mdnitedrftr
Full Access Member
This may be common knowledge, but I just found this out yesterday and figured I'd share, in hopes that others won't make the same mistake.
Let me start by telling you a quick story...
Back on super bowl Sunday, I was driving back to my house when I had to stop short. I heard a clunk and then lost all brake pressure. I pulled in to the closest parking lot and got out to see WTF happened. All I saw was brake fluid pissing out of the LR brake. Luckily I was right around the corner from my parent's house, so I limped it there to take a better look. When I pulled the wheel off I saw that the inner brake pad was no longer there, and one of the caliper pistons had completely popped out. I had never seen anything like it before, but I didn't think much of it...thought it might have been a ****** caliper. Regardless, I went to the parts store, got new pads and a caliper, all was good. I even made it to my friends house in time for the game.
Fast forward to yesterday...
My RR brake was making some noise, so I pulled the wheel off, and saw the pads (unusual wear pattern) and rotor needed to be replaced. I also noticed that the caliper pistons were both sticking out pretty substantially, but again, didn't think much of it. Drove to Advance, told them what I needed, and they asked me which rotor I needed. They had 2.
12.79" and 12.99"
I wasn't sure which rotor I needed, so I got one of each and would just return the one that didn't match the old one.
When I got home, I pulled out both new rotors to compare, and along with being 2 tenths of an inch bigger, the larger rotor was also much fatter (20mm vs 30mm)
Son of a *****...the last person to do the rear brakes on my truck used the WRONG rotors. They used the skinny, small ones. The smaller rotor would explain the unusual wear pattern on the brake pad, and would also explain why my caliper pistons were protruded so far.
Thinking back to the super bowl debacle, it all made sense. When the pads become worn, the piston can't squeeze the pads together enough, so the pad popped out of the bracket, allowing the piston itself to pop out.
Needless to say, I installed the larger, fatter rotor on the RR, and I also had to purchase another rotor to redo the LR brake.
Once I had everything back together, I also noticed a substantial difference in brake pedal feel. It's much firmer now.
Cliff notes: Smaller, skinnier rotor is for single piston calipers. Larger, fatter rotor is for dual piston calipers.
Notice the slight ridge on the top of the pad...that was because the pad wasn't making full contact with the smaller rotor.
Big difference in width.
Let me start by telling you a quick story...
Back on super bowl Sunday, I was driving back to my house when I had to stop short. I heard a clunk and then lost all brake pressure. I pulled in to the closest parking lot and got out to see WTF happened. All I saw was brake fluid pissing out of the LR brake. Luckily I was right around the corner from my parent's house, so I limped it there to take a better look. When I pulled the wheel off I saw that the inner brake pad was no longer there, and one of the caliper pistons had completely popped out. I had never seen anything like it before, but I didn't think much of it...thought it might have been a ****** caliper. Regardless, I went to the parts store, got new pads and a caliper, all was good. I even made it to my friends house in time for the game.
Fast forward to yesterday...
My RR brake was making some noise, so I pulled the wheel off, and saw the pads (unusual wear pattern) and rotor needed to be replaced. I also noticed that the caliper pistons were both sticking out pretty substantially, but again, didn't think much of it. Drove to Advance, told them what I needed, and they asked me which rotor I needed. They had 2.
12.79" and 12.99"
I wasn't sure which rotor I needed, so I got one of each and would just return the one that didn't match the old one.
When I got home, I pulled out both new rotors to compare, and along with being 2 tenths of an inch bigger, the larger rotor was also much fatter (20mm vs 30mm)
Son of a *****...the last person to do the rear brakes on my truck used the WRONG rotors. They used the skinny, small ones. The smaller rotor would explain the unusual wear pattern on the brake pad, and would also explain why my caliper pistons were protruded so far.
Thinking back to the super bowl debacle, it all made sense. When the pads become worn, the piston can't squeeze the pads together enough, so the pad popped out of the bracket, allowing the piston itself to pop out.
Needless to say, I installed the larger, fatter rotor on the RR, and I also had to purchase another rotor to redo the LR brake.
Once I had everything back together, I also noticed a substantial difference in brake pedal feel. It's much firmer now.
Cliff notes: Smaller, skinnier rotor is for single piston calipers. Larger, fatter rotor is for dual piston calipers.
Notice the slight ridge on the top of the pad...that was because the pad wasn't making full contact with the smaller rotor.
Big difference in width.
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