Collision Warning - Nice Safety Feature

[jdcollins5]

I searched and found a thread on False Alarms so I wanted to follow up with a positive thread.

I have had two Collision Warning alarms where the person in front of me stopped suddenly. The first time the car stopped very suddenly due to a chain reaction of other cars. The car started braking a second before I hit the brakes. I had enough following distance so it was no imminent impact but a sudden stop no less.

The second time this morning I had just looked away for a second when the car in front of me stopped suddenly. I received the warning a second before I saw the brake lights out of the corner of my eye and hit the brakes.

It is nice to know there is a second set of “eyes” watching out for us in such situations.

Yes I have had some false alarms when a car is making a lane change and has not completely cleared my lane. In those cases I simply tap the accelerator to cancel the braking. I will take the false alarms any day in order to have the warning and braking when it is really needed.

 

[StealthP3D]

I'm an attentive driver but I *love* that there is a second set of eyes looking out for me. Nobody wants to be in an auto collision.

I was in a collision last in 1969 when my mother was driving and a car pulled out directly in front of us as we were traveling along at about 20 mph. It was shocking how violent the impact was, even at that slow speed. We all had our seatbelts on so there were no serious injuries but my mother's ankle troubled her for the rest of her life, particularly as she got older.

Avoiding the accident is always the preferred situation but, if you are actually in a collision, there's no better car than a Tesla to be in.

 

[MajorGator-M.3]

Just had a frontal collision. I don't think the alarm went off before I slammed the brakes. Impact was low-speed, though I wish I had 5 more feet to go - there might have been no collision. Also wish the brakes on my DM 3 were a little beefier.

 

[StealthP3D]

Just had a frontal collision. I don't think the alarm went off before I slammed the brakes. Impact was low-speed, though I wish I had 5 more feet to go - there might have been no collision. Also wish the brakes on my DM 3 were a little beefier.

Automatic Emergency Braking doesn't activate in all situations. One example is if you are already braking gently it won't brake harder.

 

[Wennfred]

Mine went off this morning coming off the freeway and heading into an intersection where the car in front of me was slowing down to make the right turn, From my distance He had plenty of time to make the right turn by the time I reached him and I was still moving at a high rate of speed, the chime sounded but no breaking occurred.


Fred

 

[Wennfred]

I have it set to the earliest warning.

 

[MajorGator-M.3]

I don't recall if the chime sounded, but I don't think the car could've done more than what I was doing. I am considering asking about the cost of bigger brakes.

 

[TESLEV!]

Do you have to have auto pilot for this feature?

 

[KenF]

Do you have to have auto pilot for this feature?

For the warning? No, AP is not ncessaey.

For automatic braking to a stop as necessary to prevent an accident? Yes, AP must be engaged. Without AP engaged, Teslas will sound an alarm and may brake to slow the speed of the car before impact but the car will not stop to avoid the impact / accident.

As this point, Tesla automatic breaking during regular driving is not comparable to the automatic braking other cars that, during normal driving under 30-35mph, will sound an alarm and initiate breaking to bring the car to a stop before you impact another car (or a brick wall).

 

[Wennfred]

I don’t have AP either but you really have to start learning to think that when the alarm/chime goes off to be ready to hit the breaks, I could see me approaching that car at the intersection so i could slow down or move into the left lane to avoid him, but another time it went off for no reason.

Fred

 

[AlanSubie4Life]

I don't recall if the chime sounded, but I don't think the car could've done more than what I was doing. I am considering asking about the cost of bigger brakes.

The thing that might have helped you (assuming you have MXM4s) is better tires.

The PS4S stop in 84% of the distance (105 vs 125ft from 60mph) of the MXM4s. You’ll take a significant efficiency hit though. Guessing the cost of one collision offsets the savings. So range is really the only concern, not increased cost.

Big brakes will not help at all. I guess I could do an instrumented test with my PS4S on P3D and see whether it is any shorter than the 105ft (the 105ft was on a standard AWD, and I can test at the exact same location). But it won’t be.

 

[MajorGator-M.3]

I'll have to put so,e thought into the new tires. I drive >60 miles round trip each day for work and it costs me 70-80 battery miles. I really don't want to degrade that much more.

I previously owned a BMW 335i - a true sports car - and always felt comfortable with the brakes. It also leaned into curves like nothing else I've driven before or since. That's why I was wondering if the P3D brakes would be better. Or are they just prettier?

 

[AlanSubie4Life]

I'll have to put so,e thought into the new tires. I drive >60 miles round trip each day for work and it costs me 70-80 battery miles. I really don't want to degrade that much more.

I previously owned a BMW 335i - a true sports car - and always felt comfortable with the brakes. It also leaned into curves like nothing else I've driven before or since. That's why I was wondering if the P3D brakes would be better. Or are they just prettier?

They might well feel better and have good initial bite (due to pad/rotor combo). And they’re more durable for track use. But from a practical emergency stop standpoint it won’t matter. In that case, you’ll get plenty of bite from both, and you’ll have minimally different stopping distance. I really should go measure it sometime, as I said. But there really isn’t any doubt here about the tires being the most important factor by far.

 

[Knightshade]

I'll have to put so,e thought into the new tires. I drive >60 miles round trip each day for work and it costs me 70-80 battery miles. I really don't want to degrade that much more.

I previously owned a BMW 335i - a true sports car - and always felt comfortable with the brakes. It also leaned into curves like nothing else I've driven before or since. That's why I was wondering if the P3D brakes would be better. Or are they just prettier?

For street use/emergency stops? Just prettier.

Same is true of the BMW brakes.

The brakes don't stop the car- the tires do.

For an excellent technical explanation of why this is so, I highly recommend this article-

GRM Pulp Friction

The author teaches SAE master classes on, has published books on, and have performed for major brake and vehicle OEMs, brake system design and engineering for decades.

 

[Tron 3]

It is nice to know there is a second set of “eyes” watching out for us in such situations.

Amen. Thick traffic and between the rows I see this asshat pull what could only be described as a violent lane change two cars ahead of me with very little clearance, and the car reacted with a loud alarm and a momentary deceleration. No danger to me, but the fact that the car saw it, recognized it as a potential hazard, alerted me - and took action was impressive.

 

[MajorGator-M.3]

"The brakes don't stop the car- the tires do.

For an excellent technical explanation of why this is so, I highly recommend this article-

GRM Pulp Friction

The author teaches SAE master classes on, has published books on, and have performed for major brake and vehicle OEMs, brake system design and engineering for decades."

Wow. Just read the whole article. Good read. Didn't try to digest all the physics, mathematical computations or material science, but he does make sense of the point, 'it's the tires, stupid.' Thanks for the link.

 

[Vines]

"The brakes don't stop the car- the tires do.

Wow. Just read the whole article. Good read. Didn't try to digest all the physics, mathematical computations or material science, but he does make sense of the point, 'it's the tires, stupid.' Thanks for the link.

Yep, until the 5th or 10th full force stop the larger brakes will not help one bit. However stickier tires will. You don't have to go all the way to P4S, there are many nice tires with similar wear but none will outperform the P4S, wet or dry until the temps get below 40 degrees or so.

Below 40 degrees, the P4S is a liability. You probably wont get there in Florida, so are effectively 4 season tires. They are the best tires I have ever driven on, and even managed limited track use before chunking.