draft cross

My disc look nice and smooth, but there is a lip around the outside edge. I would guess that this is from the disc wearing. Do these need to be turned when I replace the pads. Thanks David

telephonman

Your rotors don't have to be turned when you replace the pads, unless you have vibration or pedal pulastion when you hit the brakes,IMO

CRXsi

Many times the ridge is either a rust ridge or a ridge where the pad does not contact. Nothing to worry about as long as your main friction surface of the rotor is above minimum thickness (which it likely is). I agree that new pads don't need to have the rotors machined...unless you are going to a different brand of pad. The problem is that the way brakes work effectively is that they essentially put a 'smear' of the pad onto the rotor and it is the contact between this smear and the pad that gives the most efficient co-efficient of friction (better braking). If you don't machine or at least deglaze the rotor when you change to a different brand of pad then the smear on the rotor may not like the new pads and braking efficiency may not be stellar for a while until the layer, or smear, wears off and the different pad allows a new smear on the rotor. Remember it isn't just the pad to metal contact that causes the friction needed for braking but rather the pad causing friction with this smear that creates the most friction capablities for good braking. This is partially what happens when people refer to 'bedding' in new brakes...there are other processes involved but this is the one that makes the biggest difference.

The advantage to machining is that if there was any pedal vibration or shake in the steering wheel then it will also resolve this. If there aren't any of those symptoms then most times you can either use some sand paper or a die grinder with a mild sanding disc to deglaze the surface...remember to not take off any metal, just remove the 'smear' (which isn't visual by the way) and glaze.

handymantim

If your pedal isn't pulsing or your steering wheel isn't vibrating when you step on the brakes then you don't need to have the rotors turned.

Yes, the ridge is from the old pads wearing into the rotors. Having the rotors turned when they aren't warped will simply remove metal that doesn't need to be removed.