Rear Pads need replacement before front pads

WallyF · 02-18-2011, 03:11 PM

Hi,

The OBC on my 2006 325xi is calling for the rear pads to be replaced in 3500 miles.

My experience with other than BMW cars is that the front pads wear down faster than the rear pads. This does not seem to be the case with my 2006 325xi. The rear pads have about 3/16 inch left and the fronts have over 3/8 inch left.

Does BMW use undersized rear pads? Or is there another reason?

Thanks

Wallyf

Lenaxia · 02-18-2011, 03:38 PM

If you've seen new OEM pads, the fronts are thicker than the rears I believe. At the very least, front and back thickness is not the same.

The HACK · 02-18-2011, 03:46 PM

NORMAL.

BMW's fancy DSC and DTC systems uses the rear brake pads to simulate the effects of a limited slip differential and if the car's driven mostly with DSC and DTC active, it's not out of the realm of possibility for the rear pad to wear faster than the front.

josephbet01 · 02-18-2011, 06:39 PM

Mine did the same thing. Rears wore out at 60k and I'm now at 70k and still have 50% left on the fronts. Lot of highway driving.

WallyF · 02-19-2011, 07:54 AM

The Hack,

I thought about the DSC and antilock brakes as the main cause. However, since I have X drive, the normal action is to transfer power to the front wheels before using the rear brakes for stability control.

Also, this is my wife's car. She drives non aggressively. I am more inclined to believe that BMW uses less material on the rear pads.

Any other ideas???

Wallyf

HP Autosport · 02-23-2011, 01:23 AM

There is a couple of solutions, either turn off the DTC system or get a LSD so you are not activating DTC as much. Turning off the DTC is free!

Undies · 02-23-2011, 04:07 PM

non aggressive drivers doesn't mean they drive efficiently when it comes to gas and brakes.

WilliamE92 · 03-01-2011, 11:13 PM

my rear pads are about to go out at 30k

is that normal in the 335?

9t2hoo · 03-02-2011, 01:06 PM

I'm going to be bummed when I have to pay for these on my own next year. BTW, they still haven't replaced my rear rotors. I'm hoping they'll do that during the next pad replacement while the car is still under the maintenance plan.

JonLerd · 03-05-2011, 10:41 PM

Quote:

Originally Posted by WilliamE92

my rear pads are about to go out at 30k

is that normal in the 335?

i had my rear pads replaced at 21k and i dont track or drive that aggressive.

Bullet · 03-06-2011, 08:03 PM

Quote:

Originally Posted by JonLerd

i had my rear pads replaced at 21k and i dont track or drive that aggressive.

... I had my rear pads replaced at 12,000 miles and now i had 19,000 and its telling me ill need rear pads again in 8,000 miles. Guess i just drive a bit harder?

The HACK · 03-07-2011, 12:23 PM

Okay, to answer your question...Yes the rear pads are thinner from the factory than the front pads. And NO it's not any thinner than any other BMW combinations. It's about the same proportion as any other BMW that came before it. The rear pads are typically thinner because under normal operation conditions the rear pads do less "work" than the front.

The reason why the rear pads wear out first is not because it's thinner though. It is two fold. First, BMW uses the rear brakes to simulate a limited slip. So if you're driving in low traction situations, or live in a climate where WINTER last more than 3 days, the rears are constantly being used and burned up to create artificial traction whether you like it or not, since the DTC e-Diff functionality can not be disabled. Second, and this is completely counter intuitive, how you brake will have a huge effect on the rate of wear between the front and the rear.

My wife and I used to have two identical BMWs, the only difference was the color (mine is blue and her's red). I tend to drive faster and wear through my brakes quicker, but when it comes time to replace brakes, my front is the one that needs replacing first and her rears are the ones that needs to be replaced first.

It didn't make any sense to me. I'm a lot more aggressive on the brakes, plus I typically drive faster, and I take my car to the track. While she follows the flow of traffic and brakes very gently. My speculation as to why her rear brake should wear out before the front, while my front wears out before the rear, is as follows.

When you drive aggressively and brake aggressively, you transfer weight to the front brakes and therefore make the front pads do more work, since there's far more grip up front. Especially when you go to the track, when you're constantly near the threshold of the brake's capability, the fronts will wear out faster. When you drive normally on the street, the front and rear will wear at a similar rate, since the fronts still do more work but since it's thicker it'll wear out evenly. If you are not an aggressive driver, or if you brake like my wife does, who is very gentle on the brakes and tend to rid it softly for long distances, or if you have an automatic and spend a lot of time in stop and go traffic where you're light on the brakes where weight doesn't really transfer much to the front, then the front and rear are doing equal amount of work, but since the rears are thinner, the rears will wear out first. Combine that with the e-Diff's use of rear brakes in low traction conditions, it compounds the problem and causes the rears to wear quicker than the front.

That's my theory on it anyway.

02-18-2011, 03:11 PM	#1
WallyF First Lieutenant 97 Rep 399 Posts Drives: 2023 BMW i4 eDrive40 Join Date: Oct 2005 Location: Fort Wayne, IN iTrader: (1) Garage List 2023 BMW i4 eDrive4 ... [0.00]	Rear Pads need replacement before front pads Hi, The OBC on my 2006 325xi is calling for the rear pads to be replaced in 3500 miles. My experience with other than BMW cars is that the front pads wear down faster than the rear pads. This does not seem to be the case with my 2006 325xi. The rear pads have about 3/16 inch left and the fronts have over 3/8 inch left. Does BMW use undersized rear pads? Or is there another reason? Thanks Wallyf
	Appreciate 0 Tweet Quote

02-18-2011, 03:38 PM	#2
Lenaxia Lieutenant 41 Rep 566 Posts Drives: 2006 330xi 6MT Join Date: Aug 2009 Location: Santa Clara, CA iTrader: (4) Garage List 2006 330xi [0.00]	If you've seen new OEM pads, the fronts are thicker than the rears I believe. At the very least, front and back thickness is not the same. __________________
	Appreciate 0 Quote

02-18-2011, 03:46 PM	#3
The HACK Midlife Crises Racing Silent but Deadly Class 1821 Rep 5,337 Posts Drives: 2006 MZ4C, 2021 Tesla Model 3 Join Date: Oct 2007 Location: Welcome to Jamaica have a nice day iTrader: (1)	NORMAL. BMW's fancy DSC and DTC systems uses the rear brake pads to simulate the effects of a limited slip differential and if the car's driven mostly with DSC and DTC active, it's not out of the realm of possibility for the rear pad to wear faster than the front. __________________ Sitting on a beat-up office chair in front of a 5 year old computer in a basement floor, sipping on stale coffee watching a bunch of meaningless numbers scrolling aimlessly on a dimly lit 19” monitor.
	Appreciate 0 Quote

02-18-2011, 06:39 PM	#4
josephbet01 Private First Class 6 Rep 112 Posts Drives: E93 328i Join Date: Oct 2010 Location: York, PA iTrader: (0)	Mine did the same thing. Rears wore out at 60k and I'm now at 70k and still have 50% left on the fronts. Lot of highway driving.
	Appreciate 0 Quote

02-19-2011, 07:54 AM	#5
WallyF First Lieutenant 97 Rep 399 Posts Drives: 2023 BMW i4 eDrive40 Join Date: Oct 2005 Location: Fort Wayne, IN iTrader: (1) Garage List 2023 BMW i4 eDrive4 ... [0.00]	DSC ??? The Hack, I thought about the DSC and antilock brakes as the main cause. However, since I have X drive, the normal action is to transfer power to the front wheels before using the rear brakes for stability control. Also, this is my wife's car. She drives non aggressively. I am more inclined to believe that BMW uses less material on the rear pads. Any other ideas??? Wallyf
	Appreciate 0 Quote

02-23-2011, 01:23 AM	#6
HP Autosport Supreme Allied Commander 3847 Rep 54,376 Posts Drives: F80 M3 Join Date: Mar 2007 Location: Santa Barbara, AP, Brembo, GIAC, Koni, Ohlins, Performance Friction, www.hpautosport.com iTrader: (36)	There is a couple of solutions, either turn off the DTC system or get a LSD so you are not activating DTC as much. Turning off the DTC is free!
	Appreciate 0 Quote

02-23-2011, 04:07 PM	#7
Undies Lieutenant 39 Rep 517 Posts Drives: 335i Join Date: Sep 2009 Location: Toronto iTrader: (0)	non aggressive drivers doesn't mean they drive efficiently when it comes to gas and brakes.
	Appreciate 0 Quote

03-01-2011, 11:13 PM	#8
WilliamE92 First Lieutenant 21 Rep 318 Posts Drives: 2013 EB F30 335 MT Join Date: Aug 2009 Location: CA iTrader: (1)	my rear pads are about to go out at 30k is that normal in the 335?
	Appreciate 0 Quote

03-02-2011, 01:06 PM	#9
9t2hoo Private First Class 66 Rep 133 Posts Drives: 2024 Cayman S Join Date: Mar 2008 Location: Washington, D.C. iTrader: (0)	If it helps, I'm about to get my SECOND set of rear pads in 30K miles I'm going to be bummed when I have to pay for these on my own next year. BTW, they still haven't replaced my rear rotors. I'm hoping they'll do that during the next pad replacement while the car is still under the maintenance plan.
	Appreciate 0 Quote

03-07-2011, 12:23 PM	#12
The HACK Midlife Crises Racing Silent but Deadly Class 1821 Rep 5,337 Posts Drives: 2006 MZ4C, 2021 Tesla Model 3 Join Date: Oct 2007 Location: Welcome to Jamaica have a nice day iTrader: (1)	Okay, to answer your question...Yes the rear pads are thinner from the factory than the front pads. And NO it's not any thinner than any other BMW combinations. It's about the same proportion as any other BMW that came before it. The rear pads are typically thinner because under normal operation conditions the rear pads do less "work" than the front. The reason why the rear pads wear out first is not because it's thinner though. It is two fold. First, BMW uses the rear brakes to simulate a limited slip. So if you're driving in low traction situations, or live in a climate where WINTER last more than 3 days, the rears are constantly being used and burned up to create artificial traction whether you like it or not, since the DTC e-Diff functionality can not be disabled. Second, and this is completely counter intuitive, how you brake will have a huge effect on the rate of wear between the front and the rear. My wife and I used to have two identical BMWs, the only difference was the color (mine is blue and her's red). I tend to drive faster and wear through my brakes quicker, but when it comes time to replace brakes, my front is the one that needs replacing first and her rears are the ones that needs to be replaced first. It didn't make any sense to me. I'm a lot more aggressive on the brakes, plus I typically drive faster, and I take my car to the track. While she follows the flow of traffic and brakes very gently. My speculation as to why her rear brake should wear out before the front, while my front wears out before the rear, is as follows. When you drive aggressively and brake aggressively, you transfer weight to the front brakes and therefore make the front pads do more work, since there's far more grip up front. Especially when you go to the track, when you're constantly near the threshold of the brake's capability, the fronts will wear out faster. When you drive normally on the street, the front and rear will wear at a similar rate, since the fronts still do more work but since it's thicker it'll wear out evenly. If you are not an aggressive driver, or if you brake like my wife does, who is very gentle on the brakes and tend to rid it softly for long distances, or if you have an automatic and spend a lot of time in stop and go traffic where you're light on the brakes where weight doesn't really transfer much to the front, then the front and rear are doing equal amount of work, but since the rears are thinner, the rears will wear out first. Combine that with the e-Diff's use of rear brakes in low traction conditions, it compounds the problem and causes the rears to wear quicker than the front. That's my theory on it anyway. __________________ Sitting on a beat-up office chair in front of a 5 year old computer in a basement floor, sipping on stale coffee watching a bunch of meaningless numbers scrolling aimlessly on a dimly lit 19” monitor.
	Appreciate 0 Quote