Steering and brakes: real mechanical connections?

Steering and brakes: real mechanical connections?

I've wondered this off and on. In the Model 3, is there a real mechanical connection between the steering wheel and the front wheels? Or does the steering wheel just tell the computer what you want, and it in turn tells some little steering motors to do their thing? Same sort of question with the brakes.

I'm thinking of what I hope are fringe safety situations, where, for example, the computer suddenly wonks out while driving, or I'm an idiot and run the battery to zero. Can I safely steer the car off the road and bring it to a stop?

JAD | 21 mai 2018

The 3 is just like most new cars made with regard to steering and brakes. Nothing a 3 series BMW does have with electric steering and ABS.

CharleyBC | 21 mai 2018

Sorry, JAD, I know nothing about BMWs, or indeed most new cars. My current car is a 19-year-old Honda. If it looses power, I can still steer and brake, though with more difficulty since power assist is gone. So I remain unclear what the story is with the Model 3.

djharrington | 21 mai 2018

@Charley, yes, the M3 has a conventional mechanically linked steering column and hydraulically connected brakes. The steering rack is boosted with an electric servo, as are many cars moving away from hydraulic power steering.

JAD | 21 mai 2018

Yes, and the car doesn't just run to zero battery and quit like a gas car does. You start getting warnings, then the car starts limiting power, then speed is reduced and then finally it says it will power down. It is not a sudden on/off and the battery isn't really dead, it just hits a safety buffer so it can shut things off safely and recharge when ready without causing damage.

CharleyBC | 21 mai 2018

Thank you both. I haven't run out of gas since I was young and foolish, so I doubt I'll run the battery down either. A system failure is more of a wildcard. But in either case, it's nice to know I won't suddenly be riding in a projectile!

3ngineer | 5 mai 2019

@djharrington, how does a small twist of the wheel when on autopilot not change the car's course? You can introduce a small twist. Then it will match your torque, and overcome it to bring back to original line. Then if you let go, it swings the other direction and then corrects itself back to centerline. Throughout all of this, there is no actual rotation of the steering, or at least, none I can feel. Is it just too small of a change?

Ron.Olsberg | 5 mai 2019


If I understand you post, you can slightly change the steering direction without disabling the Autosteer function? I had an instance when Autosteer was enabled where I needed to straddle two pieces of truck retread pieces on the highway. I waited to see if the car would autosteer to avoid hitting the tire debris, it did not (I have read since that this is normal). I will apply a slight torque next time and see if I can miss the debris without disengaging Autostteer.

Regards, Ron

elecfan2 | 5 mai 2019

I heard from a Tesla expert, from some website called seeking apples or seeking betas not sure, they said that the Tesla Model 3 is like a PlayStation 3, when the center console screen goes black you lose complete control of the car, it will randomly steer into oncoming traffic or drive off a cliff. This is why we named our Tesla Model 3 Performance "Toonces", after the cat that could drive a car from the Saturday Night Live skit because Toonced would frequently drive the car off a cliff. And yes, if you couldn't tell I was joking, you can completely control the car even if the center console computer crashes or the autopilot computer crashes, Tesla is all about safety and you can control the car.

Atoms | 5 mai 2019

Last comment by ewd7 is complete bullshit. Nothing is technically correct. The braking system is by Bosh
These systems have high reliability and direct connection from steering wheel to the wheels. There are redundant electrical connections for fully automated driving and fully redundant computers and power supplies. The breaking and steering systems have a separate 12v battery from the main battery. Tesla designed the system using parts already proven in the industry for reliability. Tesla doesn’t have expertise on these systems so they outsource to companies who supply to other large car manufacturers.

Frank99 | 5 mai 2019

"And yes, if you couldn't tell I was joking,..."

Bighorn | 6 mai 2019

There was also a thing around the time of Toonces called RIF—reading is fundamental. How far we’ve fallen.

derotam | 6 mai 2019

@Ron.Olsberg, no you did not understand his post, or his post needed a little more information...

I have been able to get the car to wobble while on autosteer. Thre is a little bit of give in the steering inbetween where the autosteer motor is holding the wheel. If you oscillate back and forth in that very small zone, you can make the car wobble just a bit. You can not shift the car very much at all and you can't do a shift to one side for more than a second or less probably.

Magic 8 Ball | 6 mai 2019


Toonces going over cliff had nothing to do with bad steering or mechanical connections.
Toonces was a shitty driver.

RedPillSucks | 6 mai 2019

Dudes, please read ewd7 post all the way.
Tongue firmly planted in cheek
(What the hell does that saying actually mean anyway?!)

3ngineer | 7 décembre 2019

@derotam, you're completely right, thanks for clarifying and sharing a demonstration. I couldn't perceive the steering change unless oscillating at it's natural frequency.