2018 CX-9 GT - Serious Brake Fade

S

Srad600

:
2018 CX-9AWD GT
So Im just curious if anyone else has experienced serious brake fade in their CX-9?

I recently took a trip to Big Bear Lake with the family and on our way down the mountain (in traffic) I noticed the brakes starting to get quite lumpy. Theyve never felt like that before, although Ive felt this happen on motorcycles while doing a fast pace in the past, so I had an idea of what was happening. After a while the braking action was dulled (it took longer to achieve the same speed reduction with all else being equal). Finally the fronts felt like they were just badly warped. Every time I touched the pedal the whole car shook. In the end I made a few passes to get to the front of the line, so I could use more engine braking and ride the pedal less in order to help cool them down. By the time Id gotten about 3/4 down, the brakes felt smooth again, but stopping distances were still long. After driving at highway speeds for about an hour to get home, the brakes felt completely normal again.

So, yes we all made it home fine, BUT I think this brake performance was pretty sub-par. Its a 7 passenger vehicle, and we had six passengers; two very small kids - (20lbs / 38lbs respectively) my wife, mother-in-law and myself. We did have luggage in a roof rack, but mostly light items (bulky jackets, boots and some snowboard gear). I would think we should have been well below the maximum loading for the car. Temps were low-moderate, and speeds were fairly slow. Brakes and tires were checked before we went on the trip, and pad life was still very good. Ive been going to the mountains for years in a few different vehicles, but never had a car brake fade this bad in my life. Especially considering how slow the pace was. Its got me a little concerned (a lot concerned) about subjecting the car to those conditions again.

Anyone else have issues like this? Thx.
 
I've driven fully loaded down before. Or at least, what I would consider fully loaded down, which was my wife and infant daughter plus about 300 lbs of weights in the passenger seat and 800-900 lbs in the cargo area. But I was driving mostly on flat terrain, with only moderate curves, though at slightly over speed limits. Never experienced any brake fade. Maybe the maximum loading doesn't take "excessive" braking into account. I'd raise the concern with your Mazda dealer or MNAO to see what they say, but I have a feeling they'll give you some boiler plate answer about not braking too hard with a payload that heavy.

It seems that you may have to look into upgraded rotors and pads for more peace of mind.
 
How many miles on car? I had same experience after around 35k on my 2016 GT. Just got new rear brakes and its a lot better.
Mazdas engage the rear brakes first so they wear out quicker. But if youre at low miles, it might be a different issue. I looked into any performance upgrades for brakes and theres nothing significant for this car that worth the money. I did opt for new rotors rather than turning them as its such a small extra charge these days, as new rotors are cheap.
 
sm1ke said:
I've driven fully loaded down before. Or at least, what I would consider fully loaded down, which was my wife and infant daughter plus about 300 lbs of weights in the passenger seat and 800-900 lbs in the cargo area. But I was driving mostly on flat terrain, with only moderate curves, though at slightly over speed limits. Never experienced any brake fade. Maybe the maximum loading doesn't take "excessive" braking into account. I'd raise the concern with your Mazda dealer or MNAO to see what they say, but I have a feeling they'll give you some boiler plate answer about not braking too hard with a payload that heavy.

It seems that you may have to look into upgraded rotors and pads for more peace of mind.
Click to expand...
I agree (that talking to Mazda will likely yield a boilerplate answer), especially since in *normal* driving conditions, the brakes seem fine. Although I don*t consider that type of driving *excessive*, I*m guessing they will state it*s beyond what they consider normal. I think I will need to research a BBK, just in case. It*s one thing taking a risk myself, but quite another with the babies in the car.


Rawbone said:
How many miles on car? I had same experience after around 35k on my 2016 GT. Just got new rear brakes and it*s a lot better.
Mazda*s engage the rear brakes first so they wear out quicker. But if you*re at low miles, it might be a different issue. I looked into any performance upgrades for brakes and there*s nothing significant for this car that worth the money. I did opt for new rotors rather than turning them as it*s such a small extra charge these days, as new rotors are cheap.
Click to expand...

The car is right around 22,000 miles, so very low mileage for a two year old vehicle. I*m disappointed to hear that there is a lack of aftermarket support for big brakes on these cars, but I suppose it*s not really a *performance vehicle*, so that is to be expected. I*d look into turning the rotors if the problem persisted, but as soon as things cooled down the brake operation felt normal again. Now every time I want to go boarding I*m going to second guess myself though.
 
Srad600 said:
I agree (that talking to Mazda will likely yield a boilerplate answer), especially since in *normal* driving conditions, the brakes seem fine. Although I don*t consider that type of driving *excessive*, I*m guessing they will state it*s beyond what they consider normal. I think I will need to research a BBK, just in case. It*s one thing taking a risk myself, but quite another with the babies in the car.
Click to expand...

I hear ya. Options for BBK:

WP Pro (Winner Power Pro) - This was the first option I found, but I can't seem to find their original website that actually listed the 2016+ CX-9. EDIT: Here's some more info on WP Pro, posted by a vendor on my.is.

Ceika - Their site is fantastic, and allows you to build and price a custom BBK setup. Looks like the cheapest option is $1290 for a front BBK with "X-Small" 4-piston calipers and 286x22 mm rotors and street pads. Front + rear in the same config would be $2380. But if I were spending that much, I'd spring for the "Large" 4-piston calipers and 330x28 mm rotors. Anodized color selection for the rotor hats, calipers and Ceika logo are free. Rotor surface options (slotted, drilled, drilled+slotted) are also free.

Have you considered just doing OEM-size replacements for rotors and pads? StopTech, EBC and Centric offer drilled/slotted/blank rotors and pads for ~$500 and below.
 
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Start with pads and slotted rotors, no need for a BBK set up when you only subject the car to such conditions every so often. Slotted rotors might reduce bite tho, but the added surface area will theoretically shed more heat faster. Also just use engine braking a lot. My 2019 on radar cruise control will switch to lower gears automatically when it detects that the vehicle is going downhill. It doesn't hurt the car even if the engine spins at 4k+ RPM constantly because there isn't any load on it.
 
Also has your emergency braking engaged much? As a anxious city driver, I*ve had the system engage way more than I*d like, even on the lowest setting. I*ve been suspect that it contributed to faster rear brake wear.
 
Totally agree*this is a heavy car with average brakes but it responds great to manual mode. I*m always in manual when driving in hilly conditions and it makes a huge difference.
 
sm1ke said:
I hear ya. Options for BBK:

Have you considered just doing OEM-size replacements for rotors and pads? StopTech, EBC and Centric offer drilled/slotted/blank rotors and pads for ~$500 and below.
Click to expand...

Yeah, I'm pretty open to all options at this point. My main concern is just upgrading the system to avoid fade, I'm not stuck on one route or another to achieve that goal.

azuzu said:
Start with pads and slotted rotors, no need for a BBK set up when you only subject the car to such conditions every so often. Slotted rotors might reduce bite tho, but the added surface area will theoretically shed more heat faster. Also just use engine braking a lot. My 2019 on radar cruise control will switch to lower gears automatically when it detects that the vehicle is going downhill. It doesn't hurt the car even if the engine spins at 4k+ RPM constantly because there isn't any load on it.
Click to expand...
Yeah, I'm definitely keeping my eyes open for options. Re: engine braking, I did do that in the end BUT that's not always an option. Initially I was in a line of vehicles, following one guy who was riding his brakes pretty bad. So in that situation, it's virtually impossible to control speed with engine braking. Once I was able to get up to the front of the line, then I was better able to use the motor to slow the car without braking.

Rawbone said:
Also has your emergency braking engaged much? As a anxious city driver, I*ve had the system engage way more than I*d like, even on the lowest setting. I*ve been suspect that it contributed to faster rear brake wear.
Click to expand...
That system has been activated a few times, but i'd say less than 10 total times since I bought it.

Rawbone said:
Totally agree*this is a heavy car with average brakes but it responds great to manual mode. I*m always in manual when driving in hilly conditions and it makes a huge difference.
Click to expand...
Yep, agreed.
 
Srad600 said:
After a while the braking action was dulled (it took longer to achieve the same speed reduction with all else being equal). Finally the fronts felt like they were just badly warped. Every time I touched the pedal the whole car shook. After driving at highway speeds for about an hour to get home, the brakes felt completely normal again.
Ive been going to the mountains for years in a few different vehicles, but never had a car brake fade this bad in my life.

Anyone else have issues like this? Thx.
Click to expand...
Same exact thing happened to us on the drive down the hill from Lake Tahoe to Reno. There was only the wife and I in an unloaded 2017 GT. Was trying to use the brakes sparingly, on for 10 seconds then off for 30-40. The whole front end was shaking when applied like a badly warped rotor. CX-9 has about 35K miles and pads look good. Looking at the Power Stop Z23 K7690 Sport Pad and Rotor upgrade kit for the fronts.
 
Frankly, nobody should be surprised by this. Disappointed, yes. Just about every manufacturer skimps on the brakes these days. I had the same experience in a newer minivan recently - the brakes are too small for these larger vehicles.

Brakes are heavy and kill CAFE ratings. A vast majority of people never drive in the mountains or tow anything so they will never experience a problem.
 
Brake discs don't warp. They develop uneven deposits of pad material when the temperatures are too high for the pad material. This is the cause of the brake judder.
https://www.onallcylinders.com/2016/10/07/brake-3-brake-system-myths-theyre-false/

So...(a) use engine braking. That's important to keep brakes cool.
(b) Buy brake pads with a higher temperature rating.
(c) Clean the rotors with emery cloth and brake-clean solvent to remove the uneven deposits.
(d) slots in rotors will allow the hot gases off the pads to bleed away thus helping the grip.
(e) If the brakes were hot enough the fluid was damaged from the heat. Renew the fluid. DOT3 fluid will be fine. If one wants the higher heat tolerance of DOT4 fluid remember that it degrades faster from moisture and must be renewed more often than DOT3.
 
Sounds like your brake pads overheated and got greasy. I would first try upgrading to higher temp brake pads. Hawk may make some as they make performance pads for Mazdas. Then bed in the new pads properly. You'll want to first get some brake cleaner and scotchbrite pads and scrub off the old brake pad residue from the rotors. Then install the new pads and properly bed them in.

No need to turn the rotors. that just removes metal that you need to absorb and handle heat.

I've done this multiple times replacing my pads on my RX8 for track days and never had to turn my rotors.

If you still have problems with a soft pedal the next thing I would try is flushing your brake fluid and replacing it with DOT5 brake fluid. It's better at higher temps as well.
 
flushing your brake fluid and replacing it with DOT5 brake fluid.
Click to expand...
NOOOOO!

DOT5 brake fluid is silicone based. It is not suitable for ABS systems due to being more compressible. DOT5 fluid must not be mixed with even trace amounts of DOT3 or 4 fluid due to chemical incompatibility. The mixed fluid may gel.
DOT5 brake fluid does not absorb moisture. That means that any moisture in the system will puddle at the low points, may cause corrosion, and may readily flash to steam under the heat of very heavy braking. Steam in the brake system compresses and your pedal goes to the floor.

#1, don't get your brakes so hot; use engine braking.
#2, DOT3 DOT4, DOT4+, and DOT5.1 brake fluids are all polyglycol ether compounds, and they're compatible. The higher the number the higher the temperature rating, and...the borate compounds added to the higher rated fluids also absorb moisture more readily so these fluids must be flushed and renewed more often. DOT4+ is an unofficial rating of some European fluids with a very high boiling point. DOT5.1 meets the performance spec of DOT5 but with different chemical make up.

You may see the word "synthetic" on some bottles of brake fluid. Don't get scammed. All brake fluid is synthetic; there's nothing natural about polyglycol ether or silicone. (Some tractors use hydraulic oil for their brakes. That's natural. This isn't a tractor forum.)
 
That's right. I was mistaken. It's DOT4 not DOT5 brake fluid. But start simple. Try higher temp brake pads first. See if that helps. Then try another item only if you need to do more. One thing at a time.
 
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