old axle nuts as washers and tighten the rotor down with your lug nuts as the screw holding the rotor to the hub is insufficient for testing runout. Measure with the dial indicator at a 90° angle, half an inch from the outside edge of the rotor.

I guarantee you have excessive lateral runout on the rotor. The spec only allows for .002" runout.

If you find this is the case, you have to either cut those rotors or get new ones, install them on the car and then recheck. If you have more than .002" lateral runout on brand new/cut rotors, you have to address that. Either by indexing the rotors, or putting tapered shims between the rotor and wheel hub to correct the runout.

It is common on the ATS to see the wheel hub surface rust away. If this is the case, it is likely the source of the runout and pulsation. Replace them with carquest hubs. They come powder coated.
 

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Discussion Starter · #3 ·
Oh I have a mile of runout in the rotor. That's why the issue followed the rotor to the other side of the car.

But....you make a great point on the hub. So my initial plan was to check run out on the hub. Right around the studd area. But, I couldn't because of rust build up. The only place I could check it was at the very center. Which didn't tell me much at all obviously.
 

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Oh I have a mile of runout in the rotor. That's why the issue followed the rotor to the other side of the car.

But....you make a great point on the hub. So my initial plan was to check run out on the hub. Right around the studd area. But, I couldn't because of rust build up. The only place I could check it was at the very center. Which didn't tell me much at all obviously.
I had the same problem with a nice set of EBC slotted disks and pads. My dealer installed the new discs on the rusty hubs which caused a lot of run out and warped my disks( actually thin spot on rotor). After a while I figured it out and had them turn down the original discs that still had enough thickness. Got a refund for the discs but cost a few hundred to fix the dealers messy install.
 
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