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DJK01

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#237671 12-Jun-2018 14:44
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I am convinced EVs are definitely the way of the future. In New Zealand, by far and away the most popular are second-hand Nissan Leafs. I drove one and quite liked it. But we are put off by reports of brake failure in some vehicles. See: https://www.carcomplaints.com/ and https://www.honestjohn.co.uk/carbycar/ and follow the links for more. Having the brakes suddenly fail, even if it is relatively isolated, is kind of serious! Thoughts? 


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gzt

gzt
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  #2034482 12-Jun-2018 14:54
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There was a recall for a cold weather braking issue. Brake warning light is on where it occurs. Is that the one?

MikeAqua
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  #2034513 12-Jun-2018 15:01
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Generally car companies are OK at sorting out issues and doing recalls.  The only issue might be if the particular model of car wasn't sold in NZ.  Some leaves were, some weren't. 

 

If the car was imported then the car company may not know about it being present in NZ so you would have to be proactive about staying abreast of and following up on any recalls.





Mike


 
 
 
 


DJK01

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  #2034521 12-Jun-2018 15:20
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Not just cold weather but numerous cases. It's worth looking at the threads. Brake failure has been reported for several model years.

 

For example, see: https://www.carcomplaints.com/Nissan/Leaf/2013/brakes/

 

and: https://speakev.com/threads/brake-failure.20745/

 

 

 

 

 

 

 

 


Batman
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  #2034524 12-Jun-2018 15:28
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Are they brake by wire? I never want to buy anything that is electric controlled if possible. Electric steering, electric throttle, electric braking ... why!




Involuntary autocorrect in operation on mobile device. Apologies in advance.


Wheelbarrow01
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  #2034529 12-Jun-2018 15:47
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Batman: Are they brake by wire? I never want to buy anything that is electric controlled if possible. Electric steering, electric throttle, electric braking ... why!

 

Yea I'd hate to have electric brakes when the battery goes flat...


Batman
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  #2034535 12-Jun-2018 15:54
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Wheelbarrow01:

Batman: Are they brake by wire? I never want to buy anything that is electric controlled if possible. Electric steering, electric throttle, electric braking ... why!


Yea I'd hate to have electric brakes when the battery goes flat...



They should include a dynamo with a removable crank arm for that reason.




Involuntary autocorrect in operation on mobile device. Apologies in advance.


DJK01

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  #2034538 12-Jun-2018 16:04
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I believe so. Same problems can also effect ICE cars. Regenerative brakes are supposed to alleviate wear and tear but that doesn't seem to be the problem here; more like software error or a master brake cylinder failure.


 
 
 
 


zenourn
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  #2133510 24-Nov-2018 21:22
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Are now aware of 5 of these failures in NZ - see https://flipthefleet.org/2018/leaf-brakes-failures/ for a lot more details!


Linuxluver
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  #2133746 25-Nov-2018 14:02
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Wheelbarrow01:

 

Batman: Are they brake by wire? I never want to buy anything that is electric controlled if possible. Electric steering, electric throttle, electric braking ... why!

 

Yea I'd hate to have electric brakes when the battery goes flat...

 



If the battery goes flat, you won't need the brakes.

But honestly....if you don't pee your pants, your battery shouldn't go flat.

You'd take care of either need before it became a problem.





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Linuxluver
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  #2133749 25-Nov-2018 14:10
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zenourn:

 

Are now aware of 5 of these failures in NZ - see https://flipthefleet.org/2018/leaf-brakes-failures/ for a lot more details!

 

 

Key take away: You still have brakes, you just need to press a lot harder.

Interesting issue. No experience of it myself and I generally don't tailgate......but on a downhill into a corner you could have an awkward moment if you knew nothing about this and were unlucky enough to be among the 0.001% affected.





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zenourn
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  #2133755 25-Nov-2018 14:31
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Linuxluver:

 

Key take away: You still have brakes, you just need to press a lot harder.

 

 

I think that is the main thing. I think that people get a surprise when all of a sudden the brake pedal behaves completely differently and they have to apply a lot of force. However, it can't be ruled out that the simulation of the failure doesn't fully replicate what happens and there can be a condition where the fail-safe mode doesn't work correctly. In couple of cases people were convinced they were putting as much force on the pedal as possible but still had no braking power.

 

The probability of this happening in NZ for an owner of an affected Leaf is >0.2% in a year. So is rare, but not extremely rare, and more cases are coming to light now.

 

 

 

 


RunningMan
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  #2133775 25-Nov-2018 15:22
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I expect the failure mode is not much different to what would happen on a conventional vehicle that lost the brake booster for whatever reason - brakes will still retard the car, but the pressure needed on the pedal will be far greater for the same amount of retardation. Both feet may be required to push hard enough to stop quickly.


tripper1000
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  #2133779 25-Nov-2018 15:30
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Wheelbarrow01:

 

Batman: Are they brake by wire? I never want to buy anything that is electric controlled if possible. Electric steering, electric throttle, electric braking ... why!

 

Yea I'd hate to have electric brakes when the battery goes flat...

 

 

They have hydraulic brakes are electrically assisted. It isn't fly-by-wire. There is a mechanical linkage through to the master cylinder. It replicates an ICE in almost every way but instead of using a vacuum diaphragm to assist the brakes, it uses electricity. Emulating an ICE that has a chamber that retains some vacuum energy after engine failure, the Leaf has a big capacitor bank to give you a couple of last applications if the car should suffer a catastrophic loss of power.

 

Just like an Ice, if you run out of assistance, the brakes still work, but you need to press harder. It is amazing how many drivers (ICE and EV) who don't know this and will become a passenger in a "run-away-car" only for the post crash investigators to declare that the brakes were working the whole whole time. I've known this happen in traffic jam's where people turn off their engine on a hill to save gas, and inch forward under gravity, and suddenly think they have no brakes when the vacuum runs out and crash.

 

Reading one of those links, it reminds me that the feel of the brakes can change which can be disconcerting/annoying. When you apply the foot brake it gives max regen braking and as you slow and rengen braking becomes less effective, it increases the hydraulic brake assistance to alter the ratio between hydraulic and regen braking. What this means is that the point at which the brake pedal meets resistance moves a bit, and it can give you a fright.

 

Steering is electrically assisted (just like many ICE cars now too) but just like hydraulic's, if the power fails, it still works, but is real heavy.

 

 

 

 


tripper1000
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  #2133788 25-Nov-2018 15:41
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Also, regen brakes gets disabled if the ABS or traction control kicks in as the computer can not shift the regen braking force to individual wheels but can modulate the individual wheel brakes hydraulically. So I guess if a rear wheel was to start slipping it will cut regen braking on the front wheels and increase (presumably) the hydraulic brakes, which will have a delay, change the pedal feel and momentarily alter the cars (nose-diving) attitude.

 

 


DJK01

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  #2133794 25-Nov-2018 15:46
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Very helpful reply but still leaves questions on reliability. It seems on further reading that the master cylinder has failed in a few cases. For example, http://www.carproblemzoo.com/nissan/leaf/brake-master-cylinder-problems.php It may be the 12V battery is low. There is also a possibility of a software error. (The main bugbear for modern cars, it seems.) And the brake cylinder still needs regular tip ups of brake fluid. 


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