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Plaid Vibration around 38-42MPH....
- Thread starter cytranic
- Start date
n2mb_racing
Active Member
It's the half shaft, but it can be masked over by software changes.
jebinc
Well-Known Member
Half-shaft, half-@$$ed
lbowroom
Plaid, white on black, CF, 8/27/21, Track Pack
Not really. Even if it is the half shafts that vibrate, it’s not from a defect of the half shafts. If it were there would be no software fix. If the electronics excite a natural vibration frequency of the half shafts you can say it’s a design problem, but more an electric design one.
yerEVan
Active Member
Is the accelerator peddle accelerate by wire? If not what is it connected to? If yes then why would I feel a vibration in it but not the floor board of the car as well?
I get the yoke vibrating as it’s not steer by wire yet.
I get the yoke vibrating as it’s not steer by wire yet.
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n2mb_racing
Active Member
The software fix is to turn off the front motor. It doesn't vibrate when it's just being pulled along by the rear motor.
So I have an appointment on Nov 17th to fix this vibration/knocking issue from the driver's left front through a software update. I wrote on the service ticket as much details as I could, and that's what they said.
Mine happens with my stock wheels and summers, and it's like a knocking sound when going over slight bumps at slow speeds, at first I thought it was a suspension issue, but I checked everything that I could, swaybars/endlinks and everything seemed tight. So I figured it's something to do with the left front driveshaft.
When swapping to my winter tires+spacers, I still hear the knocking. Seems to subside when the car and weather outside is cold, but more prominent when it's hotter or when the car is warmer. Also, I drive in low mode all the time, and driving it in medium/normal it worsens for some reason.
I'll update when I get the service done if that has anything to do with it.
Mine happens with my stock wheels and summers, and it's like a knocking sound when going over slight bumps at slow speeds, at first I thought it was a suspension issue, but I checked everything that I could, swaybars/endlinks and everything seemed tight. So I figured it's something to do with the left front driveshaft.
When swapping to my winter tires+spacers, I still hear the knocking. Seems to subside when the car and weather outside is cold, but more prominent when it's hotter or when the car is warmer. Also, I drive in low mode all the time, and driving it in medium/normal it worsens for some reason.
I'll update when I get the service done if that has anything to do with it.
That sounds like a separate issue from the vibrations. I have a service appt coming up to address hepa filter and some creaking noise I’m having in the interior when backing out of my driveway which is at a slight angle. It’s like the body is flexing. It’s quite unacceptable in my opinion. I’ve read that some undercarriage bolts aren’t correctly torqued from Fremont. The model S is the flimsiest feeling car I’ve ever owned or been around. Yet, when I pull the wheels off, the mechanical parts look quite robust. I’m guessing that’s where most of their money went when developing the model S back in the day. Id be curious to know if the new model 3 is more solid.
lbowroom
Plaid, white on black, CF, 8/27/21, Track Pack
Forgive my ignorance but even if they turn the motor off completely, the half shafts are still spinning and would vibrate if they were bent
n2mb_racing
Active Member
They aren't bent. They are perfectly fine. Just loose tolerances in the cv joint and excessive bend angle in the joint
lbowroom
Plaid, white on black, CF, 8/27/21, Track Pack
I agree. They aren’t bent. The light vibration under light load is induced by an electrical control issue in the front motor.
n2mb_racing
Active Member
I'm not sure about that either, because replacing the half shafts causes the vibration to go away temporarily. Maybe the stiffness in new CV joints is enough to dampen the vibration down? That would be the only way I could think the motor controller could cause the vibration. I guess we can hope it's something that easy to fix...
WilliamG
Hinge Fanatic
I doubt the official software fix shuts off the front motor. It will, I would guess, adjust how the motor delivers power, though, very slightly, through the trouble speeds. That would explain the tiny difference in range with the fix applied.
n2mb_racing
Active Member
Agreed. Probably reduces front motor torque in the 40-50 mph range to hide the problem
aerodyne
2 of 3 EV's - Defect Free!
So, all objects and especially structures and mechanical devices have a resonance or natural frequency.
If there is an external force that has a period impulse close to the natural frequency of the object in question, you will get a strong vibration that is only mitigated with damping. In some cases the forcing frequency and natural frequency can couple, overwhelming mechanical damping and cause damage or URD, Unplanned Rapid Disassembly, such as aircraft flutter.
Anyone with a CAD solid model of the driveshafts would be able to do FEM and determine the natural frequencies of the first and second orders, and see if it is the same as the shaft or motor RPM.
Tesla must have this information. If a second party were to prove this is the case, they might be forced to make a real fix, such as torsional dampers often seen on crankshaft pulleys on ICE vehicles.
If there is an external force that has a period impulse close to the natural frequency of the object in question, you will get a strong vibration that is only mitigated with damping. In some cases the forcing frequency and natural frequency can couple, overwhelming mechanical damping and cause damage or URD, Unplanned Rapid Disassembly, such as aircraft flutter.
Anyone with a CAD solid model of the driveshafts would be able to do FEM and determine the natural frequencies of the first and second orders, and see if it is the same as the shaft or motor RPM.
Tesla must have this information. If a second party were to prove this is the case, they might be forced to make a real fix, such as torsional dampers often seen on crankshaft pulleys on ICE vehicles.
Could explain why the software fix is only for the plaid despite the LR also having the problem — not enough “excess” power available on the dual motor cars to reduce front power and maintain the same performance.
