Machine or replace rotors?

[bigjl]

Originally Posted By: LeakySeals

They are not warped, thats pretty much a myth. Rotors get slick spots from the pads. Some time over the summer you had to slam on the brakes and come to a stop from high speed. The pads sat and fried on the surface of the red hot rotor, creating a slick spot. After that its grip, slip, grip, slip, thats the vibration you're feeling. No need to machine or replace. Just remove, clean, put back. Buy better pads maybe. Machining the brakes simply removes the slick surface. It also thins the metal, making the surface hotter, less dissipation for heat. So this pad glazing problem becomes worse.

That is certainly a possibility. But I have seen Discs that have been warped, which was confirmed by checking the runout. Again this was mainly before asbestos was removed from pad material. It was also only one or two vehicles. I had a problem with pad material build up on my 04 Legacy, but also had an issue with one front calliper which caused one disc to warp, the top few mm of the disc was getting hotter than the rest of the disc, notnsure what the issue was with the Caliper as the car was bought brand new and had under 5000 miles on it at the time and was rarely driven hard. The only reason they figured out what was going on was because the Mechanic at the 2bd Subaru Dealer I went into was ex Prodrive and actually knew what he wasn’t talking about rather than the parts fitters tab the previous Dealer.

 

[nthach]

Originally Posted By: bigjl

Though sometimes when people think their discs are warped it is actually just a Deposit of pad material. The only time I have experienced that is after they stopped putting asbestos in brake pads.

The Americans and Japanese embraced non-asbestos organic brake pads while the Europeans soldiered on with semi-metallic pads. The last few generations of NAO "ceramic" pads work by transferring a little pad material onto the rotors - when you apply the brakes you are creating friction by adhesion, while old-school asbestos and semi-metallic brake pads work via traditional abrasive friction. There was an article in C&D or one of the brake suppliers, I found this that explains the differences well: http://www.brakeandfrontend.com/brakefriction/

 

[DBMaster]

I used to be able to get a kit called "Brake-Tru" that allowed me to do them myself, on the car, at home. I found that if your shop doesn't use an on-car brake lathe and you started with pulsation you're going to get the pulsation back. I believe the hub and/or bearing to be the cause of pulsation more than the rotor. My old Accord didn't start with the pulsation until it had over 225,000 miles on it. I resurfaced the rotors myself with the Brake-Tru kit and it was good until the rotors wore down past their minimum thickness (at about 300,000 miles). The new rotors I installed started pulsing within 10,000 miles and I resolved it again with the Brake-Tru kit. Too bad those kits aren't available anymore.

 

[mb32]

I'm going to go ahead and replace the rotors. I found the service record from the previous owner and the front rotors and pads were last changed out about 70k km ago. There likely won't be too much life left in the rotors if I machine them. I'm going with the Centric rotors as I've had them on the rear for over 2 years and no issues to date.

 

[ATex7239]

I never had luck with machined rotors. I’d replace them.

 

[stephen9666]

I’ve looked in my area and any place that knows what they’re doing charges enough that it’s not worth it.

 

[bigjl]

Originally Posted By: nthach

Originally Posted By: bigjl

Though sometimes when people think their discs are warped it is actually just a Deposit of pad material. The only time I have experienced that is after they stopped putting asbestos in brake pads.

The Americans and Japanese embraced non-asbestos organic brake pads while the Europeans soldiered on with semi-metallic pads. The last few generations of NAO "ceramic" pads work by transferring a little pad material onto the rotors - when you apply the brakes you are creating friction by adhesion, while old-school asbestos and semi-metallic brake pads work via traditional abrasive friction. There was an article in C&D or one of the brake suppliers, I found this that explains the differences well: http://www.brakeandfrontend.com/brakefriction/

Asbestos was banned in the UK in 1999. The only exception was for some historic/classic cars which you could buy them till 2004. When did they ban asbestos in the US? As I thought it was in around 2000/2001

 

[andyd]

BMWs used pagid pads. They are dusty but when bedded in they stop. I never replaced a rotor unless a caliper stuck and chewed up the rotor when the pad wore down to steel. Pedal pulsations were mostly due to worn upper control arm bushings. Every time I had the rotors exposed I would shine them up with a knotted wire wheel.

 

[nthach]

Originally Posted By: bigjl

When did they ban asbestos in the US? As I thought it was in around 2000/2001

Last I've seen asbestos-containing pads was in 2002-2003. I used to buy parts from a small parts house and they still carried Australian-made Repco/Axxis pads that had a prominent warning for asbestos. Now, CA and WA are setting limits on copper in NAO pads.

 

[WyrTwister]

Think they banned it in building construction atound the early 1970's ?