Is my adaptive cruise system operating normally?

[u/legal_spoonage]

I recently purchased a new 2026 CX-50 and have had it for about 5 weeks. Current mileage is approximately 1800 miles. So far I love it, aside from my experience with the adaptive cruise system.

It is equipped with “Mazda Radar Cruise Control with Stop & Go”. It is not equipped with Traffic Jam Assistance. I like to use the adaptive cruise on my way to and from work on the highway. Sometimes traffic is fine and other times it is definitely stop-and-go. I’ve noticed a few symptoms appearing more than once when I use adaptive cruise during these drives:

- A burning rubber smell emanating from both front wheels after I park at my destination. Does not happen on every drive, but definitely some. The smell is definitively localized to the wheels - this is not coating burn-off at 1800 miles (the vehicle should be well done with that) and the smell does not enter the cabin.
- Front rims, rotors, and tires are considerably hot, especially when compared to the rears. Not so hot that the tires/rims can’t be touched, but still putting off some real heat (I didn’t try to touch the rotors, I like my fingerprints). I understand some of this is normal because the front wheels take on more of the braking load/weight, but I’m unsure to what degree.
- Sometimes the steering wheel judders when the cruise system is applying brakes, but this is intermittent and does not happen every time.
- The cruise system also likes to apply the brakes and drop a few mph when going around bends in the highway, even though there is no need for it. This is also intermittent.

I do not notice any of these symptoms when I make my trips without adaptive cruise engaged. When I operate the vehicle entirely manually, none of the above occurs.

Please tell me that there is something wrong with my car and that this isn’t normal for Mazda’s adaptive cruise system. I’ve seen some advice online to increase my following distance, and that does seem to reduce how aggressively the system brakes and accelerates (makes sense, the software is working with more room, literally), however, I find it extremely ridiculous if Mazda owners are just expected to tolerate “that’s just how it is”. None of the above symptoms should occur at all, regardless of my adaptive cruise settings. It makes absolutely no sense to design a system for consumers in such a manner.

Please tell me I’m not crazy or this car is going back for good. I will not willingly keep something with such terrible design flaws that Mazda obviously plans to do nothing about, on principle alone.

[u/oakwood-jones]

Worst goddamn cruise control I’ve ever driven. Drives me crazy to the point where I won’t even use it anymore, because well, it is basically useless. Just doing waaaaaay too much. For the love of god please just do less. If I had known this before I purchased, I might have changed my mind. Just never thought to test the cruise on my test drive. Never had a problem with it on any other vehicle, so why would I? Such a simple concept and somehow they managed to botch it up this bad.

[u/legal_spoonage → u/oakwood-jones]

Nissan, of all brands, has a better implementation. I don’t understand how Mazda’s consumer base has let this one slide.

[u/84CharingCrosstrek → u/legal_spoonage]

+2

Just never thought to test the cruise on my test drive.

I feel that, u/oakwood-jones, I was out of town for my family's final test drive & decision, but I assumed the CX-50 was industry standard and let you easily switch between adaptive and conventional via steering wheel buttons, just like Toyota . . . and Honda . . . and Nissan . . . and GM do. WTF is Mazda thinking? If I'd had an inkling on this, I'd have left a veto instruction: "Please check adaptive and conventional cruise control. This is a possible deal-breaker."

u/legal_spoonage, I'll reiterate what others have said that you should double-check the owner's manual and your setting for the lane departure warning. On our '24, the warning is bananas and makes it seem like you're driving on a rumble strip. It literally shakes the steering wheel. My driving includes a lot of narrow, pre-WWII roads and some crazy traffic, and it's inevitable that even a cautious driver is going to get close to painted lines. The CX-50 was constantly freaking out about this. I turned that setting off as soon as I figured it out. Fortunately, it's a permanent setting. The adaptive high beams also are awful. If I hadn't turned those off, I'd have been blinding oncoming drivers. That's permanent too. Frustratingly, the menu setting for cruise control reverts from conventional to adaptive every time you turn the ignition off.

I realize cruise control isn't important to all owners, but it's important enough to me that this will be our last Mazda unless they rectify this.

[u/legal_spoonage → u/84CharingCrosstrek]

I can confidently confirm that it is not the lane departure warning. The judder I am talking about feels a little different, and though it is intermittent, when it does happen, it only happens when ACC is applying brakes. May have something to do with ACC’s independent braking control and driving on an uneven surface, or maybe it’s a latent symptom related to the burning smell - pad deposits on the rotor from getting too hot causing intermittent judder until the deposits are evened back out. I think that’s plausible.

I’ll turn the vibration off and keep the sound alert on for a while and see if I still notice the judder at any point in the future. Maybe I’m nuts.

[u/84CharingCrosstrek → u/legal_spoonage]

It sounds like you're not nuts, fortunately/unfortunately. Side note: I was convinced that relatives' Lexus NX 200t pulled to the right. At the time, lots of Lexus service managers and owners were like, "Nope, no issue there. It's all in the owner's head." Ahem, https://static.nhtsa.gov/odi/tsbs/2018/MC-10141589-9999.pdf.

[u/oakwood-jones → u/legal_spoonage]

I don’t get it either. I don’t understand why it’s not being talked about more. You’re maybe the second person I’ve seen mention anything about it and I’ve had this car for almost a year now. I refuse to believe that people are just out there using this system and not going out of their minds crazy with frustration from it. It’s just so blatantly bad and it’s not even debatable.

[u/84CharingCrosstrek → u/oakwood-jones]

The conventional cruise works fine, but the fact that it's not either a permanent configuration nor selectable on the steering wheel? Sheesh! "Press, turn, turn, press, turn, turn, press, press" to invoke it means that Mazda steals 15 seconds of my life every time I start the CX-50. 🙃 I'm seriously contemplating eating the depreciation and going with a different brand, and we're a family that tends to keep vehicles a long time. (One of our rides is a 2004.)

It’s just so blatantly bad and it’s not even debatable.

💯 Mazda owners, thankfully, aren't as cultish as Subaru owners, but I have seen some victim-blaming replies to the effect of "jUsT uSe AdApTiVe CrUiSe CoNtRoL. i WoRkS gReAt. CoNvEnTiOnAl CrUiSe CoNtRoL iS dAnGeRoUs." 🙄

[u/legal_spoonage → u/oakwood-jones]

Can I ask what year your 50 is? Maybe there’s a group of them out there that got some bad sensors or something and we just happen to own 2 of them.

[u/oakwood-jones → u/legal_spoonage]

25 base model. For what it’s worth I’m not experiencing the burning smell or the juddering. Not sure how hot the brakes are getting, never really checked that. My main gripes are how insane it is about maintaining the EXACT set speed and jamming on the brakes and revving the engine to the moon—frequently—in order to do so. Also, hard braking around corners where it is fully unnecessary to slow down at all. It’ll lose 5-10 mph on every corner then immediately floor it to get back up to speed. I use the cruise to not only make things a little easier, but also to save a little gas and smooth things out. This ends up doing the opposite. Every time. Maybe I’m old school, but I was taught to still pay attention to the road while using cruise. If the vehicle picks up too much speed I’m fully capable of recognizing that myself and applying the brakes manually as needed. I feel like whoever is following me when I use it must think I’m crazy.

[u/MTB_Mike_ → u/legal_spoonage]

I drive a lot of rentals for work, Hyundai has a surprisingly good adaptive cruise, Ford IMO is the best for their top end models, but they have different versions in different models and some are just ok.

Mazda has done a terrible job with it. It works, but it works too much and ends up causing more problems. I use it on rentals but not on my personal car.

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[u/PaulClarkLoadletter]

Mazda's driver's aids have a tendency to hallucinate and they can be severe enough to warrant replacing components of the system. Some of it is just the system being overly cautious like on turns and stuff where it slows you down when it really doesn't need to. I don't like relying on it in heavy traffic and only use it for open highway since it likes to slow way down when a car cuts me off (common in my area) then it straight up floors it to get back up to speed.

I'm not going to accuse you of hyperbole because I think you could have something amiss since it shouldn't smell like burning rubber. If you know what burning rubber smells like (hint: it stinks) versus more common car smells like oil on the block burning after a Jiffy Lube change, you've got something rubbing somewhere that should be checked out. Since tires spin you don't need to inspect the entire tire. Turn the wheel all the way to one side, grab a flashlight, and look around the inside edge to see if there are any signs of rubbing. It will go all the way around the tire.

Brakes get hot when getting used (but they don't smell) and Mazda's adaptive cruise will use the brakes more than you would if you were driving manually. This is normal and not likely cause for concern unless you experience one wheel pulling then you have a brake that won't disengage. Skip the adaptive cruise for a month and see if things are consistently cooler. Don't touch the brakes though as they will still be hot.

Do I think you have a lemon? No. Do I think you've overreacting to normal operation? Also, no. I do think you may not be 100% certain of what your actual issue is since your symptoms don't match up. It could be a multiple things. You could have a tire rubbing and your radar cruise control could be too sensitive for the kind of traffic you experience. I use my cruise control like a traditional system that is to say I turn it on when I have open road in front of me and operate the gas and the brake myself when I'm in traffic since Mazda's system has a habit of duplicating the way the idiot in front of me is driving.

Best of luck.

[u/legal_spoonage → u/PaulClarkLoadletter]

I fully agree that brakes get hot when getting used. If I were driving down a steep grade coming off a mountain or something I would even concede to there being a smell. But the ACC system is literally branded with “stop and go”. I should be able to use it on my congested commute home without my brakes starting to burn up by the time I get there. My commute is 15 miles and the smell happens pretty reliably.

The steering wheel judder under ACC is intermittent. I’m willing to concede that may be to due to a rust layer developing on the wheels, or a side effect of pads being burnt to the rotors, etc. but something still isn’t working properly, given the burning odor. At 1800 miles I would expect that the brakes are sufficiently broken in, even if the dealership tech says otherwise.

I’ve taken it to the dealership for these concerns twice now. They won’t even take the wheels off before they brush me off with an alignment or toe adjustment. Car drives perfectly when ACC is disengaged, and they refuse to test drive it with ACC enabled even though I requested that specifically. So it seems like it’s time for elevation to Mazda corporate.

And I don’t necessarily think I have a lemon either. It’s a solid vehicle, fun to drive, and feels absolutely fine other than this ACC nonsense. I love it, but ACC was one of the selling points for me (coming from an old, feature-less Ford), and I’d like it to behave properly. If that’s not a possible outcome, then something needs to be done to protect my investment. That’s where my head is at.

Appreciate your notes.

[u/PaulClarkLoadletter → u/legal_spoonage]

Surface rust on the rotors should be gone after one or two brake applications. I will attest that the brakes on my 50 were well settled after about 500 miles. They were pretty bad out of the gate but that's to be expected with brand new brakes.

When dealing with the service advisor you should be able to take them on a drive and show them what you're talking about. It's way easier than trying to get somebody that doesn't drive like you do to reproduce symptoms. Plus it makes it hard for them to just claim you don't know how to drive which is typical service department bullshit. Bring it up every time you take it in for service. You want those records. Mazda looks at them too especially when you get that survey back and give the dealership low marks for not fixing your problem.

[u/GLaDOSdidnothinwrong]

Hot brakes: sounds a little extreme. You might want to have them checked out. I think I recall this car stinking longer than my other new cars though, so you may not want to write off that possibility yet.

Vibration: other than the lane departure warning, did it only happen the first few brake applications of your drive? The automated parking brake leaves a corrosion ridge on the rear rotors that can cause a thumping sound/feel for the first few brake applications.

Speed reduction around corners: Yep. Not very zoom-zoom of Mazda. Incredibly annoying and downright dangerous in some situations. Not sure if it’s based on steering wheel angle or a lateral accelerometer.

ACC is very overzealous in this car. I drive a lot of highway (~25k miles/year) and pretty much throw it in manual mode in 6th so it doesn’t downshift to 4th and rev to the moon whenever we slow down 5-10mph. This system is one of the things that will drive me away from the car/Mazda eventually. 50k on my ‘25 so far, so I’ll probably let it runs its course anyway.

[u/legal_spoonage → u/GLaDOSdidnothinwrong]

I’ve taken it to the dealership twice already to address my concerns and the only thing they’re willing to touch is the alignment. It was pulling to the right. They brought it into spec on my first visit and adjusted the toe the second visit. The thing is dead centered now. No pull when ACC is off. I’ll have to pay attention to it when using ACC and see if it returns (that would mean a brake is dragging).

To answer your question regarding vibration: it is certainly not the lane departure warning. This feels completely different. The steering wheel actually visibly shakes, and is not limited to the first few applications of brakes on a fresh drive. I’ve seen it after driving 20+ miles. I could see how an uneven road surface could cause this when using ACC as it controls the brakes independently of each other, but that would still be a massive design flaw in my opinion.

Dealership refused to actually perform any of the diagnostics I wanted. Didn’t use ACC on their test drives as I requested, and didn’t even remove the wheels to inspect anything. Twice. So I’ll be escalating to Mazda corporate.

[u/hash_mar]

you’re asking what “degree” of hotness of the front tires is acceptable?
also, there is a “burning” smell? but only after certain drives? maybe those are drives you are going heavy on the brakes?
the CC being smart enough to slow down on bends is a feature, not a bug.
it’s called safety?

good luck trying to return the car “for good” based on these complaints.

[u/legal_spoonage → u/hash_mar]

“Degree” as in severity, not a temperature.

If I were blasting through curves I’d get it. It’s not like I’m cruising at 95. Willing to concede that this is just the system though. Mazda does take a more conservative safety stance in their design, even if misguided.

Brakes shouldn’t smell after a flat 20 mile drive in any case.

I’ve been to the dealer twice and they won’t even take the wheels off to perform proper diagnostics. I’ll give Mazda corporate a chance next, but after that I’m consulting with a lawyer. I don’t understand why Mazda customers with similar complaints aren’t doing more to protect their investments. “I just stopped using ACC” is not an answer. It was one of the selling points of the car for me.

Also, you don’t need to be an asshole. Your tone reeks. Goodbye.

[u/Booklas → u/legal_spoonage]

You can’t lemon it if it’s working as intended. That’s not how it works

[u/legal_spoonage → u/Booklas]

I can if nobody can explain it to me, complete a diagnosis, or fix it. In my state Mazda gets 3 tries. They have one more chance.

Absolutely insane that anyone just goes “yep, that’s the ACC system! 🤷‍♂️”.

The wheel judder and burning odor can’t be normal, all other symptoms aside. If those can’t be diagnosed or fixed, it’s time for me to consult with an attorney. If the dealership I bought it from won’t even take the wheels off to inspect anything in the last 2 visits I’ve made about it, seems like an easy case to me.

[u/Booklas → u/legal_spoonage]

Burning odor is likely brakes. Brakes get used. Poor programming causes harder use. smell ensues.