Brake pad and rotor replacement question

[Mazdiod2]

Maybe the fronts are exposed to more salt brine, etc.? That stuff really corrodes the metal.

 

[yrwei52]

I heartily agree with the position that putting new pads on old rotors is like installing piston rings without honing the cylinder. My position has been: you might get by with it, but it's a really bad practice.

Same here ⋯ And good analogy!

 

[dynamho]

How would you know if the rotors are out of spec?

Too thin.

and/or warped (causes vibrations, hotspots, and uneven wear whenever you brake)

Even see a warped vinyl LP record playing on the turntable waving up and down? Same thing happens with rotors that get sufficiently thin or sufficiently hot.

TIP: After really hard braking, do not hold your brakes because doing so doesn't allow heat to escape from spots where the pads are clamping. This can warp your rotor.

 

[Anchorman]

Some interesting comments on here. Personally, I think with the nature of the questions the OP is asking, it would be better to go to Mazda.

 

[Buzzman12]

I heartily agree with the position that putting new pads on old rotors is like installing piston rings without honing the cylinder. My position has been: you might get by with it, but it's a really bad practice.

Agree there, but how about the reverse?
New rotors without replacing the pads?
I'm tempted to go that route, as my rear rotors have rusted prematurely (which Mazda refuses to cover), but there is plenty of pad left.
Thoughts?

 

[Mazdiod2]

Agree there, but how about the reverse?
New rotors without replacing the pads?
I'm tempted to go that route, as my rear rotors have rusted prematurely (which Mazda refuses to cover), but there is plenty of pad left.
Thoughts?

You can always sand the pads. It is a question of the additional labor involved in another "session".
Do you have to program the EPB to replace the rotors?

 

[Anchorman]

You can always sand the pads. It is a question of the additional labor involved in another "session".
Do you have to program the EPB to replace the rotors?

The EPB will accommodate changing pads or rotors automatically.

 

[Buzzman12]

The EPB will accommodate changing pads or rotors automatically.

The maintenance mode is required to retract the piston when installing new, thicker pads.
I'm pretty sure if I'm just replacing the rotor and not the pads, I shouldn't have to retract the piston.
There should be room enough to reassemble it with the old pads without worrying about trying to push in the piston. That's my theory anyway....

 

[Anchorman]

The maintenance mode is required to retract the piston when installing new, thicker pads.
I'm pretty sure if I'm just replacing the rotor and not the pads, I shouldn't have to retract the piston.
There should be room enough to reassemble it with the old pads without worrying about trying to push in the piston. That's my theory anyway....

Putting the brake into maintenance mode has a two fold effect. It runs the brake wide open for maintenance as the name suggests and it resets the initial proper running clearance. It can’t back off to accept new discs, it can only adjust forwards (outwards). If you put in new discs and the clearance is not sufficient to stop it binding, even slightly, all it can do is wait until enough material is worn away that it resumes automatic adjustment. If the pads and discs are binding initially, they will swell and you’ll quickly end up with a smoking mess of burned out pads and blue discs. The calipers get mauled as the adjusters are not designed to resist dynamic forces. You can try it but for what it takes, I wouldn’t risk it, just put it in maintenance mode and as you take it out it will take up the new dimension then back off to give the new proper clearance. It only does it once.

 

[TBarney]

Agree there, but how about the reverse?
New rotors without replacing the pads?
I'm tempted to go that route, as my rear rotors have rusted prematurely (which Mazda refuses to cover), but there is plenty of pad left.
Thoughts?

I can honestly say that I've never thought about it. I'm trying to picture a scenario where a rotor would be so rusted after only 5 years that it's non-usable without the rest of the braking system needing serious help, too.

Can you describe the rust you're worried about? I'm just curious, never having dealt with that. I guess living in the deep south, there are things I just don't see.

I think it would come down to whether the pads are wearing flat, or if there are any grooves. If the rotors show scoring, you can bet that's reflected in the pad surface. If they look flat, then the machined surface of new rotors will probably take care of any minor pad imperfections the first few times you engage the brakes.

But, pads being relatively inexpensive, I would probably replace them at the same time.