2013 Low-friction brakes: Bolt-on upgrade to 2011/2012?

[RegGuheert]

One of the efficiency features I have read about for the 2013 LEAF is low-friction brakes. If I understand correctly, they have a mechanism that slightly retracts the pads to reduce loss in the brakes.

I am wondering if this upgrade is simply a change in the brake caliper or if perhaps there is other hardware and/or firmware that needs to be changed to make it work. Also, I am wondering how much improvement in range is realized with this change. I cannot imagine it is much since the LEAF seems to roll quite well in Neutral, but who knows?

I guess I will check around the internet to see if parts have become available for the 2013s, yet, and see what part numbers have changed. If it makes a difference, it might be worth the trouble of purchasing some of these off a junked 2013 and retrofitting.

 

[TomT]

I expect that it would be of negligible value and certainly not worth the cost. The pads on cars tend to work away from the rotors via flex as the car turns anyway so all it likely accomplishes is to speed up and amplify the process slightly. I suspect that, at best, we are talking a small number of tenths of percent in efficiency.

One of the efficiency features I have read about for the 2013 LEAF is low-friction brakes. If I understand correctly, they have a mechanism that slightly retracts the pads to reduce loss in the brakes.

I am wondering if this upgrade is simply a change in the brake caliper or if perhaps there is other hardware and/or firmware that needs to be changed to make it work. Also, I am wondering how much improvement in range is realized with this change. I cannot imagine it is much since the LEAF seems to roll quite well in Neutral, but who knows?

 

[GeekEV]

Isn't the phrase "low friction brakes" an oxymoron? Seems to me the whole point of brakes is to provide friction...

 

[Nubo]

The friction is there. When rotating tires, etc., you can feel the brake drag when trying to rotate the wheel by hand. In the front, of course, there is drivetrain friction, but it's noticeable on the rear too.

 

[nater]

This might simply be spring clips. Does the 2011/2012 have them? If not, there's your retrofit!

Nate

 

[RegGuheert]

This might simply be spring clips. Does the 2011/2012 have them? If not, there's your retrofit!

A clip would be nice, but Nissan specifically said "Low friction brake caliper". Here is the link to the Nissan slide that SF Bay Leafs posted:

 

[edatoakrun]

One of the efficiency features I have read about for the 2013 LEAF is low-friction brakes. If I understand correctly, they have a mechanism that slightly retracts the pads to reduce loss in the brakes.

I am wondering if this upgrade is simply a change in the brake caliper or if perhaps there is other hardware and/or firmware that needs to be changed to make it work. Also, I am wondering how much improvement in range is realized with this change. I cannot imagine it is much since the LEAF seems to roll quite well in Neutral, but who knows?...

Not likely to be much benefit, IMO. I would think a upgrade of wheels and tires would give you far more "bang for the buck".

I don't think there would be very much friction on the pads until pressure is applied. A low-tech test might be to drive a distance using accelerator/decelerator pedal only, and not touching the brake pedal, and check the disc temperatures before and after the trip, and see if any heat from friction had not yet dissipated.

I did this right after I got my LEAF, as I was curious as to how much variation in disc heating occurred in my usual ~2,000 ft total descent over ~7 miles starting with either"100%" or "80%" charge.

Even though I still needed to use the brake pedal some, even at "80%", the discs were barely warmed, while at "100%" with almost no regen available, some amount of the fraction of a kWh I had put into the discs was still there, and they were too hot to touch, as expected, and similar to any ICEV after descending the same grade.

 

[DaveinOlyWA]

agree with Ed. I have checked the discs many times after a "one pedal" trip and the pads would be barely warm. Keep in mind a regular car needs only one or two normal stops to generate a LOT of heat. you dont need a mountain

 

[garygid]

To avoid burning hands and fingers, I usually use an inexpensive
digital IR temperature gauge, something like this small "fob-size" unit:

http://www.harborfreight.com/non-contact-pocket-thermometer-93983.html" onclick="window.open(this.href);return false;

 

[RegGuheert]

According to Tesla, the brakes on the Model S use about 20 Wh/mi regardless of speed:

That means that if the brakes on the LEAF are as efficient as those on the Model S, ~2 kWh or ~10% of the energy in the battery will be lost to the brakes in a drive of 100 miles. That seems like a lot to me!

 

[DaveinOlyWA]

jack up the car and take the wheels for a spin. i think in Tesla's case, its probably just bigger brakes along with the power to operate them. ABS is using power all the time. how much of that is shown here?

not sure I can say everything in the chart is due to drag

 

[edatoakrun]

According to Tesla, the brakes on the Model S use about 20 Wh/mi regardless of speed:

That means that if the brakes on the LEAF are as efficient as those on the Model S, ~2 kWh or ~10% of the energy in the battery will be lost to the brakes in a drive of 100 miles. That seems like a lot to me!

Thanks for posting that image. I was just thinking about it as the best way to visualize the large amount of kWh sucked up by the tires on a BEV.

Are you sure it is intended to illustrate the energy consumption of the model S brakes when no brake pedal is used?

I had assumed the graph was for a trip or trips with some estimated level of brake use, similar to what is shown in the "HVAC penalty" curve.

 

[palmermd]

According to Tesla, the brakes on the Model S use about 20 Wh/mi regardless of speed:

That means that if the brakes on the LEAF are as efficient as those on the Model S, ~2 kWh or ~10% of the energy in the battery will be lost to the brakes in a drive of 100 miles. That seems like a lot to me!

I'm not sure how much faith I have in that graphic. Seems like the brakes and tires are consuming a lot of power when the car is sitting still.

 

[RegGuheert]

Are you sure it is intended to illustrate the energy consumption of the model S brakes when no brake pedal is used?

Pretty sure. Here is the text which is just above the chart (bolding mine):

Road-Load

All vehicle types, regardless of what powertrain they use, need to overcome road-load. It includes wind resistance, mechanical friction (bearings, hubs, driveshaft, etc.), and tire rolling resistance. Road-load affects all vehicles. As a car speeds up, wind resistance increases; there is more air for the car to “push” out of the way. Therefore, road-load is greater at higher speeds and is dependent on the aerodynamics of the vehicle. Tesla engineers are focused on decreasing aerodynamic losses while achieving beautiful styling. Road-load can be minimized by designing brakes, bearings and other rotating components with less friction. It is also important to use tires that have low rolling resistance and make the vehicle as light as possible. Energy saved by decreasing road-load can have a significantly positive impact on range. The Model S will be one of the most aerodynamic sedans ever built with all components tuned to minimize friction and achieve the highest possible range.

It seems to me that both Tesla and Nissan consider the drag of the brakes to be an important issue to address.

 

[edatoakrun]

Are you sure it is intended to illustrate the energy consumption of the model S brakes when no brake pedal is used?

Pretty sure. Here is the text which is just above the chart (bolding mine):

Road-Load

All vehicle types, regardless of what powertrain they use, need to overcome road-load. It includes wind resistance, mechanical friction (bearings, hubs, driveshaft, etc.), and tire rolling resistance. Road-load affects all vehicles. As a car speeds up, wind resistance increases; there is more air for the car to “push” out of the way. Therefore, road-load is greater at higher speeds and is dependent on the aerodynamics of the vehicle. Tesla engineers are focused on decreasing aerodynamic losses while achieving beautiful styling. Road-load can be minimized by designing brakes, bearings and other rotating components with less friction. It is also important to use tires that have low rolling resistance and make the vehicle as light as possible. Energy saved by decreasing road-load can have a significantly positive impact on range. The Model S will be one of the most aerodynamic sedans ever built with all components tuned to minimize friction and achieve the highest possible range.

It seems to me that both Tesla and Nissan consider the drag of the brakes to be an important issue to address.

Again, I could well be wrong, but I'm just not sure the chart shows just the energy consumption of the bakes, when no brakes are used.

The main reason I'm skeptical, is that if the "parasitic" energy consumption of the brake pads was that high, I can't see why vehicle engineers wouldn't have harvested this "low hanging fruit" already.

I don't see why we would not have zero friction when not applied brakes, already on all types ofvehicles already, as they would seem to be fairly easy and cheap to develop and implement, and would provide superior acceleration and brake life, as well as greater fuel economy.

 

[RegGuheert]

The main reason I'm skeptical, is that if the "parasitic" energy consumption of the brake pads was that high, I can't see why vehicle engineers wouldn't have harvested this "low hanging fruit" already.

20 Wh/mi (or 40 if that's what a standard car is) is NOT low-hanging fruit for a gasoline-powered car. That's less than 1/10 of a gallon of gasoline in 100 miles.

I don't see why we would not have zero friction when not applied brakes, already on all types ofvehicles already, as they would seem to be fairly easy and cheap to develop and implement, and would provide superior acceleration and brake life, as well as greater fuel economy.

I'm not sure why you would think that. Everything has friction. Even if the pads did not touch the disc, there would be frictional loss between the two. If the losses were already zero, then neither Tesla nor Nissan would bother improving it.

So the question is really how many miles we lose to our brakes when we drive 100 miles. 5 miles? 10? 15? 20?

Perhaps the improvement is to reduce the friction related to how the caliper "floats" in its support. That has always appeared to be a point for possible binding to me.

 

[DaveinOlyWA]

ok, did the wheel spin and there is a very noticeable drag in REVERSE but none going forward that I can tell. I did the spin thing on only two wheels (car is parked off center in garage due to storage (ie too much junk!) constraints so not able to check other side without pulling it out of garage.

now, I have had cars where you can hear the calipers rubbing but the LEAF, nothing here. but could be just circumstance and the fact that my brakes are probably in near new condition because i rarely (and i mean RARELY) use them.

 

[garygid]

I suspect that much of the brake loss is the energy required to
run the braking system. However, then the energy consumption
per mile should get a LOT higher at very low speeds, like at 1 mph
where it takes an hour to go one mile.

So, it seems that there are some things unexplained here.

 

[edatoakrun]

The main reason I'm skeptical, is that if the "parasitic" energy consumption of the brake pads was that high, I can't see why vehicle engineers wouldn't have harvested this "low hanging fruit" already.

20 Wh/mi (or 40 if that's what a standard car is) is NOT low-hanging fruit for a gasoline-powered car. That's less than 1/10 of a gallon of gasoline in 100 miles.

I don't see why we would not have zero friction when not applied brakes, already on all types ofvehicles already, as they would seem to be fairly easy and cheap to develop and implement, and would provide superior acceleration and brake life, as well as greater fuel economy.

I'm not sure why you would think that. Everything has friction. Even if the pads did not touch the disc, there would be frictional loss between the two. If the losses were already zero, then neither Tesla nor Nissan would bother improving it.

So the question is really how many miles we lose to our brakes when we drive 100 miles. 5 miles? 10? 15? 20?

Perhaps the improvement is to reduce the friction related to how the caliper "floats" in its support. That has always appeared to be a point for possible binding to me.

OK, first, going back to your post and the graph on the previous page:

According to Tesla, the brakes on the Model S use about 20 Wh/mi regardless of speed:...

That means that if the brakes on the LEAF are as efficient as those on the Model S, ~2 kWh or ~10% of the energy in the battery will be lost to the brakes in a drive of 100 miles. That seems like a lot to me!

It looks to me like Tesla's graph is trying to show a constant energy consumption of ~10 Wh or less from the "brakes".

It would seem very odd to me if "brakes" was intended to represent friction loss from the pads and disk alone, when the brake pedal is not used, the result would be constant for speed.

But if so, and if the LEAFs brake pads/discs consumed about as much energy as the S's, when not engaged by the brake pedal, it would mean if that ~5% of the total energy consumption of a LEAF driven at ~5 m/kWh, or ~2.5% of that of a LEAF driven at ~2.5 m/KWH, would be going into the "brakes" right?

And since the friction surfaces are probably somewhat smaller on the LEAFs brakes than on the much heavier S's, the friction loss could well be even less than this ~10 Wh, right?

 

[RegGuheert]

It looks to me like Tesla's graph is trying to show a constant energy consumption of ~10 Wh or less from the "brakes".

It is the second bar from the bottom. It's 20 Wh/mi by my read. Maybe 19.

But if so, and if the LEAFs brake pads/discs consumed about as much energy as the S's, when not engaged by the brake pedal, it would mean if that ~5% of the total energy consumption of a LEAF driven at ~5 m/kWh, or ~2.5% of that of a LEAF driven at ~2.5 m/KWH, would be going into the "brakes" right?

I feel the numbers are twice that since I cannot read 10 Wh/mi from Tesla's chart. In other words 10% at 5 mi/kWh or 5% at 2.5 mi/kWh.

And since the friction surfaces are probably somewhat smaller on the LEAFs brakes than on the much heavier S's, the friction loss could well be even less than this ~10 Wh, right?

Perhaps it is less than 20 Wh/mi in the 2013s, but who knows what we have in our 2011/2012s?