Tesla Model 3 Falls Short of a CR Recommendation
consumerreports.org
consumerreports.org
That’s worrying, and almost as worrying is that Tesla says their braking is much faster. I’m sure plenty of fans will make comments about shorting stock, but this is Consumer Reports, and they have a very good reputation to protect.
I’m not thrilled by this tidbit either.
The Model 3’s stiff ride, unsupportive rear seat and excessive wind noise at highway speeds also hurt its road-test score. In the compact luxury sedan class, most competitors deliver a more comfortable ride and rear seat.
The Tesla spokeswoman says the company has the ability to update its vehicles over the air. “Unlike other vehicles, Tesla is uniquely positioned to address more corner cases over time through over-the-air software updates, and it continually does so to improve factors such as stopping distance,” she says.
I'm curious the mechanism that makes that possible, or if it's just BS.
They can probably update the settings for the brakes as well, as long as the underlying mechanicals support it.
So the goal is not regenerate the battery (and it doesn't matter if the driver was "an electric neophyte"), it's to brake hard and to repeat the process a couple of times to see if you get brake fade.
From the article: Our testers get a car up to 60 mph, then slam on the brakes until the car comes to a stop. They repeat this multiple times to ensure consistent results. Between each test, the vehicle is driven approximately a mile to cool the brakes and make sure they don’t overheat.
[1] https://www.engadget.com/2016/11/16/tesla-p100d-software-per...
Edit: why downvotes?
Maybe they have a system for warning owners about these sorts of updates?
I'm also not sure what the alternative you're imagining here is. Take it in to a shop just to have them install the update for you? I also don't see how this is any different than changing worn out brakes on an old ICE car. I had the brakes changed in my old '97 Accord, and the difference was noticeable when I pulled it out of the driveway. I think you need to give people a little more credit...
Also, the Whats Changed prompt literally takes up the entire 17in touch screen. It's sort of hard to miss.
I didn't propose an alternative but there's a huge difference in awareness between a physical in-person "update" vs an OTA update.
For something as serious as changing brake handling, I'm sure they would have some sort of prominent display/cannot continue until you agree prompt but there's always going to be people who do not read things in their entirety. For something that can be destructive as a car, I don't find that acceptable.
Def changed the way the car drove, can't say that I minded in that case though.
I suspect you would get used to it fairly quickly.
[1] http://www.documentcloud.org/documents/4458000-Waymo-Driverl...
Signing updates and checking signatures is established technology to certify that updates come from the right place and are not tampered with.
That and the updates are likely >10 GB, so you wouldn't want to download them over mobile data anyway.
That's just odd.
It's possible that the tesla software either isn't applying the extra assistive force, either due to incorrect tuning or a bug.
The Model 3 (3,800lbs for the long range model) is a fat pig of a car compared to other, conventionally powered cars in its class (3,300lbs for a BMW 3 Series) but this is countered by Tesla fitting them with relatively enormous brakes (14" rotors up front, 13.5" in the rear, larger rotors have more heat absorbing capacity for the pads).
If I had to guess the root cause for this problem, I'd say it is likely down to Tesla's focus on minimizing aerodynamic drag causing a lack of airflow within the wheelwell and across the brakes out the wheel itself. Either that or they chose an absolutely terrible brake pad compound but that just doesn't seem likely in this modern era. Either way, the brakes are getting so hot after a single stop that CR's cooling procedure (a reasonable one I might add) is inadequate to keep the brake pads from drastically overheating. This also explains why braking performance was still compromosed after letting the car cool overnight. The work hardened surface will perform poorly until it is literally ground off from further heavy use of the brakes.
That's actually a very reasonable explanation. I can't say I'm a car expert, but your logic at least sounds correct.
As for expense, brakes are simple and the parts generally cheap, at least for mass-market cars. You can get a full set of pads and rotors for less than $100 from Autozone.
They are a lot cheaper today but the cost of rotors varies tremendously depending on the manufacturer and their volume. I gather they turn rotors a lot less than they used to because they're so darn inexpensive to replace, but I'm pretty sure it's still economical for some of the higher-end stuff.
Conceivably, the car's weight may mean that aerodynamic down-force produces a relatively smaller impact on grip, and air resistance a relatively smaller deceleration. But I'm not sure that's enough to account for the difference.
But most consumer tires have coefficient of friction of less than 1. ~.9 for higher end stuff, but it could be as low as ~.5 or so. Which mean 2-tons of car will lead to LESS than 2-tons of acceleration / deceleration / turning force.
In effect, "more weight is more advantage" is only true if you have a coefficient of friction greater than 1.
Since F=MA, A=F/M. Assuming the braking force (F) is μ (coefficient of friction) * Mass * Gravity, thats F=μMG.
Combining those equations you get:
A = μMG / M
And the M's cancel, giving:
A = μG
Therefore the braking distance due to road friction alone (and ignoring aerodynamic downforce effects) is independent of the mass of the vehicle.
According to theory, the width of a tire has zero effect on tire grip. Race cars and high-performance cars prove this is incorrect: there's a reason they have wide tires (which also cause poorer fuel economy through extra friction). Tires and their interaction with the road are a lot more complex than some simple physics equations.
Its like the whole "area" doesn't matter as well. I can't help but think that maybe the Newtonian friction model is overly simple sometimes. Surely weight and surface area would have an effect?
But perhaps not really. Or at least, not in a way that's very measurable.
Alternatively, there's also "let the human do it". (Aka: threshold braking), but most people prefer to have the computer do this task during an emergency.
This algorithm has been used in anti-lock brakes for decades at this point. I'm not sure why it would need an OTA update to improve. Once this algorithm is properly implemented, then the only thing left is to buy better tires and use better rubber to get better grip.
This CR report suggests that Tesla's braking behavior is suboptimal. There's no reason for a smaller, lighter Model 3 to have a worse braking distance than the freaking F-150 truck.
That's not to say Tesla haven't decided to re-solve it / implement it themselves anew. The rest of the auto industry has been doing ABS much longer than Tesla has existed.
It's also not a prescriptive algorithm. ABS systems don't stay within the static coefficient of friction; they repeatedly retest the boundary between static and dynamic friction (hence the judder). It's a bit like optimising TCP window size for those familiar with it. There are a bunch of parameters you can tune.
Typical ABS systems typically perform far worse on gravel or sand than non-abs systems for example. It turns out on gravel locking the wheels is usually a better solution because then you start to plough deep into the gravel.
No ABS system could determine that beforehand, since it isn't to know if the gravel is deep (allowing ploughing deep into it) or shallow (where staying on the boundary of static/dynamic friction works better).
CR doesn't have a very good reputation though? I mean... they used to. But their reputation is middling at best now.
However, if this braking result is consistent across all Model 3 vehicles, that's a bit worrisome. I'm also a little concerned with the other issues they had (ergonomics, wind noise, etc). From everyone I know that drives or has driven a Model 3, they've had amazing experiences as far as actual driving
Air conditioning? Yes. On longer drives, the positioning of the sun greatly determines whether or not my AC is running. Radio stations also are frequently changed, as is volume. If someone is talking to me in the passenger's seat, I instinctively turn down the volume of the radio for example.
I personally prefer physical buttons for these various tasks. Physical buttons are always there. I don't have to look at the screen to ensure that I'm on the "correct app" or whatever before trying to fiddle with the AC or volume.
It's certainly a bad thing from a UX perspective. The number of controls in a car / aircraft is a very typical example of why modes are bad. One button for one action is the easiest to learn over the long run, there is a clear mapping in the drivers head of what each of the controls does. They all have different affordances, which is much harder on a touch screen.
However saying that, there's clearly problems with BMW's car UX [0]. Tesla have put a lot of thought into the UX [1] but it seems to be more on a grand scale with specific user cases in mind (your garage magically opening as you approach), rather than the mundane of reducing the number of clicks for the average task.
[0]: https://www.nngroup.com/articles/why-consumer-products-have-...
[1]: https://uxmag.com/articles/tesla%E2%80%99s-groundbreaking-ux...
Radios, HVAC controls, gauges, and the fancy dashboards which contain them are among the most expensive parts to develop in terms of both time and money. The amount of time Tesla saved in PPAPs (Production Part Approval Process) alone might be as much as a year and when working with a timeline as aggressive as those demanded by Musk, anything that reduces development time is more valuable than gold.
It's a genius way to reduce the time needed to bring a car to market, the final bill of materials, and the complexity of assembly and installation of such a key component as a dashboard. It's a terrible idea in terms of driver experience but those are the kinds of compromised that must be made to bring something like a Model 3 to market at the promised $35,000 price point.
Bringing a car like the Model 3, with all the features promised over the years, into mass production (100k+ per year production rate) within a timeframe required to secure a position in the market where 100k example can be sold necessitates such wild thinking. Yes, it's a terrible design for the driver, but Tesla beat every other manufacturer to the punch by at least 4 years. The "everything is contained in one, basocally off the shelf touchscreen" idea makes part of the ownership experience worse bit it got the Model 3 in consumer's hands at least 1 year earlier than it would have been otherwise and likely shaved a grand or two off the final base price.
I'd never buy a Model 3 because the touchscreen is so offensivley terrible. However, when a quarter million people are willing to put their money down to buy one simply due to the range, pricw point, and expected launch date, then any compromise that helps get the car into their hands as promised, without a revolt among depositors, is "smart" in its own right.
They put knobs with LCD screens within the larger LCD center panel, and they put tiny OLED screens on the steering wheel buttons.
Tesla's UI design is an obtuse dead end.
But then again Tesla assumes their cars will be driving themselves anyway so getting distracted trying to adjust the AC should not be a problem...
Could this mean that such a vehicle under test would brake differently than the average driver. Since the brake is constantly being slammed during repeated tests, the software adjusts breaking parameters? Still find it odd to implement such a system, but could explain the inconsistent results.
If I were to guess, it would be that in a sudden stop, something inside the brake mechanism heats up so much it bends or deforms, and then doesn't work so well after that.
If my guess is correct, it could be an expensive recall...
That explains why the poor braking performance was unaffected by an overnight cooldown. All that said, if the Model 3 is glazing brake pads with a single emergency stop then they need to issue a recall and figure out a fix.
Seems pretty stupid to evaluate cars on such a weird metric. Sure 60 to 0 or 80 to zero, but what sane person is going to accelerate up to speed as quickly as possible and try again.
Maybe Tesla's doing so poorly because it gets back to 60 quicker than it's competition.
The ability to stop quickly at highway speeds is, in fact, something worth testing, and 60-0 stopping time is a great thing to test.
Isn't that an argument for CR's test? They explicitly drive 1hr between each braking test so that it's not just "accelerate up to speed as quickly as possible and try again".
My reference is: https://www.consumerreports.org/cars-how-consumer-reports-te...
"As its name implies, CR’s braking test is meant to determine how a vehicle performs in an emergency situation. The test is based on an industry-standard procedure designed by SAE International, a global engineering association. Our testers get a car up to 60 mph, then slam on the brakes until the car comes to a stop. They repeat this multiple times to ensure consistent results. Between each test, the vehicle is driven approximately a mile to cool the brakes and make sure they don’t overheat."
But I'm starting to have real doubts about Tesla. Elon talks a great game, but they've had setback after setback after setback. I have to wonder what the long-term ownership experience will be like.
Good luck to Tesla. I'd love to see them turn out well.
I'm sorry, but that is complete bullshit. Emergency braking isn't "a corner case", it is one of the primary use-cases of a braking system. Such a statement shows a blatant disregard for the intelligence of their customers, it is shocking.