Crazy brake judder after sitting in rain for a two days?

140BPM

I've recently had to use my Z as a daily driver and have also had to leave it parked outside 24/7 while moving. Lately I've noticed an increase in feedback/vibration in the pedal after sitting in the rain overnight. But this week I left it sit for 2 full days in off and on rain. Now the brakes shake like hell as if severe rotor fade.

I took a look and I can see the distinct outline of the front brake pad imprinted on the driver side rotor, but barely visible on the passenger side. Rears look normal. These rotors are 2 seasons old (slotted aftermarket) and have been bedded in properly. I've never had an issue until the last two weeks.

One thing that has changed is I got new rear tires and alignment at the dealership. Could I have a caliper sticking or going bad? Perhaps dealership over-torqued or mis-torqued the lugs? I can't seem to make sense of it.

Oh, and trying to refresh the rotors by going through the bed-in procedure has zero effect I may take them off and try to re-hone them (it's that bad).

Any ideas much appreciated.

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2009 370Z Touring w/Sport 6MT

ban25

Well, if you see the pad imprint on the rotor, that would do it. If you've already tried rebedding them, you could try polishing them with garnet paper to remove the deposits. If that fails, replace the rotor.

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2017 Corvette Z06 7MT | 1LE | Stage 3 | DSCSport

140BPM

Right, that is causing the symptoms, but what is causing that? I distinctly recall the front brakes making a clunk while starting off that morning as if the pads were stuck to the rotors. Similar to what a rear e-brake can do if left on for extended periods, but this is primarily up front, and was only 2 days of being outside in rainy weather.

Even once I get it smoothed out again, then what? Don't let my rotors get wet?

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2009 370Z Touring w/Sport 6MT

ban25

I don't see how the pad material would transfer when cold? The only way you should be able to get that imprint is if you leave the brakes applied while hot and the rotors aren't turning. Might be worth pulling the pads out to take a look at them...make sure they aren't separating from the backing plate or anything...

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2017 Corvette Z06 7MT | 1LE | Stage 3 | DSCSport

Rusty

My pads always leave an imprint on the rotors after I park the Z in the garage if the Z is wet. When I back out of the garage. It does feel like the pads are stuck to the rotors. But I don't have the judder you are describing.

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POS VETT

That a normally-occuring phenomenon. Not just Zs, nearly all disc brakes with a steel rotor do that. It can occur the day after washing a car and pulling it straight into the garage. Some pads stick to a rotor or four and the car clunk hard when backing out of the garage. Pedal vibrates and the whole car judders when brakes are applied.

Let alone parked for two days in the rain.

2011 Nismo#91

Different rates of oxidation on the rotors, parts covered by your pads got less wet and rusted less then those exposed to the rain. Your rotors should be fine, rebed and/or sand paper should do the trick.

140BPM

So it has gotten much worse even after trying to rebed them twice. Before taking everything apart I checked the lugs with two torque wrenches... those idiots at the dealership torqued them down to 130+ ft lbs. Not sure if it's coincidence or if that could be a factor. Again, these pads/rotors are nearly a year old and never had a single issue until I got it back after inspection.

I'm taking it back in for them to sort out tomorrow. I'll be promptly checking the lugs upon pulling into my garage afterwards.

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2009 370Z Touring w/Sport 6MT

killrain

IM GETTING THE SAME THING BUT ONLY ON THE DRIVERS SIDE. SHAKES AND PULLS A BIT TO THE LEFT. HERES MY THREAD ON THE MATTER.


Opinions on my rotors, por favor!

140BPM

Everything suspension and bearing wise checked out fine. Alignment and balance fine.

I finally got all four rotors off and went to clean/hone them. After getting through the initial top layer of the buildup it was obvious it was more than just on the surface. All 4 rotors have distinct pad imprints on both sides of the rotor. I cleaned them up to the point where you could not feel any difference when sliding your finger over them it but they are still visible.

So I believe you were all correct! I'm running the stoptech street pads all around, and after doing some reading online recently it appears these are known to lay down heavier deposits than other brands. That plus the fact that I'm in stop and go traffic 90% of the time commuting to work and constantly sitting on the brakes at lights sometimes after emergency stops to avoid all the idiot drivers. So it's kinda like they were continually being 'partially' bedded in incorrectly.

I think I will just continue to run these until next summer and switch to a new brand all around. Hopefully I can afford something much better at that point.

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2009 370Z Touring w/Sport 6MT

POS VETT

Torque on a lug nut cannot be measured accurately when loosening. The initial break-away loosening torque is ALWAYS larger than when tightening. I seriously doubt that your dealership had overtightened the lug nuts.

140BPM

I checked the torque as if tightening the lugs, not while loosening. Started at 90 ft lbs and increased by 10 ft lbs until it didn't click immediately. Tested with two different snap on wrenches to verify. I would never use a torque to remove lugs. So yes, the dealership did indeed overtorque lugs. Not surprising since every shop I've ever been to does it too.

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2009 370Z Touring w/Sport 6MT

140BPM

So, problem is back just as bad as before. After cleaning up the rotors and rebedding all was good for about 3 days. This is what both of my rears look like now!

rotor1.jpeg

Again, these rotors/pads have less than 1000 miles on them. Stoptech all around but the fronts aren't quite as bad as the rears, but are still unacceptable IMO.

With the rotors in this condition, can I simply swap the pads with something better or will I be trashing the new pads?

What brands is everyone else using with success for street?

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2009 370Z Touring w/Sport 6MT

JARblue

If the new pads are similar material then they will be fine. If you go with a different pad material, you can scuff up the rotor surface and then bed the new pads.

I like OEM or Centri Posi-quiets for low noise/dust on the street.

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Spooler

I use Carbotech XP8's, dusty but none of those issues and yes I do get the rust if the car was parked after a rain or after washing. The lug nuts should have been torqued down to 80ft/lb's. If you use an extension, 85ft/lbs. If they were ran on with an impact, that would cause your issue. You may have to turn them to true them back up. Standing on the brakes at a light with hot brakes can cause issues also.