Brakes "mutate" to become grabby in stop & go traffic?

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Coffee_Slurry

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Joined
Sep 13, 2010
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Location
Broken Arrow, OK
I was stuck in slow-moving traffic going downhill, gradually releasing and applying the brakes to creep along, one car length at a time. (No accelerator at all.)

Over about 10 minutes, the brakes took on a very "binary" feel -- they were either grabbing hard, or fully released, and I couldn't gently apply them. They became very "grippy" and abrupt. I tried releasing completely, but didn't get any improvement.

I put the car in park for 10 seconds or so, and then Drive, and everything was fine.

Anyone else experience something like this?

Just to restate -- at no time did I feel "unsafe", I just had very little analog control of the brakes. With cars close behind, I didn't want to experiment further.
 
This has been mentioned in other threads. It has happened to me on a couple of occasions too. The consensus seems to be that it has to do with the anti-lock brake controller. So far it has been annoying but not dangerous.
 
91040 said:
... The consensus seems to be that it has to do with the anti-lock brake controller. So far it has been annoying but not dangerous.
Interesting. I've noticed the brakes becoming "grabby" as well, but never thought about it being in the anti-lock brake controller.

However, that would be consistent with what happened to me the other day: I had to stomp on the brakes to avoid an accident when a pickup cut me off on a 4 lane / 30 mph road. The ABS kicked in, but didn't feel like any other brake system I've felt in our other cars. Instead of the break peddle pushing back in a rhythmic pattern (like someone hitting the back of the peddle with a hammer), it felt more like a vibration.

The disconcerting part had to do with what happened next as I let up on the peddle before coming to a complete stop: the ABS system didn't disengage until I took my foot completely off the peddle. By then the car had come to a complete stop and I was checking the rear view mirror to see if someone was going to rear-end me. Luckily there was no one close behind me, so I pressed on the gas and the car took off like nothing had happened.

The next time I find myself alone on a street (and can do so safely) I plan on stomping on the break again to see if I can replicate the situation. Meanwhile I'll try putting the car into "Park" the next time the brakes feel "grabby" and see if that makes a difference.
 
See these threads.

Grabby brakes-
http://www.mynissanleaf.com/viewtopic.php?f=8&t=6086" onclick="window.open(this.href);return false;
http://www.mynissanleaf.com/viewtopic.php?f=4&t=3916&start=0" onclick="window.open(this.href);return false;

Braking after release of brake pedal- http://www.mynissanleaf.com/viewtopic.php?f=30&t=5888" onclick="window.open(this.href);return false;

Also the wiki has some info- http://www.mynissanleaf.com/wiki/index.php?title=Brakes,_ABS" onclick="window.open(this.href);return false;
 
Yep, they all seem to do that. It is most obvious (and annoying) when creeping along in very slow traffic and using the brakes to modulate your speed without taking your foot all the way off the pedal. The digital effect becomes more and more severe as you slightly apply and them remove pressure from the brakes while moving slowly. Taking your foot all the way off the pedal seems to reset the system and then the cycle starts over again and become more severe as you use them without fully taking your foot off and releasing them. I particularly noticed it the other day when I had to go a couple of miles in traffic that was only moving at best a few miles an hour - never fast enough, for the most part, to allow the brakes to be fully released. To me, it felt more like Brake Assist getting confused than the ABS. Perhaps the software algorithm is not quite what it should be...
GroundLoop said:
I was stuck in slow-moving traffic going downhill, gradually releasing and applying the brakes to creep along, one car length at a time. (No accelerator at all.)
 
Yes, I had too had been commenting about that behavior a while back.
I concluded it might be part of the "brake assist" feature.
I gather there is one panic stop scenario where they decided it is safer if the car "takes over" and brakes for you to complete the stop. Unfortunately it seems a little touchy and does that even for low speed minor stop and go incidents.

I bet Nissan will adjust this behavior in some future rev of the car (or firmware update). It is just a little too annoying and intrusive at times.
 
GroundLoop said:
I was stuck in slow-moving traffic going downhill, gradually releasing and applying the brakes to creep along, one car length at a time. (No accelerator at all.)

Is there a reason why you didn't use ECO so you wouldn't have to use your brakes so much? Even going down the mountains, I always use ECO and rarely need to use my brakes.
 
LEAFfan said:
GroundLoop said:
I was stuck in slow-moving traffic going downhill, gradually releasing and applying the brakes to creep along, one car length at a time. (No accelerator at all.)
Is there a reason why you didn't use ECO so you wouldn't have to use your brakes so much? Even going down the mountains, I always use ECO and rarely need to use my brakes.
I don't think ECO will help if you are creeping along. At least I can't seem to get any regen at all at very low speeds.

Ray
 
Are these "annoying" braking characteristics being reported to Nissan (877-664-2738)?

To help Nissan become aware and improve the LEAF, we should be reporting these "unexpected" vehicle control "problems".
 
Since I was stuck in this very slow moving traffic for more than an hour, I had a chance to play with different modes and see what affect, if any, they had. The bottom line was that the escalating "grabby" brake issue was the same in both D and Eco. And at the much slower than walking pace speeds I was going, you basically can get almost no regeneration so it was pretty much all friction brakes... Either using the parking brake or placing the car in park/neutral so you can remove your foot completely from the brake pedal on occasion seems to be the only solution to clearing the problem in such a situation. In my opinion, it definitely is an issue they need to address - and could actually be a safety consideration - and I suspect it has to do with the Brake Assist function logic.

LEAFfan said:
GroundLoop said:
I was stuck in slow-moving traffic going downhill, gradually releasing and applying the brakes to creep along, one car length at a time. (No accelerator at all.)
Is there a reason why you didn't use ECO so you wouldn't have to use your brakes so much? Even going down the mountains, I always use ECO and rarely need to use my brakes.
 
I've experienced the same thing while creeping in traffic, also in Eco mode. Happened during the gridlock of the San Diego power outage. Thanks for the tips about using Park or removing my foot from the brake completely.
 
This is very interesting, as I have never seen a car behave this way. It's very repeatable, and the other threads are describing the same thing.

I'm also coming around to thinking there might be an actual safety risk here. If stop & go traffic progresses up in speed to where you're allowing a full downhill roll, the mildest application of brakes could get you rear-ended.

I don't think it has much (if anything) to do with regen, since regen wouldn't be used at these low speeds and, after all, it works just fine for a while. The friction brakes shouldn't be this touchy.
 
Presumably, when you reach a "full downhill roll", your foot is off the brake, and the system has reset. BTW, I've noticed this brake behavior, too, and remember reading about it previously.
 
Has anyone actually talked to the mechanics at the dealer about this? It's frustrating to see people pointing out other threads on the same issue as if it's just some newbie issue. Those threads don't have any resolution and are a waste of time to read. This is a real problem and needs to be addressed by Nissan.

I'm happy to be the one who actually goes to the service department with this, I'm just wondering if anyone has tried that yet.
 
GroundLoop said:
I was stuck in slow-moving traffic going downhill, gradually releasing and applying the brakes to creep along, one car length at a time. (No accelerator at all.)

Over about 10 minutes, the brakes took on a very "binary" feel -- they were either grabbing hard, or fully released, and I couldn't gently apply them. They became very "grippy" and abrupt. I tried releasing completely, but didn't get any improvement.
I have experienced this behavior, but have not reported it because I have not spent the time to see if it's reproducible. I think my circumstance was similar to yours: stop-and-go traffic requiring irregular use of the brakes.

JustinC said:
Has anyone actually talked to the mechanics at the dealer about this? [...] I'm happy to be the one who actually goes to the service department with this, I'm just wondering if anyone has tried that yet.
I don't like going to the dealer with a problem that is not readily reproducible. It'd be a waste of my time and probably theirs too. The best I can hope for is a recorded diagnostic trouble code (DTC) that may or may not provide a clue, though I imagine if it's worthwhile for the car to record a DTC, it would have shown me a warning light or two as well.
 
You are correct about the warning light, without one there is likely nothing recorded since those codes would generate some type of alert if recurring.
 
The best thing to do is, if you can reproduce the issue, schedule a service appointment and bring the car to the dealer to demonstrate to them. They can enter it into their system and Nissan would work toward a resolution. I am going to do this, but first I'm reading other peoples' experiences here to figure out how to consistently reproduce the problem for the dealer.
 
It's not a challenge at all -- I can reproduce it 100% in a 5-minute test drive.
All it takes is a downhill grade and some patience. Stop, creep forward, stop, creep forward..
keep it up for a short while and the brakes freak out.

I'd prefer to do this in the dealer's own demo car, so mine doesn't end up in their service bay for two weeks. :)
 
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