Rear Brake Pad Wear and Electronic Parking Brake Service Bulletin

As with all noises locating the source isn't always that easy, I did have a look at the rears, but with the wheels on can't see much.

I've put up with it a year so will make more effort to check next spring when I change the wheels again.
 
If you've got an issue with front discs, you can usually feel it thru the steering wheel when braking. If you are getting the on-off rhythmic drumming noise when braking, but no vibration feeling on the steering wheel, then it may be the rear discs.

It can be hard to determine front or rear by just listening to the noise - see my original post where the Mazda tech thought it was front discs on my CX5 when it obviously wasn't, because new discs didn't fix the problem! I always thought the noise was from the rears.

Xtrailman, I agree - on mine, at times the noise is so noticeable that it is quite embarrassing! So I would definitely have your dealer look at the rears and check if your VIN number is within the range stated in the service bulletin. If it is, I would be pointing that out to the dealer!

I'm hoping that the new EPB unit will solve the problem with my car. They told me that they inspected the discs and pads and they are fine so they are only replacing the EPB unit.

We will see.....

I will post back with the results, but I may be a little while because the EPB unit is still on backorder, and is not likely to be at the dealer for at least another week.

Note that while we all tend to refer to discs as "warped", they rarely are actually warped. Mostly there is excessive run out, which basically as I understand it, in layman terms, means high or low spots on the disc. Google it and you'll find more info in this issue.

One other thing - is anyone having issues with the auto transmission gear changes when the engine is cold? Almost every time I drive off when the engine is cold, the auto gear change from 3rd to 4th at about 40km/HR "flares" - the engine revs like it has almost missed the gear change. It does change, but nowhere near as cleanly or smoothly as it should. Only happens once or twice and always on that 3 to 4 change, but as soon as I've driven a mile or so it is all good, nice smooth gear changes as you would expect.

The dealer was told and said they reset the auto and it would relearn the changes, but it made no difference. Any ideas/suggestions?
 
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I look forward to the results of the EPB unit change.

Yes I get the flare now and then, but not often and not enough to determine which gear range I was in at the time, flare is a good description.
 
So the electric brake is malfunctioning and dragging the pads so a NEW electronic brake module must be installed?
 
If the CX5 is over 1 year old and has more than 12,000 miles will they NOT warranty this TSB or will it fall under the 36/3 year?
 
There is a TSB for it XTM. It may also have worn the pads unevenly if the particular fault exists. If you are saying the Mazda pads are cheap, you are wrong. They will have been thoroughly tested and approved. Have a read;

Thanks for the TSB. I think that's my CX-5's problem. My car's VIN is outside the US VIN range listed (newer than the vin's listed) and hopefully they will do the repair per that TSB. My CX-5 has only 7,100 at this time and it's make a loud squeaking noise that turn people's head for the wrong reason.

 
Ok, reporting back.

The local dealer installed the new EPB control unit on Wednesday last week.

As I picked the car up, I said to the service advisor, "well, let's hope this fixes it, how sure are you?" The response - "definitely!". My reply: "I'll let you know!".

Immediately I have noticed a big improvement. The "warped disc" noise has almost totally gone. Initially, I thought there was maybe just a faint noise remaining. But after having driven it for a week now since the EPB control module was replaced, I am fairly certain the noise has gone.

I'm going to keep listening, but as of right now, the problem seems to be resolved.

Will update again if anything changes.

So in summary, it does seem confirmed to have been the EPB issue, as per the TSB, causing the "warped rear Brake disc" noise.
 
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Bumping this thread for awareness. Mine also has brake squeak and its almost unbearable, not to mention embarrassing, when coming to a stop. I took it in to the dealer today and they didn't do anything about it, even after showing them R052/16C. They said I can call Mazda customer support if I want. Really disappointed in Mazda.
 
Bumping this thread for awareness. Mine also has brake squeak and its almost unbearable, not to mention embarrassing, when coming to a stop. I took it in to the dealer today and they didn't do anything about it, even after showing them R052/16C. They said I can call Mazda customer support if I want. Really disappointed in Mazda.

The TSB referred to in this thread does not mention brakes squeaking or squealing.

If you read it, there are some simple and specific tests, some you can quickly and easily do yourself, that will soon tell you whether you have the problem identified in this TSB or not.

The simplest test is to park on a flat piece of road, with the electronic park brake activated, put the car in gear and drive off. If the EPB releases both rear sides simultaneously and there is no pulling or dipping to one side, then likely your problem is something else. An inspection of the pads and comparison between one side and the other will also verify that.
 
I have a 2016 CX-5 that was just in for an oil change and installation of winter tires. The service agent informed me both rear brakes needed replacing as well as the routers. My car is at 44,000km (27340 miles). I'm not very mechanical but I always thought front brakes took a lot more of the load than rears. On the inspect sheet they provided, my fronts are an "8" and I believe he said the rears were a "2" and they had dug groves in to the routers. I've not had an issues with noise from my brakes. I could visibly see lots of rust on side of the router that is visible when looking at it. I had the work done, as I realize brakes are important and I didn't want to take any chances, however I am feeling more robbed than usual (as I never feel great after leaving any service department). I've rarely used the e-brake. I read about CX-5's from 2014 and earlier with rear brake issues. The service guys explanation for how this could happen just went over my head, which I am unsure if it was intentional or not. I'm still trying to figure out if this is normal for the distance I drove or not as my first Google answer is that brake pads can wear out from 15K - 85K (not sure if it was miles or kilometers), which I feel within the range of. Without the noise most of you reported, I'm not sure if this is a plausible explanation or if its something else that should or shouldn't be paid by me. Thanks
 
Hmm, well, Ive had some astonishing conversations with dealers over brakes and having spent 17 years in the Research and Development Dept of Ferodo - one of the major friction material manufacturers in the world, I can usually put up a pretty good fight.

Lets discuss your question first. There is no way of declaring what the life of friction material should or could be. It can range from indefinite at the top end to surprisingly short at the bottom. There are lots of variables but the main driver is temperature. Brake pads are made up from about 60-70% steel fibre. This provides physical strength to hold it all together and withstand the tremendous shear force involved with braking. The rest is made up from the abrasives and lubricants that stabilise friction through a wide temperature range and the resin system that binds it all together. The resin system degrades with temperature and constantly presents the friction element to the disc. Here is the crux of the matter. If you dont get the pads warm, you wont wear them out. If you get the pads very hot, they will wear out very quickly - its all down to duty level and it is on a non-linear scale so if you get a certain level of wear at a certain temperature, you might triple or quadruple it by doubling the temperature.

In a practical example, a very steady driver that lives in a flat location or only ever drives on a highway may rarely get the pads hot. This will lead to very long pad life. Somebody who drives a car hard, fully loaded with cargo and in the hills might get only 5000 miles or less. Pads react to the way they are used so getting them hot will excite friction and wear the resin which compounds the wear rate and pads that stay cool will go to sleep and reduce in friction - they get conditioned to the duty they are subjected to. Thats how temperature effects wear.

Now consider what happens to the vehicle. If you take an average duty cycle on a vehicle with varying duty and varying speeds and therefor varying temperature you can arrive at a suitable specification for the brakes. The rate of deceleration is measured as a percentage of 1g. 1g = 9.81 metres per second squared. Its about 32 ft per second squared. In practical terms, easing up at traffic lights might be about 30%g, a harsh stop where loose items would roll off a seat is about 50%g and a hard emergency stop will be about the point where the tires lose grip with the road surface and will be up at 75%g on a dry road. Using statistics, designers will calculate the amount of weight transfer during and average stop. This tends to be about 65% of the work done at the front and the remaining 35% at the rear and that is typically how big the pads are by surface area. That means that under average conditions, the pads will wear evenly despite the large difference in area. Are you with me so far?!!!

If the pads wear unevenly, in other words the fronts wear out before the rears or vice versa, there is something interfering with that predicted typical duty cycle. If the car is predominantly loaded and driven hard, it will transfer more weight - especially if there is a high centre of gravity - maybe a roof box and four or five passengers. If the car is driven normally with a loaded cargo floor or heavy weight in the back, the load apportioning valves in the hydraulic system will apply lots of pressure to the rear and the rears may wear out quickly.

Now for my prediction on what happened when your service dept hit you with this unexpected news. Firstly, and I say this with good and bad intentions towards the dealer, anything to do with brakes on a car is an easy money spinner for dealers. If they follow the manufacturers recommendations, the brakes should be in near to perfect condition with plenty of pad life and very little disc wear. The trouble is that they are designed wearing parts so that goes out the window soon after you start racking up the miles. The dealer is on a bit of a sticky situation because if the car has an accident after an inspection that can be in any way apportioned to the brakes, he is liable. If a mechanic inspects the brakes on a vehicle, he usually does it with the wheels on and that presents a problem because he cant easily get square on to the pads to get a good view - there simply isnt enough room. A good light and a mirror on a stick helps but still not ideal so he ends up taking a considered guess as much as an accurate measurement. Ill give you a good example of this. When I booked my 2016.5 in for service, they wanted to charge me for an oil change and a brake inspection. I wasnt having any of this as I do my own oil change and I am reasonably well qualified (read that as as expert as any brake engineer in the world) to measure my own pads. I told them that I would be changing the pads during my own inspection before the service. When I did this inspection, the pads were a lot less worn than I expected and I calculated they would do at least another 12 months so serviced the brakes and put the pads back. When I collected the car, they listed all the items that justified the bill and one of them was weve inspected the pads and are documenting them as 20% worn", the minimum the computer would allow them to enter. This was nonsense - they were approaching half worn but I didnt engage them, I just made a mental note to ignore any future life predictions.

Where does this leave you? Not an easy one. If my TV breaks I have to rely on an electronics expert to mend it. As far as Im concerned its a box full of magic and they could tell me anything, I would just have to trust them and cough up. I have to say that Im as surprised as you that the rears are so worn if they really are but its not impossible for all those reasons above and I cant get my head in from over here so Im not much use in that respect. I think I would go to a reputable local garage and ask them for a second opinion. If you do give in to the dealer, ask to see the new pads and ask them to keep the old ones and let them explain the difference in wear if it really exists.
 
Anchorman - I thought I read somewhere in the shop manual that under light braking the rear brakes were applied to a greater extent to aid directional stability? I understand that under heavy and panic braking due to the weight shift most of the work is done by the front but reviewing the brake wear experience of posters here, a lot of them have a higher wear rate on the rear pads than the front even before the new electronic parking system...
 
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Anchorman - I thought I read somewhere in the shop manual that under light braking the rear brakes were applied to a greater extent to aid directional stability? I understand that under heavy and panic braking due to the weight shift most of the work is done by the front but reviewing the brake wear experience of posters here, a lot of them have a higher wear rate on the rear pads than the front even before the new electronic parking system...

I’ve had a look through all my stuff including media release descriptions and I can’t find anything of that nature. When cars are tested to EU or US legislation, they have to meet a set of guidelines called “adhesion utilisation” legislation which governs how the brakes behave under dynamic braking. Applying the rear brakes before the front brakes is actually quite unstable and something the designers would normally avoid but look, I don’t know what you have read and with the scope of a modern computer controlled system you can do much more. There is one thing only that suggests very strongly to me that the front brakes still lead the rears and that is the fact that the area ratio between the front and rear pads have not changed. One of the fundamentals of braking is that friction is independent of area. In theory, you could have a slice of a brake pad narrowed down to any width and you wouldn’t detect the difference by driving the car. This is because in this small pad there is more pressure per unit of area. However, what would change is the rate of wear and that links back to how hot it would get and the time taken to get hot. In other words, if they were going to change the bias towards the rear brakes under low-pedal pressure, they would have to increase the rear pad area to compensate and they haven’t. They might also benefit from using a vented disc as they are pushing more heat to the rear. I know all this seems to justify accelerated rear pad wear and although it gives a solution to our problem, it doesn’t have the changes in design that would need to go with it. BTW, if you can find what you read, please let me see it so I can understand what they are trying to achieve.
 
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