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Normal on these cars or normal overall? Seems even weirder that the left pad on the first picture is worn at an angle...
 

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99% of my experience is with Volvo, and I don't think I've ever seen one in 10 years with even pad wear. That may be different on another brand, but that's my experience with Volvo. And it's different between models as well. P2's usually wore the front left outer pad and right rear outer pad way faster than the others, sometimes a 3mm difference in pad wear. The P3's tend to wear a bit faster on the right rear inner, and left front inner pad, but sometimes the left rear outer. Go figure.
 

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Discussion Starter · #6 ·
99% of my experience is with Volvo, and I don't think I've ever seen one in 10 years with even pad wear. That may be different on another brand, but that's my experience with Volvo. And it's different between models as well. P2's usually wore the front left outer pad and right rear outer pad way faster than the others, sometimes a 3mm difference in pad wear. The P3's tend to wear a bit faster on the right rear inner, and left front inner pad, but sometimes the left rear outer. Go figure.
That's really funny. I've seen several different cars and while the pads never wear totally evenly, they are always within a couple millimeters of each other.

In this case, per wheel everything was normal, One pad worn out maybe a millimeter more than the other one in the same wheel. However, between wheels you can see that one set of pads is barely worn half through, whereas the other set is almost to the metal. It also happened on the rear axle, but I don't remember which side worn faster... If it was crossed I could assume that one line is receiving more pressure than the other one. And in the brake section of this forum there is some safety valve on the old volvos that could cause this behavior if improperly bled.

All this theory is useless if every Volvo wears pads like this, though... Have you seen a new one, on the first brake pad change to behave weirdly as well? just trying to rule out a bad bleeding procedure....
 

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I can't see how some brakes would receive more pressure than the others. Brake force is as far as I know electronically distributed today compared to mechanically on older cars. I think a lot older, but still. Not sure how MOT's work in the states but I'm guessing brake force is tested on some kind of roller that should give you kilo-Newton readings on each wheels braking performance. That should tell if it's poorly distributed. Or a simple hard braking, should reveal if the problem's occuring one sided.
 

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Discussion Starter · #9 ·
I can't see how some brakes would receive more pressure than the others. Brake force is as far as I know electronically distributed today compared to mechanically on older cars. I think a lot older, but still. Not sure how MOT's work in the states but I'm guessing brake force is tested on some kind of roller that should give you kilo-Newton readings on each wheels braking performance. That should tell if it's poorly distributed. Or a simple hard braking, should reveal if the problem's occuring one sided.
There is no brake testing here, at least not in my state. I agree with you that the only cause of this uneven wear would be different pressure applied. The car doesn't show any adverse behavior when braking in any conditions. I am left to believe that the right wheel has less weight on top of it so if locks up easier than the left one. the computer reduces pressure in that circuit more often and therefore the pads wear less. It is hard to believe though since in light braking it should not have any pressure control since there is absolutely not lock up or differential slip.

thebracko

Thanks for the info!
 

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I think that sounds a bit like a stretch and doesn't really explain why the rear pads would wear unevenly. Aside from that I don't really have any better explanation. I'd go see a volvo dealer and tell them about your uneven wear. Hopefully they'll be at least familiar with it or know its cause. Unless it really is as normal as #2 suggests, which I hope it isn't.
 

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My 09 3.2 will wear the front inner pads twice as fast as the outers, more so on the left side. First time it happened I pestered the techs at my dealer and was advised that it is absolutely normal.


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Brake force is as far as I know electronically distributed today compared to mechanically on older cars.
^ I think this is the root cause.

I've seen this on two P2s. Seriously confused me at first, as I was used to the consistency of the older systems. Under braking, the newer cars are constantly adjusting the brake pressure to optimize each wheel's effectiveness and prevent lockup. Meanwhile, under acceleration, or even cornering, the traction and stability control systems are also kicking in to limit wheelspin, control yaw and maximize traction... so it is no longer an equally-apportioned hydraulic pressure for each caliper all the time. Intuitively, I feel like things would wear evenly from one side to the other, but that theory doesn't seem to hold true.
 

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It does make sense that interference from STC/DSTC systems could cause the uneven wears from wheel to wheel (though not sure about inner/outer pads though). However, I'm fairly confident the systems never interfere proactively. If it senses you've started slipping it'll engage but I very much doubt it'll interfere under acceleration or cornering (during acceleration I think it might use software to proactively prevent wheel-spin though as kickdowns feel a lot more abrupt in terms of power application when I've disabled DSTC. I have an older car though compared to todays haldex 5 and most likely way more updated softwares).
 
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