2012 RT - what's needed to compress rear caliper piston?

[LouW]

I’m replacing the rear brake pads on my 2012 RT. Look like they need to compressed and not screwed in like the more modern units. Appreciate and comments on this job.

[Snowbelt Spyder]

Yep, that's all you do. The manual and some videos talk about using a small C clamp - while the old pads are still in there to do the compressing on. But using a large, bladed screw driver in between the old pads to wedge them apart works just as well and is less awkward to use. And that's how you compress the front calipers, anyway. One thing to remember, you'll need to remove the parking brake pulley, and then be sure to turn the parking brake shaft fully CCW. It won't fall out. If it's not backed off fully, then the piston can't retract far enough.

When you put the parking brake pulley and cable all back together, have that right side panel off so that you can watch the front parking brake pulley and cable as you test the brake. When you disengage the parking brake, the front pulley will always rotate CCW until it actuates that micro switch. When the parking brake is disengaged you don't want a slack cable. Otherwise, you get a big bow at the front pulley and the end can pop out. So, you're adjusting the parking brake cable with those two nuts on the bracket in the back, so that when the parking brake is disengaged, there is still spring tension on the cable coming from the rear pulley. If the cable is slack and bowed, adjust the nuts to tighten the cable until the rear pulley just begins to turn. That’s how you keep the spring tension on the cable. Check that the brake doesn’t drag.

When engaging the parking brake, the front pulley rotates CW until the brake engages and the cable gets tight. It then turns itself off. It doesn't operate the switch. If you run out of cable adjustment with the two nuts, you remove the rear pulley and rotate it to another spline on the shaft. If you mark the pulley and the shaft before you remove it, then you can put the pulley back onto the same splines that it was. You never make brake or cable adjustments with the front pulley, only the rear. You may want to observe how the parking brake system operates before you disassemble the rear pulley.

There's a tab that sticks out the back of the rear parking brake pulley. You'll see that it acts as a backstop for rotation as the brake is disengaged. You want a small air gap between that tab and the bracket it goes up against when disengaged. And of course, don't forget to hook the spring as you put the pulley back on the splines.

It'll all be less complicated once you get into it. It sounds worse than it is.

[LouW]

Thanks for the information it’s been helpful however I’m don’t think this caliper is completely compressed so I attached a picture. I haven’t been able to find any video that includes this caliper. Everything on YouTube is 2014 or newer. BF5BBBFA-756F-42EB-825A-F72FBEE43AFA.jpg.

[PW2013STL]

Thanks for the information it’s been helpful however I’m don’t think this caliper is completely compressed so I attached a picture. I haven’t been able to find any video that includes this caliper. Everything on YouTube is 2014 or newer. BF5BBBFA-756F-42EB-825A-F72FBEE43AFA.jpg.

That should be fine, but if you do need more clearance a C clamp works great.

[LouW]

I can’t get this to compress any further but still need more clearance. Is this supposed to go down until it’s completely flat??

[PW2013STL]

I can’t get this to compress any further but still need more clearance. Is this supposed to go down until it’s completely flat??

Did you back off the parking brake?

[CopperSpyder]

I can’t get this to compress any further but still need more clearance. Is this supposed to go down until it’s completely flat??

Did you take the cap off your master cylinder? Make sure and take a little brake fluid out before you retract the piston or it will dip down the side of the cylinder.

[Peter Aawen]

Yep, that's all you do. The manual and some videos talk about using a small C clamp - while the old pads are still in there to do the compressing on. But using a large, bladed screw driver in between the old pads to wedge them apart works just as well and is less awkward to use. And that's how you compress the front calipers, anyway. One thing to remember, you'll need to remove the parking brake pulley, and then be sure to turn the parking brake shaft fully CCW. It won't fall out. If it's not backed off fully, then the piston can't retract far enough.

......

I can’t get this to compress any further but still need more clearance. Is this supposed to go down until it’s completely flat??

It is supposed to go down until the top of the piston is level with the caliper body.

Most people doing this on those early Spyders that don't get it down that far haven't turned the parking brake shaft fully Counter-ClockWise as per Snowbelt Spyder's earlier response (see the quoted bit ). Is that your issue too, or have you done that already??

[Snowbelt Spyder]

Hey Lou. The piston in the rear caliper does not go in and become perfectly flush with the caliper body. It's close, but not entirely. It still sticks out some. But, as said, be sure that the parking brake shaft has been turned fully CCW until it stops. It will turn by hand. Then just compress the piston until it stops going in. You can use the C-clamp if you want, but I've never needed to. You don't need a lot of force. The C-clamp just gives you a different angle on it. However, it can be a bit deceiving - when you put the new pads on and try to install the caliper, everything is a bit out of alignment still and it feels too tight. It just takes a bit of wiggling and twisting of the whole assembly to get the disc to go in between the pads. When everything aligns up, it will suddenly just slip right on.

[LouW]

Thanks everyone. I going to give this a try again tomorrow. The parking is turned completely turned CCW. The center of the piston is about level with the body it must be right but the edges are up as pictured. It must be in the right position.

[pegasus1300]

apparently my thumbs aren't as strong as they used to be so I went to NAPA and bought a brake piston compressor. It fits down into the caliper so you get a straight shot at the piston and don't cock it off to one side. It was pretty cheap.

[LouW]

So the end of this story is I purchased the brake piston compressor. I couldn’t get a good enough grip the the c-clamp. I was able to compress it until it was almost flush and install the new pads. Even at this point they were a tight fit. Test drive complete.

[cptjam]

We put a socket over the parking brake shaft, and then a good sized C clamp. Works perfectly, and no strain. Ann usually turns it while I hold it in place. Gets very close to flush. Pads go right in. Fits!

[davev1pa]

Oh me likey the socket tip placed over the actuator!! Thanks! Dave