"Pulsating" braking force

[dgpcolorado]

Does the grabby brake problem go away when you are in neutral or at 100% charge (no regen)? If so warped rotors can be ruled out. I'm going to repost this from the grabby brake thread:

Grabby at high or low speeds? There's a (temporary?) fix if it happens at low, which is: Turn off traction control, inch forward, hold and press down the brakes FULLY for about 30 seconds. That's it. Mine used to be super grabby on/off style at low speeds, but now they're normal.

I have no idea why this works but it does for me as well. The grabby brake problem went away for weeks and when it returns I just do the procedure again to fix it. [And no, it has nothing to do with driving with traction control off, after doing the procedure one turns it back on.]

FWIW, costs nothing to try it.

 

[neverpa]

I have been trying to figure out what this is too. I guessed that it was salt or dust interfering with some component of the regen. system. I washed the wheels which seemed to temporarily fix the problem. I will try the brake pedal holding technique mentioned in this thread today. 2012 LEAF almost 25000 miles. Dealer suggests bleeding brakes and/or changing brake fluid.

 

[Nubo]

Dealer suggests bleeding brakes and/or changing brake fluid.

Yes. Get the non-pulsating type. :lol: :roll:

 

[abasile]

Some weeks ago, we charged our LEAF to "100%" and took it to our mechanic for a tire rotation and requested a brake inspection. The idea of doing a full charge was to force the use of the friction brakes as much as possible. It also didn't hurt that the battery was relatively cool (four bars).

The mechanic did do a fair amount of driving, as the car had about 25% less charge when we picked it up. The friction brakes actually checked out just fine, with no work required. While the mechanic has a reputation for being honest and competent, I'm sure they would have been happy to charge us for brake work had it seemed necessary. But they didn't.

I'm now feeling pretty certain that the "pulsing" I was encountering had to do primarily with the brakes getting hot while descending our mountain.

Thankfully, I'm no longer commuting to a job down the mountain, so this is not as big a deal for me anymore. (It would have helped if I could have charged regularly at work, thus enabling me to leave the mountain with a much lower SOC, but that's now water under the bridge.)

 

[KenB]

I too am experiencing this problem. Happens during a full charge or any charge. Happens in Eco mode or D mode. Trying to figure out why this happening. At times it feels as though the regen braking is not happening.

 

[TomT]

It still sounds like a classic case of warped rotors to me...

 

[jclemens]

I really do not think it is warped rotors. I have my energy screen on all the time and I am quite certain this is a regen issue. If the rotors were warped, I'd feel this pulsing brake force at other speeds, and it would be vibrating at highway speeds. It is as smooth as a baby's ass.
I tried the disable traction control trick, I am still not sure, but it seems to have worked. I just drove with it off for my commute during a couple dry days here.

It is really hard to reproduce in regular traffic. I'm not going to bother talking to my dealer about it. I can just imagine their bewilderment.

 

[ttweed]

It still sounds like a classic case of warped rotors to me...

The "classic case" of warped rotors is a myth that has been perpetuated for many years. Rotors do not warp, even under the extreme stress of racing applications, which is far more strenuous than any Leaf will have experienced in road driving.
http://www.stoptech.com/technical-support/technical-white-papers/-warped-brake-disc-and-other-myths

From this article by Carroll Smith (a highly respected automotive engineer):

With one qualifier, presuming that the hub and wheel flange are flat and in good condition and that the wheel bolts or hat mounting hardware is in good condition, installed correctly and tightened uniformly and in the correct order to the recommended torque specification, in more than 40 years of professional racing, including the Shelby/Ford GT 40s – one of the most intense brake development program in history - I have never seen a warped brake disc.

In fact every case of "warped brake disc" that I have investigated, whether on a racing car or a street car, has turned out to be friction pad material transferred unevenly to the surface of the disc. This uneven deposition results in thickness variation (TV) or run-out due to hot spotting that occurred at elevated temperatures.

I have not experienced anything but the "low-speed grabbiness" and the high-speed ABS brake assist anomaly with the Leaf, and I think they are both functions of the complex programming for consumer safety and for integrating regen braking with mechanical braking that is necessary on the Leaf. I seriously doubt that there is any mechanical/physical fault with the braking system--it is software related, IMHO. After 41K miles, my brake rotors and pads looked barely worn when I inspected them on the last tire rotation. They certainly have never been stressed enough to "warp."
YMMV,
TT

 

[Nubo]

In fact every case of "warped brake disc" that I have investigated, whether on a racing car or a street car, has turned out to be friction pad material transferred unevenly to the surface of the disc. This uneven deposition results in thickness variation (TV) or run-out due to hot spotting that occurred at elevated temperatures.

Agreed. "warping" is a misnomer. Brake rotors can get hot enough to visibly glow, and still be within design specs -- that's their purpose; to turn motion into heat. Heat only becomes a problem if it goes beyond the limits of the pad material or causes the brake fluid to exceed its boiling point.

 

[TomT]

Yes, that is true, but they can and do develop variations in thickness. While technically not warp, that generic but inaccurate name for the symptom has persisted over the years...

It still sounds like a classic case of warped rotors to me...

The "classic case" of warped rotors is a myth that has been perpetuated for many years. Rotors do not warp, even under the extreme stress of racing applications, which is far more strenuous than any Leaf will have experienced in road driving.

 

[blackleaf]

I'm now into my 3rd winter with the leaf, and I have run into the grabby and pulsing brake force issues each winter.

It goes away in spring and comes back about February. Seems obvious that it is not a hardware issue like "warped" rotors. Must be in the SW of the regen or something in the hydraulics side of the brake mechanism. Something that would change with temperature, humidity, or something that cares what the temperature is like the regen SW.

Obviously, I'm not much of a complainer. I have not asked Nissan or dealer about this issue. But seems like there are enough people with this issue, and it continues now in 2014 after the 2011 product launch, that maybe Nissan is aware? It can get a bit unnerving at times when I am decelerating off of the freeway and the brakes start pulsing as I go into a turn at the bottom of a ramp. Dare I say unsafe?

Is anyone aware of any comment/fix or whatever from Nissan? I see the grabby brake fix noted above. I'll try that this week and see if it does anything for me.

Thanks everyone!

 

[blackleaf]

Tried it out...worked great, no more pulsing/touchy brakes. Strange but simple solution.

 

[KenB]

What worked??? I too have this problem. Happens when it is cold outside. When it warms up outside, it goes away. What is this fix?
I tired to disable the traction control and the pulsating remains.

 

[kubel]

What worked??? I too have this problem. Happens when it is cold outside. When it warms up outside, it goes away. What is this fix?
I tired to disable the traction control and the pulsating remains.

Release the brake entirely and reapply. That will stop the pulsating brakes temporarily. It's the exact same temporary fix as the grabby brake issue, so I think they are related. It feels like it's regen-friction hand off related. It just started back up now that temperatures are reaching the upper 20's and lower 30's.

To clarify, this is not warped rotors. Warped rotors pulse at the speed of wheel rotation. In this case, the pulsing is not fixed to wheel speed at all.

 

[TickTock]

Neither this nor the " press brake hard for 30 seconds" worked for me. I don't think it has anything to do with the regen mixing - at least not directly. It appears to just be an issue with their brake-by-wire algorithm. I have the regen and fiction pressure displayed at all times and have been watching its behavior during these episodes. I've seen it happen at full friction and at mostly regen. The target *total* breaking force seems to be what is going non linear. It becomes digital ( you can choose high brake force or no brake force - nothing in the middle).

 

[rpmdk]

Press the brakes hard did seem to work for me. When I got the software update last year that appeared to fix the brakes, but just a couple weeks back I noticed it starting again. I tried holding down the brakes hard at a red light on the ride home and then didn't seem to have the grabby brakes after. I hope it is a software glitch and not a brake problem that needs fixing.

 

[TRONZ]

Had the pulsing for about a month now. Not cold here and does not happen every time. Usually felt under light steady braking with no pedal modulation. My guess has been regen software/sensor having a disagreement with thinning brake pads.

 

[rpmdk]

Had the pulsing for about a month now. Not cold here and does not happen every time. Usually felt under light steady braking with no pedal modulation. My guess has been regen software/sensor having a disagreement with thinning brake pads.

What is odd is that it started suddenly, the software update seemed to fix the problem, then one day it just started again. Maybe there is a threshold for thinning brake pads?

 

[fishstunts]

likely the same sticky brake problem starting to show up that many others seem to have. Turning off traction control, inch forward slightly and then hold the brakes for 30 seconds firmly and see if that helps any. It seems to help in some cases but I have found that the brake pads are part of the problem on mine. If I take off the pads, sand them down a little to clean them and clean the rotors with rotor spray, the problem is greatly reduced for a while (few weeks at best). I am going to try another type brake pad if I can find an option available. If that does not work, then I need to figure out the brake boost system to see if any mods are possible. I don't think it is a computer coding issue.

Our leaf is very bad with the sticky brake problem and making me think of getting out of the lease if I don't figure it out. It's driving me nuts.

 

[fishstunts]

UPDATE:

I went to Pep Boys auto parts and bought some better ceramic pads and rotor cleaner. Installed the pads last night and cleaned the rotors. Drives perfectly. No sticky brake problem at all. Now lets see how long that last.

The OEM pads were the long lasting metalic type. The new pads are ceramic type. If the problem comes back, I may try altering the pad mounts for lack of a better performance caliper available. One thing I noticed while working on the brakes is that the car has super slack control arms. They move too easy in any direction. Its just a ball joint type connection on the lower arm instead of a performance car setup with bushings.