2015 CX-5 Rear Brake Piston Question: How Does It Work?

[BlueReflex]

I recently did a rear brake pad, rotor replacement. When I "screwed" the parking brake piston in, at some point it wouldn't go in any further. I couldn't get the caliper to fit over the pads. I had to take the backing plates off the new pads, install them, assemble everything then drive around in the neighborhood. After that, everything fit.

My question is how does that piston work? It has to be screwed in, but it comes straight out when you step on the brake pedal. How does it decide it doesn't want to screw in any further. I was using the tool. Is there a YouTube video that explains the operation? It's working, but I'd love to know for the next time.

 

[theblooms]

Wait, you took the backing plates off of the friction material of the pads? You ruined them. Get them off of there IMMEDIATELY. This is a dangerous situation you put yourself in! I'm not kidding! Do NOT drive the vehicle until this is repaired!

Do you have a real emergency brake with a handle, or a button? Because if you have the button, you didn't do the proper procedure. You have to play the Hokey Pokey with the switch to retract the caliper pistons.

 

[CarpeDiem]

If your CX has the electronic parking brake, you may be in trouble if you did not enter the “maintenance/service mode” prior to replacing the pads. What you describe is typical for those owners who did not do this first.

2017~2023 - Need CX-5 parking brake help!

Hi everyone, I replaced the rear brake pads on my 2018 CX5, and now I am having trouble with my parking brake not fully disengaging from one of the discs, causing the pads to drag slightly. I have a lot of experience with brake pad replacement, but this was my first time replacing pads with an...

mazdas247.com

Guide - Maintenance Mode for 2016 / 2017 CX-5 electronic brakes

Great post. Is this the same for 2018 CX-5? Yes, same for 2018 and 2019

mazdas247.com

 

[BlueReflex]

Mine is a 2015 CX-5, the last year with a pull handle parking brake. Any thoughts on the theory behind that device? How come you have to screw it in, yet when you are done, you can just press on the brake pedal and it comes straight out? I'm trying to figure out why when I screw the piston in, I don't have enough room to put my caliper over the pads.

 

[theblooms]

It's because the piston doubles as the emergency brake. It goes out with far less effort than it takes to go in. Hence why you have to twist and push.

And those cubes are straight up awful. They simply don't work.

 

[Jack Rabbit]

Mine is a 2015 CX-5, the last year with a pull handle parking brake. Any thoughts on the theory behind that device? How come you have to screw it in, yet when you are done, you can just press on the brake pedal and it comes straight out? I'm trying to figure out why when I screw the piston in, I don't have enough room to put my caliper over the pads.

You need leveragr.

Use your largest ractchet and extenstions, the larger the better.
Also, see if after brake pads removed, see if you can rotate up and hold caliper out away from rotors and put one caliper pin back in and tighten it...that way you have some extra leverage... Hold the caliper tight when wrenching,. You dont want to break the pin...it's just there to give you a little extra leverage. Most of the force applied should be on your hand/caliper.

 

[HyFlyer]

Just going off of memory but I seem to recall that the action of the pull handle parking brake works with the rotating feature of the caliper piston. It serves two functions ... 1) applying the mechanical parking brake and 2) adjusts the pads closer to the rotor as necessary to compensate for pad wear when you apply parking the brake.

The reason (IMHO, going off memory) you are having an issue with installing your new pads is that you need to both rotate the piston back in AND afterwards (carefully) compress it with a C-clamp.

Surely there is an official procedure in the shop manual

 

[theblooms]

This is the best tool.

Disc Brake Pad and Caliper Service Tool Kit, 11-Piece

Amazing deals on this Service Tool Kit Disc Brake Pad & Caliper at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

 

[yrwei52]

I recently did a rear brake pad, rotor replacement. When I "screwed" the parking brake piston in, at some point it wouldn't go in any further. I couldn't get the caliper to fit over the pads. I had to take the backing plates off the new pads, install them, assemble everything then drive around in the neighborhood. After that, everything fit.

My question is how does that piston work? It has to be screwed in, but it comes straight out when you step on the brake pedal. How does it decide it doesn't want to screw in any further. I was using the tool. Is there a YouTube video that explains the operation? It's working, but I'd love to know for the next time.

Try to review your rear disk brake pad replacement steps with the steps in the FSM:

Mazda CX-5 Service & Repair Manual: Rear Brake (Disc) Removal/Installation

I’d get the much better rear brake tool set like theblooms mentioned above and give it a second try following the FSM. You can borrow similar brake tool set from AutoZone for free, or get one cheap at Harbor Freight Tools.

If you use the better brake tool to turn the caliper position to the proper position indicated in the FSM, and you still have trouble to fit in the new pads, my theory is your aftermarket pads may be too thick than they’re supposed to. Get a different pads or the OEM pads.
.

 

[madar]

Wait, you took the backing plates off of the friction material of the pads? You ruined them. Get them off of there IMMEDIATELY. This is a dangerous situation you put yourself in! I'm not kidding! Do NOT drive the vehicle until this is repaired!

Do you have a real emergency brake with a handle, or a button? Because if you have the button, you didn't do the proper procedure. You have to play the Hokey Pokey with the switch to retract the caliper pistons.

I think he might be talking about a shim. Hope he is anyway.

 

[theblooms]

I think he might be talking about a shim. Hope he is anyway.

I hope so too...

 

[Jmaz]

This is the best tool.

Disc Brake Pad and Caliper Service Tool Kit, 11-Piece

Amazing deals on this Service Tool Kit Disc Brake Pad & Caliper at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

View attachment 314787

Absolutely the way to go. These kits make it easy. Those little cubes are breakable BS and needle nose pliers are apt to break. I bought one of these kits with both LH and RH tools and a bunch of adapters for about $20 from ebay 5 years ago. The auto parts store prices for the kits are expensive.

 

[yrwei52]

⋯. The auto parts store prices for the kits are expensive.

Or just rent one from AutoZone for free. This brake tool eventually wil be obsolete since newer cars will be more likely to use EPB which doesn’t need such tool anymore.

 

[theblooms]

newer cars will be more likely to use EPB

Such a stupid answer to a question that literally no one was asking. But that's a different discussion entirely.

 

[RedBaron]

My question is how does that piston work? It has to be screwed in, but it comes straight out when you step on the brake pedal. How does it decide it doesn't want to screw in any further. I was using the tool. Is there a YouTube video that explains the operation? It's working, but I'd love to know for the next time.

Well, in answer to your original question, this is how (many cars use the same system):

Classic Broncos .com - Tech: Rear Disc Brakes using Cadillac/GM Calipers - 66-77 Early Ford Bronco

Better stopping power for your Classic Bronco with rear disc brakes

classicbroncos.com

 

[yrwei52]

Such a stupid answer to a question that literally no one was asking. But that's a different discussion entirely.

Just saying that you don’t want to buy that brake tool (although I’ve bought one) as it’ll be not very useful with the popularity of the EPB in the future. Just rent it for free.

 

[Jmaz]

Or just rent one from AutoZone for free. This brake tool eventually wil be obsolete since newer cars will be more likely to use EPB which doesn’t need such tool anymore.

Good point for some people. I plan on keeping this car a long time so a kit made sense for me, especially at that price. I've used it twice now and saved trips to AZ and hoping the correct adapter plate is in their rental kit. I don't know what's in AZ's kit but mine has a separate tool for both CW and CCW rotation, so both bases are covered.

 

[yrwei52]

Good point for some people. I plan on keeping this car a long time so a kit made sense for me, especially at that price. I've used it twice now and saved trips to AZ and hoping the correct adapter plate is in their rental kit. I don't know what's in AZ's kit but mine has a separate tool for both CW and CCW rotation, so both bases are covered.

Free tools offered by AutoZone usually have pretty good quality. This’s what the AZ offers for rear disk brake tool set:

 

[BlueReflex]

To clear something up, I removed the clip-on plate to get the caliper on, then drove around the neighborhood. I reinstalled the clip-on plate on the inner and outer pads then everything went on like it has when I did a Mazda6 and a 2007 Accord.

I've looked in to this as much as I can and I still don't see: 1) how can the piston turn and screw in, but finally keep turning, but not go further in. 2) In my case, am I supposed to screw it in until it won't go in any further, then use a C-clamp to get that little extra bit of clearance (the thickness of the shims front and rear)? No one addresses this when explaining a brake job. I think it is rare for this to happen. I got it done and ended up with an extra set of pads unintentionally.

For the person that thought I removed the friction material from the thick metal plates, really??!

 

[theblooms]

To clear something up, I removed the clip-on plate to get the caliper on, then drove around the neighborhood. I reinstalled the clip-on plate on the inner and outer pads then everything went on like it has when I did a Mazda6 and a 2007 Accord.

I've looked in to this as much as I can and I still don't see: 1) how can the piston turn and screw in, but finally keep turning, but not go further in. 2) In my case, am I supposed to screw it in until it won't go in any further, then use a C-clamp to get that little extra bit of clearance (the thickness of the shims front and rear)? No one addresses this when explaining a brake job. I think it is rare for this to happen. I got it done and ended up with an extra set of pads unintentionally.

For the person that thought I removed the friction material from the thick metal plates, really??!

Yeah, really. That's exactly what it sounded like you did. And yes, it absolutely is possible to do. Ever hear old guys saying they needed to "get my brakes relined"? Because that's exactly what it entails. Removing old friction material from the steel backers and installing new. But *nobody* does this anymore, because while it works, it doesn't last, and if you don't know exactly what you're doing, can be dangerous.

Well, I guess I shouldn't say no one does this anymore, because it still is a thing for specialist shops who restore very old classic cars where no other option for new brakes exists. Try finding new brake shoes for a '33 Cord. Nope. So you reline them.