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Many times you will unknowingly bend the inner sheet metal heat/splash shield and it will rub the rotor. This is often done on the rears because the wheel is heavy and can drop downwards and hit the heat shield altering its shape. Take off your wheels and check the heat shield clearance and bend it away from the rotor when you find the one causing the noise.
Your rotors/pads are fine. The 1 month old pads will quickly wear into place. Nothing special needs to be done except don't expect maximal brake ability until the pad matches the rotor face completely.
Ever since I started tracking cars and seeing how well brakes perform, especially on a 996 C2, I realize what a waste it is to replace rotors and pads at the same time. As long as you still have enough surface, even with grooves, to get into the ABS then you have max braking performance. I've put new pads on a well grooved set of rotors and had no problem getting max braking on a set of slicks. I'm not sure what additional benefit replacing the rotor would have gotten me.
Ever since I started tracking cars and seeing how well brakes perform, especially on a 996 C2, I realize what a waste it is to replace rotors and pads at the same time. As long as you still have enough surface, even with grooves, to get into the ABS then you have max braking performance. I've put new pads on a well grooved set of rotors and had no problem getting max braking on a set of slicks. I'm not sure what additional benefit replacing the rotor would have gotten me.
In fact, one could even make an argument that grooved rotors perform BETTER. More surface area for the pad to bite, so it's effectively a greater swept pad area, and more surface area for cooling air to act on to reduce rotor temps. It's just less efficient in the early days when the pad is only touching the ridges, and hasn't worn to reach the bottom of the grooves. I'm actually kind of surprised we haven't seen somebody in F1, WEC, etc. run rotors with a heavily grooved surface.
Away for the weekend, so nice to come back and see the responses on the forum.
Pads are Textar and rotors and Sebro (both from Pelican). Funny enough about the holes that look like they weren't machined properly...the stock photo on Pelican actually shows the dimpled holes that are on mine.
So I took off the rotors and reinstalled...grinding noise is completely gone. And yes, the pads were installed in proper orientation.
As for the 'premature pad wear', I have no idea what's going on there...a number of you have opined on what the cause could be and I'm certainly aware and appreciative of all posts.
I'm driving the car now and actively monitoring wear points to see if they even out or continue to wear unevenly.
So I took off the rotors and reinstalled...grinding noise is completely gone. And yes, the pads were installed in proper orientation.
In removing/reinstalling, did you figure out what was causing the grinding noise? Backing splash shield rubbing the disc? Debris stuck in the caliper rubbing the disc?
You're kidding, right? This is nothing to worry about and is pretty common with any new pad/rotor combination, whether one side of the interface is used or not. Even with brand new parts they will not line up exactly. The mating surfaces will continue to adopt each other's shape until they are matched over the next few miles and this will be a thing of the past. This will not appreciably affect the life of the pads or the rotors. It hasn't even worn through the cross-hatch pattern on the rotor yet.
The only question here is what is the scraping noise. Backing plates? Rocks or other debris stuck in the caliper? Caliper not retracting and dragging the pads on the rotor? I suspect the noise is a totally separate issue from this preliminary wear pattern.
Actually not kidding , if you check the rotor manufacturers instructions and the factory manual ( this is also something every first year apprentice learns, pop down to your local Midas brake shop and ask any mechanic) ) brand new rotors should get brand new pads . But if you don't care about reduced rotor life , they will eventually bed in . The old rotors were at the end of their life so the lands and grooves can be pretty pronounced and that pattern imprinted in the pads , the old pads will squeak and cause grooves if placed on a new rotor.
I wouldn't do this on a customers car ( or one my family was riding in) , but amateurs can do what they like I guess , it depends on how long you want the new rotors to last, until it's bedded in you'll get more reduced performance ,. So go easy for a few hundred miles.
Last edited by Vancouver996; 04-18-2017 at 01:58 PM.
Certainly new rotors + new pads at the same time is the optimal thing to do, and I'm not sure why OP didn't do it all at once when changing pads 1 month ago. But he's not going to ruin his car by adding new rotors to 1-month-old pads.
If all we're talking about is trying to maximize component life, which I assume is driven by trying to spend the minimum number of dollars, it would be pretty silly to throw away 1-month-old pads and buy new ones, under the guise of possibly squeaking a little more life out of the rotors. Any slightly reduced rotor life is going to cost a lot less than a new set of pads.
This is just stupid. You are wasting money changing rotors every time you change pads. Having put my brakes through the most extreme conditions, including 40 laps in a day at TWS where you go from 140MPH to 35mph at maximum braking among other things, I can tell you that this is a myth. Changing your rotors before they are due will cost you way more rotor life than changing the pads at a separate time.
Umm , nobody was suggesting that . Not for a second
Standard mechanical practice is to put new pads on when you change rotors . Not the otherway round as you should get multiple pad changes on a rotor
New pads on new rotors, It's a best practice , as it avoids the situation experienced here. Those marks and scraping noise are exactly what you'd expect in this situation .
If you want the pad surface to mate flush with the rotor, place a piece of sandpaper on a hard flat surface and rub the pad around in a figure 8 pattern until it's flat.
Umm , nobody was suggesting that . Not for a second
Standard mechanical practice is to put new pads on when you change rotors . Not the otherway round as you should get multiple pad changes on a rotor
New pads on new rotors, It's a best practice , as it avoids the situation experienced here. Those marks and scraping noise are exactly what you'd expect in this situation .
If it's your car , do what you like .
Of course the mechanics want you to put everything new, it makes the most money for them.
+1 for only replacing what's worn. Pads will embed fairly fast if done properly. Don't go ape$hit on them until that happens are you'll be fine.
I had the same problem, reputable shop highly recommended by everyone. I waited hours for them to do a simple brake pad change. I rarely drive the car but when I did I would hear scraping under light braking but not all the time.
I noticed the rotor wear and brought it to another shop. Happens to be that the caliper bolt was not tightened. I am not sure why the other shop took them apart but that explains why it took so long that day.
04-16-2017, 11:33 PM
