I've recently had a problem with my rear pads (Hawk HPS) sticking to the
rotors. It only happens if the e-brake has been on overnight AND it's been
raining to the point that there's rust on the rotors. The problem disappears
with an audible crack once the car moves forward the first inch. The calipers
aren't sticking and the e-brake isn't sticking. The brakes aren't dragging once
you start off. I think the somewhat worn pads are just bonding to the rotor
discs in humid weather. If I park with the e-brake off, it doesn't happen.


The pads are about 3/4 worn, but have at least 3 mm of braking pad
material left on them. I have a different compound (CoolCarbon) on the
fronts and they never do this. I also have slotted cryo rotors front and back.


Anybody else have the same problem?


I'm due to change the pads and resurface the rotor later this year, and I
expect the problem to go away with that, but, we'll see.

 

I don't have this issue on my MINI, but then it parks in the garage.

However, our 2010 Mazda 5 does this, same situation: parked outdoors, after a good rain and time to dry/rust. All OEM pads/rotors. That first roll backwards breaks them free, audibly, then normal operation. Just a data point for you.

 

Happens to all (4) of our current cars. It's relatively normal.

 

Semi-matlic pads and cast-iron rotors do this....(most have some steel wool as a filler....
Guessing that ceramic might be less likely....but then again...a couple feet, one touch of the brakes...no issues...no why worry...just normal....
Now if the caliper is sticky... It is bad...meaning if it is noticibly hotter or dragging... Some mini's do have this issue....

 

It's normal - rotors' surface rusts a bit when left overnight in the rain, the brake pads get to clear that rust the first time you apply them. If you parked with the e-brake on, the brake pads are left pressed on the rotors, and may bind to the rotor, but will break free once wheels start to move.

BTW, the emergency brakes use the same pads on MINIs and BMWs (vs. inner drums in older cars). You are just manually compressing the caliper via the hand-brake cable, instead of the hydraulic fluid pushing on them after you press the brake pedal.


Please don't waste money and rotor material on "resurfacing" or "turning" the rotors. Just put the new pads on, and after brake-in, they will clear whatever old pad material may have been stuck on the old rotors. "Turning" the rotors usually does more harm than good, and is guaranteed to waste rotor material and your cash.

a

 

Thanks, all for the info and reassurance.
I do have a bit of a lip on the outer edge of the rotor and some grooves, and still
have plenty of material left measuring by micrometer, so when I get around to
replacing the pads in early summer, I'll do a quicky DIY resurfacing to the rotors
(take wheel off, spin the disc by hand via one of the lugnut holes and carefully
apply a file to both sides).
Sounds crude but it actually worked very well when I did that while replacing
the front pads last fall.

 

You can do that, but why?

If there is a lip there, it's because the pad is not touching that area of the rotor. Assuming the new pad is the same OEM size as the old, it wont be touching it either.

Unless you derive some exotic pleasure from beveling rotor edges, you can just as safely leave them alone ;-)

a

 

As someone who teaches this for a living... That is wrong.

Turning rotors does the following;

Removes brake thickness variations
Removes parallelism issues
Ensures rotor surfaces are fresh for new pads to be bedded in.

A good brake tech will only need to remove as little as .016" (less than the thickness of two business cards) to accomplish this.

If the rotor passes thickness variation (< .005") and parallelism (< .002"). Then they don't need to be machined.

A proper professional noise free brake job is much more than a pad-slap..

 

As someone who has seen far too many friends ripped-off by "let me turn your rotors" artists, allow me to elaborate.

1). If your old rotors are not warped (e.g.: no steering wheel shake when you apply the brakes), suggested issues #1 and #2 are not present by definition. STOP RIGHT HERE. Your rotors are good, assuming they have enough thickness left in them.

If they are warped, you are WAY better off replacing the rotors with new ones anyway. More on that later.

2). There are very few race/track brake pad compounds that need to be cleaned off the old rotors to avoid excessive pulsation until new compound wears in. This absolutely does NOT apply to street pads.

3). New MCS front rotors are 294 mm (diameter) X22 mm (thickness). Minimal thickness level is 20.4mm. That means you only have 1.6mm of rotor material to be used up. Different sizes, identical usable amount of rotor material in the rear.

I can not recommend, in good conscience, for anyone to pay a "brake artist" to shave some of that material into the trash bin. Especially .016" == 0.4mm == 25% of useful rotor life!!!

4). New front rotors can be had for $40 each, rears for $20 each (www.tirerack.com). Double that at the MINI independent. Triple that at the dealer.
A "brake artist" will charge you between 0.5 and 1 hours of labor ($30-$80) to WASTE 25% of your rotor's useful life.

Do your own math.

a

 

Your right, you've found me out. I'm a sham out to get you and your friends.

I'll go back to making fries.

 

I like fries... hey do you know anything about brakes? My buddy has a looney and wears a tinfoil hat.

 

aaanyway yes. the evo would only move after a big BANG and the pads break free from the rotors at times after rain lol

 

This doesn't happen to me after driving in the rain, I park in a garage and any remaining water must get dried off by the brake heat before the rust forms, but it does happen after washing the car and driving the twenty feet back into the garage. Entirely normal.

 

My Mini does the same thing Spiney...wash it, back up 20 feet and the next morning it feels like it's stuck to the floor.

 

Dude, don't take it personal.

I stated my arguments against "turning" rotors.
It is also the stated recommendation from all the auto manufacturers that I am personally familiar with: MINI, BMW, and Audi.

If you still disagree, do state your reasons and value proposition that underpin your position.

As one of my grad school profs used to say: just because it can be done, doesn't mean that it should be !

a