Need Expertise on Rotor Wear | 2009 C350
11-11-2016, 08:21 PM
#1
Super Member
Thread Starter
Need Expertise on Rotor Wear | 2009 C350
I know most mechanics try to sell you on pads and rotors.
My understanding is that you replace the rotors once they get grooves in them.
My rotors have grooves in them but did not look too bad. *See photo.
The car has 85,000 miles. I bought certified pre-owned at 48k.
Q. What is the rule of thumb here?
Rotor wear C350 2009
My understanding is that you replace the rotors once they get grooves in them.
My rotors have grooves in them but did not look too bad. *See photo.
The car has 85,000 miles. I bought certified pre-owned at 48k.
Q. What is the rule of thumb here?
Rotor wear C350 2009
11-11-2016, 11:03 PM
#2
Senior Member
I don't change rotors with light superficial grooves if there is no pulsing noticed at the brake pedal and they measure within tolerances .
Last edited by dennish; 11-12-2016 at 01:56 AM.
11-12-2016, 01:30 AM
#4
MBWorld Fanatic!
[QUOTE=Nicholi2007;6967137]I know most mechanics try to sell you on pads and rotors.
My understanding is that you replace the rotors once they get grooves in them.
My rotors have grooves in them but did not look too bad. *See photo.
The car has 85,000 miles. I bought certified pre-owned at 48k.
Q. What is the rule of thumb here?
FYI :My disc original thicknesses & wear limits. :-
Front - Ventilated :-
Original = 28 mm
Minimum before repair = 26.5mm
Minimum limit = 26mm
Max runout = 0.12mm
Rear- Solid.
Original = 10 mm.
Minimum before repair =8.8mm
Minimum limit =8.3mm
Maximum disc runout =0.15mm.
I found it difficult to measure accurately without a micrometer.
Ask the mechanic for the figures then you can make the decisions on when they can be replaced.
My understanding is that you replace the rotors once they get grooves in them.
My rotors have grooves in them but did not look too bad. *See photo.
The car has 85,000 miles. I bought certified pre-owned at 48k.
Q. What is the rule of thumb here?
FYI :My disc original thicknesses & wear limits. :-
Front - Ventilated :-
Original = 28 mm
Minimum before repair = 26.5mm
Minimum limit = 26mm
Max runout = 0.12mm
Rear- Solid.
Original = 10 mm.
Minimum before repair =8.8mm
Minimum limit =8.3mm
Maximum disc runout =0.15mm.
I found it difficult to measure accurately without a micrometer.
Ask the mechanic for the figures then you can make the decisions on when they can be replaced.
11-12-2016, 11:32 AM
#5
Micrometer is cheap at harbor freight ... Yep a little bit of grooving might be ok - but also check the "lip" on the edge of the rotor - and any cracking around the cross-drill vent holes -some autoparts stores will "turn" rotors for you - which might be a lot cheaper than getting new ones if they still meet thickness spec and otherwise look ok ...
11-13-2016, 06:37 AM
#6
Member
Well, is very easy to check if rotors need replacement.
I too will change my front rotors this days (its a w204 c220 cdi with ventilated discs at front).
In the life of the rotors, i have surfaced them once (theu had some grooves, ask to surface, cost me 5 € both).
But the rotors have a physical limit on them. Just search on the edge of the rotor a lip on it. Thats your limit!
Dont forget to check right, because the the rotor surface could more inner than the limit lip!!
By the way, i will buy ceramic pads for front!
I too will change my front rotors this days (its a w204 c220 cdi with ventilated discs at front).
In the life of the rotors, i have surfaced them once (theu had some grooves, ask to surface, cost me 5 € both).
But the rotors have a physical limit on them. Just search on the edge of the rotor a lip on it. Thats your limit!
Dont forget to check right, because the the rotor surface could more inner than the limit lip!!
By the way, i will buy ceramic pads for front!
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11-15-2016, 10:09 AM
#8
Super Member
Thread Starter
I ended up replacing the pads before I posted this as braking was extremely bad. I was concerned the brakes would go any minute 
I was hoping someone could look at by sight and tell. Wishful thinking.
I bought rotors so maybe next time.
Braking still feels a bit soft. Perhaps a break in period....
I was hoping someone could look at by sight and tell. Wishful thinking.
I bought rotors so maybe next time.
Braking still feels a bit soft. Perhaps a break in period....
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