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Hold Mode in a Rear Accident

DerbyDave

Member
Jul 2, 2020
618
317
Kentucky
My Audi and Mercedes Hold Mode had collision sensors to tighten the seatbelt, adjust the headrests, and apply the brake forcefully in anticipation of a rear end collision so the car would not be pushed into the cars in front after the impact, and to further protect the passengers. It seems Hold Mode on the Tesla just tries to use regen forces to hold the car in place with no real guarantees, and the manual says it may not even work well on steep inclines. I am wondering why the car doesn't figure out when to apply brakes to maintain the held position until the driver decides to release it, or perhaps in the event of a pending rear collision. Am I correct in assuming not to rely on Hold except as a convenience and to apply the brakes (and pray) if I see a car approaching too quickly from the rear -- that the car will lurch forward in Hold mode and the brakes will not be automatically applied?
 

2101Guy

Active Member
Jan 6, 2020
1,451
1,259
USA
i think you are confusing accident/collision safety features with a feature that simply is designed to keep the car from rolling/creeping forward at a stoplight....
 

pabla

Member
Oct 17, 2016
220
120
Vancouver
My Audi and Mercedes Hold Mode had collision sensors to tighten the seatbelt, adjust the headrests, and apply the brake forcefully in anticipation of a rear end collision so the car would not be pushed into the cars in front after the impact, and to further protect the passengers. It seems Hold Mode on the Tesla just tries to use regen forces to hold the car in place with no real guarantees, and the manual says it may not even work well on steep inclines. I am wondering why the car doesn't figure out when to apply brakes to maintain the held position until the driver decides to release it, or perhaps in the event of a pending rear collision. Am I correct in assuming not to rely on Hold except as a convenience and to apply the brakes (and pray) if I see a car approaching too quickly from the rear -- that the car will lurch forward in Hold mode and the brakes will not be automatically applied?
I’ve always thought of this too, since I have an Audi and it has the rear impact safety feature too. However the Tesla brake hold uses the friction brakes to hold, not regen. I assume if you are read ended hard enough the car would lurch forward a bit, but I think the car would still try to hold the brakes.
 

DerbyDave

Member
Jul 2, 2020
618
317
Kentucky
i think you are confusing accident/collision safety features with a feature that simply is designed to keep the car from rolling/creeping forward at a stoplight....
I wonder why it isn't the same, and why a true hold feature is not implemented. Forgetting even the safety aspects, if Hold is engaged, and the hill is too steep for the car to hold without brakes, why wouldn't Tesla apply the brakes automtically to hold the position, rather than let the car roll into another car or pedestrian?
 

DerbyDave

Member
Jul 2, 2020
618
317
Kentucky
I’ve always thought of this too, since I have an Audi and it has the rear impact safety feature too. However the Tesla brake hold uses the friction brakes to hold, not regen. I assume if you are read ended hard enough the car would lurch forward a bit, but I think the car would still try to hold the brakes.
Why does the manual discuss the car might roll in a steep incline if Hold uses the brakes to hold the posiiton? Seems like the brakes would hold the car on any incline, or it isn't configured properly.
 
Oct 10, 2019
269
126
So-Cal
so I've done testing on the hold capability because my friends an i get bored sometimes.

When the hold is on but on a flat surface and you barely hit the brake (and release) to engage it the car will move forward relatively easily if pushed, like 4 people pushing the car.
However on a flat surface but pushing the brake heavily (and release) to engage hold the car will not move by being pushed and if pulled it is extremely difficult and wont move without being drug. The second test was to simulate a hill in our opinion.
 
  • Informative
Reactions: pabla and DerbyDave

MIBryan

New Member
Mar 5, 2021
2
0
Saginaw, MI
Why does the manual discuss the car might roll in a steep incline if Hold uses the brakes to hold the posiiton? Seems like the brakes would hold the car on any incline, or it isn't configured properly.
It is called CYA! By saying this, Tesla can claim they warned you if for some reason the car actually rolled.
 

klufkee

Member
Aug 22, 2019
22
2
Pennsylvania
Sounds like it’s just using a line-locker type setup that drag cars have used. Whatever pressure you set is what is held as it’s just not letting the pressure drop. This may only apply to pre-Raven though. Agree on the cya move with the manual wording.
 

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