Oh my! What big brakes you have!

[DarkStar]

From Edmunds Inside Line (http://blogs.insideline.com/roadtests/2011/03/2011-nissan-leaf-suspension-walkaround.html).

Rockin' two-piston calipers:

Personally, I had the opportunity to do a panic stop in the rain yesterday morning and the LEAF did NOT let me down! When I saw this article I learned why!

 

[Herm]

either the caliphers are oversized or the rotor is undersized, going by the looks... I dont think anyone will ever wear out a set of Leaf brakes. Sure looks nice!

Interesting bit on the rear supplemental stabilizer bar, its welded on so not an easy task to experiment with oversteer/understeer settings.

 

[davewill]

either the caliphers are oversized or the rotor is undersized, going by the looks... I dont think anyone will ever wear out a set of Leaf brakes. Sure looks nice!

Interesting bit on the rear supplemental stabilizer bar, its welded on so not an easy task to experiment with oversteer/understeer settings.

The presumption has been that there are scenarios where the brakes will have to stop the fairly heavy Leaf with no assistance from the drivetrain. Hence, these monster brakes.

 

[DarkStar]

The presumption has been that there are scenarios where the brakes will have to stop the fairly heavy Leaf with no assistance from the drivetrain. Hence, these monster brakes.

In the event of a sudden acceleration issue, the brakes are required to be able to stop the vehicle with the engine (or motor in this case) being fed 100% throttle (or accelerator). That's why they're huge!

 

[TomT]

The main consideration is the requirement that the brakes have to be able to handle a long downhill run with a full battery, which means no help from regeneration and, of course, no engine braking. That accounts for their size more than anything else.

But just a point: The size of the brakes really has nothing to do with how well they will stop you in a typical single panic stop. The brake balance and tires have more to do with that. And virtually any modern braking system can overwhelm the propulsion system at rest. What the size does have an affect on is how many times you can stop that way or how long you can continuously use the brakes. Their ability to handle and dissipate heat in other words.

The presumption has been that there are scenarios where the brakes will have to stop the fairly heavy Leaf with no assistance from the drivetrain. Hence, these monster brakes.

 

[Electric4Me]

Oh my! What big brakes you have!

This reminds me of when my wife and I were driving along and we came upon a Mercedes AMG convertible with huge front brakes...and a beautiful blonde at the wheel. When I saw the huge brakes the car guy in me fortunately got to my mouth first and I said something like "Holy Cow! Look at the size of those brakes!"

She laughed and said "that's not what I thought you were going to say!"

To which I replied "How dumb do you think I am?" :lol: :lol:

 

[mark13]

That was a interesting pictorial..Thank You

 

[aqn]

The presumption has been that there are scenarios where the brakes will have to stop the fairly heavy Leaf with no assistance from the drivetrain. Hence, these monster brakes.

The main consideration is the requirement that the brakes have to be able to handle a long downhill run with a full battery, which means no help from regeneration and, of course, no engine braking. That accounts for their size more than anything else.

But just a point: The size of the brakes really has nothing to do with how well they will stop you in a typical single panic stop. The brake balance and tires have more to do with that. And virtually any modern braking system can overwhelm the propulsion system at rest. What the size does have an affect on is how many times you can stop that way or how long you can continuously use the brakes. Their ability to handle and dissipate heat in other words.

I agree. This contributes to why ABS became widely implemented: even the wimpiest brakes can lock up the wheels of the lightest car with the stickiest tires at all but the crawling-est speeds. Big brakes mean more stopping force, better brake feel and control, better fade resistance, etc. However, it's but one factor in the "whoa" equation; tires is another (big) factor.

On the quite porky LEAF, with fairly narrow tires that are relatively long-wearing (warranteed for 65K (!) miles), i.e. hard, with a UTQG of 400, versus 180 for a Bridgestone "high performance" tire, the Potenza RE-11) and therefore not exactly sticky, I would think that the two-piston calipers are there for a purpose other than short stopping distances.

 

[kaelev]

Anybody seen this? Looks like a lawsuit waiting to happen!

panic stopping observation on the LEAF

by GeneF Jun 29, 2011; 08:10am ::

I was wondering if any of you have had experience with sudden stopping
performance on the LEAF, or other EVs with regenerative braking.

Last week I was accelerating behind a semi truck going up I-5.
Frankly I got too close and somebody must have pulled in front of the
truck; the trucker slammed his brakes on.
I did the same. (Commonly called a panic stop.)
The brakes locked up,and I heard the tires screeching. The car maintained
its direction, thank God, and I did not spin out.
When I realized I wasn't going to rear end the semi, and he was not
stopping anymore, I released the brake. At this point I was probably under
35 MPH. What happened next came as a surprise to me. The brakes seemed to
be still stopping the car; wheels still screeching. I thought I was going
to come to a complete stop, but they finally relented, and I accelerated
back up to speed.
I think the time I applied the panic stop brake was only for about 3/4 of
a second, the continued braking seemed to last at least another 1/2
second, by then I think I was down to 20MPH, and the gap between me and
the truck was several hundred feet.

I went into Tonkin yesterday to discuss this with the service writer; he
said that is "normal" regenerative braking! He said I should have pushed
on the accelerator pedal to get it out of that mode. He says as long as
the warning lights did not come on, everything was working normally. I
told him I disagreed that that was NOT NORMAL behavior and that if I was
designing the braking model, I would detect a panic stop and apply full
brakes, but as soon as the pedal was released I would not assume that I
wanted any significant regenerative braking. BTW wheels screeching is NOT
regenerative braking.


I just thought I would throw this out for the general group because some
of you are more mechanically adept than I am, and would have some thoughts
on the proper braking performance.

I told the service advisor that I would elevate this issue with NISSAN. (I
haven't done this yet, but will soon.)


Thanks for any input.

Gene Fifield

>>>This has nothing to do with regen!!

--Kaelev
2011 LEAF
2003 Rav4EV, 7 years experience, 89,000 miles

 

[planet4ever]

See this thread: Scary braking problem

 

[TRONZ]

For fun I went out and did a full panic from 45 and then let off around 25. ABS pulsed (no lockup) and the brakes disengaged when I expected them to. Did rearrange the stuff in my trunk though. Has anyone else tried to reproduce this type of braking?

 

[aqn]

For fun I went out and did a full panic from 45 and then let off around 25. ABS pulsed (no lockup) and the brakes disengaged when I expected them to. Did rearrange the stuff in my trunk though.

I suspect that if this problem is consistently reproducible, there would be an entirely different discussion happening right now.

 

[LTLFTcomposite]

The main consideration is the requirement that the brakes have to be able to handle a long downhill run with a full battery, which means no help from regeneration and, of course, no engine braking.

And to borrow a quote from the E-trade baby, you have a better chance of being mauled by a polar bear and a regular bear in the same day than that happening :lol:

 

[TomT]

Actually, from where I live upon mount high, that could happen almost every day if I routinely charged to 100 percent...

The main consideration is the requirement that the brakes have to be able to handle a long downhill run with a full battery, which means no help from regeneration and, of course, no engine braking.

And to borrow a quote from the E-trade baby, you have a better chance of being mauled by a polar bear and a regular bear in the same day than that happening :lol:

 

[LTLFTcomposite]

Actually, from where I live upon mount high, that could happen almost every day if I routinely charged to 100 percent...

The main consideration is the requirement that the brakes have to be able to handle a long downhill run with a full battery, which means no help from regeneration and, of course, no engine braking.

And to borrow a quote from the E-trade baby, you have a better chance of being mauled by a polar bear and a regular bear in the same day than that happening :lol:

Any polar bears up there?