New pads and drilled rotors - scraping noise

[leftfield6]

So, I have finished up my rear suspension and brake work on my 99 Boxster.
All new:

• Struts
• springs
• coffin arms
• track arms
• long control arms
• drop links
• sway bar bushings
• new ceramic brake pads
• new rotors drilled/slotted
• SS brake hoses
• Rebuilt all C/Vs

So, all this is back together, right now the alignment is ballpark, using paint marks from old suspension. I'm sure all bolts/nuts are torqued down to the right torque setting.

The brake rotors are one of the "black coated" brands, so the black on the rotor face will wear off really quickly, but the rest of the rotor still keeps that protective coating.

Okay, so there is the set-up. Here is my issue/maybe not an issue.

Took it out for a round the block run to see if any problem popped up. I have triple checked that everything is tightened down and I didn't miss anything. This quick shakedown was to basically see if anything fell off.

Good news? Nothing fell off. Even better, all of the creaks/thuds/bumps that my old worn out rear suspension was making is GONE.

Bad news? Holy cow do I have some grinding/screeching sounds going on. On brake or off brake, not much difference. Sounds for all the world that my brake dust shields are rubbing on the rotors, but best I can tell without pulling the wheels back off is that they are not.

How likely do you think it is that this is just my pads/rotors getting to know each other? I need to go to an empty parking lot and do the whole brake bedding in process, but I kinda wanted to get my alignment done before doing that.

Anyone had experience breaking in new coated rotors?

[JayG]

Don't know if it is causing the noise, but you need to bed the pads
Do a web search for instructions

Basically, you heat the crap out of the pad with a bunch of hard stops. Its a little more involved than that, but that's the gist of it.

[leftfield6]

Originally Posted by JayG

Don't know if it is causing the noise, but you need to bed the pads
Do a web search for instructions

Basically, you heat the crap out of the pad with a bunch of hard stops. Its a little more involved than that, but that's the gist of it.

Yep, Not driving the car until I get that done and hopefully the alignment as well. Got the recommended process from Pelican's website.

[RandallNeighbour]

There's a high likelihood that your brake backing plates behind the rotors. These can make an awful noise that's consistent or only makes a creak or squeak or rubbing sound when the suspension is compressed or decompressed.

check all four with the suspension loaded and unloaded. It's a common issue after the car has undergone all the suspension parts swaps you've indicated you've done.

[epapp]

Just installed my eBay rotors and pads too - there was an initial scraping noise before I bedded them. After bedding, noise gone, all works as normal.

Turns out there was a burr on the rotor that made a 'schhhlak schhhlak schlep' each time the front left wheel rotated before I bedded them. After bedding the burr was reduced to almost completely flat and sound gone.

[thstone]

Very common. Bed the pads and you should be fine.

[tommy583]

It could also be your emergency brake shoes rubbing on the inside of your rotors.

[leftfield6]

Great advice all. i DID adjust the parking brake shoes, so maybe I need to back that off a notch or two

So I took it down the street to a closed for the night office park to do my brake pad bedding process. Nice big empty parking lot.

Well, did not get it done. Two high speed (60 mph) accelerations and hard braking convinced me to get my azz back to my garage. Had a serious pucker moment. Apparently my "ballpark alignment" using the paint marks from the old suspension is nowhere close. The back end was all over the place not during the braking, but during the hard acceleration. It was ALL OVER THE PLACE. So I headed home (less than 1/2 mile) at a pretty slow pace.

When I eyeball my rear wheels, it looks like I have excessive toe in. Maybe a little more on the driver's side tire. So I did a really really basic check. I marked a spot on both tires about 4 inches from the ground, both on the front side of the tire and the backside, right in the middle of the tread. My tires have a prominent center groove, so I used that as my reference. I then stretched a tape measure from tire to tire on the front of the tires. 57 3/4 inches center of tire to center of tire. Then I did the same on the back of the tire 59 1/4.

Yikes, that can't be good. Think I better lay off any high speed maneuvers until I get the alignment done.