
Tesla Model 3 Falls Short of a CR Recommendation - whatok
https://www.consumerreports.org/hybrids-evs/tesla-model-3-review-falls-short-of-consumer-reports-recommendation/
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DmenshunlAnlsis
_The Tesla’s stopping distance of 152 feet from 60 mph was far worse than any
contemporary car we’ve tested and about 7 feet longer than the stopping
distance of a Ford F-150 full-sized pickup._

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._

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tshannon
This part really intrigued me about the stopping distance:

 _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.

~~~
ensignavenger
To me, it is disturbing. I get used to the way my vehicle handles, for it to
suddenly change because of a software update could potentially be dangerous-
but would almost certainly result in a trip to the mechanic for a checkup.

Maybe they have a system for warning owners about these sorts of updates?

~~~
audionemesis
Well, yes. You get prompted to update your car (you can choose not to). And
then after the update is complete, you get a Whats Changed prompt the next
time you're in your car. Essentially a patch notes for your vehicle

~~~
whatok
For something as major as changing the way a car breaks, do you think "patch
notes" (if read at all) are able to properly convey the magnitude of the
change?

~~~
audionemesis
Yes? My 75D had an entire second shaved off of its 0 - 60 time. I was aware of
the change and was able to deal with it just fine...

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.

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whatok
I'm talking about the general populace not only actually reading a prompt but
understanding it. Based on how people interact with computers/phones, I do not
have a lot of faith in their abilities on this end.

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.

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zippzom
Seems like a terrible design choice to make lots of basic adjustments use the
touch screen. Adjusting the mirror and AC vents with a touch screen is almost
guaranteed to be a terrible experience, especially since people do those often
while they're driving.

~~~
craftyguy
You frequently adjust your mirror when driving? That's something I do once in
a few months (if that), twice if someone drives my car and adjusts the mirrors
to fit them.. Perhaps you should adjust your seat instead?

~~~
timeisapear
Living in a city, I must manually retract side mirrors when parking on small
streets and extend them before driving. Often need to readjust the mirrors
each time after extending them.

~~~
greglindahl
I take it that you don't drive a car that folds its mirrors when you put it in
Park, which is now a common feature.

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gldalmaso
> _past driving behavior that may have affected the brake system_

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.

~~~
londons_explore
Since they did more tests the following _day_ and didn't see improved
performance, it doesn't seem likely related to thermal limiting in software.

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...

~~~
cc439
I can almost guarantee the brake pads glazed over due to overheating. The
pad's surface will begin to work harden once a certain temperature threshold
is exceeded and that hardened surface has a much lower coefficient of friction
than the original unhardened pad. This work hardened material will never
return to normal so full braking performance will not be restored until it is
ground away by further use of the brakes (light use, you don't overheat them
again and make the problem worse).

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.

~~~
sliken
The whole brake from 60-0 10 times quickly seems like a stupid metric. Would
you rather have shorter stop times, but a design that fails at 15 times? Or a
brake that adapts to that load and progressively stops more gently. Any sane
driver would adjust.

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.

~~~
cjhopman
> The whole brake from 60-0 10 times quickly seems like a stupid 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.

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".

~~~
sliken
I dug for information like that. I only found "Our automotive engineers
conduct a series of brake tests from 60 mph to a standstill on wet and dry
pavement to measure stopping distances." Do you have a reference for the 1
hour between brake tests?

My reference is: [https://www.consumerreports.org/cars-how-consumer-reports-
te...](https://www.consumerreports.org/cars-how-consumer-reports-tests-cars/)

~~~
cjhopman
Ah, it's not 1 hour, it's 1 mile. It's in the article. Still clearly not
"accelerate up to speed as quickly as possible and try again".

"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."

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RickJWagner
I love cars, all kinds of cars. I bought my son a Prius, I even enjoy driving
that (just for the unusual driving experience.) I like to see how long I can
go on just electric power.

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.

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mdekkers
_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,_

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.

