A surprise: Back brake pads worn out, not front

[Emory]

Last week, my warning light went off, indicating my brake pads were low. I've got 52,800 on my car. I had replaced my pads on my prior BMW, an E36, which gave me lots of satisfaction when I had completed the work (and it really wasn't that difficult if you followed the instructions.) There aren't any E90 instructions online, but I was aware the BMW brake technology hadn't changed.

I ordered the front brake pads and rotors and the sensor online. I had today off, so I was eager to do this. I had made one assumption (a fairly safe one, I thought) - that it was the fronts that were worn.

So, this morning, I got everything ready - the pads, rotors, hex head sockets, C-clamp, brake cleaner, brake fluid, hydraulic jack. I even got out the camera and was ready to document each step, as a service to this board. The first step was, hey, where's the brake fluid reservoir? (It's hidden under a snap-off cover to the left of the cabin filter cover). I then played with the reset button next to the speedometer to see how I would reset the warning light. As the service interval icons went past, I saw the brake pad warning lights, and .... no, this can't be right! ..... the back pads were lit up red. Sure enough, when I took off the front wheel, there was plenty of pad left. The back pads showed they were down to 2 mm.

I am stunned. When the warning light went off last week, I felt the rotor without taking off the wheel, and there was a good ridge on the rim. The back rotors had no ridge. On my E36, I sold it at 118,000 miles, and I never did the back brakes (they were not worn.)

Anyone else have this experience? Let this be a precaution to all.

[sickem]

as I understand it, this is a well-known phenomenon. did you search?

[Emory]

as I understand it, this is a well-known phenomenon. did you search?

I was not aware it was a phenomenon. I do read this and other E90 boards and I've never seen it mentioned. As the median E90 is around 2-3 years old, most owners have not had to deal with brake wear. I'm at the end of the bell-shaped curve because I have the first production year E90.

I'm surprised because my back rotors showed very little wear and that in rear wheel drive cars, the fronts absorb about 60-70% of the brake load. My front wheels are always covered with brake dust; my rear wheels, not so.

[gary88]

The rears can wear out faster when the traction control kicks in a lot, no real surprise.

[Emory]

The rears can wear out faster when the traction control kicks in a lot, no real surprise.

I'm in the San Francisco Bay Area. Not a lot of snow, ice or slippery roads here.

[spitpilot]

I'm in the San Francisco Bay Area. Not a lot of snow, ice or slippery roads here.
Seems like maybe BMW has followed VW in setting up brake bias...more on rears than fronts...In the daze B4 ABS automotive engineers always leaned hard on the front brake bias to make sure the rear wheels never locked up B4 the fronts did and cause a spinout. Now with ABS that's not a concern, so putting more bias on the rear is safe, and doing that reduces "dive" on hard braking.

[mattjw916]

Pretty sure my 325 has gone through a set of rear pads as well... it was covered under maintenance so I really didn't ask when they replaced them IIRC.

[Mach2]

I had to change rear on my 06 330 at about 46k milie. But the jap cars were holding up much longer.

[sickem]

I'm in the San Francisco Bay Area. Not a lot of snow, ice or slippery roads here.

a lot of hills though, no?

[spitpilot]

a lot of hills though, no?

But not tall enuff to put much strain on brakes!...What usually goes in SF is clutch..cause folks don't know how to drive..."hang car on clutch" at intersections etc...instead of using "hand brake start"..which the BMW's hill holder feature renders obsolete...If you really know how to drive manual car..no issues in SF..and brakes aren't an issue..not like living up in the mountains above Santa Cruz or tahoe, where brakes might get a real work out!:(

[sickem]

But not tall enuff to put much strain on brakes!...What usually goes in SF is clutch..cause folks don't know how to drive..."hang car on clutch" at intersections etc...instead of using "hand brake start"..which the BMW's hill holder feature renders obsolete...If you really know how to drive manual car..no issues in SF..and brakes aren't an issue..not like living up in the mountains above Santa Cruz or tahoe, where brakes might get a real work out!:(

gotcha

[Guerc]

But not tall enuff to put much strain on brakes!...What usually goes in SF is clutch..cause folks don't know how to drive..."hang car on clutch" at intersections etc...instead of using "hand brake start"..which the BMW's hill holder feature renders obsolete...(


Depends where you are. Cupertino or East Bay are pretty flat. In the city of SF, the taxi drivers can go through a set of brakes a month. Those guys haul ass though, and they don't avoid the hills (probably seek them out to avoid traffic on the main streets).

[Tamsupremepower]

I was surprised when my SA told me too! :D

[mattjw916]

Some new information: Just took 335 in for routine service and mentioned the brakes were squealing a bit as I pulled away from lights, etc. SA said there was an uprated sensor for the rear brakes to fix the squeal so they swapped that and the rear pads.

[Chromisdesigns]

Seems like maybe BMW has followed VW in setting up brake bias...more on rears than fronts...In the daze B4 ABS automotive engineers always leaned hard on the front brake bias to make sure the rear wheels never locked up B4 the fronts did and cause a spinout. Now with ABS that's not a concern, so putting more bias on the rear is safe, and doing that reduces "dive" on hard braking.


I think this is the case, as well. Same thing happened with my E36 M3, much to my surprise! Front brakes outlasted rears about 2 to 1.

[krobo65]

Mine rear brakes went out at 48k and BMW on replaced the pads, I just the fronts at 72k and they still had some padding left, but I was told to replace them before the sensor goes off and won't have to replace the sensor.

[grazhoppa]

I had to change rear on my 06 330 at about 46k milie. But the jap cars were holding up much longer.

Do you have to use language like that?