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-   -   My 3's First Brake Job at 76K (http://www.bimmerfest.com/forums/showthread.php?t=648541)

jertronic 09-27-2012 11:25 AM

My 3's First Brake Job at 76K
 
Last week my 'brake' pad wear sensor tripped the dash warning light for the front brakes.

Mileage is 76K, I am the original owner and the computer indicates that the rears will be due in 3300 miles.

The time has finally come to have my trusted Indy replace the pads and rotors.

I have to mention that the lifespan of my brakes leave me completely impressed with BMW.

2 Questions:

-What is the typical lifespan interval of BMW 3 series brakes?

-How do BMW brakes compare with the competition in terms of lifespan?

Zooks527 09-27-2012 11:59 AM

Quote:

Originally Posted by jertronic (Post 7100064)
Last week my 'brake' pad wear sensor tripped the dash warning light for the front brakes.

Mileage is 76K, I am the original owner and the computer indicates that the rears will be due in 3300 miles.

The time has finally come to have my trusted Indy replace the pads and rotors.

I have to mention that the lifespan of my brakes leave me completely impressed with BMW.

2 Questions:

-What is the typical lifespan interval of BMW 3 series brakes?

-How do BMW brakes compare with the competition in terms of lifespan?


1 ) Totally dependent on how you drive. I do 90% highway and I'm at 82,000 on the original set now.

2 ) Based on the "miles to go" indicator, the BMW's brakes will last about about the same as my VW Passat's original brakes lasted.

matts335 09-27-2012 12:06 PM

My rear pads had to be replaced at about 22,000 miles (about 3-1/2 years). Fronts still had a long way to go. I thought that was pretty odd.

I do spend a lot of time sitting in traffic, but I'm not that hard on my brakes. Or at least I didn't think I was. ;)

DSXMachina 09-27-2012 12:25 PM

Quote:

Originally Posted by matts335 (Post 7100140)
My rear pads had to be replaced at about 22,000 miles (about 3-1/2 years). Fronts still had a long way to go. I thought that was pretty odd.

I do spend a lot of time sitting in traffic, but I'm not that hard on my brakes. Or at least I didn't think I was. ;)

It is odd, rear pads generally last at least two sets of front pads. (In a hard stop, more than 90% of the braking is being done by the front brakes. In fact there is a device called a proportioning valve which reduces the pressure to the rear brakes to reduce the chance of lockup which would activate the ABS.)
What was the reason you needed rear pads? Excess wear? Was it warranteed?

matts335 09-27-2012 12:39 PM

Quote:

Originally Posted by DSXMachina (Post 7100181)
It is odd, rear pads generally last at least two sets of front pads. (In a hard stop, more than 90% of the braking is being done by the front brakes. In fact there is a device called a proportioning valve which reduces the pressure to the rear brakes to reduce the chance of lockup which would activate the ABS.)
What was the reason you needed rear pads? Excess wear? Was it warranteed?

It never reached the sensors, but the computer said they were due soon (don't remember how many miles left...maybe 1000, maybe 2000), so my SA had it done under warranty while I was there for something else. I certainly wasn't going to complain about getting free pads.

I don't know if they looked at them and found that there were actual worn down....just one of those "computer said so" type of things I guess. :dunno:

He didn't seem surprised and said it was common for the rears on these cars to wear out first.

I actually got the same story on my old VW jetta. Rears wore out way before the fronts, and the mechanic also said it was common for those cars.

Bemo 09-29-2012 05:57 AM

My rear ones are on track to wear out about 15K sooner than the front ones...I also thought it was "normal" until I read DSX' response above. Hmm....

laser 09-29-2012 06:23 AM

Quote:

Originally Posted by Bemo (Post 7103421)
My rear ones are on track to wear out about 15K sooner than the front ones...I also thought it was "normal" until I read DSX' response above. Hmm....

It's widely reported that the BMW 3 and 5 series wear the rear brakes out faster than the fronts. This has been my experience on three 3's and two 5's.

Some have speculated that the DSC is often applying the rear brakes on hard acceleration. I don't drive that hard regularly but have always replaced the rears first on these cars.

Bemo 09-29-2012 08:14 AM

Quote:

Originally Posted by laser (Post 7103446)
It's widely reported that the BMW 3 and 5 series wear the rear brakes out faster than the fronts. This has been my experience on three 3's and two 5's.

Some have speculated that the DSC is often applying the rear brakes on hard acceleration. I don't drive that hard regularly but have always replaced the rears first on these cars.

I wonder if the rear brakes are being applied a tad more to prevent body roll during hard braking but this line of thinking runs contrary to DSX's comments...

Snipe656 09-29-2012 08:25 AM

I have read that the rears go out quicker because the cars apply them automatically for some scenarios. The two I remember being cruise control and traction control.

DSXMachina 09-29-2012 10:00 AM

Quote:

Originally Posted by DSXMachina (Post 7100181)
It is odd, rear pads generally last at least two sets of front pads. (In a hard stop, more than 90% of the braking is being done by the front brakes. In fact there is a device called a proportioning valve which reduces the pressure to the rear brakes to reduce the chance of lockup which would activate the ABS.)
What was the reason you needed rear pads? Excess wear? Was it warranteed?

Quote:

Originally Posted by Bemo (Post 7103421)
My rear ones are on track to wear out about 15K sooner than the front ones...I also thought it was "normal" until I read DSX' response above. Hmm....

Quote:

Originally Posted by laser (Post 7103446)
It's widely reported that the BMW 3 and 5 series wear the rear brakes out faster than the fronts. This has been my experience on three 3's and two 5's.

Some have speculated that the DSC is often applying the rear brakes on hard acceleration. I don't drive that hard regularly but have always replaced the rears first on these cars.

Quote:

Originally Posted by Bemo (Post 7103571)
I wonder if the rear brakes are being applied a tad more to prevent body roll during hard braking but this line of thinking runs contrary to DSX's comments...

Quote:

Originally Posted by Snipe656 (Post 7103586)
I have read that the rears go out quicker because the cars apply them automatically for some scenarios. The two I remember being cruise control and traction control.

Very interesting comments. From a brake size standpoint(pad surface area and rotor swept area) there is nothing unusual about the E9x rear brakes. They seem to compare favorably to the E46 brakes and the brakes on similar sports sedans and coupes, too. So from a mechanical standpoint I can't see a reason that rears would wear before the fronts.
Because the E9x's are just coming off warranty my shop has not seen many for brakes, and the ones we have seen (including mine) have shown front pads to wear the same as, or more than, the rear pads.
It is very possible you are on to something with the point about DSC activation, and traction control with the 'phony' LSD effect. That certainly would increase the activation of the rear brakes while not activating the fronts. Maybe we'll learn more as time goes by and our sample increases.

Edit: The next time I have a chance I'll compare rotor temperatures, front vs. rear, after some spirited driving. That'll give a real indication of what is going on with the brakes. Then I'll shut off DSC and do it again. If DSC is responsible for increased rear brake application I should see a significant drop in rear rotor temperature when it is shut off.

Snipe656 09-29-2012 10:04 AM

BTW my car was saying it was going to need rears soon and upon visually inspecting things found it was lying to me. Since it is still under warranty I mentioned it to the dealer while they had it, they looked at the pads and reset the computer due to it clearly lying about when things need to be done. But I am a far cry away from the OP's mileage, I am sitting right around 31k miles right now.

harkirath 09-29-2012 10:07 AM

My '09 is showing 900 until rear brakes and 30k until the fronts.

It's at 26k right now with brakes not being done before. The SA said average for front breaks is 15-25k.

Snipe656 09-29-2012 10:20 AM

Quote:

Originally Posted by harkirath (Post 7103725)
My '09 is showing 900 until rear brakes and 30k until the fronts.

It's at 26k right now with brakes not being done before. The SA said average for front breaks is 15-25k.

Since mine is an 09 as well I'd have to wonder if yours is "lying" just like mine did. Or if it truly does need pads.

harkirath 09-29-2012 10:28 AM

I was at the dealership yesterday because I'm hearing a lot of squealing coming from the back brakes as well as a metallic scratching sound.

He said the backs are worn and the sensor is probably touching the rotors. I could get them replaced right now but as it still shows 900 on the rear brakes, I am waiting in an attempt to get the rotors below the threshold and replaced before my free maint ends.

The SA did say that the rear brakes do wear quicker than the front ones. Something about how it applies them to prevent oversteer.

Lufthansa 09-29-2012 11:47 AM

I noticed on a cross-country trip last year that when I used the cruise control to decelerate by pulling the stalk in to decrease speed at 5 mph intervals, the car appeared to brake down to the new speed selected. When I disengaged the cruise, no braking was evident. My admittedly unsupported belief is this could be a major factor in the rear brakes needing replacement prior to the fronts.
I haven't decelerated using the cruise control since.

matts335 09-29-2012 01:27 PM

I'm having a hard time believing the "DSC and traction control" theory. I've probably driven aggressively enough to trigger those things maybe 20 times in the life of the car. And for short bursts, not long drawn out sessions. (I know, shame on me). I also have AWD, so the traction control is less of a factor....if at all.

Perhaps they just overcompensated...giving the fronts way more than they needed? I know the front rotors are bigger...not sure how much bigger. I don't know. I'm just glad I got them changed under warranty.

Saintor 09-29-2012 02:36 PM

I don't rely on sensors.

My rear pad were changed at 40000 miles and I am still on original front brakes (pads and rotors) at 70000 miles. This despite I have heavy traffic every day. Go figure.

astirling 10-04-2012 06:58 AM

Quote:

Originally Posted by Lufthansa (Post 7103893)
I noticed on a cross-country trip last year that when I used the cruise control to decelerate by pulling the stalk in to decrease speed at 5 mph intervals, the car appeared to brake down to the new speed selected. When I disengaged the cruise, no braking was evident. My admittedly unsupported belief is this could be a major factor in the rear brakes needing replacement prior to the fronts.
I haven't decelerated using the cruise control since.

Do you think that cruise control might be using the rear breaks to maintain speed when going downhill? That could explain the wear a little.

Snipe656 10-04-2012 07:04 AM

Quote:

Originally Posted by astirling (Post 7112954)
Do you think that cruise control might be using the rear breaks to maintain speed when going downhill? That could explain the wear a little.

I have read many times that the cruise control uses the rear brakes for any slowing down. Makes sense that it would be using the brakes because my BMW does not pick up speed going downhill with the cruise control but all of my other cars do.

Lufthansa 10-04-2012 07:44 AM

+1.

Bemo 10-04-2012 08:45 PM

I've used cruise control maybe 5-6 times in the past 2 years. I don't think this explains the 15k-mile difference in the CBS indicator, claiming that the rear brakes will be due 1st.

DSX - any luck with taking the temperature measurements? I might have to beat you to it by using my fine, laser thermometer, which gets its typical workout with our outdoor pizza oven. :p

Snipe656 10-05-2012 03:55 AM

Quote:

Originally Posted by Bemo (Post 7114692)
I've used cruise control maybe 5-6 times in the past 2 years. I don't think this explains the 15k-mile difference in the CBS indicator, claiming that the rear brakes will be due 1st.

With my car it was claiming rear brakes were due soon and it was not the truth at all. I know this happened to one of my friends as well. As far as why that happened then who knows for sure, perhaps BMW programmed flawed logic to calculate wear on the pads based upon assumptions "traction control" and cruise control and so on would be used more often OR perhaps it is flawed logic in how it calculates wear/tear when those items are used OR ... well who knows for certain.

astirling 10-05-2012 04:26 AM

How do you deal with this then? Do you just ignore the warnings on the idrive until they're actually due for a change? Can dealerships get out of completing warranty type work by claiming that you did not have the brakes changed on schedule?

Yeoman 10-05-2012 05:32 AM

Quote:

Originally Posted by Snipe656 (Post 7103586)
I have read that the rears go out quicker because the cars apply them automatically for some scenarios. The two I remember being cruise control and traction control.

:loco:

Snipe656 10-05-2012 05:37 AM

In my case I had seen my brake pads were fine when at a tire shop. So next time I was at the dealer for some other service I told the that the rear brake indicator is coming soon and can they look at the pads. I never told them I had looked at the pads. They looked at it and said pads are fine and reset the computer. I forget how he explained the reset though because it did not seem like they simply told the car it had a rear brake job.


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