TrueDrezzer

Today I noticed that my LF disc brake looked rather scored... almost as if the pads were gone. The other discs on the car look normal. However, there is no metal-on-metal scraping noise or any other odd braking behaviour. I took the wheels off and found out that all of the front pads have at least 5mm left except for the LF outer pad, which was down to 1mm!

I put the wheels back on and tried re-bedding the pads in again, and the brake disc looks more normal.

This pad will need to be replaced soon. Do I have to replace all the front axle pads at the same time? The other pads are still in great shape.

However, the root cause bugs me. How could one of the pads wear out so quickly? It is on the side of the caliper opposite of the piston. None of the dust boots or seals on the caliper look damaged. Time for a caliper rebuild? Is this a dealer-only job?

///Robin

alexf20c

Grease the sliders on the left-front caliper and you'll be good to go.

Replace the worn pad, of course. (Most front pads are sold in axle sets (all 4) so it would be pretty dumb to just replace the worn pad, but it's up to you. And turn the rotor if it needs it.



EDIT: You could rebuild the caliper if you wanted. An overhaul kit consists of a few seals and boots, and is very cheap.

TrueDrezzer

"Sliders" as in the pins that move the caliper back and forth, near the caliper bolts? Any special grease I should use on this?

Guess I'll pick up an overhaul kit. Sounds like a fun project. Should be a piece of cake, eh?

Thanks dude,
///Robin

alexf20c

Robin,

When you pop out the piston with compressed air, stick a piece of wood or a roll of shop towels in between the piston and the caliper body. Do NOT try to catch the piston with your hand, or it will shatter your fingers; it comes out with a lot of pressure behind it!

And yes, "those" are the sliders. Just pick up a tube of normal "caliper grease" at your local auto parts store.

alexf20c

When you have the piston out, it wouldn't hurt to run the bore with some steel wool, just to clean it up a bit and remove any burrs. You want the piston to retract easily when you let off the brakes. The piston boot (outer diameter rides in a groove in the piston bore, and the inner diameter grabs a land in the piston) is what pulls the piston back into the bore when pressure is released. A clean bore makes it that much easier.

alexf20c

While you're at it, you may want to pick up a set of Speed Bleeders. They're relatively cheap ($5/ea) and allow you to bleed your brakes without a second person (or vacuum/pressure bleeder). They replace the existing bleeder and never have to be removed. All you do is open them as you would a normal bleeder, and a check ball inside the Speed Bleeder will act as the second guy ("Alright pump 'em... Alrigh again... Again...") with the open end wrench.

Worth the money, IMO.

TrueDrezzer

Thanks for the info! I already have a set of SoloBleeders that I enjoy.

///Robin

TrueDrezzer

Right, took a look at the brake caliper today. I pulled the pads... and found one with 5mm as I had visually inspected before, and the offending one was between 0-1mm. There was more pad remaining on one edge, but on the other side it was down to the backing plate! Well that definitely was the problem.

So I removed the caliper guide bolts. They seemed a bit sticky when I tried pushing them in and out. I lubed them up with some grease and put them back in. They slide better now. The rubber bellows around the pins are fine. Then I sprayed brake cleaner around the caliper and put on new pads. After a bit of bedding-in, the scored disc looks more normal again.

Let's hope that was that. If this happens again, should I go ahead with a caliper rebuild?

///Robin
///Robin

slalom44

Originally posted by TrueDrezzer:I hope that you didn't use conventional grease. You should use silicone grease (like Sil-Glyde) on these pins. The use of bearing grease will break down the rubber parts.

TrueDrezzer

Hmmm the stuff I used was some Liqui-Moly LM47 grease with MoS2 longlife additive and "guaranteed safe lubrication under demanding conditions." Unfortunately, there is a picture of a wheel bearing on the tube! It's exactly the same colour as the stuff that I found still remaining on the caliper pins.

Think I should do it over? How different is the proper stuff from the anti-squeal paste that goes between the pads and the piston? I have several tubes of Plastilube anti-squeal lying about. There was another product I found that stated the following: (according to their website)

"Brake anti-squeal paste / spray

Special synthetic material for brake systems. Extremely adherent and resistant to road salt and splash water. Prevents and eliminates brake squeal arising between the brake calliper piston or from the moun-tings and the brake lining. Secures the operation of the whole brake system.

Operational area: For the whole brake system on the disc-brake pads, bolts, pins and points on drum-brake systems."

This description is similar to a description of the Sil-Glyde product you mentioned (don't have that here in Germany)

///Robin