Frozen rear caliper pins, options?
 

Doing a brake inspection because I felt stopping power was low and I find that the REAR lower caliper pin (the one with a boot) is frozen on BOTH sides. I suspect previous owner didn't notice as well. One side still rotates but both sides can't be pulled out by hand, gonna try hammer/crowbar later. Here's the picture of the caliper pin with boot I'm referring to.

Has anyone run into this issue and does the support bracket usually needs to be replaced in this scenario? If its seized and I do manage to get it out will there be melted rubber boot/crap that I have to clean out from the bracket anyways?

You can see the inner pad on both sides is worn much more than the outer, so I've been driving around with 6/8 stopping power.

@FrickingReallySlow

It's somewhat normal to have slightly uneven pad wear on sliding calipers. It's part of the trade-off of the design. Looking at your image (assuming that's your caliper on the bottom), I don't see a sign of abnormal pad wear.

The pins aren't necessarily supposed to rotate. They should just be able to slip in-and-out with some ease to enable the bracket to adjust to the pad position. I would associate initial pin seizure with excessive heat/wear due to the pads unable to release contact with the rotor. I would also check the condition of your brake fluid and ensure there isn't any grease or contaminant on your pad/rotor system for loss of braking power.

1. Are the dust boots still in good condition and intact?
   • Dirt and dust getting into the grease and contaminating it can cause the pins to seize.
2. Have you or the previous owner repacked the pin grease before the seizing occurred? What kind of grease are you repacking those pins with?
   • It's a known issue that improper pin grease will cause swelling of the rubber and seizing

Hard to say if you need to replace the bracket. I doubt it though. You'll need to make that judgement call once you get them apart. You could opt for brackets or calipers from a wrecked car, remanufactured ones, or new ones if you need peace of mind.



With regard to your caliper pins seizing, I'm not sure the potential cause. I have never had an issue with any of mine in 120k miles of ownership. I've only had to maintain/replace them once at around 100k miles plus track days. I never had trouble pulling mine out or spinning them, and they moved just fine. During the maintenance check, I did replace a couple of the bushing inserts due to wear/cracking as well as a few torn dust boots, but they didn't give me any trouble. I got some off-brand ones that fit the system from my local auto parts store, which fit fine. I later overhauled a totally different set of rear calipers from another track car using the OEM Toyota/Subaru rebuild kit, which also went smoothly and easily. Note that both these sets saw decent track time, they saw a lot more heat and load than they typically would on the road.

Forgot to add that the pads on the front were worn evenly (inner vs outer) which made me think the back should be even as well. Got both caliper pins out finally and those bushings definitely expanded. 1mm in length and 1mm in diameter. More than enough to get caught and stuck. And you're probably right someone might have used the wrong grease inside.

Interesting enough, I just bought new rear caliper pins from Subaru and they came with bushings installed but no grease between the bushings and pins even though the factory manual says to grease between the bushing and pins. They're hard to take off and will probably expand if I do so just gonna leave it like that and grease the outside with silicon grease this time

I wouldn't worry about the bushing expanding. They're rubber; they can handle the the stretching. The brake rebuild kit sold by the dealership has the bushing separate, so you have to stretch them over to install them (which is how they got them in there the first place)


I recommend getting the good stuff from the dealer. Buy once and never have to think about it again: https://parts.toyota.com/p/Toyota__/...888701206.html ; I use it on all sorts of other stuff now that needs a tiny bit of lubricant; rubber intake hoses slip fittings, wire pulling, etc.

I'm sure Subaru has an equivalent spec which will work just as fine.