[Carjack]

320D rear brake disc diameters too small?

I have now completed just over 11000 miles in my 320D M-Sport. The service info on idrive advise that the brake pads will require replacing as follows:-

Rear in 32000 miles time
Front in 45000 miles time

So it looks to me as if the electronics of the 320D (DSC?) are somewhat more advanced than the mechanical brake components. I am assuming that the rear pads show more wear due to the electronic braking the system gives when going round bends etc.

If this is the case, the rear brake diameter & pads should be increased to give a greater surface area for braking, to reduce lining wear pressure, to compensate for this extra wear.

Assume the new 3 series due out the near future will have this modification.

My previous was a 2005 reg 320 and I certainly cannot recall the rear pads showing greater wear than the fronts. Or is it just my driving of the 320D? Can’t be! Or is it the electronics playing up on my 320D? (More likely!)

Has anybody any ideas?

[- Paul -]

one press of the button will probably sort that out. You a "fast" driver?

[HighlandPete]

I don't follow why the discs are too small, the bigger engine cars can do the same, with bigger rear brakes, they would logically need even larger discs.

What are you after, even wear, front to back? Does it really matter? Bigger rear brakes and another driver will then have the opposite issue, fronts wearing much much earlier than the rears.

Driving style, conditions of use etc., etc. We've a few options, I suggest you either adjust your driving style, just replace pads when worn out, and/or activate DTC and get a bit more freedom, with a little less security from the on board DSC system.

HighlandPete

[m1bjr]

Originally Posted by Carjack

the rear brake diameter & pads should be increased

is it just my driving of the 320D?

Has anybody any ideas?

Turn off the FREDS and learn to drive RWD again?

Seriously, you must be leaning on them more than you think.

[Carjack]

Re my original post: it is no doubt quite amazing that after 11k miles of motoring I still might have left on the pads 32K on the rear & 45k on the front.
So I should count my blessings, as they say!
On considering my driving, on reflextion, I do tend to keep the motor tight on the bends, which could well be a deal faster than I did with the 320i.
I surpose, without really thinking, I am using the caperbilities of the 320D.
(Well, the BMW adverts do say: 'Enjoy'!)
I am just very surprised that the rear pads are wearing that much quicker than the fronts, after all when braking normally most of the cars weight by momentum is transferred to the front pads for braking.
If I want to eqaulise the wear a bit, front & rear, I will just have to slow down a bit round the bends, which is going to be a bit difficult!
Cheers!

[Carjack]

Have now had my 320D just over two years with 20500 miles on the clock and the on board info on brake pad wear is now showing as:-

Rear Pads: 28000 miles
Front Pads: 50000 miles

The increased wear on the rear pads presumably due to the Dynamic Stability Control (DSC) applying braking during cornering.

All this is leading me to think that possibly the up & coming F30 for March 2012, may have equal size brake disc diameters front & rear.
Or even smaller discs on the front! OMG!

Or are the above wear figures for the pads just my motor? Anybody else out there have similar?

As a matter of interest my previous 55 reg 320i at about 23500 miles the front pads were coming up for replacement. The rear pads, at that time, in the distant future.

This leads me to think that BMW Engineers have improved the wear rates of the pads & discs since 2005 quite considerably, as I don’t think I was dashing around quite so quick in the 320i.

[AlwynMike]

During the past year looking at many 335d's for sale, I saw that every one I looked at had greater pad wear at the back than the front.
Is it the DTC, DSC or Cruise that's doing it?
Who knows? - but it's not just you, most of them seem to do it.

[FNQ]

Originally Posted by Carjack

Have now had my 320D just over two years with 20500 miles on the clock and the on board info on brake pad wear is now showing as:-

Rear Pads: 28000 miles
Front Pads: 50000 miles

The increased wear on the rear pads presumably due to the Dynamic Stability Control (DSC) applying braking during cornering.

All this is leading me to think that possibly the up & coming F30 for March 2012, may have equal size brake disc diameters front & rear.
Or even smaller discs on the front! OMG!

Or are the above wear figures for the pads just my motor? Anybody else out there have similar?

As a matter of interest my previous 55 reg 320i at about 23500 miles the front pads were coming up for replacement. The rear pads, at that time, in the distant future.

This leads me to think that BMW Engineers have improved the wear rates of the pads & discs since 2005 quite considerably, as I don’t think I was dashing around quite so quick in the 320i.

When my service light came on, I serviced the vehicle myself. I purchased the parts from the BMW dealer and after I serviced it I had the dealer cancel out the service indicator. I also mentioned that the brakes had very little wear and when necessary I would replace them. I have serviced the vehicle a few times now with the same happening. I replaced the rear brake pads at about 80,000 kilometres still with plenty of meat left on them. I have now knocked up over 110,000 kilometres and haven't touched the fronts yet. I do have a new set of pads ready to be fitted when required. The reason I get such high k's is that the majority of my driving is on the open road, highway trips. I would have had to replace my pads long ago if I was just driving around town.

[xenon]

Increased wear on the rears is due to the rearward bias for greater stability and anti-dive. The DSC makes a dab on the brakes here and there but not enough to significantly affect pad life as mostly it backs off the throttle rather than driving against the brake. Even if it didn't you'd have to be driving in a manner such that if the DSC was off you'd be spinning the wheels virtually all the time.

[m1bjr]

Smaller diameters, less pad area and less swept diameter - plus poorer cooling.
Airflow is poor at the rear, and there is a huge hunk of metal for the handbrake.
And if you brake gently then they are working harder than if you stand on the pedal (relatively speaking).

[gangzoom]

Originally Posted by Diseasel

i think its more to do with the computer being out than wear unless there is something wrong.

my rears lasted 65k and the front around 43k

How do you guys make your brakes last so long!! I've never had a set of pads on the front last more than 15K...average is about 10K

[HighlandPete]

Originally Posted by gangzoom

How do you guys make your brakes last so long!! I've never had a set of pads on the front last more than 15K...average is about 10K

"Don't brake much...." is the simple answer. I'm at 50k on the original pads, and "computer says" about 25k left for both front and rear. A visual check suggests that is about correct.

Seriously, a lot does depend on the use of brakes, I can drive for miles and never need to touch the brakes.

HighlandPete

[fastloop]

Originally Posted by gangzoom

How do you guys make your brakes last so long!! I've never had a set of pads on the front last more than 15K...average is about 10K

Wow, any track days included in that or just "normal" driving? My fronts lasted 46K, first set of rears 30K and 2nd set will probably last 22K. That's including a number of Ring trips.
The last trip in April did send the OBD into a panic on the wear rate. Fronts went from 7K to 2K and rears from 11K to 5K in 9 laps.

[Jon D]

Originally Posted by HighlandPete

"Don't brake much...."...Seriously, a lot does depend on the use of brakes, I can drive for miles and never need to touch the brakes.

I'm with you there - I never cease to be amazed and faintly amused at the frenetic flashing of brake lights on cars in front of me, whilst I drive mile after mile without touching mine - it's all about the 2 to 3 second rule; easily maintained by throttle alone.

[dopper99]

Originally Posted by Carjack

.....If I want to eqaulise the wear a bit, front & rear......

Are you saying you ideally want BOTH front a rear discs to wear out at the same time? If so, you'll have one hell of a bill to replace both at the SAME TIME. I'd rather stagger the changing of the front and rear over several months to stagger the cost and not care if the front or rear wear first.

Same principle goes for tyres. I'm glad the fronts and rears wear at different rates as I wouldnt want to be replacing all 4 every time.