Squeaky front brakes

[Jason Leung]

My front brakes seem to squeal when braking at low speeds (<30km/hr).  Any ideas on what to check/try?  Here are the details:
- Front brakes squeak when braking at low speeds only.  No squeaking when braking at higher speeds.
- Doesn't seem to squeak when the tires/rotors are cold (ie first few blocks)
- Could be one corner only but I haven't confirmed yet.
- Lug nuts torqued to spec
- Rotors are the AEM big brake rotors.  Pads are the Porterfield R4-S's
- No visible marks/damage/warpage on the rotors
- Lots of brake pad left
- Only squeals with the summer rims (17x8 w/ 35mm offset) and tires (225/45/17) on
- No squeal with the winter rims (stock 17's) and tires (225/45/17) on

TIA

[Wayne Wright]

Are the sliders/pins lubricated?

The "at low speeds but not a high speeds" kinda boggles me, do you mean hard braking vs soft braking?

[Ryan Lore]

AEM rotors are harder on pads.

Remove the wheel and take off the caliper and inspect the inner pad
I bet it's down to the squeeler

I had the EXACT same symptoms and the "inspection hole" in the caliper misled me because the inner pad had a lot of tapered wear

New Pads will silence your brakes whether its from worn out pads or heavily tapered ones

It will be obvious when you take them apart

[John Hartman]

I agree, take them apart, I betcha the inner ones are worn, and like Ryan said, tapered.

We get lots of people who think thier brakes are great and when we call a brake job, they get pissy until we show em the inner pad.  

Do it before you wreck those expensive rotors.

[Wayne Wright]

Haha, well, that was the obvious thing to do, and he said lots of brake bad left, no marks on rotors, so I thought he had checked that out. Squealers are a softer meterial then the rotors thought, so they're wont be any marks unless it's been like that for along long time.

[Mike Schmid]

The other thing with the AEM rotors is I noticed the pads don't completely touch the rotors.  There's a thin strip on the outside edge of the rotor that doesn't touch the rotor and doesn't wear.  If you looked at that it'd look like the pads are great when in fact they're undercut and worn.

[John Hartman]

and the squealers might be softer material, but they are still steel.

[Wayne Wright]

Oh I know, but they usaully don't gouge the rotor unless they're rubbing for awhile....but you can usally see a mild line.

[Jason Leung]

Thanks for the replies.

I've been trying to capture the exact symptoms a little more closely.  It seems to squeak when I apply light pressure on the brakes.  For example, if I'm slowly slowing to a stop and I'm only lightly applying pressure, it squeaks.  It doesn't seem to squeak when I lightly apply the brakes at higher speeds though.  (Hence my original thought it only squeaked below 30km/hr).  However, when I apply "firm" pressure to the brakes, they don't squeak.  And it doesn't squeak during the first few stops when I first start the car.

I only visually inspected the pad left with the calipers on the rotor so yest the inner pad could be worn.  I'll take them off and inspect more closely.  

Thanks again.

[Mike Schmid]

If your pads are indeed good I know you can get "stop-squeel" or something.  I've never used it so I can't vouch for how well it works.

[Kevin Chan]

I just had the same thing, and I changed the pads, but it didn't change a thing... so it must be the discs for me. what can I do? the stop squeel thing that bonds with the disc surface to make it smooth? where can I get them and which one should I buy???

[John Hartman]

if you just put new pads on a worn rotor, you can get squealing.

if you have glazed used pads, it can squeal.

if you have siezed slides or other non-functional parts or missing parts you can have squeal.

When we do a basic brake service(no changing parts) we take it all apart, clean it all very well, lube the sliding parts, put a piece of heavy sand paper on a flat surface and rub the friction surface of the pad on this until the glazing comes off.  Also you can lightly chamfer the edges of the pads. Then you spray the pad surface with graphite spray.  It seems to take care of alot of problems with squealing. Make sure its all in good working order.  Then put it all back togeather again.

IF it still squeals, you will have to turn the rotor.  If your pads are nearly new, you can deglaze them and reuse them, but its unlikely.  Put in new ones.

Mind you, I don't do any work on AEM or Baer Brakes etc.  Just stock systems.

[Kevin Chan]

do you work on drilled rotors?

[John Hartman]

personally no, but I could ask.

I would think that as far as basic maint goes it should be the same tho.

[Kevin Chan]

OK, so far, I've changed my front rotors to power slots, and my pads to another pair of Hawk HPS, but I changed the pads for about 3 days before I changed the rotors... and I've already driven about 190 miles on the rotors... but it still squeaks basically just like before... what can I do? :evil: