"Pulsating" braking force

I started noticing the following in the past few weeks. When slowing down, at around 20 ~ 30 mph, the braking force sometimes seems to be “pulsating”, i.e. while I am keeping constant pressure on the brake pedal, I can feel the braking force fluctuating in a repeated pattern with a period of around 1 to 2 seconds. It is as if I am moving my foot up and down on the brake pedal.

Anyone experienced this?

At first I thought doing the NTB12086 will fix this issue but it didn’t.

I've noticed similar "fluxtuations" a couple of times in the past few months but it was hardly noticeable to the point that I'm not even 100% sure it wasn't caused by the road condition. However I'm pretty sure that I haven't got any "grabby brakes" for quite some time. What about you? IMO those two might be related: In order to reduce "grabby brakes" at low speed Nissan engineers might had to tweak some settings which have introduced the fluctuations at higher speed. The system which balances mechanical braking with regen is probably very tricky to adjust.

ABS? Traction control?

I'm pretty sure I am not imagining the "fluctuation" in braking force. I don't think it is the ABS in action because this happens when the braking force I am applying is gentle to moderate (I am not slamming on the brakes).

I had both this fluctuating brake force and the grabby brake issues. I took it to the dealer to have the brake unit reprogrammed. The grabby brake issue seemed reduced but this brake force fluctuation remains.

My experience is this is worse in cold/cold,wet weather. My brakes are behaving crazy now and they weren't like this in Oct. Just going to ride out the winter. This weekend should be 55*F we'll see what happens then when we're back at "normal" operating temps.

Warped brake rotor?

rslatkin said:

Warped brake rotor?

Click to expand...

That could be since with cold batteries we're doing a bajillion times more friction braking than relying on regen.

ABS would be a much more rapid pulse, as would warped rotors at 30 mph. I think it's more likely a modulation of the regen intensity. I've always noticed somewhat variable deceleration with the car as this happens. Particular states of charge and/or temperatures could make the difference of whether you're on the cusp of a transition (speculation).

Was ECO mode on at the time?

Not in ECO mode. I think Nubo's words "modulation of the regen intensity" is an accurate description.

So it seems that I am not the only one experiencing this.

I've noticed too, but rarely, and yes, it does feel like the regeneration is pulsing. Definitely not warped rotors.

I experience this as well, but at very slow speeds. Typically I am coming to a stop at a red light and I get it when my speed is in the single digits. I bit disconcerting.

I got some decent data yesterday and today. First of all it was happening in the morning so there was a little dampness in the air and the battery was at its coldest. What I did was turn on the energy use monitor on the dash. When it pulsed the display was bouncing between 15-20 kwh on the regen. You could actually see the "needle" move in time with the pulses on the brakes. It was definitely NOT the ABS. It happened again this morning and the monitor showed the same data. It seems to be worse in ECO than drive (2012 model). In both instances there were only 2 bubbles of available regen showing on the dash. The center bubble that's always lit and then two to the left. The last two on the left were not available for regen and there were only 8-9 bars of charge displayed so like 70% SOC?

This didn't happen last year to this extent. I wonder if the extreme December cold had something to do with it. However, Sunday was 50-60*F and the battery warmed up to 5 temp bars even though it cooled off again to 4 yesterday and today (40*F).

Note...there was no one in front of me or behind me so I could stare at the data screen while braking. Duh, I was careful.

I noticed this after the grabby brake fix was released last year. It feels like a grabby brake, except it lets go, then grabs, then lets go (pulses). Happens at the same speed and in the same type of conditions that a grabby brake occurs.

My grabby brakes went away about the same time I had a seatbelt repaired in the spring of 2013. Thought they must have installed the update.

When it got cold this winter, they came back. I've experimented alot with it. I am pretty sure that it the regen braking, because if I shift to neutral when slowing down and apply the brakes it doesn't happen

My $0.02

I'm in the same camp here and notice it only seems to happen in the cold as well. I wonder if it has anything to do with a weaker 12V battery?

I've been experiencing this issue, at least at low speeds.

However, I also suspect that my LEAF's brake rotors might be warped, a consequence of having lousy regen at ~70% SOC while descending our big mountain (4900' descent). From time to time, the brakes seem to overheat and cause the car to shake violently. Needless to say, I try to avoid letting the brakes get that warm by driving more slowly (for more regen) and/or stopping for a few minutes to let them cool.

This morning I got one case of this which lasted the most for me since I noticed it for the first time. I would guess it did last for 3 or 4 seconds. The conditions were: very gently brake to decelerate from around 40-50mph while in ECO mode. Altough I kept the same pressure on the brake pedal, the car slowed down unevently in a pulsating way (between 1 and 2 oscillations per second) until I had to brake harder to not rear end the car in front of me. My tires are new, brakes and rotors are fine. Road was flat and smooth. No wind, no earthquake. I do believe the regen's causing this.

I have been experiencing this, and sometimes it seems like I may not be able to control the vehicle. Fortunately, it's at slow speed, but in traffic is is really disconcerting.
Temperature may be a factor. When it was around 0-10F I had a bad case, which is worse in the snow and ice. My battery temp gage was at 1 bar.
I would have thought the rotor was warped, but then it would not change with temperature and moisture.
I love my 2011 Leaf, but this is a significant flaw.

I don't think it's a warped rotor. It happens to me when the battery is very cold and it can't seem to decide if it's going to use regen or friction for braking. When it gets even colder then the problem doesn't occur because regen is down to less than 10kWh. Seems to happen most when capability for regen is between 10-20 kWh and the battery is cold. When it warmed up the other day all was good and when it chilled out again the problem reoccurred but when it was stupid cold like 5*F there was no problem.