Mercedes-Benz GLA Forum banner

1 - 15 of 15 Posts

·
Registered
Joined
·
20 Posts
Discussion Starter #1 (Edited)
I haven't found a good guide anywhere that describes how to do the brakes on the GLA45 so I decided to make one. This brake job is just like any brake job with two notable exceptions:

  1. Mercedes uses E Torx, which not everyone has in their toolbox
  2. The electronic parking brake has to be released from the multifunction display
Notes:
  • When the brake pad wear indicator comes on in the car, there is still 40% of the pad left (see picture). Mine came on at 59,000 miles.



  • The rear calipers do not require the special caliper tool which rotates the piston in order to compress it. Because the car has an electronic parking brake, there is no need for a ratcheting/rotating piston like there is on most other cars that have mechanical parking brake.
  • The rear rotors can be changed WITHOUT removing the caliper carrier.
  • The front calipers are quad piston front load style (the pad slides in from the front of the caliper)
  • I am 100% certain that the OEM front brake pads and calipers are manufactured by Brembo because both had stamp/casting marks. I am 98% certain that the OEM rotors are also Brembo. I bought Brembo rotors for less than 1/2 the cost of rotors from the dealer and from what I can tell they are identical to the OEM ones. The only thing I am not sure about is whether they use a different coating from Brembo's "Green" UV coating. Time will tell how well the Brembo coating holds up.
Weird Tools:
  • 10mm External Torx bit (E10) (wear sensor holder)
  • 18mm External Torx Bit (E18) (caliper carrier bolts)
  • Torx bit/driver (forgot to note which size - needed to remove the rotor retaining screw)
  • Skinny 17mm Box Wrench (Optional - for rear caliper pins)
Normal Tools:
  • Small mallet/hammer
  • Small drift pin to drive the front brake pad pins out
  • Small Pry bar
  • Ratchet
  • Flat screw driver
  • 13mm Socket
  • 17mm Socket
  • Large Channel Locks
  • Some wire or zip ties to support the calipers while you install new rotors

Process:

Access the Brake Service Menu to release the pressure in the rear calipers.
  • key in accessory position
  • all doors and hood closed
  • Go to trip menu
  • before trip dissapears, press and hold call button
  • then press and hold OK button
  • hold both buttons down for 5+ seconds
  • The service menu should appear
  • Find the brake service line in the menu
  • Press OK to enter service mode
  • If it says "Conditions not correct" make sure your foot is off of the brake pedal, and possibly release the parking brake (pull the parking brake lever on the left bottom side of the dash)
  • When you are finished installing the rear brakes, you have to use this same menu to exit the fitting position.
Removing the rear calipers & pads:
  • The caliper slide pin bolts are removed first
  • The slide pins have a 17mm nut, but there is not enough space for a normal thickness box wrench. To get around this, I used a flat screw driver and wedged it against the bolt - by prying down I could achieve enough friction to hold the pin still while I loosened the bolt. An air ratchet makes doing it this way much easier.
  • After the slide pins are out, use your pry bar to pry between the caliper and the carrier to remove the caliper.
  • The pads should stay in the carrier (pry them out too)
  • Use channel locks to squeeze the piston back into the caliper. DONT PRY/SQUEEZE ON THE PASTIC part of the caliper.
Removing the front calipers, pads and rotors
  • The passenger side has the wear sensor - use the E10 bit to remove the sensor holder. Unplug the old sensor and move the wire out of the way so it doesn't get damaged.
  • Using a drift pin and your hammer, carefully drive the two brake pad retaining pins out. The push from the outside toward the inside. Once both pins are out, the spring clip will be free - save the pins and spring for re-installation.
  • Wedge a small pry bar or flat screwdriver in between the brake pad and the rotor, then pry in order to push the pistons back into the caliper.
  • After the pistons are collapsed, remove the pads
  • Using a piece of wire or zip ties, wire the caliper to the shock tower so it won't hang on the brake hose
  • Using the E18 bit, remove the two bolts holding the caliper to the steering knuckle.
  • With the caliper removed, you can now remove the torx screw holding the brake rotor to the hub. My new rotors came with allen drive screws - which are awful to deal with once they are rusted. I re-used my torx screws since torx is less likely to strip.
  • Put the new rotor on and install the retaining screw
  • Bolt the caliper back to the steering knuckle. I don't have the torque specs - but tight is good and loose is NFG.
  • Install the new sensor into the hole in the out side passenger side front brake pad. The Pagid pads I bought were directional - they had to be installed with the arrows pointing down (read the instructions for whichever pads you buy)
  • Remove the sticky back from the pad and slide them into the front of the caliper
  • Re-install the retaining pins - use a small hammer to tap them in. The spring will put tension on the second pin, I had to use my screw driver the push down & in on the pin as I tapped it into place.
 

·
Registered
Joined
·
146 Posts
Good.

Brake on this car have a pretty simple setup, very simple to do.
 

·
Registered
Joined
·
274 Posts
Thanks for posting this.

How do you like your rotor and pad selection, two months later? equal to the OEM performance? I am 100% happy with OEM and don't need an upgrade, but if you say the brembo rotors seem to be identical and are half price, that is very compelling to me, since OEM everything If I recall was around $1300 in parts from AutohausAZ. I'd also like to know which Pagid pads you selected and if you are happy with them now.

Do you have any thoughts on rotors that are not drilled or slotted? A buddy of mine prefers non drilled/non slotted with the same material choice, and just uses excellent pads to go with them. Claims he has no issues with heat, and he drives harder than I ever will.

I value the extra hand holding. This car is going to be the first car I tackle brakes on. Reason is exactly economic. For training, I tagged along with my buddy when he did his brakes recently (actually I did the whole job while he directed, who wouldn't want free labor? :)) and it seems straightforward. Though his caliper was 2 piston, not 4 piston or 1 piston. Anyway I'm still green so I appreciate extra info since I'll be tackling my car solo.

Another question, you said the pads have a sticky back, so does that mean you did not use brake grease on them?
 

·
Super Moderator
Joined
·
365 Posts
Thanks very much fahrvergnuugen for the outstanding writeup/pictorial. Really well done.

Whiterabbitt, if I may jump in here: There're good arguments to be made for slotted, slotted/drilled and solid rotors with respect to their relative heat dissipation. Over the years I've tried them all but my rule of thumb [now] is to follow what the OEM designers provided, as they did much research and testing and had a good engineering reason for same... at least on high end performance vehicles where beancounter interference is lessened.
The sticky backs on the shown pads keep them in place, negating the annoying sound reason for using grease on the backs of more conventional floating pads.
 

·
Registered
Joined
·
20 Posts
Discussion Starter #6
Regarding slotted/drilled vs solid, solid is better performing. Cross drilled is purely for aesthetics. https://www.good-guys.com/hotnews/truth-drilledslotted-brake-rotors/


I’ve had a major problem with vibration due to rust being left by the oem rotors on the hubs. I took everything apart and thoroughly cleaned the hubs with scotch brite pads, but there is still runout on the rotors which causes the brake pedal and steering wheel to vibrate when braking.

As I said in my original post, I’m 98% sure that the oem rotors are Brembo, so I’m quite sure this problem I’m having has nothing to do with oem vs non oem supplier.

My next step is to recheck the runout and put the rotors in a lathe to isolate the problem and answer the question: is it the hub or the rotor?
 

·
Registered
Joined
·
274 Posts
That was the conclusion my friend came to as well, claiming he can even feel the pad passing over the slots, so preferring a solid rotor surface.

What Pagid pads did you select? They seem to have a compound available for every kind of driving style.
 

·
Super Moderator
Joined
·
365 Posts
However the slots are there, in theory, to better allow airflow and thereby promote cooling. Again, there are compelling rationales for each type (but I too now favor solid).

That was the conclusion my friend came to as well, claiming he can even feel the pad passing over the slots, so preferring a solid rotor surface.

What Pagid pads did you select? They seem to have a compound available for every kind of driving style.
 

·
Super Moderator
Joined
·
365 Posts
I apply a thin coat of copper grease to the hub-rotor mating surface after similar scotchbrite cleaning. It helps preclude rust but of course not road dust.

...I’ve had a major problem with vibration due to rust being left by the oem rotors on the hubs. I took everything apart and thoroughly cleaned the hubs with scotch brite pads, ...
 

·
Registered
Joined
·
205 Posts
Regarding slotted/drilled vs solid, solid is better performing. Cross drilled is purely for aesthetics. https://www.good-guys.com/hotnews/truth-drilledslotted-brake-rotors/


I’ve had a major problem with vibration due to rust being left by the oem rotors on the hubs. I took everything apart and thoroughly cleaned the hubs with scotch brite pads, but there is still runout on the rotors which causes the brake pedal and steering wheel to vibrate when braking.

As I said in my original post, I’m 98% sure that the oem rotors are Brembo, so I’m quite sure this problem I’m having has nothing to do with oem vs non oem supplier.

My next step is to recheck the runout and put the rotors in a lathe to isolate the problem and answer the question: is it the hub or the rotor?

The hub mounting surface is likely your problem. Every vid I've seen they took a high speed wire wheel or light sanding wheel to completely shine the hub surface. Then apply anti-seize lube very lightly to surface for no more rust.


I'm surprised you got so many miles on your brakes, if you search here it seems the indicator comes on around 30k. I have 22k on my 2015 and last Christmas went and bought the complete OEM brake kits (excluding fluid and grease, but front/rear rotors, pads/clips, and sensor kit). At Christmas it was on sale for like $900 ish, but then ebay sent me a 20% code which I used, so I got the kit for $700 ish, below 800.
 

·
Registered
Joined
·
205 Posts
Also, I just checked my kit, the rear rotors are stamped on the lip around the outer part not only the size/dimension, but they say Brembo at the end. I was also told the rear calipers are Brembo and very expensive. Strangely my front rotors are not in like stamped around outer lip that they are Brembo, but they must be if genuine MB OEM parts as we know the front calipers are obviously Brembo. I forgot to check the MB boxes for rear, but front rotors say they are made in Italy.


I'm not sure I would jump to the same conclusion on solid rotors being "better". The drilling is done such that it can take advantage of the vein structure between the rotor surfaces on the inside, likely forcing cooling. Sure if you are not hard on the brakes and don't track the car, a solid rotor would be fine. These rotors are a softer, dense steel, so they have the mass due to sheer size and density of steel used, however they are also lighter in design due to rotor surface thicknesses, and drilling. A good overall design with what came with the car based on it's size, weight, AWD, etc. vs. a retro or mod where Wilwood is supplying a lot of the braking, including disc brake conversions on cars that are not anything remotely like our vehicles.
 

·
Registered
Joined
·
20 Posts
Discussion Starter #12
The hub mounting surface is likely your problem. Every vid I've seen they took a high speed wire wheel or light sanding wheel to completely shine the hub surface. Then apply anti-seize lube very lightly to surface for no more rust.
I used these and scoured the hubs clean:



I still have 5 thousandths runout on the edge of rotor hat and I am making an assumption that is the vibration I feel in the brake pedal.

The car is currently back up on stands while I try to figure out wth is wrong.


I'm surprised you got so many miles on your brakes, if you search here it seems the indicator comes on around 30k. I have 22k on my 2015 and last Christmas went and bought the complete OEM brake kits (excluding fluid and grease, but front/rear rotors, pads/clips, and sensor kit). At Christmas it was on sale for like $900 ish, but then ebay sent me a 20% code which I used, so I got the kit for $700 ish, below 800.
Even at 50k, I still had 30% life left on the pads.

My Golf R went 80k on the original brakes - I attribute the increased pad wear on the GLA compared to the Golf R to its added weight plus the fact that its an automatic.
 

·
Registered
Joined
·
20 Posts
Discussion Starter #14
Does anyone know what the acceptable amount of runout is for a fixed caliper brembo setup like what we have on the front of the GLA45?

I'm measuring 0.005" at the edge of the rotor hat. It doesn't seem like a lot to me, but something is causing the car to shudder like crazy and I don't know what else it could be.
 
1 - 15 of 15 Posts
Top