1. Hey I am getting ready to do brakes on my E 320. I noticed the rear discs are held on by a strange axel nut. What size is this thing or how can I remove the disc to get them turned.

2. Are there any tips or tricks to doing the front brakes. I am also turning the rotors there also.


Thanks
Brian Felts

 

Brian your back rotors as well as your front rotors use a 5 mm hex screw to hold them in place. But first you must remove your brake caliper which is held in by 2 caliper bolts. So first remove your caliper bolts and then loosen your hex screw. You might have to use a hammer to loosen the rotor.

 

Hey thanks for the reply, I had the back tires off and it look like there was a large axel nut holding the rotor to the hub (in the rear) I did see the hex screws you spoke of. Are the Hex's the only thing holding them to the hub.


Thanks
Brian

 

Yes, the 5mm hex screw is the only device holding the discs to the hubs. The large nut you speak of is the wheel bearing.

Machining the old discs is not a recommended practice for Mercedes. You will be best off buying new discs; they're not expensive.

 

I have seen where Benz does not want the rotors turned but I believe that is just to sell more when you are at the dealership. There is only a micron of metal removed. I had a 740 IL (RIP) and BMW wanted the same thing but turning them never hurt. I could see it if they were way out of spec. I don't have any warpage just want to give the pads a good clean surface to seat to.


Thanks
Brian Felts

 

Yep...you can certainly turn them once or twice...not a big deal, especially on the rears. True, MB doesn't recommend it, nor do they recommend synthetic fluids...but so far they have been fine in my car for several years.

Rear rotors are like $38 each for Brembo replacements from TireRack btw.

 

Depends on who does the turning. If done wrong, then heat treatment of the metal is changed and the disks can get warped again just the same. Have you measured the run out on the disks and is it out of spec? I have turned brakes to correct runout before and had the same warp reappear in very short time. Also, removing metal, no matter if you think its only going to be a micron, it straight up bad practice on these disks. Every gram of metal is needed to help the brakes from fading. Same deal on motorcycle disk brakes, you never ever turn them. The rear disks are really cheap. Either just throw on a new set of pads and let them bed into the old disks, or replace both disks and pads together. MB does have a special set of pads they use in the shop to scour the disk surfaces. They install them, drive the car around a bit, then remove them and install new pads. Not worth the hassle really. Either bed in new pads onto the old disks really well, or if out of spec with the micrometer or runout with a dial gage, replace them. Hell, you can replace them for less than $30 per disc. It would probably cost you more to get them turned than that, unless you have your own lathe.

 

I get charged $5.00 a disc for getting them turned. I just know that on every car I have done brakes on except Mercedes or BMW they are usually giving us two turn downs before the rotors go out of spec. I have just never liked the idea of bedding the new pads on the rotor surface with out roughing up the metal somewhat. I don't have any pulse in the brakes but the pads have crystalised. I believe the previous owner must have rode them a little but not hard.

I did get my Bentley manual today and WOW what a help!

Thanks All
Brian