Hi all,

When changing wheels a few days ago, I noticed that for the rear brake pads, the outer pad is wearing noticeably faster than the inner pads (driver and passenger). The rears don't have the same guide pins as the front and I'm wondering, when we release pressure on the brake pedal, how does the floating caliper move the pads off the surface of the rotor. For the inner pad/piston, I assume there's a square cut o-ring that retracts the piston ever so slightly. What about the outer pad? I know that the floating part of the caliper attaches to the carrier via 2 bolts. There's a part that screws in the caliper and a smooth shaft that goes into a rubber component. I always assumed this was mobile and I lubricate this part when servicing the brakes. I'm going to redo them, but wondering if there's anything I'm missing. Would appreciate any insights from the knowledgeable car gurus here!

 

So I put rotors/pads on mine like 40k ish ago. Noticed the rear pads were low to what I was expecting.
The drivers side rear pad was cooked while the pass side rear had a lot more life on it.

I would check your slide pins and grease them up. Either that or the caliper is going bad and likely needs replaced.

 

Thanks Matt. This is happening on both sides so I don't think it's a caliper issue, unless both are going bad at exactly the same time which seems unlikely. I just want to make sure I'm greasing all the parts that should be greased up. Other than those two bolts I talked about which I do lube up with silicone grease (Shin-etsu, Acura OEM), anything else?

 

The rear brake slide pins that go through the rubber bushings is not supposed to have any grease/lubricant. Mine didn't have any from the factory, the service manual also doesn't specify any grease for it. Just need to make sure the pins are clean and smooth, grease might attract more dirt and cause it to seize up since the pins are partially exposed and the whole caliper clam shell with the rubber bushing slides along those pins.

Need to make sure where the pad ears ride in the caliper bracket are smooth and lightly lubed.





The front brakes are traditional style, those slide pins for sure need silicone lubricant grease.

 

Thanks rahcu2! I lubed them thinking that was supposed to slide, but perhaps you are right, and I lubed an area that didn't need it, and maybe it gummed things up. Next time I take them apart I will give them a good cleaning. Thanks again for your help.

I do lube the brake pad ears and where they sit in the caliper after sanding them smooth.

 

I found the same wear pattern with my 2019 which I had purchased used. The Carfax report indicated the car had pads and rotors replaced twice at an Acura dealership. I noticed the rear pads were pretty much done this past spring at winter/summer tire change-over time, so I replaced them then. The outer pads definitely thinner than the inner pads. Interesting info from Honda provided by rahcu 2. This style of caliper I am familiar with from previous Volvos I've owned, and I have always lubed the these style of pins. Maybe better left dry?

 

Thanks for taking the time to reply MA73, good to see another Ontarian here. Yeah, I didn't even think that the pins should be left dry, I just always assumed that any moving part should be lubricated. I used silicone grease (which shouldn't affect the rubber bushing (other lubricants might cause the rubber to crack/swell or something which might bind the part that's supposed to slide). I have no idea what the right answer is. If I don't lubricate and the pin/bushing is exposed to the environment, wouldn't that be a risk factor for binding? On the other hand, if I do lubricate, and that stuff traps a lot of dirt, that could also cause binding. This is my first time dealing with this style of slide pin where there's no boot to isolate it from the environment. May I ask, for the Volvos you've owned, did you ever notice any asymmetric pad wear?

 

Don't recall any problematic assymetric wear on my Volvos. Even with what I see with the RDX I don't see as a problem, rather just the nature of this particular beast. And at this point I'm undecided about lubricating or not.

 

Yeah, the asymmetry is noticeable but it's not like one side has 2 mm and the other has 10. There's a difference of maybe 2 mm between the inner and outer pads, and this is a car that's had more than 54000+ km on the rear pads. So it's not a huge deal if I change them now as opposed to, say, at 70000 km. Still, it would be nice to maximize pad life or know that I didn't screw anything up by lubricating the pins. Next time I take them apart I will see how easily the pins slide. The very first time I serviced the rear brakes, before I ever put on any lube, I didn't think the pins slid very easily. It would be interesting to see what the pad wear pattern is like for a car that's never had the pins lubricated. It's entirely possible that my slide pins are normal and that this is just the nature of the beast as you say.

 

The longer I think about this issue of whether or not to lubricate the pins on these rear brakes, the more I'm inclined to continue to lubricate unless I come across a good reason NOT to, or a directive or maintenance diagram stating the pins SHOULD NOT BE LUBRICATED.

 

Yeah, rahcu2 said that in the service manual, they don't mention lubricating rear slide pins. I'm usually pretty type A about following instructions to the letter. At the same time though, service manuals don't say put anti-seize on wheel hubs and whatnot, and a lot of us do it because we know it's a good idea and that the service manuals weren't necessarily written with Canadian winters and salt slush roads in mind. Maybe some other members on here will chime in with their experience/insights.

 

I mean there's applying a small layer of grease and then there people putting enough to cause the pin not to move LOL! So I don't see a little being an issue.

OP, I'd def have someone help you check and actuate the EBrake while you have the caliper off to ensure it moves in and out freely too. Just things to check and check off.