Has someone actually measured that tradeoff (weight versus regenerative braking) to determine where it is an even tradeoff? And surely regenerative braking has its own shedding of particles from all the moving parts.
Because there is less extreme (and earlier) braking and less weight shift (drive motors on the rear or all), regenerative braking should lead to less overall tire degradation than comparable friction brakes for even a significantly increased weight.
Though this is contraindicated by Tesla drivers in the extreme Regen mode that induce motion sickness in their passengers and / or are replacing their tires very often (though conflated with rapid acceleration)
From what I understand, Ford did some really significant work on lightening the F150 maybe 5+ years ago, I was surprised at how light they are. Looks like a Tesla Model S for comparison is $4,300-5,000lbs.
Owning a hybrid with regenerative braking vs a non-hybrid of the same class of vehicle, there is a noticeable reduction in brake wear and replacement with regenerative braking.
surely regenerative braking has its own shedding of particles from all the moving parts.
It adds tire wear, but no more than traditional friction braking. I can't see how there would be any measurable wear from any other moving parts, since it's just using a magnetic field for resistance. There are moving parts that touch, but modern, sealed bearings last a ridiculously long time.
Regenerative braking has much less tire wear than traditional braking because it's done much more slowly and smoothly.
Also, none of these discussions use up-to-date information on EV tires. Consumers aren't willing to replace their tires much more often for an EV except at the high end of the market, tire manufacturers are already making tires last much longer for EV purposes. New designs are already shedding less dust per unit mass of the vehicle than they were a few years ago.
Plus, some manufacturers are now working to reduce the toxicity of their formulas. This will eliminate the issues a lot more.
That’s nothing compared to an i3: I don’t even get 10K miles per set. Some people report getting as many as 12K with conservative driving.
Part of the problem is the instant torque, but the narrow geometry is a bigger issue. Also, they did something to the formulation that achieves less rolling resistance for increased wear.
I also don’t think the weight is the main issue. The i3 is a bit under 3000 lbs. That’s the same as a Volvo station wagon, and they didn’t have this problem. (If I remember right, you could get 50K mile Michelins for them.)
My model 3 is 5 years old and I'm still on my original set of tires (though in recent years I do put on winter tires for a few months a year). I don't usually drive like crazy (and it's an SR+ which is the least powerful model).
True, and you can do engine breaking and do milder acceleration curves in ICE car and that will significantly reduce the pad/tire wear. But if you drive like, I would speculate, most people do, Tesla will go through tires like a track car (half joking)
Agreed, the only thing I would say here is that electrics kind of give you this torque/weight combo for an every day car so I would guess in the real world electric cars end up being worse on dust production. Hopefully tires can get optimized for this as well.
I could be wrong and be using outdated information, but aren't Tesla's stock tires also low rolling resistance tires? Which does mean less road friction and less wear, but also means lower maximum traction which is a tradeoff most anybody could make if they wanted.
As a Tesla owner, I'm 33k in on a set of all seasons and still in the green on two. You can't move the goalposts like that - the same is true on an ICE sports car.
Regenerative braking has much less tire wear than traditional braking because it's done much more slowly and smoothly.
Absent any evidence, I don't believe that claim. Unless you're skidding, I don't see how braking slowly and smoothly over a longer period causes any less tire wear than braking more rapidly for a shorter time.
Additionally, since this is intrinsically tied to EVs, they weigh more and thus increase tire wear in all conditions.
That seems plausible to me. Tires are made from rubber. If friction forces exceed how strong the rubber particles stick to each other, they get pulled loose. And road surfaces aren’t perfectly smooth, so when you’re accelerating, some rubber particles will experience more force than others.
It seems believable that hard braking, even without leaving skid marks, could pull more rubber off a tire than gradual braking.
The same exact reason that accelerating quickly causes far more tire wear than accelerating slowly, only in reverse. By applying more torque to brake/accelerate, you cause more lateral force on the tires (think, smearing the rubber itself) which is what causes tire wear. With more force the rubber is stretched further, which fatigues it and breaks off pieces of it over time.
Slower braking is generally accepted to cause less brake pad wear. I was only able to find this article, but I'm sure more convincing evidence can be found if you do more research than the quick ddg and clicking on the first result I did.
Hard Braking: Less experienced drivers often react late to situations, slamming on the brakes instead of slowing down gradually. This creates more friction and heat, reducing pad lifespan.
Weight shift is a good reason, rear and all wheel drive Regen should result in 2+x as much contact patch, versus friction brakes typically favor the front 70/30, applying 70% of braking to only 2 tires.
Acceleration and deceleration is calculated the same way: m/s^2. If you decelerate faster you put more stress on the system in a non-linear way - the square of it actually. This is why sport and race cars have huge brakes. The tire friction will also augment non-linearly - it will hold a certain acceleration and then quickly give up (slipping point), but the energy has to be transferred and partly absorbed all the time.
> they weigh more and thus increase tire wear in all conditions
Then get a lighter one if that is your concern. Defaulting to ICE is the wrong idea because they have much more externalities (like one ton of fuel per year that needs actually around 1.5 if you include the extraction and transport).
There are EV's which have drum-brakes. That's only possible because the regenerative braking takes most of the load. Also, there are stories of brake-discs rusting out on EV's. Both point to less (friction)-brake use on an EV compared to an ICE.
I suspect drum brakes were chosen by the electron pinching EV engineers. They're the only brakes that are friction-free when not applied. Disc brakes rub (and slow the car) even when not applied.
They use drum brakes because drum brakes are protected better from the environment while brake discs are not and will quickly get covered in rust and dirt when not used for awhile and then be less effective when they are actually needed for an emergency braking situation.
We only ever really went to disc brakes because they were slightly cheaper and easier to manufacture and since racing vehicles used disc brakes (because they benefit from the extra cooling capacity that commuters don't need) it was easy to convince customers that they were "better" and they became standard.
There was also a time when they didn't figure out traction control very well using brake drums while they did manage it with brake discs, but part of that could be just because brake drums were out of fashion in racing where traction and stability control were invented and implemented first and nobody bothered improving drum brakes to take advantage of that tech until decades later.
Now that EV drivers can go weeks without touching their actual brakes and just rely on regen braking, disc brakes have become a liability since they aren't worn down smooth and cleaned whenever someone stops at the end of their driveway.
I've used drum brakes in older cars and motorcycles, and their stopping power is terrible, fade is terrible, and they are horrible in the rain.
The only recent cars I've had with drum brakes used them for the parking brake. They tended to corrode and not work well. Also, as an emergency brake even with a pedal you could push hard on, they were beyond terrible, even dangerously ineffective.
Seems like EV manufacturers should set their cars to use the friction brakes for the first few stops of each trip, both to clean off the rust & dirt, and also to test whether they still work.
An electric motor is really good at arresting high rpm movement while charging, not so great at bringing low rpm movement to a stop. EVs blend together Regen and friction at slow speeds.
> An electric motor is really good at arresting high rpm movement
I don't think any EV that I've heard of has full-range electric brakes.
There are two interesting kinds of things that I think EVs could use...
brake resistors - if the battery can't absorb the full power of regenerative braking, maybe giant resistors can take the dissipate the rest of the energy.
eddy currents - it might be cool to use eddy currents to brake.
Not significantly. Otherwise they’d get hot and work less well. Pads ride very closely to the disc so that road stuff can’t get wedged between the surfaces, and so that you don’t waste break pedal travel just getting the pads close to the surface. Well adjusted drum brakes should be arranged almost exactly the same way.
Are you familiar with how disk brakes on a car operate? They’re essentially a hydraulic piston clamping the brake pads against the rotor. When you let off the brake pedal, the pressure is removed, but there’s not a “retraction” of any kind. So there’s no pressure but nothing is actually making that gap. That article was articulating basically that the piston, when not compressing the brake pads, should not be too far out, because that’s just unnecessary travel of the pedal, but it does not mean that the brake pads are somehow gapped away from the rotors.
Drum brakes by contrast have springs that retract the pads from the braking surface, so the OP has a very valid point.
I'm very familiar, having changed many sets over the years. If there's no air in the system, pulling fluid away from a hydraulic piston must retract it. It can't just sit there unless there's an air bubble to expand or so much negative pressure that it forms a vacuum somewhere. Even then, pressure on the atmosphere-facing side would push the piston back toward wherever the vacuum or air bubble is.
The rotors push the pads away from the surface if the slides and spring clip seats are maintained. I have seen many unbalanced brake systems with uneven pad wear of all kinds due to rust/dust/heat impacting the system.
Something makes them retract slightly - how they’re seated in the caliper retaining clip maybe I’m not sure because trivially you can take the wheel off and press the brake and see it.
It’s even easier to see on a bicycle with hydraulic discs.
> When you let off the brake pedal, the pressure is removed, but there’s not a “retraction” of any kind. So there’s no pressure but nothing is actually making that gap.
Technically there is a slight amount of rubber spring back for a fraction of a millimeter and the air traveling with the rotor surface puts a small amount of pressure back on the pad and pushes it imperceptibly backwards. Of course that is only really effective if your rotors are perfectly flat and warp free, which most peoples are not because rotors never get resurfaced any more and 95% of them are super cheaply casted and turned which leads to warpage extremely quickly.
The default for drum is less friction (gap increases, takes more pedal) over service life whereas pads default to more friction (slides gunk up and spring clip faces rust and swell) from failing to retract as well.
Yeah, my VE id.3 has drums on the back and disks on the front. Apparently the brake pads are effectively life-of-the-vehicle items under normal driving conditions.
I’ve only had to change them one time on any car newer than 1990, after ~200k miles/10 years of use. For most people that qualifies as life of the vehicle, but there was plenty of life left.
Anecdotally, it’s very dependent on driving cycle and driving style, but EVs use their brakes much less in general. It would be interesting to measure the total mass of brake pads sold per vehicle mile for different vehicles, though this would likely be more challenging than it seems.
My Chevy volt has 199k miles and it's original brake pads and rotors are definitely almost new looking, but I'd say to be conservative they are 60%.
My cheap Chinese Walmart tires have lasted me 50k miles and are due to be replaced soon, but I spend zero attention to driving smoothly or in an eco mindset.
I heard from someone working at a big car producer that they force EV’s to use the mechanical brakes every now and then because if not, they rust away.
