Rear Brakes Wearing Faster than Fronts

[bcredliner]

Sounds like you don't think I have any BMW ownership experience. That's not the case. I'm not challenging anyone's first hand experience but pad experience varies. Even in the link you posted to endorse excessive rear pad wear had posts saying that is not their experience.

I haven't had rear brake pads wear significantly more than front but that doesn't count. The 4.6 has bigger brakes than a 3.0 and 4.4. And what I have experienced has been with many mods of both engine and suspension that has impacted pad wear one way or the other. Most of the time I drive very hard. DFW overpasses are great for testing handling. I can only speak for myself but there have extremely few times the front tires on my X5 start to sing. When they do it is way past the point of driving hard. Doesn't matter if everything is stock or not, the line between front tires singing when the system is not operational and electronic stability can't help because X5 is too far gone is an extremely fine. When system kicks in one is over their head. Think about how many times you go there.

I'm not challenging that in an understeer condition the electronic stability applies braking to the inside rear wheel. I was correcting that understeer is not when the backend brakes loose, that is oversteer which would apply braking to the outside front wheel.

I don't recall ever seeing any X5 brake bias numbers so I don't know if it changes by model or year. But, if a particular year and model X5 is rear biased that could increase rear pad wear though the larger rear pads and calipers should offset at least some of the wear. Brake bias is hardly ever, if ever, 50-50 as that usually results in a vehicle hard to control under braking even with electronic help.

I haven't heard of adjusting brake bias to reduce how much the front suspension compresses under braking. That's what the suspension components are supposed to address. With all the different circumstances important to safe braking addressed with brake bias I have no idea why BMW would add reducing front end dive to the already very complex primary job of brake bias. Especially since front end dive varies by speed and how hard one brakes and brake bias does not change. Where is the logic?

[StephenVA]

Guys
We have not even discovered if these pads are of the same manufacturer much less if the pads are indeed wearing at a faster rate than normal. Nothing short of measuring each pad and driving will determine the issue. Could be after 15 years the calipers are hanging up and dragging the pads for a few extra mins on every pedal pump. Could be the fact the brake fluid has never been flushed correctly and the rear line are stuffed with rust.... I could go on and on but I think we all get it. The OP will report back on temps of the caliper/rotors and we will go from there.
Who knows what the issue really is? It could just normal wear.

[PropellerHead]

Originally Posted by StephenVA

Who knows what the issue really is? It could just normal wear.

+1

[PropellerHead]

Originally Posted by bcredliner

Sounds like you don't think I have any BMW ownership experience.

I haven't responded to you at all. The point of the thread isn't served by splitting this and that here and there. It rarely is.

[Fifty150hs]

Originally Posted by StephenVA

Guys
We have not even discovered if these pads are of the same manufacturer much less if the pads are indeed wearing at a faster rate than normal. Nothing short of measuring each pad and driving will determine the issue. Could be after 15 years the calipers are hanging up and dragging the pads for a few extra mins on every pedal pump. Could be the fact the brake fluid has never been flushed correctly and the rear line are stuffed with rust.... I could go on and on but I think we all get it. The OP will report back on temps of the caliper/rotors and we will go from there.
Who knows what the issue really is? It could just normal wear.

Same manufacturer - Power Stop. Installed at the same time. The rears have been confirmed to be wearing at a higher rate than the fronts. About 1mm more than the fronts. I still have to check the rotor temps.

[andrewwynn]

I would do some hard stops in sand/gravel with DSC disabled to see if the rear lock up before the front. If they don't I wouldn't worry about it. If the rear do lock up easier than the front there might be a problem with the fronts not doing their share.


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[bcredliner]

Originally Posted by PropellerHead

I haven't responded to you at all. The point of the thread isn't served by splitting this and that here and there. It rarely is.

Splitting this and that here and there--I have no idea what that means.

[wpoll]

Originally Posted by PropellerHead

The traction control system sits there listening for a chance to squeeze in just the right place and it does it. Often- my bet is most often- we don't even know.

I can't speak for the petrol cars but on my diesel, I definitely know when the DSC kicks in - the 4x4 lamp on the dash lights up!!

I have experimented with how hard I can push the car in a wet corner before the tail steps out, just so I know the limits. Using a slightly downhill constant radius curve, on a wet day with either slight or trailing throttle, the back steps out quite suddenly and just as suddenly the DSC kicks in (lamp on the dash flashing) and the tail resumes it's correct trajectory. All rather exiting! No way could I correct it fast enough - the DSC has sorted it before I can barely react.

And as for pad wear, my fronts seem to wear WAY faster than the rears. When I got the car, all four pads were near-new (from the look of them) and similar in thickness. 40,000kms later the fronts are gone (along with the wear indicator!) and the rears have only worn about 1/3 down on what they were.

Granted, I have no idea what the pads were, or even if they were the same front and back. But I can't see this thing ever wearing rear pads faster than fronts. Not the way I drive, anyway...

[PropellerHead]

Originally Posted by Fifty150hs

About 1mm more than the fronts. I still have to check the rotor temps.

Does it offer pause to consider that these are just brake pads? I don't intend to be rude or anything, but I'm thinking.. like ~ 1mm over the pad's life.. Sooo... what's the math on that? An extra $100 every few years?

I mean, sure... You could have some nefarious gremlin causing a module to wonk one way or the other, but is it *really* the kind of thing that's gonna total the X5? Among the mechanical failures we've seen so far that will bring an E53 to the crusher, uneven brake wear just isn't on the list.

Drive, man. Just drive. When you get a front sensor that says you need pads, replace them and the sensor. Rear? Same. Repeat for just as many miles as your 3.0 takes to consume more oil than gas, your M62 hops a guide, or your N62's seals get wider than they should.

In short, the main problem with E53's has not ever been with their sustained ability to stop. Quite the opposite.

[Crowz]

The proportioning valve setup in a bmw is front brake bias. If rears are wearing faster than the front something is wrong and normally its easy to test.

Turn off the dsc find a gravel or dirt road and press the brakes hard while moving. If the back lockup before the front then you found your problem. The front should lockup first.

On a bmw that should be a bad master cylinder. If a single rear lockups in place of both then a bad caliper but if both are wearing faster than the front they both should lockup before the front.

I wrote this series articles for the corvette community but it covers about everything you want to know brakes and might help explain how it works better brake bias wise.

Brakes | Crowz Nest