How long does it take to break in new rotors? (And other related questions) - PeachParts Mercedes-Benz Forum

EricSilver · #1 08-04-2004, 02:40 PM

It’s been about 500 miles of city and some highway driving since I installed new Brembo high-carbon rotors and PBR Deluxe pads up front. I rotated my tires yesterday and in the process discovered that my rotors are as smooth as they day I bought them, with only minor cosmetic scratches – no brake pad grooves of any kind.

Is this is why I need more pedal pressure to stop? Is the high-carbon rotor too hard for the pad?

I was prepared to replace my calipers and possibly the master cylinder because of this, but now I am not sure. Something is definitely problematic since I noticed the pads and rotor I replaced on the driver’s side had asymmetrical wear, and the car (still) intermittently shudders a bit when braking.

Any thoughts?

Duke2.6 · #2 08-04-2004, 04:05 PM

PBR Deluxe pads are VERY easy on rotors. I don't why you would buy anything other than an OE or equivalent quality aftermarket rotor, and they likely have nothing to do with increased pedal effort.

The OE brake system is satisfactory for every class of driving including racetrack hot lapping. The PBR Deluxe are not a good track pad - no where near as good as OE, but they are fine for any level of street driving, plus, the don't, dust, squeal, or chew up the rotors.

The PBR DeLuxe pads require more pedal effort than OE and many aftermarket pads because the DeLuxe have a lower friction coefficient, but this low coefficient is one reason they are easy on the rotors and the pads last so long. The higher pedal effort is something you will get used to as you accumulate miles, and you won't even remember six months from now. Although the ABS will automatically balance the system on a max performance stop, I recommend you install them on all four corners, to restore the basic mechanical balance designed into the system.

If the pads are not wearing evenly on each side of the caliper, you need to replace or overhaul the sliding pins.

Duke

EricSilver · #3 08-04-2004, 04:43 PM

Sounds like sliding pins will be my project for the weekend.

I got the PBR Deluxe pads because I have heard nothing but good things about them in various threads here. My main objecdtive is adequate stopping power and low/no dust.

I had MetalMasters which had great stopping power, and were not too hard on the rotors, but dusted as much as OEM pads (except with a brownish/rust color that also stained the wheels).

I bought the Brembos with the MetalMasters in mind, but chose the Deluxe at the last moment. Also, at $37 each, they were the same or less than OEM rotors.

I am currently searching "sliding pins" here and via Google. ANy warnings I should be aware of, or is it an easy job?

EricSilver · #4 08-06-2004, 10:58 AM

Car: 89 260E
Brakes: Girling single piston -- Front

I will delay this maintenance until after I get a caliper repair kit from FastLane. Although I have replaced pads and rotors twice, I have never done a caliper cleaning/repair and want to be sure I do it right.

I plan to simply detach the brake lines from the caliper and then take them indoors for cleaning and repair. I am concerned about air getting into the brake hose, so my plan is to use a large binder clip (the mega-paperclips) to clamp the hose just above the point where it connects to the caliper. Is this feasible? Will it damage the hose?

Also, is simply unscrewing the hose from the caliper all that is required, or is it attached in a way that requires finesse or special tools?

Finally, would it make sense to buy a set of remanufactured (Cardone) calipers just in case (and return them if I don't need them)?

EricSilver · #5 08-12-2004, 12:29 PM

Early this week I had a chance to examine the calipers. My pads were rattling and I discovered that the bolts were not very tight, allowing the floating part to move. This is what I saw:

Driver’s side: The rubber boots around the sliding pins were torn and detached on one end. The pins had some slippery fluid/lubricant on them. Pins slid freely in and out.

Passenger side: One rubber boot was intact and there was the squishy feel of fluid as I moved the pin back and forth. The other pin’s boot was torn, but not detached.

After adding shims, replacing pads and properly tightening the caliper bolts, the shudder is gone, my braking is smooth, and no undue pedal pressure is required. I assume the loose bolts caused one or more pins to stick.

However, because three rubber boots were damaged and had leaked most of the fluid within them, should I still go ahead and replace the calipers?

Also, disregard my remark about clamping the brake hose. I see now that they are non-compressible.

Ali Al-Chalabi · #6 08-12-2004, 05:17 PM

If you remove the calipers, just do a good bleed on the system when you reattach them. If the boots are torn and dirt and moisture has entered into the caliper bore and rusted the piston bore then you will need to replace the calipers if they are leaking or sticking. Did you replace the boots?

psfred · #7 08-12-2004, 09:24 PM

It's normal for one side to wear a bit more than the other, but if there is a pronounced difference on one side and not the other, one side is binding.

You have two things to check here -- the condition and performance of the piston seal and the condition of the pins and bushings on the floating caliper.

If you have a bad seal, one side will drag more than the other, leading to some steering pull after a stop and greater pad wear.

If the pins and bushings are worn, the floating side of the caliper will wear to a taper, the brakes will rattle, and you will have reduced braking and higher pedal effort. You can check this either by looking at the pad for taper front to rear, or by attempting to move the floating caliper sideways. If it moves in any direction other than straight in and out, you need new pins and bushings. They just screw in, new ones will have locktite on the bushing thread.

Replace the torn boots and relubricate the pins in any case, else they will rust and stick.

Peter

Duke2.6 · #8 08-12-2004, 11:14 PM

It sounds to me like your calipers needed to be overhauled or exchanged for rebuilt calipers.

Duke

EricSilver · #9 08-13-2004, 01:33 PM

Thanks for all the good replies.

What I plan to do next (perhaps around Labor Day) is replace my front calipers with with rebuilt ones. The cost is reasonable ($70 each) and I assume I can do it quickly.

I looked online for instructions on how to do this, but found little. I can see just two hoses that need to be disconnected. Is that all there is to it, and the reason why there are no details online, because the job is that simple?

Duke2.6 · #10 08-13-2004, 10:49 PM

That's about it. I've never had mine off - just removed the lower pivot bolt to fold the caliper up to replace pads. But all that's left IIRC is the second sliding pin bolt, brake hose, and connector for the pad wear sensor.

One thing I like about these old Mercs it that the basic normal maintenance and wear part replacement tasks like fluid, filter, and brake pad changes are about and simple and easy as I've ever seen on a car.

Brake pad changes are especially easy because of the nifty pad holder. On a lot of cars you have to remove the caliper, load the pads into the caliper, then wrestle the caliper/pad assembly back on. On these old Mercs it's also easy to push the piston back in since the caliper is still attached. I just attach a hose to the bleed valve, open it up, and push the piston back in with a wooden hammer handle.

Make sure when you fold the caliper back on that the little leaf springs on the pads engage the caliper housing and don't get jammed in the inspection slot.

Duke