taeandji

I'm trying to replace my brake pads and rotors for 2011 GL350 which now has about 51,000 miles. I know pads are gone and I can see lines on outer edge on rotors. Do I need to replace rotors at the same time as I'm replacing pads ( I know it needs to be measured though)? For pads, I'm going with Akebono pads but not sure about rotors...
As I was browsing RockAuto.com and noticed that there are 2 different sizes of rotors... 373mm vs 350mm. I called my dealer and found the part number for front brake rotor of my GL350 is 1644211412... can someone tell me if this is 373 or 350? Also, should I go with oem rotors or after market rotors?

taeandji

I guess I'm answering to my own post lol
found out that part number 1644211412 is for 350mm in case someone needs it.

BTW, should I replace my rotors?

N_Jay

I would bet you don't need rotors. But do measure them.
Are you doing all the brakes or just front?
Generally you can get 2 sets of pads between rotor changes.
Seems front pads run about 50K and backs about 100K but depends on driving style.

MJ50

u should resurface the rotors b4 u put new pads...
but for the cost of resurfacing, might as well spend little more and get new rotors IMO...

N_Jay

If you think they need resurfacing, just replace them. If they are relatively flat, have no grooves and no irregular wear (and the brakes stop smoothly), you are probably just as good not resurfacing.
It is a personal choice.
Fronts I tend to be a bit pickier as to how good they have to look to keep them.


P.S. Not arguing with a MOD, just showing there are a range of opinions on the topic.
P.P.S. I have never seen the value in resurfacing, unless you REALY can't afford new rotors, the old rotors NEED it, and you can get it done WELL and CHEAP.

BlownV8

I didn't resurface mine. They were good to 100k. Only resurface if necessary.

alx

The x164 rotors have well defined lip which does not denote wear.

Unless bent or badly scored (typical for the plebeian single piston rear setup) you do not need to resurface or replace rotors.

texas008

Thanks for the tip.
FCPeuro website says the rotor needs to be replaced if there is a lip. I almost placed an order on new rotors.

N_Jay

I have NEVER seen a rotor with a lip from the factory.

lkchris

Yes, it’s simply incorrect to state new rotor has lip.

STANDARD practice with these vehicles is replacement of pads and rotors at same time, every time. New pads for these vehicles are quite thick and their life is essentially that of the rotor — 2mm wear. It’s forbidden to put used pads against a new rotor, and if you do just replace pads, it’s guaranteed the rotor will reach its wear limit before those new pads are worn out. That is a waste of money, then.

resurfacing Mercedes rotors is never authorized by Mercedes and it’s in fact ridiculous to think it would be.

just understand … experience with ‘merikun iron is 100% irrelevant to Mercedes.

Diamond Dave

I find this sentiment both derogatory and pompous. First of all, you are leveraging information from the same company that insisted the 722.9 transmission was a lifetime fill and it clearly isn't. Second, It successfully scares of many owners or budding DIY'ers. The truck will not implode if you surface the rotors. Mercedes brake rotors are not exempt from basic physics and engineering, although it does help to understand the engineering design language.

N_Jay

Issue is years ago rotors were way over built.
they had a lot of extra metal to shave off and could usually be cut two or more times.
All carS have upped the precision of their engineering and efficient design. So there is much less wasted material and less margin.
given that rotors have generally gotten less expensive, and labor has gotten more expensive, so it hardly ever is worth cutting them.

Max Blast

A 2mm allowable wear range between new and min thickness pretty much means no machining authorized. There’s little chance you'll be able to clean up a normally worn rotor within those values.

eric_in_sd

lol well put

There are those who think MB has a warehouse of pixies from which magic dust is extracted to sprinkle into various components like brake rotors.

eric_in_sd

I don't have the components to compare side by side, but I disagree with the first part. The MB rotors, front at least, are massive, not skimpy.

I believe what has changed is expansion of product liability. MB is safest just telling people they have to change the rotors. MB is thus shielded from liability due to people improperly machining rotors, and bonus gets to sell more rotors.

N_Jay

Yes, heavy cars have big brakes, but the margin between new and minimum service thickness is not what it was.

I don't think it is liability, or we would see it on all cars, but more about maintenance philosophy.
MB seems to work on the premise that their owners want to bring the car in once a year and never more.
All service seems to start with thinking that car should be as close to new as practical and remain so for the following year of service.
When you bring it in, if there is a chance the brake pads won't last a year, you end up buying new pads.
If there is a chance the rotors won't last the pads, you also get new rotors.