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.

 

[terranx]

@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.

So I took a drive out and paid attention just to add a data point.

Driving in plaid mode (not track mode) or in track mode set to full rear bias, WOT hands off steering wheel - no pull whatsoever.

Setting it to full front, there is certainly some torque steer, but it’s manageable and the direction it tries to pull varies. Feels like a high powered FWD car would.

 

[sorka]

So I took a drive out and paid attention just to add a data point.

Driving in plaid mode (not track mode) or in track mode set to full rear bias, WOT hands off steering wheel - no pull whatsoever.

Setting it to full front, there is certainly some torque steer, but it’s manageable and the direction it tries to pull varies. Feels like a high powered FWD car would.

That sounds like typical torque steer...darting a little left or right and just for a split second.

In my case, application of a small amount of easing into it acceleration results in it pulling right every time. On roads with crowns, I tried driving in the wrong lane (long straight away with no traffic) with the same results.

My total front camber is -1.6 degrees (so averaged -0.8 per side). I can only measure total since I can't absolutely verify I'm on a flat surface and don't have an alignment rack.

Spent some more time playing with it this morning and checking tire pressures. Going to weight the car first on my wheel wheel scales and make sure there isn't more weight on one of the diagonals vs the other. i.e. how close is Front Left + Rear Right == Front Right + Rear Left. If it's not close it could be ride height calibration.

 

[sorka]

Weights look good. So no gross cross ride height calibration issues. That said, the right rear is 0.25" higher than the sensor says while the front left is 0.25" lower than the sensor says so the entire car is titled slight forward and left but it shouldn't be enough to cause the issue I'm seeing.

11 lbs lighter than curb weight spec. The car is completely empty. I haven't even added my mobile charger yet.

Now out to take the front wheels off, inspect everything including checking nothing under torqued, and then swap front wheels when putting them back on.

 

[sorka]

Figured it out. It's now pulling to the left instead of the right. Update when I get back from Costco.

 

[sorka]

Problem shifted to the left when I swapped the two front tires. So now the question is which tire is it? The one that is on the side that the car turns towards? i.e. is the bad tire the left one since it now turns left on acceleration? I only had this happen once decades ago with Dunlop's on my 300ZXTT sometime in the mid 90s.

 

[sorka]

I checked the torque on everything except the frame side of the upper control arm as I'll need to get access to those bolts from the frunk. Not sure it's necessary now. The bolt that holds the upper control arm to the knuckle on the left side started turning at 28 ft-lbs while the one one right started turning at 31 ft-lbs. I did not tighten them all the way to the 44 ft-lb spec as I find it suspicious they were both undertorqued about the same amount. I'll add it to the service ticket for them to check.

 

[terranx]

I think it would depend on what's actually broken. If it's a bad cord, I suspect you'd be turning towards the good side while accelerating (diameter expanding under load, greater distance being traveled on the bad tire)

 

[sorka]

I think it would depend on what's actually broken. If it's a bad cord, I suspect you'd be turning towards the good side while accelerating (diameter expanding under load, greater distance being traveled on the bad tire)

Ooh. Good point. Sounds like it could be dangerous.

 

[sorka]

Almost forgot, tire pressure differences aren't the cause in this case

 

[sorka]

I can see the problem now. It's the tire that's currently on the right. It has "conicity". The right left side, the tire tread is flat from left to right. On the right tire, the inside tread, second from the very end, is pushing further out than the outside of the tread.

 

[terranx]

I can see the problem now. It's the tire that's currently on the right. It has "conicity". The right left side, the tire tread is flat from left to right. On the right tire, the inside tread, second from the very end, is pushing further out than the outside of the tread.

Odd. That certainly should be covered under some sort of warranty

 

[sorka]

Odd. That certainly should be covered under some sort of warranty

Well yea, since the car is brand new with less than 200 miles on it

The sucky thing is the ride height calibration is done first and then the alignment but the ride height calibration won't be correct with a tire that had conicity. So they're have to redo the alignment which includes ride height calibration.

 

[trimotor]

I can see the problem now. It's the tire that's currently on the right. It has "conicity". The right left side, the tire tread is flat from left to right. On the right tire, the inside tread, second from the very end, is pushing further out than the outside of the tread.

Very interesting, thanks for sharing. Glad you found it and should be easily fixed. Can you post a picture of this tire showing the defect?

 

[sorka]

Very interesting, thanks for sharing. Glad you found it and should be easily fixed. Can you post a picture of this tire showing the defect?

Didn't take a picture but I did measure the inner and out bands and only the one I mentioned previously was out but only slightly. Entire circumference was only 1/4" more than the outer band which was also 1/4" more than the inner and out bands of tread on the other tire. However, THIS is the tire that the car turns towards which is opposite of what I expected.

Also, the problem is far worse once the tires have warmed up. When starting off cold, there's very little pull. It takes about 10 minutes of driving for full effect.

 

[buckets0fun]

That said, the right rear is 0.25" higher than the sensor says while the front left is 0.25" lower than the sensor says so the entire car is titled slight forward and left but it shouldn't be enough to cause the issue I'm seeing.

I assume you’ve not had a vehicle with aftermarket air suspension before?

This is absolutely what happens. You can make this happen on a coilover suspension as well by setting the suspension incorrectly. It’s effectively spring rate problems, since air suspension gets its height from air pressure. You have 2 (spring rates) airstruts that aren’t matched per axle.

 

[sorka]

I assume you’ve not had a vehicle with aftermarket air suspension before?

This is absolutely what happens. You can make this happen on a coilover suspension as well by setting the suspension incorrectly. It’s effectively spring rate problems, since air suspension gets its height from air pressure. You have 2 (spring rates) airstruts that aren’t matched per axle.

I wasn't particularly concerned about it but it is consistent. No matter how many times the car moves and re-parks or changes level, the relative difference is always the same which means they were a little sloppy in the rack to battery heigh measurements when doing the ride height calibration as part of the alignment. I've seen this before with my previous S and re-running the ride height calibration routine has resolved this in the past.

 

[sorka]

Tesla replaced my front right tire today which fixed the pulling to the right issue for me. Now accelerates and decelerates straight.