Shimmy - 2013 Tesla Model S Long-Term Road Test
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2013 Tesla Model S: Shimmy

December 18, 2013

2013 Tesla Model S

During my road trip, I drove over some coarse pavement. At the time, I thought what I was feeling through the seat of my pants and the steering wheel rim was simply road texture.

But many, many miles later it occurred to me that it might not be the pavement that was causing what I was feeling. It was, in fact, the car.

Here's what it was doing. Every ten seconds or so while traveling at about 70 mph, I'd notice a vibration (if you can call it that) that would increase in amplitude and then fade away to nothing. About ten seconds later, it'd be back. This shimmy continued, never worsening or improving, irrespective of pavement. It was most noticeable on smooth tarmac, almost certainly because rougher pavement would mask it.

Mind you, this is a subtle shimmy. Very subtle. More like a faint zizz that comes and goes. My passenger didn't notice it until I pointed it out. Then, it couldn't be un-felt.

I'm not sure what's causing it. Could be something as simple as an out-of-balance tire, though the periodic nature of this shimmy is unlike any tire balance-related shake I've ever experienced.

Jason Kavanagh, Engineering Editor


Comments

  • jasond52 jasond52 Posts:

    I wonder if its related to the tire problems you've experienced?

  • csubowtie csubowtie Posts:

    I wonder if had something to do with the EV nature of the vehicle. Possibly an alternator cycling on/off, or some kind of battery cooling pump/fan that was cycling on/off. This car has electric assist steering right? Does that mean it electrically produces hydraulic pressure to run the steering? Maybe that pump would be cycling on/off?

  • dunning15 dunning15 Posts:

    Jason doesn't SOUND like a female name....hmmmmm....

  • duck87 duck87 Posts:

    Ten seconds would suggest that it's not an unbalanced rotating component, although it's possible that you're hitting almost the right natural frequency of some component to make it vibrate like that. My guess would be a component that cycles on and off as CSUbowtie suggests. Have you cycled the AC, heat, fans, etc? Let us know what you find out!

  • fordson1 fordson1 Posts:

    If he said he felt it through the seat only, I would agree, but he says it's felt through the wheel, too, so I would doubt it's an alternator or battery cooling pump. I would also doubt the EPS pump, since it sounds like it's happening on straight roads where you would not think there would be a demand for assist. Is it happening in response to suspension compression/rebound that might be causing some subtle changes in camber or toe? Or is this really something that is happening regularly like he says...like every 9.23 seconds or whatever?

  • actualsize actualsize Posts:

    Update: We have not posted it yet, but we had to replace a tire because it was later discovered that a pothole strike caused a pinch that induced a subtle sidewall bubble in the left-rear tire. This may have been the cause. We had to replace the tire and are monitoring the situation. So far it seems to be gone, but we're not ready to call it yet.

  • fordson1 fordson1 Posts:

    OK, so it's been around 5k miles since you replaced the rear tires when they ate themselves (can't really tell...JKav does not give odometer readings when he posts about cars), so does this mean you were OK with just replacing the one rear tire? I assume that with 21" wheels and short sidewalls, heavy wheel/tire [non-permissible content removed]'y, lots of unsprung weight, etc. you guys made sure the wheel was not bent - ? Good thing you guys are saving all this money using the Superchargers...

  • actualsize actualsize Posts:

    Yeah, they were pretty new at the time. Jay will have details the post after next. Just wanted to put that out there.

  • jim_in_nj_ jim_in_nj_ Posts:

    If the tire replacement eliminates the shimmy, then that's it. If the shimmy remains, it's possible that it's something normal like a battery-coolant pump cycling on and off. In order to save electricity items that would normally run constantly in a regular car will cycle on and off in an electric car. To use this example, but in many cars the coolant is constantly circulating because the mechanical coolant pump causes just a miniscule drag on the engine power. In an electric car, every watt-hour counts and these items are often put on a cycle unless a sensor indicates that it needs to run more often.

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