Brake and steering behavior

[ether100]

Just picked up an FFE on Sunday. Everything is great so far, but I have one question:

I notice that while braking below 25 mph, if the steering is being held slightly off-center (to follow a slight curve for example), I feel a force trying to bring the wheel back to center while the brake is being pressed. This is the same for turning right or left.

Anyone experience something similar?

Thanks.

 

[jmueller065]

Most likely torque steer during regen.

 

[ether100]

Thanks, so I assume you feel it too?

 

[jmueller065]

Occasionally, I also notice some torque steer during acceleration as well.

More disconcerting is when you hit bumps during regen braking and one of the front wheels pops off the ground for a few seconds. Feels like sliding around on ice for a sec...

 

[studio460]

I've had the car for four weeks and noticed that the FFE has a significant amount of torque-steer upon rapid acceleration (it's also more noticeable since I usually drive rear-wheel drive vehicles).

 

[ether100]

It would be good to understand how regen from braking induces torque steer. I searched the web but couldn't find any explanation.

I wonder if driving in 'L' exhibits the same behavior.

 

[WattsUp]

It would be good to understand how regen from braking induces torque steer.

The following article seemed to have a good explanation of how torque steer occurs in front-wheel drive (FWD) cars under acceleration. I assume the same principles simply apply in reverse when braking.

http://www.aa1car.com/library/torque_steer.htm

I wonder if driving in 'L' exhibits the same behavior.

It should. In fact, the effect should be greater since L engages an increased level of engine braking.

 

[davideos]

I wouldn't think that regen would cause torque steer because it really isn't "hard" DEceleration. I'll give it a try tomorrow and see if it drifts when in pure regen.

 

[WattsUp]

I wouldn't think that regen would cause torque steer because it really isn't "hard" DEceleration. I'll give it a try tomorrow and see if it drifts when in pure regen.

No, but "harder" braking would. The car can slow down just as quickly (if not faster) than it accelerates.

"Pure" regen (by which, I think you mean coasting in either D or L) may indeed not generate "hard" enough braking force to cause noticeable torque steer, but you can apply even greater regen braking force (without engaging the disc brakes) by pressing the brake pedal. Isn't that still "pure" regen? (i.e., when the brake score is close to 100%)

The application of regen isn't limited to coasting in D or L. You can also modulate the level of regen (to an even greater degree than coasting in L) by applying the brake pedal.

 

[ether100]

Since there hasn't been confirmation that this is common to all FFEs, I wonder if what I'm observing is unique to my car. Is it possible that the electric power steering is somehow being affected when strong regen is initiated?

 

[Rogerschro]

Since there hasn't been confirmation that this is common to all FFEs, I wonder if what I'm observing is unique to my car. Is it possible that the electric power steering is somehow being affected when strong regen is initiated?

I owned a 2012 Focus SEL before I got my FFE. What you describe could be felt with the SEL as well. It really isn't too noticeable at any speed other than as you said 25- and even then I quickly forgot about it. (I came from a 4x4 Ranger so I just assumed it was due to a FWD car and the electric assist steering.) The assist feature will cause the steering to get easier or harder depending on the force applied to the steering so just off center in the situation you described it may transition from tight to loose feeling causing you to feel it 'pull' The first time I accelerated through a corner with the FFE I thought it was going to straighten up for a second as the torque messed with the electric steer and 'pulled' the car straight rather than having a nice even resistance to the turn. I hardly notice that any more either. But, if it is really noticeable and causes you effort to hold the turn you should have it looked at, it may need the program re-calibrated to not over-steer. ( TC can also be acting up). Good luck!

 

[WattsUp]

( TC can also be acting up)

Note that (perhaps just as a test for this steering pull problem) you can disable Traction Control via the left-hand dash display. I believe it is under the "Settings" menu.

Btw, disabling TC only lasts until you turn the car off. It always defaults to enabled again when you next turn the car on.

 

[ether100]

Thanks, I disabled TC and it didn't make any difference.

This article sheds some light on the electric power steering technology used in Ford vehicles, and which may be what I am observing:

http://wardsauto.com/news-amp-analysis/ford-s-electric-steering-enables-pull-drift-technology

I wonder how much this "Pull-Drift" can be configured.

 

[ether100]

Thanks Rogerschro. You say "...in the situation you described it may transition from tight to loose feeling causing you to feel it 'pull'...". But, if the steering wheel gets looser as the speed decreases, it should be easier to hold it off-center. Is this incorrect?

I also notice that the 'pull' stops at around 5mph, probably when friction braking fully takes over from regen braking(?).

In summary: During regen braking, the steering wheel (only if being held a couple of degrees off-center) pulls towards the center from 25mph down to 5mph, but then returns to the originally held position below 5mph.

I'm surprised that this characteristic of the FFE hasn't been previously discussed on this forum.

 

[Rogerschro]

Thanks Rogerschro. You say "...in the situation you described it may transition from tight to loose feeling causing you to feel it 'pull'...". But, if the steering wheel gets looser as the speed decreases, it should be easier to hold it off-center. Is this incorrect?

I'm not sure I have an answer for that question. It seems to me that there is a very slight lag in the electric programing that is more noticeable around the 20ish speed that isn't noticeable above or below that. This is just my guess. So I feel it sometimes as the program corrects for resistance. But again, it is just a guess.