Steering on the throttle - pulling right on acceleration and left on deceleration

[Jonathan Mason]

Hi, I'm a new Model S Long Range Dual Motor (2020) owner.
I've noticed that my car pulls fairly gently to the right on hard acceleration and to the left on hard regenerative braking.

I don't think this is quite the same issue as discussed on another thread where another car lurched from left to right, as a result of some non-tight toe arm bolts.
( 2014 Model S lurches left when accelerating, right when regen braking. Steering wheel 10-15 degrees off center to the right. ).

This behaviour on my car generally only happens on the open straight roads, where I can hoof it. Certainly on the UK motorways, and I don't think road camber is a factor.
I'm not saying it doesn't happen on bends but I haven't noticed this - whereas on the open road it is a very noticeable and re-creatable behaviour.
It's not huge and it's never caused me to do so much as change lanes, but then again as soon as it happens I of course act on the steering wheel to correct it.

Ordinarily the car drives in a straight line, save for going over a white line or something where a bit of natural tracking occurs. It is only upon hard accel or hard regen that the movement occurs.

I've not been to have the alignment checked yet, as I expected this to be correct from when I purchased the car (form a reputable Tesla specialist), and the problem occurred from day 1.
I did put a service request in on the app - for several other things too - but the SC said alignment issues were not covered under warranty so they didn't look at this.

To me, it feels like this isn't a wheel alignment issue - as the pulling goes both ways under accel/regen, and the car is capable of driving true and straight normally.
It feels more like an issue with one of the motors working harder than the other one.

To compare, I also drive a Model 3 Long Range Dual Motor (2019) and this sort of behaviour is not at all present. Same roads, same driving style etc, but the Model 3 is 100% true and straight under all conditions.

Has anyone any opinions as to:
1, whether this behaviour is normal, and within tolerance
2, what the problem might be
3, should this be covered under warranty
4, how this might be fixed

Many thanks.
J.

 

[dsm363]

Welcome. I’m sure someone here will have a good answer for you. I don’t think I’ve heard of this issue before.

 

[terranx]

I've had this happen on other cars where one of the rear tires had a broken cord

 

[Usher]

It could be a bad bushing or ball joint, or even a bad wheel bearing or loose axle nut. I've had all of these things cause those symptoms on my rally car. If you really only notice it during very hard acceleration / braking, I'd suspect a suspension bushing first. You'll probably have to jack up the car and see what you can wiggle by hand, although if you pay attention while driving you can probably narrow it down to one corner of the car first.

 

[philip295]

If there is nothing loose , the thrust angle is probably out

 

[Aggmeister2010]

I had (have) this issue on my 2016 Model S. Truthfully, I was never able to fully remedy it. I swapped tires side to side, replaced all the suspension components....nothing ever 100% fixed it.

I did do an alignment and specified that the 'steer ahead' angle and cross-camber / cross-caster be 0, and that helped a good amount. So, perhaps try that as a cheap next step.

TBH, I think the S has a bit of torque steer. The half shafts are not the same length, and any FWD driver knows that differing half shaft lengths means youll pull to the shorter side on acceleration.

 

[terranx]

TBH, I think the S has a bit of torque steer. The half shafts are not the same length, and any FWD driver knows that differing half shaft lengths means youll pull to the shorter side on acceleration.

Unequal length halfshafts is pretty common, including with the car in your avatar

 

[Aggmeister2010]

Unequal length halfshafts is pretty common, including with the car in your avatar

Right, but with FWD cars it's worse because the transmission sits off to the side by design. And you feel it more, because the driven wheels are also steering.

 

[sorka]

Not sure what you mean by one of the motors working harder than the other. That's of course going to be the case since the rear motor puts down more power than the front motor. Are you thinking your car is tri-motor like the Plaid?

I had the same problem on my MXP. It was never fixed and the primary reason I sued for Tesla to buy it back.

It did it from day one. Alignment was checked and ride height calibration performed 3 times. No difference. I personally checked the torque on every single suspension component nuts and bolts.

I discovered I could make the problem vanish if I changed the suspension height during a sweeping right hand turn such that the suspension adjustment completed while in the turn. When straightening out, the problem would be gone for a minute or so until the suspension height re-adjusted to compensate for it being slightly unlevel when performing the previous adjustment during the turn.

This led me to believe that it was a thrust angle issue caused by some asymmetry in ride height calibration.

Tesla looked multiple times but could never figure it out. They finally started telling me it was normal and they'd produce documentation to that effect. They never did. Given the other issues plus the 105 days in service and another 60 some odd says of not being able to use the right Falcon Wing Door, I contacted a lemon law attorney.

One other clue. The right side of the rear cradle was about 5 mm higher than the left when compared to the battery itself. Since the ride height calibration measurement points are on the bottom of the battery, my suspicion is that this introduced an asymmetrical error effecting the thrust angle. Had I kept the car, I would have obtained lowering links and adjusted them asymmetrically in the opposite direction to produce an inverse of this 5mm adjustment. Never got that far as I surrendered the MXP last August.

My original suspicion before I figured out how to temporarily alleviate the symptom with ride height change while turning right was that the right rear motor was putting down more power than the left.

I also had a second set of wheels with winter tires and the symptoms were identical with those so it wasn't tire related.

Alignment IS covered under warranty if it's not correct when it leaves the factory. That's the law regardless of what the SC told you.

 

[sorka]

It could be a bad bushing or ball joint, or even a bad wheel bearing or loose axle nut. I've had all of these things cause those symptoms on my rally car.

From day one when it was brand new?

 

[sorka]

BTW, I searched and couldn't find a single report of this every happening to any other Tesla so I assumed it was super rare. Your report has me nervous about my MSP order. I'm wondering if it is super common and most just don't notice it.

 

[sorka]

Here's a video showing my issue:

 

[terranx]

BTW, I searched and couldn't find a single report of this every happening to any other Tesla so I assumed it was super rare. Your report has me nervous about my MSP order. I'm wondering if it is super common and most just don't notice it.

I have nothing of the such in my Plaid going full throttle to 160mph.

Your video and your description sure makes it seem like some suspension piece was shifting under acceleration - whether due to a failed bushing or something being physically loose. My suspicion would be that the toe was changing under load. Not uncommon with cars that have trailing arm suspension, though that's not what the S/X have.

 

[sorka]

I have nothing of the such in my Plaid going full throttle to 160mph.

Your video and your description sure makes it seem like some suspension piece was shifting under acceleration - whether due to a failed bushing or something being physically loose. My suspicion would be that the toe was changing under load. Not uncommon with cars that have trailing arm suspension, though that's not what the S/X have.

I personally inspected every single bushing and torqued to spec every single bolt. This was an issue from the very first drive leaving the factory. In fact, I pulled over minutes after leaving Fremont and filed a service ticket so that it would be documented as an issue with just a few miles on the odometer.

One thing I did NOT do is loosen the the bushings that require being torqued at ride height. If a bushing on one side was torqued or slipped because it wasn't properly torqued and then retorqued, I wouldn't have found it. That said, every single witness mark on the bushings, which they put there after installation to make sure the bushings did not slip on rotation in the future all still matched up, so unlikely unless the witness mark was placed on a bushing that slipped before marking it.

 

[CKwik240]

I would check for a binding left caliper. If the left side brake is dragging enough, it would increase torque to the right side of the axle with the dragging brake when accelerating and during Regen. If it's binding enough to cause this though, I'm thinking it would pull left when you let off the accelerator with Regen off.

Just throwing out an idea.

 

[sorka]

I would check for a binding left caliper. If the left side brake is dragging enough, it would increase torque to the right side of the axle with the dragging brake when accelerating and during Regen. If it's binding enough to cause this though, I'm thinking it would pull left when you let off the accelerator with Regen off.

Just throwing out an idea.

I would think the thrust angle wouldn't change since the binding caliper would be dragging all the time whether your accelerating or regen braking.

 

[CKwik240]

I would think the thrust angle wouldn't change since the binding caliper would be dragging all the time whether your accelerating or regen braking.

Again. I'm just throwing out an idea. Thrust angle doesn't really explain the different directions of pull. Torque multiplication through the diff does if the left side binds.

 

[sorka]

@Jonathan Mason , did this get sorted out for you?

Similar issue with my new MSP. Not exactly like it was with the MXP but similar to that. Pulls to the right when lightly accelerating. If I put it into track mode and switch it to front wheel drive only, the issue is magnified.

 

[Jonathan Mason]

Hi all. Thanks for your replies and insights. This is not sorted for me yet - I'm waiting on my mechanic jacking up and taking a good look at the bushings and stuff mentioned above.
My error with thinking it could be one motor working harder than the other, of course it is a dual motor not tri motor, so equal drive to L/R for each motor front and back, but the half shaft size and the possible suspension height differential might be possible. If so, I'd consider it a defect to the individual vehicle - as this simply shouldn't happen.
Will update with mechanic findings in due course. J.

 

[sorka]

Hi all. Thanks for your replies and insights. This is not sorted for me yet - I'm waiting on my mechanic jacking up and taking a good look at the bushings and stuff mentioned above.
My error with thinking it could be one motor working harder than the other, of course it is a dual motor not tri motor, so equal drive to L/R for each motor front and back, but the half shaft size and the possible suspension height differential might be possible. If so, I'd consider it a defect to the individual vehicle - as this simply shouldn't happen.
Will update with mechanic findings in due course. J.

Did you get an alignment?