Braking distance concern by Consumer Reports

[PhantomX]

I'm not saying the software was not wrong, I'm saying the 0-60-0 mile 0-60-0 mile 0-60-0 mile test routine is not a typical use profile and does not directly indicate the braking software is still in development.

Why should the software care the number of times the car had gone through hard braking? Braking consistency should always be hardware based, and the software should only be there to ensure consistency of application, not to compensate for lack of hardware capability.

 

[juanmedina]

Yeah, I may deserve some flack for that item one, but here is my thought process:

I'm not referring to two panic stops over the life of the car (or back to back days). Though that shows the induced change is persistent.

The non-typical use case I was referring to is 60-0, one mile drive with 0-60-0, one mile drive with 0-60-0 ... repeat within one drive cycle.

Total speculation on my part: if the tests were spaced out, or performed on different ignition cycles, the system would have behaved differently. It may have triggered the ABS internal calibration routine (if so, it should have a factory mode command/ or done flag added to the code). Sort of like the oil monitor reset sequence (key on, full accelerator press 3 times in 5 seconds, engine start).

I agree! their test doesn't represent real life. I could care less about what they think. Who even subscribes to CR? lol

 

[mongo]

Why should the software care the number of times the car had gone through hard braking? Braking consistency should always be hardware based, and the software should only be there to ensure consistency of application, not to compensate for lack of hardware capability.

The purpose of the ABS software is to monitor the brake hardware/ vehicle dynamics and intervene during a braking force > traction situation. When that occurs, it is the job of software to reduce braking force to point where the wheel start spinning again, then reapply braking force to initiate braking again. So the whole system is software compensating for hardware (available braking force should always be greater than traction).

The scenario I am raising is not hard braking in general, it is multiple hard braking evens in close proximity, potentially without soft braking events separating them. That might trigger an adaptation routine in the SW due to the high number of lock up events in a short time.
i.e. if 90% of braking events in X time cause lock up reduce braking parameter Y. Theoretical real world situation: scored brake rotors that are more grabby.

 

[voip-ninja]

The car CR used was not a press car. They purposely buy their own cars to avoid this situation.

It does highlight a point though which is Elon slightly admonishing some of CRs complaints around wind noise and suspension with "you should try our newer production".

Is he inviting every early adopter like CR to simply trade their early build M3 for a newer one that doesn't have these issues? Otherwise at most he can invite them to bring their car in and have service done on it to improve it, but that's not at all the same as "try our newer production" cars.

CR experience should be similar to that of the thousands of other of early buyers who purchased a car that was built Oct/Nov/Dec/Jan/Feb before many of those "small improvements" were introduced.

 

[RDoc]

The purpose of the ABS software is to monitor the brake hardware/ vehicle dynamics and intervene during a braking force > traction situation. When that occurs, it is the job of software to reduce braking force to point where the wheel start spinning again, then reapply braking force to initiate braking again. So the whole system is software compensating for hardware (available braking force should always be greater than traction).

The scenario I am raising is not hard braking in general, it is multiple hard braking evens in close proximity, potentially without soft braking events separating them. That might trigger an adaptation routine in the SW due to the high number of lock up events in a short time.
i.e. if 90% of braking events in X time cause lock up reduce braking parameter Y. Theoretical real world situation: scored brake rotors that are more grabby.

That scenario seems pretty unlikely to me. The wheel spin or lockup is measured in real time, it's a feedback system, it shouldn't be part of a tuning parameter. Among other things the most likely reason for lockup is changing road surfaces, e.g. ice. If multiple stops on a snowy road cause wheel lockup, it would be a very poor program that then caused the car to have much longer stopping distances 2 minutes later on bare pavement.

If Tesla has programmed their brakes to do anything like that they've got major problems.

 

[Trevor B]

It does highlight a point though which is Elon slightly admonishing some of CRs complaints around wind noise and suspension with "you should try our newer production".

Is he inviting every early adopter like CR to simply trade their early build M3 for a newer one that doesn't have these issues? Otherwise at most he can invite them to bring their car in and have service done on it to improve it, but that's not at all the same as "try our newer production" cars.

CR experience should be similar to that of the thousands of other of early buyers who purchased a car that was built Oct/Nov/Dec/Jan/Feb before many of those "small improvements" were introduced.

True. This is a bogus argument by Elon.

 

[mongo]

That scenario seems pretty unlikely to me. The wheel spin or lockup is measured in real time, it's a feedback system, it shouldn't be part of a tuning parameter. Among other things the most likely reason for lockup is changing road surfaces, e.g. ice. If multiple stops on a snowy road cause wheel lockup, it would be a very poor program that then caused the car to have much longer stopping distances 2 minutes later on bare pavement.

If Tesla has programmed their brakes to do anything like that they've got major problems.

My scenario could indeed not be correct (I was originally promoting hot pads). It does seem like some self adjusting could be useful, perhaps their learning gains were cranked up.

The variables involved:
Wheel speed change needed to trigger ABS
Time between isolation valve activation and dump valve activation
Wheel speed change needed to trigger re-application
Time/ pressure for pump to recharge brake circuit
Time until de-asserting isolation valve.
Along with the control pressures based adjustment.

Physical variables:
Caliper hysteresis
Brake line compliance

 

[mongo]

True. This is a bogus argument by Elon.

Tesla has built what 20k -30k Model 3s so far? It seems reasonable that a magazine that is catering toward providing information to people who have not yet bought a car might serve its readers better by reporting on the type of vehicle they would actually be purchasing.

Hey readers! the suspension you cannot get anymore is too stiff. The wind noise on the first 20,000 cars was bad, don't buy one from the used lot.

@voip-ninja
I'd say "Admonishing" is disingenuous. The early builds truly are not representative of current production (esp regarding ride).

 

[drawfour]

True. This is a bogus argument by Elon.

I don't think it is. Consumer reports is for people who will be buying in the future, not for people who have already bought. There is no "return to manufacturer" option with a car or indeed with most products if beyond some initial time period. If CR came out with their report back in Jan, then it would make sense, because those issues were still issues. But it comes out now, and from cars that were built back in Dec/Jan is not indicative of the car that people ordering/buying NOW would get. People reading CR now would think that their report is indicative of the car they would be buying for delivery in 3 months, and that simply is not true.

 

[cronosx]

It does highlight a point though which is Elon slightly admonishing some of CRs complaints around wind noise and suspension with "you should try our newer production".

Is he inviting every early adopter like CR to simply trade their early build M3 for a newer one that doesn't have these issues? Otherwise at most he can invite them to bring their car in and have service done on it to improve it, but that's not at all the same as "try our newer production" cars.

CR experience should be similar to that of the thousands of other of early buyers who purchased a car that was built Oct/Nov/Dec/Jan/Feb before many of those "small improvements" were introduced.

Yes, and at the same time, no
CR need to say what you would get when you buy a new car, an early adopter has alredy bought the car so who care what cr has to say? they have already brought it.
At the wrost they could say "in the older model there was a problem with the wind noise" just for who take an old used car, but saying that the car has problem with wind noise when this is not true is not doing their job.

Of course if Tesla continued to produce the same car you would be correct, but it's not the case, they found a problem, they solved the problem so from now on, the problem is not here

 

[voip-ninja]

Yes, and at the same time, no
CR need to say what you would get when you buy a new car, an early adopter has alredy bought the car so who care what cr has to say? they have already brought it.
At the wrost they could say "in the older model there was a problem with the wind noise" just for who take an old used car, but saying that the car has problem with wind noise when this is not true is not doing their job.

Of course if Tesla continued to produce the same car you would be correct, but it's not the case, they found a problem, they solved the problem so from now on, the problem is not here

Has Tesla provided a TSB list of all of the things they've improved from the time the CR car was built compared to what is rolling off the line today?

If not how could CR possibly know what differences there are between the car they bought compared to one someone is buying right now?

Well, they could just run down to the local dealer and borrow one of the new production cars for a day and compare it that way.... oh, wait a minute....

 

[insaneoctane]

I'm legitimately confused about what Elon actually means with this tweet:
"Looks like this can be fixed with a firmware update. Will be rolling that out in a few days. With further refinement, we can improve braking distance beyond initial specs. Tesla won’t stop until Model 3 has better braking than any remotely comparable car."

I tweeted this back (no answer, of course):
"Does this mean after the update that my Model 3 will brake quicker than the Audi A4 (105 ft) or BMW i3 (108ft)? Fingers crossed! Thanks for an amazing car!"

So what is everyone's interpretation of his tweet? Certainly an Audi A4 and BMW i3 are "remotely comparable" cars?

 

[GreenT]

I'm legitimately confused about what Elon actually means with this tweet:

"Looks like this can be fixed with a firmware update. Will be rolling that out in a few days.

You and everyone else! The tweet is patently false! WTH does firmware have to do with braking distance? Nothing! Like the distance is deliberately crippled by firmware? Pay $10,000 more for better braking?
A few Elon days. Like 2019. I lose more respect for him with every tweet! Like someone else

 

[Zaphod]

You and everyone else! The tweet is patently false! WTH does firmware have to do with braking distance? Nothing! Like the distance is deliberately crippled by firmware? Pay $10,000 more for better braking?
A few Elon days. Like 2019. I lose more respect for him with every tweet! Like someone else

How is it patently false? ABS is still controlled by electronic systems. If the control algorithm is limiting actuation timing and/or force, stopping distance will suffer.

 

[mongo]

You and everyone else! The tweet is patently false! WTH does firmware have to do with braking distance? Nothing! Like the distance is deliberately crippled by firmware? Pay $10,000 more for better braking?
A few Elon days. Like 2019. I lose more respect for him with every tweet! Like someone else

ABS is software driven, ABS controls braking force, braking force control braking distance, ergo software controls braking distance.

May be something simple like the time between wheels spinning again and re-application of braking force.

@insaneoctane
Regarding minimum distances, with comparable tires, it might. MT was getting ~120 ft stops.

 

[MP3Mike]

Certainly an Audi A4 and BMW i3 are "remotely comparable" cars?

I wouldn't consider the BMW i3 a "remotely comparable" car. (It is significantly smaller and the Model 3 weighs 33% more.)

And what kind of tires were on the Audi A4 for that test?

 

[D3xDt3Reaction]

I'm legitimately confused about what Elon actually means with this tweet:
"Looks like this can be fixed with a firmware update. Will be rolling that out in a few days. With further refinement, we can improve braking distance beyond initial specs. Tesla won’t stop until Model 3 has better braking than any remotely comparable car."

I tweeted this back (no answer, of course):
"Does this mean after the update that my Model 3 will brake quicker than the Audi A4 (105 ft) or BMW i3 (108ft)? Fingers crossed! Thanks for an amazing car!"

So what is everyone's interpretation of his tweet? Certainly an Audi A4 and BMW i3 are "remotely comparable" cars?

You and everyone else! The tweet is patently false! WTH does firmware have to do with braking distance? Nothing! Like the distance is deliberately crippled by firmware? Pay $10,000 more for better braking?
A few Elon days. Like 2019. I lose more respect for him with every tweet! Like someone else

I’d like to give Elon the benefit of the doubt on this one. While it seems unlikely that a firmware update alone would cause the Model 3 to best the Audi or BMW brake specs, I’m inferring he means Tesla is committed to continuous improvement longer term until the Model 3 specs do surpass them.

 

[PhantomX]

How is it patently false? ABS is still controlled by electronic systems. If the control algorithm is limiting actuation timing and/or force, stopping distance will suffer.

How does that explain the big difference in stopping distance though? Is the software wrong, or is the hardware not capable and Tesla is trying to tweak the software to compensate?

 

[nvx1977]

You and everyone else! The tweet is patently false! WTH does firmware have to do with braking distance? Nothing! Like the distance is deliberately crippled by firmware? Pay $10,000 more for better braking?
A few Elon days. Like 2019. I lose more respect for him with every tweet! Like someone else

Just because you can't wrap your head around something doesn't mean it's wrong or false. People who think the world is flat believe that in part because they can't observe firsthand the curvature of the earth.

Unless you have insight into the engineering of the brakes, both hardware and software, you are in no position of declaring anyone a liar.

 

[mongo]

How does that explain the big difference in stopping distance though? Is the software wrong, or is the hardware not capable and Tesla is trying to tweak the software to compensate?

Guessing:
ABS is spending longer than needed in a lowered pressure mode. Like if you were pumping the brake yourself, but lifting off more than needed.

Brake HW is good enough, otherwise it could never get short distance (assuming regen off).