Braking Under "Spirited" Driving

[xponents]

A good bit of these braking distance differences has to do with tire sizes and vehicle weight, not with the brakes themselves.

The Air GT 21" tire widths are 245mm front and 265mm rear. The Plaid's 21" tire widths are 265mm front and 295mm rear.

And the Model S Plaid weighs 386 pounds less than the Air GT.

Yes, hence my grand tourer comments at the end. The Plaid is "built for the track" (but maybe fails at that mission) but the Air is meant for efficiency and the ability to still go fast outside a track and be comfortable (which is the definition of a grand tourer).

 

[hmp10]

There is another factor to consider in talking about braking distances, especially from high speeds: driver reaction time.

Studies have shown that it can as much as double the stopping distance of what the brakes themselves can deliver. And, as the reaction time elapses while the car is traveling at initial speed whereas braking time factors in deceleration during braking, the faster you are driving the higher the reaction time component is of the total stopping distance. In other words, the faster you are going the more relevant your reaction time becomes and the less relevant the car's braking ability.

https://nacto.org/docs/usdg/vehicle_stopping_distance_and_time_upenn.pdf

 

[borski]

MotorTrend: “The Air brakes and handles well for a luxury car, too. It lapped our figure-eight course in 24.6 seconds while averaging 0.83 g—reasonable, but among the slower times in the segment. Its best 60-0-mph panic stop required 115 feet. We suspect wider tires would help the Air find both more grip and better times, though you'll find no complaints from us behind the wheel.”

Edmunds: “While the tires and brakes felt sufficient stopping from 60 mph, the distance of 127 feet is on the long side for a modern car. Also, quickly slowing from over 135 mph was a little hairy since those all-seasons didn't have the bite we'd have liked for the amount of inertia built up at that point.”

The stopping distance is fine. Edmunds, as anticipated, still sucks, and ran the test on the 19” All Seasons.

More discussion here: https://lucidowners.com/threads/60-0-braking-distance.714/

 

[borski]

I always hate when people call the Plaid's brakes trash, because that is absolutely not true. When you use it for its intended purpose (not track driving, repeated hard stops), they actually have a very good stopping distance. The only reason people say the stock Plaid brakes are bad is because they fade with track use and they "feel" like the brakes are bad since the car accelerates harder than it decelerates (which is very rare, or it used to be). The same goes for the Air which I consider a grand tourer car vs a dedicated sports car (think of an Aston DB vs an Aston Vantage).

Now.

When it shipped, it shipped with the same brakes as the normal Model S for a very long time. I drove that. It was terrifying, and the car felt like it was going to squirrel away from you when you hit the brakes.

The Plaid was underbraked. Tesla effectively admitted this by releasing their “track pack”

 

[hmp10]

. . . the car [the Plaid] felt like it was going to squirrel away from you when you hit the brakes.

It feels the same when you get hard on the accelerator.

As a reviewer once noted, "Tesla says to Plaid owners, 'Here's a third motor. Good luck.'"

 

[terrycs]

Something to be aware about brake pads/rotors ... they work more consistently and predictably when they reach optimum operating temperature. The problem with brakes in EV applications are the pads are intentionally located further from the rotors to minimize drag so I think the brakes rarely reach nominal temperatures. Properly bedding-in brakes also provides more consistent performance. The attached bed-in procedure is from Stop-Tech which is a highly regarded performance brake manufacturer.

 

[Cosmo Cruz]

Bedding in. Oh you touched a nerve. People who have not had their rotors/pads bedded... "Oh, my rotors are warped!"
Mechanics love this,
because they can charge the customer for "turning" the rotors to "true",
or even more dishonest, replacing them.

Or, they can go out and do a dozen hot stops and make sure the rotors are evenly coated with pad material and the pads don't get glazed.
(when they are not evenly coated with pad material = they vibrate between sticky and not so sticky = feels like warped.)

a cast iron cook pan is seasoned with cooking oil....
because iron is porous.
It will take the oil,
or it will take pad material.

Probably the brakes on your Lucid have not been bedded...or maybe I'm so old this is not done any more. But it wouldn't hurt to take the Lucid out on a straight empty stretch and hit it hard a half dozen times, if for no other reason than to see what your car will do.

I used to be bothered when even "experts", like Bob and Ray (PBS Car Talk) said: "warped rotors" I even think I remember a show or two when they mentioned "bedding in the pads" ... but never explained what it is, or why it's part of a proper brake job.


Imagine if every time you had hot rotors and hit an icy puddle: you got "warped rotors" = that half-inch iron disc just can't take it.

I'd be in the rotor business !

PS: my last car had carbon fiber / ceramic brakes. They are fantastic. I don't know if they get bedded , but they sure as heck yank you.

 

[Cosmo Cruz]

Oh, and brake temps. As a young idiot I put "track pads" on the family wagon. After completing the job I went out to bed them. It was a bit cool. Well. No brakes. Nada. Seems that "track pads" are not meant to be driven on the street. Huh. Who knew ? (they need to be hot to work).

 

[borski]

It feels the same when you get hard on the accelerator.

As a reviewer once noted, "Tesla says to Plaid owners, 'Here's a third motor. Good luck.'"

Yeah, agreed. Just didn’t seem related to brakes.