Weird brake pad wear

Hella JDM

Hella JDM

Well-Known Member
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I took my Hawk HPS pads off today because I am going with a more aggressive setup for the track. They don't have very many miles on them, maybe 2,000. The rear brake pads are wearing on only half of the pads on the outer pad, and like 80% on the inner pads. I bedded them in well so I cannot figure out why they are like this. Any insights?

2vufxhw.jpg
 
What do the rotors look like? Did you lube your slide pins when servicing your brakes? Have you had your rotors machined/replaced when putting these pads on? How many miles are on the car currently and when did you swap to these pads?
 
I'm no expert but it seems like your caliper is not properly aligned to the rotor. It's odd that this would occur so evenly on both sides of the car. It looks like your actually compressing the rotor at an angle. I would check out the way the caliper is mounted and make sure everything is set and cleaned properly.

If you can maybe have some press the brake while you watch the caliper move. This often lets you see the problem more clearly.
 
How do I align the caliper? Car is a 14' with less than 10k miles. I put the pads on a few thousand miles ago. The slide pins I did not lube but they are clean. It's like the pads aren't seated properly but I couldn't imagine how.
 
Some pad sets have different outside/inside pad shapes that can cause your concern. Haven't checked to see if our's is like that. From the pic it looks like they all are the same
 
If you still have the stock pads........... Try matching them up to see if they are the same, the only thing that would be different would be the pad material.... If they match, then you probably aren't installing them correctly........ If it was just one than it would be a system issue, but both wheels?......... Could be they only fit left/left, r/r.......Just my guess.........
 
The stock ones are not like that but they were on the car longer, the more I think about it, the more I think these pads only have 1000 miles on them. The wear indicators were installed facing down, on the inside of the disc. I have never heard of side and direction specific pads, that would be a first for me. The fronts are perfect, and honestly there's nothing abnormal looking about the pads other than a portion hasn't made contact with the rotor, meaning there isn't significant wear on the part of the pad that has made contact, no grooves or gouging etc. I'm wondering if the fronts are biting so hard that the rears haven't had a chance to fully bed...
 
I honestly have no idea since one side is normal and the other has that weird angle to it. Especially since it happened on both sides. Shot in the dark but, when you compressed the rear piston back in did you use the correct tool that spins the piston back in? It might be wedged funny so it presses out the bottom of the pad. Maybe the top of the pad is getting caught on something in the caliper so only the bottom half moves toward the rotor?

The other possibility I can think of is that the pad surface was not flat from the factory. Since its both outer pads and with the same wear line I suspect this to be the most likely option. If you drove on them more the pad would most likely wear flat and you would get contact on the whole pad face. I believe your pads will eventually seat fully with more miles. The brake pad friction is not dependent on pad surface area anyway. The force applied to a smaller surface area will just increase the friction on the small area and the grab will be similar but that part of the pad will just wear down faster. That is why putting pads with a larger surface area do not increase bite, they just reduce the wear rate.

So your braking effeciency is not hurt by the smaller area, the pad will just wear faster on that small area until the entire pad contacts the disc and then the wear rate will return to normal.


If i'm wrong about anything @jrotax101 will have the correct answer. He's way smart about these things.
 
"One of these things is not like the other, One of these things is not the same!":pianodance: lol
 
I would agree that it's either different backing on the pads causing a weird bind/clamping angle. Pads can be designated inner/outer like I've said and @Monk said(I've been bit in the *** by this before on a car). I assume you'd know if your forced the caliper over the pads to cause a bind(done this also being in a rush). Unless your rotor is a trapezoid of some kind from factory I'm leaning towards improper install of some kind on the pads.
Wait...did you line the bump on the back of the rear "inside" up with the grove(s) in the piston? I BET that's your issue, that bump not being in the grove of the rear piston wont allow and even clamping force (I've done this too in a rush). You need the special rear brake service tool to line up the piston.
 
So I examined the pads a bit further and I have come up with something that might be causing this... The inside rear pad has a large peg that aligns the pad shim onto the pad and keeps it in place. As you can see it protrudes beyond the shim, and this is where the piston contacts. The wear is higher towards the top of this peg. The outside pads do not have this large of a peg, and the fron't pads don't either. This is the only thing I can think of.

This is the large peg as you can see:
309tpp4.jpg


Another view:
folw2h.jpg


The outside pads do not have this:
16m2ex2.jpg
 
Echo echo lol I'm 99% sure this is your issue. You'll never feel it in the car during braking.
 
Repeat...... Do you have the old oem pads you can compare with, to see if all the parts of the after market pads match in size and in configuration.
 
Well I'm not seeing any designation. Of inner and outer. The wear indicators for the factory are on the inside so that's how I installed them. I screwed the rear pistons in before I installed. That peg isnt meant to fit into the channel on the rear piston is it? I am assuming the piston has to twist as it compresses the pad so that would not make sense to have that peg fit in the channel
 
Monk said:
Repeat...... Do you have the old oem pads you can compare with, to see if all the parts of the after market pads match in size and in configuration.
Click to expand...

Yes I did compare the stock pads, I actually put them back on the car while I decide on which pads to really go with next. There was no large peg on the rear pads like the HPS have, other than that they are identical
 
Hella JDM said:
Well I'm not seeing any designation. Of inner and outer. The wear indicators for the factory are on the inside so that's how I installed them. I screwed the rear pistons in before I installed. That peg isnt meant to fit into the channel on the rear piston is it? I am assuming the piston has to twist as it compresses the pad so that would not make sense to have that peg fit in the channel
Click to expand...

For the third time saying it now, yes it needs to fit in the channel of the piston.
 
Darkout said:
I would agree that it's either different backing on the pads causing a weird bind/clamping angle. Pads can be designated inner/outer like I've said and @Monk said(I've been bit in the *** by this before on a car). I assume you'd know if your forced the caliper over the pads to cause a bind(done this also being in a rush). Unless your rotor is a trapezoid of some kind from factory I'm leaning towards improper install of some kind on the pads.
Wait...did you line the bump on the back of the rear "inside" up with the grove(s) in the piston? I BET that's your issue, that bump not being in the grove of the rear piston wont allow and even clamping force (I've done this too in a rush). You need the special rear brake service tool to line up the piston.
Click to expand...

I thought you read that and answered after practically saying the same thing so I half repeated by saying Echo echo lol If you didn't see it no big. So in all 1 1/2 really. But yea you need to have the peg/nipple/bump in the groove of the piston. That goes with any car
 
Oh I totally missed that! Yea that has to be the issue then for sure. Thanks again.
 
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