Took delivery of our 2012 coming up on a week ago.
Before we bought it, it had sat on the lot for approximately 4 months.
It appears that as part of the certification it did receive new brake pads front and rear, but I noticed at pickup that the rear rotors showed abnormal contact patches.
Having put 500 Kilometers+ on the car now (over 300 miles) these are the wear patterns we are seeing now. Passenger side rear rotor first, drivers side second.
It seems to me that the calipers are partially seized, as despite the rust and such on the rotor from sitting on the lot for several months, after 500K (and enough friction vs regen braking) I'd expect to see nice clean contact patches now.
Thoughts? We have a short term warranty and will be getting this addressed, but if it's a somewhat common issue then I'll have some more talking points. Seem to me that the only way to address this is to replace the calipers, knowing what I know about what happens when they start to seize up.
The rear brakes rarely get used. Only under extreme braking or under 3mph. We've had problems on both of our 2013s. The best thing you can do is to put the car in neutral and hit the brakes every couple of weeks. It will force the car to use the friction brakes. And will keep them nice and free.
Rear disc brakes in general operate at about 25% of the Front discs due to forward weight transfer when the brakes are applied. The Front end Dives while the backend Lifts. I would go out and purposely use heavy braking pressure to see if the rears Clean themselves better. If you don't see any positive results after a couple weeks, then by all means, have the rears gone through. I have heard it's not uncommon to see stuck calipers on the Volt due to the heavy use of L to maximize Regen mode during in town driving. Some are suggesting you should pull the calipers apart every couple years and rebuild them to keep them fresh. This is something you don't normally need to do on any Regularly driven standard gas vehicle.
Have to see the pads to really know. It appears the bottom of the pad is touching first but it could also be the rears aren't really being applied and just dragging with the bottom of the pad slight out (could be it's unclipped or tilted from the piston.) I would do whatever is necessary to get the hydraulics to apply the brakes hard a couple of times and see if the rotor rust is removed. Rust from water could also be what is cause that pattern since the edge sees water from the road. It's normal to get get surface rust in just a couple of days. It's not harmful but does sound ugly until the pad removes it.
Perhaps letting others chime in before attempting, but would pulling the parking brake switch while moving be more effective for cleaning the rear pads and disks? I know it won't engage fully unless stopped and only applies brakes while the switch is held down when the vehicle is moving.
The advantage of the parking brake would be that you could continue using the accelerator while applying the brakes, and only the rears are used. However, depending on how the parking brake cable(s) is/are adjusted, it might not apply equal pressure to both sides, and you could draw an incorrect conclusion if the patterns on the two sides were different. If you use the parking brake and only one side gets cleaned, I would try Ravadac's suggestion of shifting to neutral, and thus get strong, equal pressure.
bentbiker, you do bring up a point that I think may need addressing. I know in most cars, the rear brakes are adjusted through the use of the parking brake mechanism which has a ratcheting screw like device inside which manually engages the pads and when disengaged the pads maintain proper clearance. Do the volt rear calipers also have such a mechanism? and if so, would regular operation of the parking brake be necessary to keep the rear brakes adjusted properly?
Here is how the Electronic Parking Brake system works and self calibrates
This is a copy& paste from my AlldataDIY subscription.
Your Vehicle: 2013 Chevrolet Volt L4-1.4L Elect
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Vehicle » Brakes and Traction Control » Parking Brake System » Parking Brake Cable » Service and Repair » Procedures » Parking Brake Cable Adjuster Enabling
Parking Brake Cable Adjuster Enabling
The park brake cable tension is controlled by the electronic park brake (EPB) module. Cable tension needs to be set and the EPB module needs to be calibrated following the cable tension disabling procedure. Perform one of the following two methods to fully restore cable tension.
Electronic Parking Brake Cable Tensioning
With Scan Tool - Preferred Method
Block the drive wheels.
Install a scan tool to the vehicle.
Turn the ignition switch to the ON/RUN position with the engine OFF.
Select Configuration/Reset Functions from the electronic parking brake control module menu.
Follow the instructions on the scan tool.
Without Scan Tool - Optional Method
Block the drive wheels.
Turn the ignition switch to the ON/RUN position with the engine OFF.
Apply the brake pedal.
Place the automatic transmission in PARK or manual transmission in NEUTRAL, as equipped.
Momentarily lift then release the EPB switch to apply the EPB.
Momentarily press down then release the EPB switch to release the EPB.
Repeat step 5 and 6 to cycle the EPB on then off an additional 4 times.
The EPB module will be calibrated and proper tension will be applied to the parking brake cables.
bentbiker, you do bring up a point that I think may need addressing. I know in most cars, the rear brakes are adjusted through the use of the parking brake mechanism which has a ratcheting screw like device inside which manually engages the pads and when disengaged the pads maintain proper clearance. Do the volt rear calipers also have such a mechanism? and if so, would regular operation of the parking brake be necessary to keep the rear brakes adjusted properly?
Are you by any chance thinking of drum brakes where the adjusting ratcheting screw is turned when the drum brakes are applied while in reverse? I'm not familiar with a parking brake being used to adjust pads on disc brakes.
Thanks for the post on that DMC5180. It does explain how the cable adjustment and equalization part works, but I was more referring to the caliper itself where the cable attaches. Granted my knowledge on brakes tends to be pre-2000 models mostly, but I was referring more to the caliper itself and the mechanical portion that the cable attaches to. In past vehicles, even having the cable properly adjusted and working, you could still have maladjusted rear brakes because the preload that is created through the ratcheting effect of the brake caliper lever. This is part of why on rear brakes you generally had to twist the caliper piston back in rather than the traditional method of using a c-clamp which would be done on the front.
Engaging the EPB multiple times as the optional method describes should accomplish the preloading that I was initially referencing. Although on older cars it was generally done with the brake pedal at rest, engage parking brake, apply brake pedal, release parking brake, repeat.
Are you by any chance thinking of drum brakes where the adjusting ratcheting screw is turned when the drum brakes are applied while in reverse? I'm not familiar with a parking brake being used to adjust pads on disc brakes.
No, this was on disks. I had intimate experience on an old Fiero I used to have. The parking brake assembly is a severe source of headache on those cars. Also my '94 Olds was similar. The lever in question is pulled by the parking cable, and turns a screw inside the caliper which is attached to the piston to engage the pad to the rotor, when the cable tension is released, the lever returns to the rest position but the piston stays in it's "new" position. When replacing the pads on these types of calipers one generally has to twist the piston back into the bore rather than the traditional push with a c-clamp or other device.
edit: Usually disks don't require adjustment in such a fashion since the fluid is sufficient, but on the units I have experience on, the rears didn't self-adjust due to the parking brake mechanism design. I know if I went a few weeks without using the parking brake, it wouldn't be immediately noticeable however after I used it, you could definitely tell a change in brake operation from the rear.
My daughters 2000 Grand Prix had rear discs, but the Parking Brake was a Mechanical drum system with small brake shoes inside the rotor mounting flange. We also had a Lincoln Mark VII that had the mechanical Piston setup where you had to rotate the piston with a special tool to push it back in for new pads.
Take the car out on a nice back road and make about 10 hard stops from 70 mph down to 30 or less. And by hard stops I mean stand on the brake pedal! That should clean it up, or reveal if they are sticking or frozen up.
Perhaps letting others chime in before attempting, but would pulling the parking brake switch while moving be more effective for cleaning the rear pads and disks? I know it won't engage fully unless stopped and only applies brakes while the switch is held down when the vehicle is moving.
I realize it will engage as I did it myself to test since I like to know what my backup options are in an emergency situation. I just wasn't sure if others had a legitimate reason why this shouldn't be done. What I meant by it won't engage fully is that on dry pavement it shouldn't lock the rear brakes up, but it will definitely pull your speed down.
Every year I take the calipers off all our cars and lube the pads/slides and never have an issue. This is needed, along with rotor and pad replacement on this car.
The OP has some nasty looking calipers/rotors. I guess that is from living way up north. I have 64K miles and they still look like the day I bought it.
Yes, seized callipers, strip and replace slide pins, clean pad carrier, clean everything up, you'll be fine. Just tell the vendor what the situation is, if they know they had to replace the discs then they should already realise this is a possibility.
The OP has some nasty looking calipers/rotors. I guess that is from living way up north. I have 64K miles and they still look like the day I bought it.
Yes...Canada. The rust belt does take it's toll on any sort of unprotected metal such as calipers and rotors. Thankfully the rest of the car is spotless so far as rust is concerned.
I'll try the rapid deceleration option and see if that seats things better, but I'm not expecting much - we've had a few rapid decels (unexpected yellow lights, etc) and this is all that's shined up so far over 700KM of driving now.
I'll try the rapid deceleration option and see if that seats things better, but I'm not expecting much - we've had a few rapid decels (unexpected yellow lights, etc) and this is all that's shined up so far over 700KM of driving now.
Perhaps you already realize, but even aggressive application of the brakes (while in gear) might not engage the actual friction brakes -- the increased regeneration from heavy foot pressure makes it hard to tell if the calipers have been called into service. Use of either the parking brake, or shifting to neutral before using the brakes, takes regen out of the picture, and ensures that the friction brakes are activated.
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