[davidkotok]

Hi there,

Had a tire mounted on friday and the shop told me that my rear brakes were pretty much on their last legs but that the fronts are at 90%...

Could this be cause of DSC? Ive owned many bmws... and many cars in general and front brakes always go quicker. Anyone else have this experience?

[MrCairo]

I've seen this type of behavior from brakes where the calipers don't retract the pads enough and there is still drag on the pads. Did the mechanic physically check the break pads? I've heard of a software issue that caused the system to think the pad is lower than it actually is. I've also read that for some reason, E9x owners tend to see more rear break wear. I just forgot where I read that. . .

[davidkotok]

thanks for reply. it was from a visual inspection, I was hesitant to listen to them anyway, I keep good care of my cars and am usually on top of these things. I had other tires switched about 2 months ago and they told me rears were at 50%. Mainly i was alarmed about the huge delta between front and rears, and the fact that I typically run through fronts much quicker than rears but my first set of brakes for this car made it 40k and still had significant life left.

[Taipei-TT]

OP

I have had the same experience with my E92. I had the rear pads changed at 28000km whereas the fronts are still OEM at 40000km with more to go.

My first reaction was that something must be wrong with my rear brakes. (In other words, my rears wore out prematurely given how long the fronts were lasting.) However, no problems were found. The BMW independent shop I took it to is very well-regarded here in Taipei, and the owner, with years of experience under his belt, told me this is very normal in E92s. Depending on driving style, he has seen cars that the fronts get replaced once for every two changes to the rear pads.

[John 070]

Same experience here, I think my rears have 18k left, and the front 44k, with 32k on the odometer. In the old days premature wear was due to calipers being frozen (these one-sided floating ones). But today, I think it's DSC, traction, hill holder, etc. Look at the Honda Accord class action lawsuit--they had people needing new rear pads as frequently as every 15k, and the dealerships were telling customer that's normal. until the lawsuit....

[1QuikWS6]

Rear pads on my 09' replaced under warranty around 22k miles - fronts still original.

[EQUANT]

Rear pads in my E90 are at 54,000km and iDrive shows 1900 more km to go before change. I looked at them and, indeed, seem pretty worn, but they still have a few mm of thickness on them.
Will replace them when the sensor tells me to.

[Brad from the OC]

Originally Posted by davidkotok

Hi there,

Had a tire mounted on friday and the shop told me that my rear brakes were pretty much on their last legs but that the fronts are at 90%...

Could this be cause of DSC? Ive owned many bmws... and many cars in general and front brakes always go quicker. Anyone else have this experience?

Yes, I've been watching the threads to see someone else mirror my experience. I just changed front and rear pads on my 06 325i at 47K miles. At that mileage CBS indicated 16K for fronts and 19K for rears. Upon removal in inspection, the fronts had about 75% of pad thickness left and rears had about 25% of pad thickness left. This was my first pad change since purchasing the car as new.

If anyone on these threads know, I am curious why there was such a great disparity in the accuracy of the CBS regarding remaining pad life. From this experience, I think I will use visual inspection in the future to determine remaining pad life. I'm debating if it is worthwhile to spend the time and money to change out the sensors if I don't trust they are accuate. Visual inspections don't lie, and for years that was the way remaining pad life was determined.

[MrPig]

Don't quote me on this, but I believe (seen this explanation floating around here) the car uses the rear brakes only when you're on cruise control. That's why the rears wear out faster than the fronts. I see the same behaviour on my e90 and I frequently use cruise control.

[DFW_M]

Originally Posted by MrPig

Don't quote me on this, but I believe (seen this explanation floating around here) the car uses the rear brakes only when you're on cruise control. That's why the rears wear out faster than the fronts. I see the same behaviour on my e90 and I frequently use cruise control.

What?
I NEVER used the cruise control.
The computer says 45k left on the fronts and 13k left on the rears...

[Brad from the OC]

Originally Posted by MrPig

Don't quote me on this, but I believe (seen this explanation floating around here) the car uses the rear brakes only when you're on cruise control. That's why the rears wear out faster than the fronts. I see the same behaviour on my e90 and I frequently use cruise control.

I never use cruise control. Something else to think about in my situation, I replaced my OEM pads with Cool Carbons S/T. Since the CBS does not know what I installed and the appropriate wear rate for the pad material, how accurate will the CBS be in the future with my new pads? Does the CBS determine remaining pad life on pad thickness measurement or use some type of algorithm that use driving style?

[MrPig]

That's why I said not to quote me, as I wasn't 100% sure


I was under the impression the CBS used some sort of wear sensor that had to be replaced with the pads/discs.

[Brad from the OC]

Originally Posted by MrPig

That's why I said not to quote me, as I wasn't 100% sure


I was under the impression the CBS used some sort of wear sensor that had to be replaced with the pads/discs.

I purchased new front and rear sensors along with new front and rear pads when I did my brake pad change. With the new pads and the CBS reset, it now shows 50K pad life remaining. But even with new sensors and pads, and from my past experience I will doubt the accuracy of the sensors regarding remaining pad life. Maybe the new sensors will serve the purpose of indicating when pads need to be changed.

Does anyone on these threads have any experience where they waited until the red light came on indicating pads must be changed and upon pad removal found that the CBS was accurate? Also if the CBS was accurate in determining when pads needed to be changed, did the CBS also properly trend remaining life from the time the pads were new?

Maybe all of this discussion is for those who don't do their own pad replacements and brake fluid flushes. Since I do my own for both, I'm just going to use visual inspections every 2 years when I do my brake flush. I think from my experience, I trust my eyes more than the CBS.

[davidkotok]

I agree with you, we are talking about both a visual inspection and iDrive in my case.

I always wait till the real sensor trips, and then wait a bit more but I was just surprised - my car says fronts have 60k left and rears have 1600.

[Taipei-TT]

Originally Posted by Brad from the OC

Does anyone on these threads have any experience where they waited until the red light came on indicating pads must be changed and upon pad removal found that the CBS was accurate? Also if the CBS was accurate in determining when pads needed to be changed, did the CBS also properly trend remaining life from the time the pads were new?

Hi Brad,

I didn't wait for the red light and, like you, prefer to rely on visual inspection. However, the computer indicated 1200km left when I changed my rear pads. After taking them off, that estimate looks pretty accurate. In addition, though my front pads seemed initially to be fairly worn, the computer indicated 27000km to go. 15000km later, my pads are still fine. I would have changed them at 27000km had it not been for the car's estimate...which proved to be more accurate then the shop's guess that it was about time to change.

So overall, the CBS seems to be a very useful guideline that complements qualified visual inspection.

On another note....I need to change my brake fluid in July (2 years at that point.) I've read it's a good idea to change the brake pads and then the fluid, true? If so, I will change out my front pads a little earlier when I have the fluid changed.

[Brad from the OC]

Originally Posted by Taipei-TT

Hi Brad,

I didn't wait for the red light and, like you, prefer to rely on visual inspection. However, the computer indicated 1200km left when I changed my rear pads. After taking them off, that estimate looks pretty accurate. In addition, though my front pads seemed initially to be fairly worn, the computer indicated 27000km to go. 15000km later, my pads are still fine. I would have changed them at 27000km had it not been for the car's estimate...which proved to be more accurate then the shop's guess that it was about time to change.

So overall, the CBS seems to be a very useful guideline that complements qualified visual inspection.

On another note....I need to change my brake fluid in July (2 years at that point.) I've read it's a good idea to change the brake pads and then the fluid, true? If so, I will change out my front pads a little earlier when I have the fluid changed.

If the two year interval or within a couple of months since the last brake fluid change is due and if your pads need to be replaced, then it might make sense to change the pads and then flush the fluid. If you are doing the job yourself, the advantage is that your car is already up in the air, the tire and wheel is already removed, the hood is up and the brake fluid reservoir is exposed. That's about more than half the time to do a fluid flush from the beginning representing a large time and effort savings. Also by doing the flush after the pad change insures that any air bubbles or contamination from the pad change is flushed out and replaced with new fluid.

Since you change your pads before they are worn out, you might as well time it so that you do both jobs on the same day.

[ed1981]

Originally Posted by davidkotok

I agree with you, we are talking about both a visual inspection and iDrive in my case.

I always wait till the real sensor trips, and then wait a bit more but I was just surprised - my car says fronts have 60k left and rears have 1600.

Mine is that same, 2000 remaining on rear and 60,000 on front. I'm asking Service at BMW to check it along with my next oil change.

[Taipei-TT]

Originally Posted by Brad from the OC

If the two year interval or within a couple of months since the last brake fluid change is due and if your pads need to be replaced, then it might make sense to change the pads and then flush the fluid. If you are doing the job yourself, the advantage is that your car is already up in the air, the tire and wheel is already removed, the hood is up and the brake fluid reservoir is exposed. That's about more than half the time to do a fluid flush from the beginning representing a large time and effort savings. Also by doing the flush after the pad change insures that any air bubbles or contamination from the pad change is flushed out and replaced with new fluid.

Since you change your pads before they are worn out, you might as well time it so that you do both jobs on the same day.

Thanks! I will do the brake pads at an independent shop, but for used car value, I need to get the brake fluid done at BMW so that my maintenance schedule documents all routine maintenance done by BMW. Thanks for the information!

[Rydicule]

2007 335i e90, no X-drive.

I have the same experience. The rear brakes got down to about 1500 miles left on the system screen, with the fronts at about 26,000 miles left.

So I said eff it, spent about $800 on 4 sets of pads, 4 rotors, brake fluid, and a 1-man bleeder tool. Did the rears, and the system was pretty accurate. The rear pads were fairly chewed, which doesn't surprise me. The car had 75,000 miles on it and had the original pads.

However, the front brakes shocked me. I expected them to be at least as worn, but they weren't. In fact, they were really in pretty good condition with at least 4X as much pad left as the rears. I decided to just bleed the fronts and then I reset the rears. Right now it has them at 49,000 miles of life left.

Odd thing though... about 3 weeks after I did that, the brake indicator came on as if the sensor was tripped. I can't really think why changing the rears would cause the front to wear any faster, let alone THAT much faster, aside from the bedding process. However, I decided to see if it was just playing tricks on me and reset the lights. So far, fronts say 90,000 miles life and the rears 49,000...

should be interesting.

[Cisco661]

the rear pads on my 330i have seemed to wear out faster than my fronts. not for sure but i figured since the non XI models are rea wheel drive that thats why the rears wore out faster. i just figured that the breaks had to use more force on the rears becuase thats where most of the power to wheels went. i could be wrong though. ive learned to trust what my the CBS on my IDrive says. Also everyone should make sure to change out the sensor whenever doing a pad change because it might be a reason for bad readings or squeaky tires.

[Potty_Pants]

yes this is normal.

my last car G35 experienced the same...

please note the following...

larger brakes on the front = longer life

smaller brakes on rear and they will activate with traction control and consequently wear out.

no worries.

ppp

[n55x3]

you gotta also take into account that most new cars with electronic brake force distribution tend to brake mostly with the rears under light braking situations which probably accounts for most of your stops. These newer cars, and not just in BMW, drag the rears quite a bit to make the stop more comfortable, essentially trying to eliminate nose dives.

If you stopped very aggressively on the daily you'd see much more even wear. In hard stops the brake force is applied more evenly, probably even a little front biased, thus getting a quicker stop due to using the larger more powerful front brakes.