Why non-symmetric brake pad wear?

[Pableras]

Hello everyone,

I just replaced the front brake pads of my car for the first time, and I noticed that the left side pads were noticeably more worn compared to the right side pads: the thickness of the fricition material of the left side was 2.4 mm less than the right side. The inner and outer pad wear is the same, the difference is from side to side.

The pads were 120 000 km old, and it was the original set that the car came with from the factory.

I was expecting symmetric wear and I wonder if I should be worried about it.

My car is LHD and I usually carry no passengers. My driving style is relaxed (I get very good fuel economy), with occasional spirited drives, I remember using the ABS only a few times. The car brakes perfectly straight in all situations. When the car was 80 or 90 000 km old I remember feeling a very slight brake judder after descending a mountain pass, but that dissappeared eventually.

What could be the cause for this?

Cheers

[finlo]

Not sure why but i've always found the kerbside pads wear quicker than the offside.

[S0 What]

Me too, i allways put it down to puddles cooling that side more than the offside but in reality i have no sure reason behind it ?

[GreenV8S]

That is odd. Could it be that you tend to brake most on bends such as approaches to road junctions and the outside wheel, since it is traveling slightly faster, sees more wear? That's the only explanation I can think of other than a fault in the brake system.

Edited by GreenV8S on Monday 28th January 01:45

[phumy]

It could be that if you have slider (guide) pins they could be corroding on that side and not allowing the pad to slide freely on the pins and slightly binding thereby not getting the full equal application of the pad against the disc when you brake. Does the car pull to one side when you apply the brakes?

[E-bmw]

My thoughts would be to check the more worn side calliper to make sure the slider & pistons release freely, check the discs for any correspondingly unequal wear and if all looks OK just change the pads & monitor next time you change them/in a year for arguments sake.

It could well be nothing & is unlikely to be anything to worry about, let's face it you don't know if the PO didn't have a squeaky brake after 6 months & have the supplying dealer change just one set of offending pads.

[Evolved]

Slightly sticking calliper maybe. I’m amazed you got 120k out of a set of pads. Frugal with that brake pedal obviously

[HustleRussell]

Not a cause for concern. It has passed MOT after MOT for years with those pads so there isn't an axle imbalance.

I have never seen four pads come off an axle with equal wear, it never happens- not even with opposed pistons.

When the pads are changed just clean up and re-grease the sliding pins and it'll be good to go again.

[Pableras]

phumy said:

It could be that if you have slider (guide) pins they could be corroding on that side and not allowing the pad to slide freely on the pins and slightly binding thereby not getting the full equal application of the pad against the disc when you brake. Does the car pull to one side when you apply the brakes?

Good point, but both the pads and the caliper slide properly (at least when I dissasembled them). I brushed al the contact points to ensure free movement.

The car brakes perfectly straight, that is what worries me...

[Pableras]

E-bmw said:

My thoughts would be to check the more worn side calliper to make sure the slider & pistons release freely, check the discs for any correspondingly unequal wear and if all looks OK just change the pads & monitor next time you change them/in a year for arguments sake.

It could well be nothing & is unlikely to be anything to worry about, let's face it you don't know if the PO didn't have a squeaky brake after 6 months & have the supplying dealer change just one set of offending pads.

I think I will dissassemble it again and check the discs and the left caliper, to be honest I didn't pay attention to the pads until I was finished and about to bin them.

I bought the car new, so I'm sure that the pads were original on both sides, the car has necer seen a mechanic except me, except for the tires

[Pableras]

Evolved said:

Slightly sticking calliper maybe. I’m amazed you got 120k out of a set of pads. Frugal with that brake pedal obviously

You would be even more amazed if I told you my average fuel consumption over those 120k (km) is just 5,08l/100km of unleaded gas (no tricks, I keep a record of each and every refuel). The car is a 1.2tsi 90hp Seat Toledo.

Honestly, the pads should have been changed before, but yes, I try to push that pedal as least as possible.

[stevieturbo]

Evolved said:

Slightly sticking calliper maybe. I’m amazed you got 120k out of a set of pads. Frugal with that brake pedal obviously

When I was doing 85-90k a year in my van ( Vaux Combo ) I could easily get over a year out of discs/pads, although I usually just changed them every year anyway. Always OEM parts. And always a good mix of driving.

If anything the discs wore more than the pads, although always still a good friction surface.

I think cars that stand about more and see disc corrosion more often wear things out faster in some respects. And strangely...it only started to get hard on rear pads after the disc backplates had corroded and been removed.

[Pableras]

HustleRussell said:

Not a cause for concern. It has passed MOT after MOT for years with those pads so there isn't an axle imbalance.

I have never seen four pads come off an axle with equal wear, it never happens- not even with opposed pistons.

When the pads are changed just clean up and re-grease the sliding pins and it'll be good to go again.

Not exactly, my first MOT (in Spain the equivalent is called ITV) will take place at the end of this year, 4 years after purchase. I'm curious to confirm whether both sides brake the same in the brake test.

Good to hear that you've seen it before, when I changed pads in other cars before I never saw such a big difference.