Date: Fri, 4 Dec 2015 18:32:08 -0500
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: Brake rotors - 1988 GL
In-Reply-To: <CA+az7_4-eY3wJ1XJxbDvVMnOxtARkZ4mfjC46GyVX3xzf_KBXw@mail.gmail.com>
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Except for some rust that ridge is the thickness the rotor used to be. Yes the pads wear them a bit. Also, since the outer part of the rotor travels faster-further per revolution then the center it is common for the pads and rotors to wear as a taper. This needs to be checked-measured. If the taper is there then the new pads will not seat properly, you will get hot spots and you will likely end up with bouncing breaks. In addition part of brake operation is that transfer film where some of the pad material transfers and imbeds into the rotor surface helping to create more friction. A good pad design will also clean (wear) some of this off so that the rotor surface does not get glazed. There is a lot of stuff going on here now that asbestos is not used.
As for rotor wear, the original thickness is 15mm and he wear limit is 13. Some rotors in addition to having the limit stamped on them will have some type of wear indicator on them. So even if they barely make minimum thickness after trueing they may wear to the point of needing replacement before the next pad replacement.
So, if I am doing front brakes and taking it all off to service the wheel bearings I will suggest truing or replacing the rotors while in my hand.
If the customer only wants pad replacement I don’t want to know about bouncing or squeaking or poor performing brakes. Pads on these things last a good long time. Worn pads is an indication of worn everything else including hoses and the calipers.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of John Rodgers
Sent: Thursday, December 3, 2015 5:00 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Brake rotors - 1988 GL
Undertook replacing brake pads today. No problem. Done it before. But this time, noticed a ridge at the outer rim of the rotors. Decided to have them machined down but have been unable to find anyone to do the job. Excuse - "We can't do it unless 'WE' take the rotors off the car. Corporate Policy! " or " We don't turn VW rotors because you are supposed to just replace them!" I never heard such bunk. These rotors were brand new last brake job. There is no scarring, grooving or scratches on them. They are snooth as a baby' behind. The ONLY thing wrong is that little ridge. The rotors are still quite thick and easily would withstand one machining, maybe even two. In fact, all that really needs doing as a practical matter is to take the ridge of. The discs would perform well without any further ado. I'm frustrated, needless to say. Any suggestions?
Johnl