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Comment by netsharc | Hacker News Reader

So, OTA software update improved the brakes (dear commenters, please spell this word correctly). Why not have the brakes with that strength from the beginning? If I were to speculate, could it be because this setting would cause high brake wear on the long run?

And, what's stopping them from selectively applying this setting? Heh, Volkswagen would probably have loved this capability a few years ago.

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So, Model 3 has regenerative brake (uses magnetic resistance to slow car) and regular brakes that every other car has. I believe the tradeoff / timing about when to switch between the two braking systems was slightly off, favoring more energy efficiency rather than the best stopping distance. When this was pointed out they simply adjusted their algorithm for a better overall tradeoff.

It's extremely embarrassing/telling that it took Consumer Reports to point out their new car doesn't stop well.

Alternately, it's amazing and inspiring what just happened; other high-end car makers with a century of experience have shipped imperfect brakes for years (1) and only redesigned them on new models in response to complaints. Tesla, by comparison, is applying the Apple model (when Apple is at its best) of continuous over-the-air product improvement, which can change one’s sense of a product's value for money.

1. MERCEDES CANCELS BY-WIRE BRAKE SYSTEM; DECISION A BLOW TO TECHNOLOGY'S FUTURE. "When the system failed, the hydraulic system took over. But that resulted in a longer stopping distance and additional brake pedal effort by the driver." http://autoweek.com/article/car-news/mercedes-cancels-wire-b...

Mercedes had a hardware problem and Tesla had a software problem, I really don't see how this is a win for Tesla. Tesla has done physical recalls before as well, not everything is a software bug.

https://repairpal.com/recall/05V133000

Well, I have the car and stopping distance was never an issue at all. With regenerative braking you start braking as soon as you take your foot of the gas so you’re usually stopping short of where you actually need to stop, not having trouble stopping fast enough. I really don’t think it was that big of a deal, but it could be fixed and so they did it to get the recommendation. And im sure it’s safer too which is what’s most important.

This was not an issue on all cars.

Hit and miss braking on a single product line seems... kind of worse?

I had my Mercedes SLK350 try to launch me into an intersection once while stopped at the red light with my foot on the brake. The dealership reset the ECU and said “Let us know if it happens again.”

Why everyone thinks these issues are Tesla specific is beyond me. They can at least address them over the air.

When I think about it, my BMW 3 series, also had a strange loss of accelartion in certain situations (very minor). Was fixed during a service interval, by flashing the ECU.

Unless the Model 3 is very different from the other Tesla cars, there is no such tradeoff. In a Model S, regenerative braking is triggered by releasing the accelerator pedal. Mechanical braking is triggered by stepping on the brake pedal.

I assume that Tesla just screwed up the antilock breaks. If you push the brake pedal all the way down on a dry road, you’re supposed to get full braking power by a mechanical linkage. No software needed.

In a Camry Hybrid, the "tachometer" has a charging section, to show how much of the regeneration you're using when braking. Above the crawl speed, it also trims the car speed as regenerative braking. Pressing the brake pedal increases regenerative braking - up to maximum, and engages the mechanical brakes at some point.

I'd hope Teslas aren't wasting all of their stopping energy as brake heat, and instead regain some through regeneration as well. Ideally, both braking systems would be combined to maximize stopping ability. However not combining them might explain the Model 3's abysmal (longer than an F-150!) stopping distance.

> antilock breaks.

Break is what the car does when the brakes don't work. Petals will be on the flowers if you don't press the pedal. English is fun.

Toyota and Tesla do braking completely differently. Tesla has one pedal driving, same as the Bolt. Taking your foot off the accelerator does regenerative braking. Pressing the brake pedal also engages the mechanical brakes.

>> antilock breaks

antilock brakes

That still doesn't answer why the braking distance differed between the first test, and all subsequent tests, results which were repeated on two different Model 3s.

The original CR article noted inconsistent braking performance, performing very well the first time they tested it and very poorly every time afterward. Frankly it just seems like a bug that Tesla never noticed in their own testing. The fact that they screwed up the brake control software and did not realize this until some journalists complained about it makes me very concerned about Tesla's overall design/QA/QC process.

Move fast and brake things?

Seems like an update on the ABS, so less to do with strength, more to do with how ABS are performed. My guess is this probably won't have much effect our everyday driving, but when in emergency, the updated ABS will perform better.

> If I were to speculate, could it be because this setting would cause high brake wear on the long run?

No idea why it wasn't this way in the first place. That said on an EV you'll almost never replace the brakes. On our Model S I only touch the brakes in panic situations or < 2mph to come to a stop. Regen braking cover all other cases sufficiently.

This sounds awfully similar to a well-known Prius problem, where the transition from regenerative to friction braking takes on the order of a second and can lead to significantly increased stopping distance.

I doubt it was intentional. It seems that the anti-lock brake system was miscalibrated.

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