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P3D Add performance checkbox removes on new custom orders
- Thread starter Circci
- Start date
It’s not ‘you guys’....it’s one guy...the same f”#$ guy every time....really is getting quite old at this point. Makes this whole forum unreadable and unlikeable.....it’s really a shame. Should be banned. TOTALLY unproductive. I mean Jesus H. Out.
Ski
Knightshade
Well-Known Member
I think it's a pretty limited list of possibilities- most of which were already covered? But to try and get em in one place (and maybe add one?)
Possible reasons you can no longer order a P3D-
1) They realized nobody was taking it at the current price, so they're gonna go back to randomly having batches of inventory ones you can "ask" for but with no choice of color/wheels besides whatever they made, and a 4k markup over LR AWD instead of the old 2k one since 2k makes no sense since the AWD boost came out.
2) They realized nobody was taking it at the current price- so simply dropped the option to simplify manufacturing (no longer a reason to ever build a dual motor 980 car without the P+ stuff on it)....this would make less sense if they were still putting 980s in the LR AWD and it was just a SW flash- but since that's not the case this remains a valid possibility
3) They're about to redo the P in some way (maybe offering the track package upgrade included, or some ludicrous variant, etc)- this seems less likely to me as I don't expect the P to be upgraded in any meaningful way until some time after the Plaid S/X are out
4) Kinda the opposite of 2, the 990 is some failed experiment and they're gonna bring the 980 back in the LR AWD and just sell a 4-5k P unlock- least likely for reasons I think already covered in some detail
1 or 2 really seem the best possibilities- there were lots of threads of folks who couldn't understand why anybody would take the - at the full + pricing after all.
I think about sums it up? Any I missed?
lbowroom
Plaid, white on black, CF, 8/27/21, Track Pack
I saw my first Y in person. Performance with the 19” wheels. I asked the owner why he chose that config. “I don’t like big wheels, too expensive for tires”.
It was difficult to resist the temptation to shake my head.
It was difficult to resist the temptation to shake my head.
it's really not.
It's a bunch of actual, known, facts, and then the only conclusion we can draw from that fit all of those facts.
Again- if you think you can draw a DIFFERENT one that fits all the actual facts- please let us know what it is.
So far nobody else has one.
The answer is... what you're about to say
No, all of it.
Here it is-
d= v^2/2ug
d=distance for car to stop
v=velocity of car
u=coefficient of friction between tire and road
g= acceleration due to gravity (9.80 m/s^2)
Notice how the formula doesn't ask about your brakes, but DOES ask about your tires?
Because the maximum deceleration (which would be what's going on during a panic stop) is every single time limited by the friction of the tires... and MOAR BRAKES!! does not change that. At all.
I'd encourage you to read the article I posted from the guy who designs brake systems for a living.
He covered what each part of the system does, and why none of them stop the car (other than the tires).
It was in fact the entire point of the article- with math, physics, and everything included.
Sure. In fact I already gave the same type of example earlier (though making the tires instead of the road frictionless) to make the same exact point. The tire/road friction is what actually stops the car
It's weird you're trying to repeat back my own example to me.
I think you're getting lost now... it's the friction between the tire and road that does it.
See, again, the actual formula for stopping distance. It's the only part of the equation that cares about any actual parts on the car.
This is 100% completely wrong.
Period, full stop.
Brembo says you're wrong (already quoted them doing it)
Car and Driver says you're wrong (already quoted them doing it)
So does stoptech and a ton of others... here's Road and Track for example debunking your claim-
Road and Track
How Changing Tires Can Improve Your Braking & Stopping Distances - How Tires Upgrade Your Braking System
In fact- they even toss in some math not entirely unlike what I gave you earlier... pointing out that u (the coefficient of friction of the tire) is the single thing that dictates the stopping distance of the vehicle. Because that's the maximum force the tire can apply to the road. Which is the force that actually stops the car
And since the stock brakes can already maximize that by engaging ABS, well, let's quote them again-
Then (somewhat like the Pulp Friction article) then mention some of the OTHER things changing brakes parts CAN do for you... but that stopping shorter is not one of them
Then they reiterate:
Because- as (most of us) understand- the tires are what stop the car.
100% nonsense.
It's explicitly debunked in the GRM pulp friction link in fact where he discusses compliance and why that can't stop you any shorter
Same with the other parts you mention- each of which he explains what they CAN do for you and what they CAN NOT (spoiler: stop shorter is one they can't do)
To feel? Sure.
To stopping any shorter? 100% nope.
Weirdly- they do not provide their testing methodology or their raw data.
I bet it's because what they did was test from speed like 10 or 20 times in a row with no cool down....
Meaning they were testing fade resistance- not stopping distance.
(they don't mention that of course because they don't want the average sucke^h^h^h^h^h customer to realize their pads won't do jack to stop them any shorter in a normal highway panic stop- because they can't.)
Because, as physics (and Brembo, Stoptech, Road and Track, Car and Driver, professional Braking systems engineers, and more) tells us- brake pads can't change that second one for a normal single panic stop.
The National Law Enforcement and Corrections Technology. Center does tests like that... (because they expect that unlike a normal civilian driver, a cop might need to repeatedly be braking hard from 100 mph or more over and over)... Interestingly they too make the point you are wrong about this when they explain why they do not measure stopping distance in such a normal civilian panic stop situation-
https://www.justnet.org/pdf/EvaluationBrakePads2000.pdf
Instead they test fade- by repeating braking from 90 mph over and over, heat soaking the system to see how much abuse it can take.
This type of thing matters for police work- and for race tracks- but not normal, legal, civilian street driving.
Plus- of course- fade measures how much longer stopping takes after things get very hot... the stopping distance is never shorter than the first normal panic stop- no matter how great the brakes are- it can't be...since it's the tires that stop the car
Glad you asked!
Because the code controlling the ABS computer had a bug in it. (and as we established- in a correctly working car ABS engages when the tires are at their limit of friction.... so if it's NOT correctly working it's failing to maximize the tires friction limit- and will take longer to stop).
Notice how they fixed it with computer code- and not changing any hardware (including brake parts).
Once they did that, the tire was able to once again maximize available friction and distance got shorter.
Here's a better question for you-
Why does the non-P model 3 with 19s stop shorter than with 18s?
The only difference after all? The tires.
For that matter, why does a P3D+ with BIG BRAKES stop in the same distance as an LR AWD without BIG BRAKES once you swap PS4s tires on the LR AWD?
(Spoiler- it's because the tires are what stop the car)
But I thought it was the tire/road interface that stopped the car, or is it just the tires?
(Sorry everyone, I'm curious how much further I can help to derail this thread
)ECE R90 Regulations are for cold braking tests. Those Ferodo tests were done with cold pads. If the vehicle is exactly the same with the exception of the pads and testing done with cold brakes, why would a pad change on the same tires result in significant changes in stopping distances? Dynamics maybe? The same reason for why the ABS reprogramming changed stopping distances for the Model 3. Using deductive logic (your favorite), it must be that something other than the tires can affect stopping distances on a stock vehicle. Cut a brake line and you're stopping distances are going to change by more than a few feet.
I spent a lot of time reading through Stoptech's whitepapers when researching brake system design when I was helping to lead a FSAE team in school. Funny thing is, your favorite author, James Walker Jr. either wrote, or co-wrote a bunch of those papers. Here's an interesting one for you:
https://www.apcautotech.com/getmedi...epaper_A2-Brake-Bias-Performance_8-2018_1.pdf
"In summary, your tires certainly still stop the car, but if your bias is out in left field you might not be able to use everything they have to offer. Your braking system is just that – a system.."
If you're interested, someone curated a bunch of equations for calc'ing brake system performance and dynamics. Engineering Inspiration - Brake System Design Calculations
I know a couple people that have Performance 3s...none of them drive at the legal limit. lol. A good canyon run will have noticeable brake fade and a performance upgrade is useful for that type of spirited driving. The normal brakes just aren't up to par on something like that and doesn't require a track to notice stupid brake fade which is annoying as hell. I'd wager that owners of the Performance do more of that type of driving than track which tears a car apart pretty good (expensive too with all the tires and brakes and track time). I really value the upgraded brakes as they have a much better feel too. I doubt I will last 100k miles on my brakes like most Model 3 drivers...drive too fast and "spiritedly" for that.
Knightshade
Well-Known Member
The friction between tire and road of course- as explained multiple times.
The tire being the only part that's actually attached to the car and you have the ability to control... you can bring your own road everywhere you drive after all.
It wouldn't- hence why I'd like to see their actual methods and specific results instead of one cute chart with no details.
Because as I mentioned all the other folks who are more honest when selling their brakes like Brembo and Stoptech explicitly TELL YOU that a pad change can't stop you shorter.
You appear, again, confused.
A problem in the braking system (like a malfunctioning ABS computer running bad code) can make stopping longer
And fixing that will restore the car to stopping at the shortest distance the tires (the part of the car that actually stops it- by acting against the road surface) can stop the vehicle.
But continuing to futz around beyond that can't shorter that minimum distance. Not ever.
Again it's why the actual formula in physics for stopping distance doesn't ask about your brakes.
As long as they can lock the wheels (or on newer cars engage a properly working ABS system)- then MOAR BRAKES physically can not stop you shorter
Yes- again- a malfunctioning system can lengthen stopping distance.
Upgrading a correctly working one (other than stickier tires) can not shorten it
Two entirely different things.
It's a shame you claim to have read it- but then so badly fail to understand it.
He's telling you the same thing I am.
He's pointing out a lot of clueless people randomly pick a BIG BRAKE KIT that doesn't actually work right regarding the proportioning.
So now you have a worse stopping distance, instead of a better one.
Because part of your system is no longer working correctly.
Fix that... and you go back to the same stopping distance you had with a 100% OEM STOCK CAR
He's telling you that you should insure your "brake upgrade" properly accounts for the OEM proportioning setup for the car you are upgrading.
He's not in any way, ever, at any point in that whitepaper claiming that upgrading your brakes will stop you shorter than the OEM stock system did.
One way we know this is if he HAD said that you'd have quoted it.
In fact, there IS a quote in there that... I dunno.. guess you missed? Or didn't understand? Still not clear- but here it is:
Source YOU embarrassingly provided for us said:
Huh... look... he's telling you if you screw up your upgrade you can make stopping distance worse
He's not at all claiming it can ever be any shorter than what the tires could already do on a properly balanced factory system.
Man- that sounds so familiar.
Oh- right- it's exactly what has been repeatedly explained to you over and over again.
KEEP DIGGING MAN! CHINA CAN'T BE FAR NOW!
And again the ABS computer glitch is a perfect example-Due to a glitch, CR saw increasingly longer stopping after their first test.
Once they fixed it- the OEM system got back to the original stopping distance they got on the original first stop.
It never got shorter than that though- because they didn't change the tires.
On the other hand- when folks tested the same model car with the same brakes but it had the 19" optional wheels (which are stickier tires) they did get shorter stopping distances.
And, to the surprise of nobody who actually understands brakes if you swap the same tires a P3D+ has on that car- it then stops in the same distance as a P3D+ does.
Even though the P3D+ has MOAR BRAKES.
Because, of course, the brakes don't stop the car. The tires do.
Knightshade
Well-Known Member
huh- I guess that'd explain the bot thinking citing a source that matched the keyword of an author I mentioned- but if you actually read it agrees with me, was a good idea
You're not going to fool me anymore!huh- I guess that'd explain the bot thinking citing a source that matched the keyword of an author I mentioned- but if you actually read it agrees with me, was a good idea
lbowroom
Plaid, white on black, CF, 8/27/21, Track Pack
I don’t understand the controversy here. Correctly implemented upgraded brakes resist fade longer than OEM. barring a defect in OEM system, they won’t shorten initial stopping distance. Nothing spiritual or magic involved.
Exactly. Upgraded brakes resist fade and thats what Performance drivers are mainly after. Yes there are better aftermarket solutions but the stock PUP is good enough for most users that want to drive Angeles Crest on weekends and not actually take it to a track.
Knightshade
Well-Known Member
Exactly.
But as is pretty evident these days- a surprising number of folks aren't interested in science (or facts in general).
Still the great thing about facts is they remain true even if someone doesn't believe in em... so in normal everyday legal street use (outside of the autobahn) upgrading your brakes won't do anything functional (though it can do things for look or feel)- and for tracking a car it can do lots of useful, functional, things (though ever stopping shorter the first time ain't one of em)
Back when the "cheap" version of the P was available it was a no brainer to go that way- the P3D- gave you the lighter, less prone to damage, wheels and better range and if you didn't track it you just saved 5k.... and if you did that extra $5000 in your pocket could get you better-than-P3D+ brake upgrades (while retaining more wheel choices than the + has) if you really did want to flog the car on a track or in Germany.
The several months where + and - were the same price never made any sense, so glad that's gone now- just a question of what (if anything) comes next regarding the - version.
So, let me get this straight, tires are the only thing that stop the car, but issues with the brake system affect stopping distances? Which is it? Brakes do or do not work as a system with the rest of the vehicle, including the tires, to stop a vehicle? You've claimed it several times here. Like this:
Oh man, you're hilarious and incorrect. He's explaining the physics and dynamics of braking on a vehicle. Which also leads to my next point. You assume an OEM has perfectly calibrated their system and selected the best available components to maximize the traction of the tire under braking. We know this is not true by this:
Was not a glitch and it wasn't just that their tested stopping distances got longer and longer. It was poor calibration of the ABS system that caused both an initial longer stopping distance than other vehicles in its class (and some full size trucks), but also continued to get longer. Tesla was able to rectify this due to their vehicles' OTA update ability (and only after 3rd party testing exposed the issue). How many other vehicles (Tesla or not) are out their with poorly calibrated ABS systems? Which OE tire package did the OEM calibrate to? Did they have to make concessions because maybe they used a non-ideal pad for cost reasons that doesn't develop friction as quickly as another pad, or that they have a lot of different tire options depending on trim level and they calibrated in the middle? Is the ABS system correctly handling and maximizing the slip vs. normal force vs. friction coefficient of the tire? You assume Tesla and any other OEM is infallible in this exercise, when in fact, they've shown that they are not. So it must be that the braking system matters.
But, I thought it was the road/tire interface that stops the car? But now its just the tires again? Should probably get your story straight. You seem confused, because you keep circling around. Which brings me back to vehicle dynamics and the main point you're missing, especially when you continue to proclaim that its ONLY THE TIRES THAT STOP the car, and disregard what I originally said, which is that its the entire system that works together to do that. Hence, only partial understanding of the problem. Vehicle dynamics matter. Weight transfer matters. Transients matter. The braking distance formula you cite is a simplification and ignores the non-linear responses of the components (tires + braking system) and chassis to illustrate in simpler terms why performance oriented owners should do tires first to improve stopping distances. What it does not say though, is that there isn't room for improvement in the OEM braking system that could better maximize the OE tires under braking to minimize stopping distances (something which we know they may screw up, or not fully optimize based the Model 3 ABS issue we've discussed).
This is a simplification:
d= v^2/2ug
d=distance for car to stop
v=velocity of car
u=coefficient of friction between tire and road
g= acceleration due to gravity (9.80 m/s^2)
Because, u is not static. That number changes with the tire slip coefficient and the normal force on the tire for a given tire/road interface. Pacjeka tire models ring a bell (Tire-road dynamics given by magic formula coefficients - Simulink)? The normal force on the tire changes with weight transfer. Weight transfer is affected by the suspension and Cg (which is also a non-static and non-linear interaction) and how much and how long it takes for the braking system to generate friction and brake torque at each wheel/axle. Brake input torque is a non-linear response to driver pedal input, ABS transient response (if activated), braking system compliance, and suspension system compliance.
Here's a fun link showing the non-static/linear response of tires related to tire normal force (which varies based on the braking and suspension system).
Tires - Vehicle Physics Pro
Translation - an assumed static u is not the full story, particularly since the resultant tire/road u is dependent on so many factors that are affected by the braking system, because tires require a both a normal force input and a rotational torque to slow.
Going back the White Paper I posted earlier from your favorite author:
"Typically, the auto manufacturers design their cars to be 5% to 10% more front-biased than optimum for maximum deceleration, but they provide enhanced brake stability in return." change to a more aggressive rear pad (within reason) will likely net better braking distances on a factory system at the sacrifice of some stability.
and there's this:
https://www.apcautotech.com/getmedi...1-The-Physics-of-Braking-Systems-8-2018_1.pdf
On page 7, Mr. Walker states this about the simplified formula:
"Note that this equation assumes a step-input deceleration from a fixed speed followed by a linear and constant rate of deceleration until the vehicle comes to rest. In practical application, deceleration cannot be achieved instantaneously, nor can deceleration be assumed to be constant for the duration of a stopping event."
And when taking into account weight transfer effects (which are affected by brake sizing and component selection), he is still providing a caveat on page 10:
"Note that in this analysis it is assumed that µpeak,f and µpeak,r are independent of deceleration, when in practice they are sensitive to the loading changes brought about by the weight transfer phenomenon. Consequently, as weight is transferred the total vehicle deceleration capability is diminished by a small amount."
And again when looking at brake balance and how it affects tire vertical force (thus affecting tire/road u) on page 10, he states this:
"From this relationship it becomes apparent that while the ratio of the front and rear braking forces is a fixed parameter based on the mechanical sizing of the brake system components, the ratio of the front and rear vertical forces is a variable based on deceleration and vehicle geometry. This dictates that relationship can only be optimized for one vehicle deceleration level and loading condition (typically at maximum deceleration with the highest percentage of static front weight)."
So, it must be that both the tire, braking system, and vehicle (and driver) work together to stop the car, and not only the tires. Factory braking systems are likely not fully optimized to minimize stopping distances in ideal conditions on original tires due to the complex interactions and trade-offs that must be made during the design process. There is likely room for improvement even on factory tires, because it cannot be that only the tires matter.
Everyone else, this appears to be working, so I'm just gonna roll with it
Can keep the commenting party busy with this thread and away from clogging up other threads.First of all, I think that idea of exhausting any chatbot is questionable.
But then, I would trust average OEM more on ability to do balanced brake system than any aftermarket. If you put stickier tires on a car - thats not OEM system already. And removal of P3D- could be explained by Tesla decision that standard brakes are not good enough for the power.
But then, I would trust average OEM more on ability to do balanced brake system than any aftermarket. If you put stickier tires on a car - thats not OEM system already. And removal of P3D- could be explained by Tesla decision that standard brakes are not good enough for the power.
Knightshade
Well-Known Member
I see you're confused again. I'd again suggest you go back and read pulp friction.
It explains what each part of a braking system does, and does not, do. Why none of them are the thing that stop the car (that's the tires-specifically their friction against the road surface). And what upgrading brake parts can, and can't, do for you.
In pretty basic detail even.
Again though- the point is if you have a correctly functioning braking system (ie one that can engage ABS- which is basically every from-the-factory braking system going back at least a couple decades now)- then UPGRADING your brakes can not stop you any shorter.
That's pretty basic physics (again explained in detail in the article).
If your braking system is NOT correctly functioning then that can certainly make your stopping distance worse
But "upgrades" can't make it better.
Because- again- your shortest possible stopping distance, every single time is limited by your tires.
You know- the things that actually stop the car.
So you can do things to the brakes to stop LONGER than the tires are capable of. But not shorter. Ever.
It's remarkable you still don't get this basic point after a bunch of sources and simple explainations.
Ironically- even the one you cited as a source explains it- apparently you don't read your OWN sources- let alone anyone elses.
Naah- I'm 100% correct.
Again we know this because you were unable to quote anything from your own source that agreed with you but I was able to quote something from your source that explicitly agreed with me
I do agree that's hilarious though!
Yes- and if you read the actual quote from your own source I provided you see where he reiterated that an incorrectly functioning system can make your stopping distance longer but he never says that "upgrades" can make it shorter
And even points out why- (spoiler: it's because the tires stop the car- the tires always are what determines your shortest possible stopping distance- every single time
Screwing up your brakes can lengthen that, but "upgrading" them can't shorter it.
Just as your own source confirms
Again- hilarious indeed.
Of course it was- Specifically one in the ABS calibration algorithm
Which is why pushing a software update was able to fix it.
Are you going around looking for new stuff to be wrong about now or something?
...and now you're just outright lying.
Tesla Model 3 Falls Short of a CR Recommendation
Consumer reports said:
Their first stop was perfectly fine.
Just like you lied and said it wasn't.
It was later stops that got longer.
Once, of course, Tesla fixed the glitch via an OTA update the stopping went back to consistently being similar to that first stop.
Since nearly all new cars are testing by CR and various other magazines, and none showed a similar issue, I'm gonna go with none?
In fact CRs article mentioned that Car and Driver had found the same issue with the Model 3 they did- and their tester specifically called out no other car he had tested in the last 11 years showed such an issue.
Almost like- as I said- properly working factory braking systems are virtually universal and have been for years.
Thanks though for once again pointing us in a direction that finds multiple sources confirming what I have already told you
That question doesn't even make sense.
Calibrating to a "specific tire" isn't how they do this- just like they don't calibrate to a specific road surface because amount of traction on those varies greatly too.
The car has no idea what brand of tire is on the car. It only knows what its sensors tell it.
It knows how much traction the tire/road interaction is currently producing (among a bunch of other relevant factors).
Do we now need to explain to you how ABS works?
Good news! I have a link for that too (that doubtless you'll either not read, or not understand- maybe both!)
ABS and Brake Kit fundamentals
He takes a slow-motion look at ABS in action and how/why it does what it does. All without needing to know what brand of tire is on the car.
What's great of course is once again he points out that a poorly designed brake upgrade can actually make things worse
But that a properly designed one just gets you back to "working correctly" like the factory OEM system did- plus the track-specific brake upgrade advantages like fade resistance for when you're beating on the car.
At no point of course does he claim upgrades can ever stop you shorter. Just that bad upgrade can stop you longer.
Man that sounds so familiar by now doesn't it?
Almost like the same basic facts keep coming up!
Again you seem to completely not understand how/why ABS works, and what factors go into calibrating the system.
I suggest you specifically check the ABS link I gave you, the section titled:
Pressure-Torque And Pressure-Volume Relationships
Where he explains some of the important considerations in designing an OEM braking system to work properly... (spoiler: the tires don't come up here...because the ABS system has no control over how much traction your tires have (or how much the road has)- it has to read those things in real time from the sensors and then adjust the things it CAN control in relation to them).
On the contrary- thanks to you we got the quote from Car and Driver that in over 11 years of testing (as of a couple years ago even) other than the Model 3 glitch no other car they tested had such an issue.
So I suppose the one Tesla error means they're not "infalliable" but the car industry in generally is damn near- and the one mistake that slipped in going back over a decade was caught quickly by multiple industry sources and made public and corrected.
So your weird paranoia that this is gotten wrong a lot appears just as unfounded as the rest of your...let's generously call them arguments...
Again- no.
Go read Pulp Friction 20 or 30 more times till it sinks in.
Both matter- but only one is something actually attached to the car and that you always have control over.
You can put better tires on the car. That shortens stopping distance.
You've no control over the condition of all roads everywhere though.
Not sure how you keep screwing this up.
That's true.
Just like it's true your rotors, pads, and choice of brake fluid won't, assuming your brakes work correctly to begin with, have no effect on u
Bigger rotors can't magically make your tires stickier.
Still nope.
Go re-read Pulp Friction another 20 times
All those things (except the tires) work together to allow the tires to maximize the amount of friction they apply to the road.
Which, again, is the thing that actually stops the car
Screw up your brake setup and you can end up taking longer to stop than the tires are capable of.
But no amount of "upgrades" to properly working OEM brakes will let you stop shorter than the tires are capable of.
or- as the article you keep refusing to read or understand puts it-
Pulp Friction said:
At making it obvious you're increasingly desperate to find anything you might not be wrong about- even to the point of outright lying about CRs results?
Interesting definition of "working" ya got there
You're right, it is pretty basic physics. Its easier to explain to the lay person that way. We'll get to that later in my response. You're also right, shortest possible stopping distance is limited by your tires. But that isn't what I commented. It was your assertion that only the tires matter. There are a whole host of reasons why that's not true.
Wrong again: Stopping Distance Retest After an ABS Firmware Update - 2017 Tesla Model 3 Long-Term Road Test
"Our initial 2017 Tesla Model 3 full-ABS panic-stop measurement of 133 feet was indeed below average. But it didn't seem outrageous, especially given the characteristics of the standard 18-inch tires. They're hard (with a treadwear rating of 500), they run at an abnormally high tire pressure (45 psi), and their 235 mm tread width isn't generous considering the car's 3,884 pounds of weight. It all seemed to fit, but that was before Consumer Reports reported a 60-0 mph stopping distance of 152 feet, nearly 20 feet longer than ours...
I didn't suspect ABS calibration after our test because, frankly, that's hard to screw up. And the obvious safety implication involved means that ABS calibrations are typically optimized to the nth degree before a car goes on sale...
Our first stop with the revised firmware measured 123 feet, exactly 10 feet shorter than our previous best. The second stop came in slightly better at 122 feet. In terms of feel, the initial "bite" of the brakes was more positive, and the ABS system pulsing was smoother throughout the stop. Our Tesla Model 3's stopping distance is now right where we'd expect it to be. Not better or worse than average, but solidly midpack...
This alternative explanation was apparently bunk. Tesla has since reached out to say my handover theory was not the issue. The carmaker put it all down to ABS calibration. I'd say it was a particularly bad ABS brake calibration if we could measure such a sizable difference on such a smooth surface."
Interesting that you claim I have difficulty reading, but it appears you forget about the information in your (recently) Googled links: "a quick calculation, the ABS determines that in order to have slowed 1 MPH in a 50ms period the wheels must be decelerating at a rate of 0.91g's. Because you are driving a sports car, the engineer who calibrated the system 'taught' the ABS that your car is capable of decelerating at this rate, so the ABS continues to hang back and watch the event from the spectator's booth. No problem so far."
Weren't you saying something earlier about when Edmunds swapped on the 19" wheel and tire combo, and the car stopped shorter? Which value (rather, envelope) does the engineer calibrate to then? The stickier 19" tire or the 18"? Optimizing for one results in sub-optimal effects for the other, because as you've stated, the vehicle doesn't know what tire is on the car.
But, I thought it was all about the tires? Why wouldn't they come up? Where are they? Did they forget what you taught them?
Both matter?! But, I thought it was only the tires as you've so fervently and verbosely explained to all of us over and over again.
With the exception that rotors can't make the tires stickier (just like tires can't make the rotors bigger), 100% incorrect. They won't change the tire, but they will change how you use that tire under braking. Why, because tire friction isn't static? This is the part that you seem to have trouble understanding and way out of your element on. Something that a few Internet articles can't explain. Your formula that you like to use, uses an average tire u under the deceleration event for the entire vehicle - kinematic equations from high school physics. When you direct your attention to the tire itself, the resultant force that the tire produces back on the suspension assembly (as a result of the brakes operating) is the combination of the normal force on that tire (which changes from static with weight transfer and road irregularities) and the available u (which also changes with normal force and the slip ratio of that tire). Do you know what slip ratio is? You seem to know it all, so please educate us on how maximize longitudinal tire friction using slip ratio data and load sensitivity of the tire.
If this was all figured out, then why would researchers continue to work on ABS control dynamics to improve control and potentially stopping distances? Like these:
Anti-Lock Braking System Using Predictive Control and On-Line Tire/Road Characteristics Estimation - ScienceDirect
An optimal control for a novel ABS based on vehicle dynamic load transfer effect for reducing stopping distance - IEEE Conference Publication
https://pdfs.semanticscholar.org/f0cc/abf56133806b19ca0ef692b196a92bb7eeea.pdf
Fuzzy Life-Extending Control of Anti-Lock Braking System - ScienceDirect
The first link in the set is excellent, because there's a funny equation in there (5). A small expansion on the simplified equation you keep talking back at everyone where we move beyond average deceleration rate of an entire vehicle with an averaged static u, and move to the tire where the resultant force is equal to the friction coefficient times the normal force.
Still nope.
Go re-read Pulp Friction another 20 times
All those things (except the tires) work together to allow the tires to maximize the amount of friction they apply to the road.
Which, again, is the thing that actually stops the car
Screw up your brake setup and you can end up taking longer to stop than the tires are capable of.
The GRM Pulp Friction is great for people that need the engineering and physics simplified, particularly those without any actual engineering dynamics experience. If you want to read a real book on how vehicle dynamics work (or for anyone else interested), take a look at this: https://www.amazon.com/Vehicle-Dynamics-William-Milliken-Hardcover/dp/B00GSCTN2U - its probably the bible of vehicle control dynamics. I'd suggest taking a dynamics and control system class first. It's a little dense. You could also sign up for this seminar: Seminars | OptimumG. Claude is an interesting guy, but you'll definitely learn something. I know I did.
My guess is, you'd be the person trying to explain what you read in Pulp Friction back to Mr. Walker when he moves beyond his basic introductory information, especially when trying to optimize a braking system for minimum stopping distances. You work from the tires, but not only with the tires, because each component affects the other. They work as a system (key word there). OEMs have to design for the entire system (multiple tire options + brakes + chassis + variant mass loads), which always includes compromises. Whether its pad compounds, brake disc sizing, caliper construction, etc... for cost, material availability, suspension limitations, GVWR limitations, and a whole host of other things. The compromises likely result in sub-optimization of the specific tire that the vehicle came with.
What say you about Mr. Walker's comments on the trade offs for brake bias design between braking distance and stability?
DING DING DING! By golly, I think we're starting to understand. Those last five words are the important part. What are the tires capable of, and how to do you maximize that? Well, that's the million dollar question. You assume the OEM has designed their system to do that perfectly. Sure, to the untrained person, they're likely to not gain anything from brake upgrades for cold stopping distances (unless someone did their homework for them), and would be better off first focusing on tires.. But, to someone who knows what they're doing, they could probably find some items in the braking system (and suspension) to better optimize the tires that came on the vehicle for even cold max decel events. The tires are the most important part, but not the only important part.
(Everyone, better off clicking ignore, this is gong to take awhile. But, more time on here = less time in other threads
)
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For those who are saying that the brakes don't affect the braking performance, need to think of the WHOLE car as a dynamic system.
Yes the tires affect the stopping distance. BUT so does the suspension, which controls the weight transfer under braking. Tires under more load, can grip more, and exert more braking force. Weight transfer, (and dynamic changes to the weight transfer) cause changes in the amount of stopping force available.
Interacting with weight transfer, the brakes affect how the weight transfer is applied. There is an interaction between the speed at which braking is applied, the shocks, and the springs, and even the weight loading in the vehicle.
If you 'snatch' the brakes, you can lock the wheels well before the weight transfer takes place, and then maximum weight transfer, tire loading, and thus traction is not reached, as the slipping tire unloads the suspension even more.
If the braking 'bite', is more compatible with the weight transfer, suspension compression, tire deformation etc, then you can achieve an overall shorter stopping distance. So the dynamics of the way the brakes apply the stopping force can definitely affect the overall stopping distance.
If anyone rides a motorcycle, and especially sports-bikes, they will know all about weight transfer. Less obvious in a large car, but still has a significant affect.
Yes the tires affect the stopping distance. BUT so does the suspension, which controls the weight transfer under braking. Tires under more load, can grip more, and exert more braking force. Weight transfer, (and dynamic changes to the weight transfer) cause changes in the amount of stopping force available.
Interacting with weight transfer, the brakes affect how the weight transfer is applied. There is an interaction between the speed at which braking is applied, the shocks, and the springs, and even the weight loading in the vehicle.
If you 'snatch' the brakes, you can lock the wheels well before the weight transfer takes place, and then maximum weight transfer, tire loading, and thus traction is not reached, as the slipping tire unloads the suspension even more.
If the braking 'bite', is more compatible with the weight transfer, suspension compression, tire deformation etc, then you can achieve an overall shorter stopping distance. So the dynamics of the way the brakes apply the stopping force can definitely affect the overall stopping distance.
If anyone rides a motorcycle, and especially sports-bikes, they will know all about weight transfer. Less obvious in a large car, but still has a significant affect.
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