[Chazzy J]

I'm interested to get everyone's thoughts here. I've got 40k on the car and haven't experienced any brake related problems at all. So I'm at a stop sign today with two cars in front of me. The two cars in front of me sped off ahead. So it's my turn to stop at the stop sign, so I released the brake and the car starts to roll forward and all of a sudden the car's brakes clamp down. Completely shocked and surprised, I put my foot on the brake pedal to find it's stiff as a rock. There's no car in front of me and there was no reason for the car's brakes needed to clamp down.

I put the car in Park and got ready to get out and see what was going on, but went to put my foot on the brake pedal once more and it started to depress again. My ride to work was completely fine otherwise. I could not get it to replicate.

Again, the two cars in front of me were long gone by the time this issue happened. So I know it was not Smart City Brake Support (SCBS), nor did I receive any notifications that SCBS was triggered. It all felt very mechanical in nature, not like there were electronic overrides taking place.

I've never had anything like this take place. What's your guys' thoughts? Even the dealership isn't sure about this one. Sounds like a brake booster and vacuum issue to me, but again, very strange in how it happened.

 

[lordnikon]

That's pretty scary. May be it's a software glitch?

 

[Back2Mazda]

My guess would be the stiff pedal is because the brakes were used (heavily). This bleeds the vacuum booster temporarily... hence the stiff pedal. OR the brakes were still engaged.
The real question is of course, why did the brakes get applied in the first place? I would guess that the smart city brake support did (mistakenly) engage. I don't know why you wouldn't get a dash light, though. But sensors can give false readings. I often get blind spot warnings when no car is present. I once got the SCBS light on my dash for no reason (it actually scared me a bit... I was afraid my car would brake, but it did not and the light went away seconds later; there was nothing in front of me).

For now, I think you have a mystery on your hands.

 

[Chazzy J]

You know, having never had the SCBS actually trigger, I would have no idea what to expect. Any chimes, dash lights, any of that? I mean I have no idea, and YouTube is less than telling and I am definitely not brave enough to aimlessly go drive my car at a wall at 8mph (haha -- joking...).

It all happened so fast, maybe there was a dash light I missed? Anyone else have their SCBS kick in and result in a hard pedal while it's activated? I did read that the system will release the brakes after 2 seconds of being completely stopped. Maybe that was the time it took me to realize the brake pedal was able to be depressed again?

I would love to chalk this up to SCBS -- that's much more palatable than thinking my baby is just in the business of randomly applying its brakes without warning now...

 

[InKontrol]

To me it sounds like SCBS, because I had it trigger once when I drove up towards the arse of a truck that pulled out on me at a roundabout. Brake pedal was firm for a second or so before releasing pressure and I was able to get going again.

If I remember you do get a message on the instrument cluster when it activates. You could always put a large inflatable in the road and drive towards it to see if it will react in the same way.

 

[Chazzy J]

@InKontrol

Thanks Mate. That helps calm me down a little bit. Really unsettling as I'm sure people can imagine when it seemingly had no reason to do this and I've had no problems inside 40k miles. Don't need anyone to rear-end me because my car decided it wanted to put the brakes on for no reason.

As I was browsing videos, it definitely appears that Europe/Russia has a system that beeps at them. Saw a few videos on the inside of the vehicle and it did beep and notify. While the four I could find of people in the U.S. doing it, it doesn't appear the beep happens unless collision in imminent. All the videos just showed the vehicle silently applying the brakes.

I'll find a nice beach towel to suspend from the garage door (open of course) and see if I can get it to replicate and put this thing to bed.

Cheers

 

[CerealKiller]

My SCBS activated on me today... a car made a right turn in front of me without signalling. I was close, but the other car was already out of my path when the system activated.

A large BRAKE warning message popped up on my heads up display, the brakes then activated a split second later and then they disengaged after a second of being applied. Really jarring experience, as I wasn't expecting it.

Unfortunately, a warning light is triggered on your display when you turn this feature off. If it wasn't for that, I'd leave the feature off and trust my own ability to apply the brakes when needed. Same for the lane departure warnings. Have you ever purposely cut a corner a little for better handling or coming out of the turn faster? Having your steering wheel vibrate every time you do is a little annoying... to say the least.
CK