Ethan

I ordered the front rotors since they were so close to "bad" I couldn't stand it! Are there any little tidbits of info I should know about changing the front rotors before I get started?

Curt

Purchase new brake caliper MOUNTING bolts and disc retaining screws.

Honestly, I wear a cheap respirator and surgical gloves when working on brakes.

Car must be securely supported, place tire under chassis as a final safety stop.

once you have the pads off, take off the two bolts holding the caliper bracket from the steering knuckle.

take off wear sensor and use string to tie caliper from upright / spring so it dosen't hang and stretch hose connections.

take oof the disc mounting screw- I think it is a 5mm hex, may need a smack to lossen. Like wise disc may need a smack from behind to dislodge forward.

I use a small cheap disk sander on my drill to clean smooth and shiney hub mating surface. I also usually dab a few grape size smatterings of synthetic cheap Amsoil grease on the hub surface away from spindel.

Everything back together,
brake disc retaining screw is tightened to 7 lbf ft
caliper to steering knuckel tightened to 85 lbf ft

Mercedes OEM rotors come covered in a grey protective paint, just assemble as is no rotor prep is needed

(1) Whoops! I didn't order new mounting bolts and "disc retaining screws". I asked the folks here when I ordered to tell me what I needed. That got missed. Is there a reason for this?

(2) By "hub mating surface", what specifically do you mean?

(3) If I don't have OEM rotors, what prep is needed?

Thanks again!

Curt

When you get the rotors off, you'll be looking at the hub mating surface.
Make sure it is SQUEAKY clean, to prevent possibly a wobbling wheel.
As for the new rotors, buy a can of Brake Cleaner & spray the new rotors before mounting them.
This will eliminate any oily residue that may have been applied to the rotors to prevent rust. ;)

Ahhhhh! I understand now! Thanks so much for the great advice! I am looking forward to starting this job now as soon as my parts arrive!

Curt

Can't say you haven't done your homework. :D

some bolts once they are used the threads stretch and when they are reused you don't get the proper tightening with the specified torque.

also don't cross contaminate grease on your hand to the new disc surface.

the discs should come with instructions on handling and break in procedure
for the first 100 miles. only short smooth braking.

The only place I have been able to find the mounting bolts online is Performance Products. These should be replaced because they have a self locking compound built in. It is also a bolt that is commonly removed and reinstalled in the industry with an impact wrench.

As far as the disk retaining bolt, there only purpose in life is to make shure the disks dont walk off the studs on the assembly line and fall on the floor. I would only replace these if it looked like the head might become striped on the next removal.

The hub mating surface is that surface between the rotor and hub. It should be cleaned so that the rotor mounts true to the hub. For example you want to make sure there is no build up of rust on one part of the hub that would cause the rotor to be mounted with a wobble when tightened down.

If there is no preservative on the rotors, no prep is necessary otherwize use brake cleaner. These days I have not seen any rotors comming through with preservatives.

John Roncallo

Ok, I have all my parts and have started the job with the left front wheel first. I cannot seem to get the rotor off. I am sure it is rusted, but what is the preferred method to SAFELY get these dudes off?

clankford, back off the set screw then use a block of wood as a softener and hit it with small sledge hammer ... turn the rotor in 90 degree increments and give it another whack until it breaks free. Remove the set screw and take off the rotor then clean the hub and back of the rotor with a wire brush. To prevent future rusting apply a thin coat of anti-seize to the hub or the back of the rotor before reinstalling the rotor.

I guess the problem I am having is to calibrate how much the "whack" would be? I am afraid of hitting it too hard, even with the wood "buffer". Can I totally hose up my front end alignment with too much "whack"? I have soaked the center edge of the rotor and the mounting holes with Liquid Wrench for about an hour. I used a small ball pein hammer with a piece of wood and hit it around the face of the rotor in 90 degree increments. No luck so far.

Hit it harder. ;)

remove the rotor locating screw, ( You have all the caliper brackets, lug bolts out of the way ? )

I use a twenty pound short handle sledge, hit it like you mean business from inside out.

Make sure you don't bang anything else, and make some noise.

clankford, a ball pein hammer is not enough mass. Use a short handled sledge hammer and give it a good rap. As far as the set screw ... it would be better to remove it, and instead leave one lug bolt engaged a turn or so because when the rotor does break loose it will do so suddenly. You wouldn't want a rotor landing on you if you're laying under the car to whack it from behind. Also, if hitting the rotor from the back doesn't work give it a few whacks from the front too.

Yes, I had the calipers hung from above with the locating screw removed and a lug bolt loosely installed for protection. I think I now understand how hard to hit it! (make some noise!) THAT is something we understand in Texas! :D