What would cause my rotors to wear unevenly?

[houtan]

Took a look at my front brakes today and noticed the inside rotor and pad are wearing faster than the outside. Both rotor and pad are about 1.5mm thinner on the inside. Both the left and right wheels look like this. Any ideas what would cause this?

For background, the brakes work great. Stock BMW rotor and pads. No shimmy, stop normal. These pads and rotors have been to one half mile event, one track day at buttonwillow, and a bunch of canyon runs, really hard braking.

Is the inner rotor and pad getting hotter than the outer because less air is getting to the inner side causing the inside rotor to wear faster? Would appreciate any insight you may have.

[NorthernDancer]

Definitely strange; if inside was wearing much faster then there you should be able to feel a very significant difference in the "lip" between the 2 sides. Lip is the very outside of the rotor which doesn't touch the pads. It's strange but I'm thinking it's normal also but I'm sure others with far more experience than me will chime in.

[houtan]

Originally Posted by NorthernDancer

Definitely strange; if inside was wearing much faster then there you should be able to feel a very significant difference in the "lip" between the 2 sides. Lip is the very outside of the rotor which doesn't touch the pads. It's strange but I'm thinking it's normal also but I'm sure others with far more experience than me will chime in.

Thanks. Anyone else have any ideas?

[juld0zer]

This is not the first time i have seen rotors on a BMW which are thicker on one side. As for the pads wearing unevenly, that is definitely odd. Opposed piston calipers usually have very even wear except for taper. Have you exercised the pistons one by one? I had sticky pistons in my fronts.

[ShocknAwe]

My inside pads have worn more than the outside on all 4 corners. BUT, I don't have uneven wear on the individual pads. My thought on that goes to a sticky piston, maybe it has some dirt in between the piston and the caliper wall.

[houtan]

Originally Posted by ShocknAwe

My inside pads have worn more than the outside on all 4 corners. BUT, I don't have uneven wear on the individual pads. My thought on that goes to a sticky piston, maybe it has some dirt in between the piston and the caliper wall.

Thanks. Adjusted the picture so it is upright. So your rotors wear evenly?

I guess maybe this is normal then. I picked up a set of OE blanks from ebay for $245 and textar pads from autohauz for $68. Going to clean up the calipers, check the pistons for smooth operation, and slap the new HW.

I will check out my rear rotors this weekend to see if they are wearing the same way.

[ShocknAwe]

Originally Posted by houtan

Thanks. Adjusted the picture so it is upright. So your rotors wear evenly?

I guess maybe this is normal then. I picked up a set of OE blanks from ebay for $245 and textar pads from autohauz for $68. Going to clean up the calipers, check the pistons for smooth operation, and slap the new HW.

I will check out my rear rotors this weekend to see if they are wearing the same way.

They seem to be wearing evenly, but the only way to tell for sure is if I measured them, which I haven't done.

[juld0zer]

I just had a look at the F20 front discs off an M135i i have at home. The outer surface is thicker than the inside

[houtan]

Thanks for the feedback fellas. Sounds like everything is normal then. Going to install the rotors and pads before my halfmile event in october. Should be good to go. Hopefully the textar pads are as good as the OE pads!

[houtan]

So I feel like a bit of a dummy. New OE rotors camenin today. The inner rotor is thinner than the outer rotor by design!!!!! Lol. So my rotors are completely normal. To add salt to the wound, my current rotors measure 25.6mm, which means I have 1.3mm of margin left and didn't even need to buy new rotors!

[juld0zer]

Originally Posted by houtan

So I feel like a bit of a dummy. New OE rotors camenin today. The inner rotor is thinner than the outer rotor by design!!!!! Lol. So my rotors are completely normal. To add salt to the wound, my current rotors measure 25.6mm, which means I have 1.3mm of margin left and didn't even need to buy new rotors!

Sometimes it takes first hand experience to be convinced

[houtan]

Originally Posted by juld0zer

Sometimes it takes first hand experience to be convinced

Seriously. It's not that I doubted rotors looked similar on other cars, I just had no clue they start out like this brand new. Oh well, posted the rotors for sale in the California forum. Got a great deal on them, but I have no use until the next set of pads.

[juld0zer]

I always wondered the same too, and expected the inner surface would be thicker since that is the piston side on a sliding caliper used on most BMW models.