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Hello AI, I have a 2011 Scion tC with a 2.5 L, four cylinder engine and ~65k miles on it, it is stock besides some window tinting. Over the past year or so the car has developed a very strange, uh, wiggle? Shake? Shimmy? Something that is disconcerting. My best attempt to describe it is this: above a certain speed the rear of the car feels like it moves as though I just jerked the steering wheel to correct something. The critical speed depends on the road surface, on some roads I can do 75 mph with no problem, on others it'll begin to move oddly at 35. It's even lane dependent, some roads are fine at 45 in the left lane, but not the right. It's worse/more pronounced when the road is wet, and when I'm going around a left turn, and I think even when it's cold but that part is new. There's no steering wheel feedback at all when this happens. I've driven behind the car and it really does look like the driver has spaced out a bit and then jerked the wheel a bit to catch up to whatever turn they were supposed to be making, the back end moves rather noticeably. Initially it was just a weird movement when taking left turns at speed, like a flyover interchange, in the rain. Now it's pretty frequent. Stuff that probably isn't within "normal" car use: I drive over a lot of speed bumps. Like 10+ a day. I work on a military base and the gate lanes have at least five rather aggressive bumps in both directions. It can get to 20 times a day if I leave for lunch or a meeting or whatever. I probably need to replace the shocks, but I also don't think just the shocks could be responsible for this issue? My wife is hard on vehicles. Particularly the rear passenger tire, which she runs into curbs with some frequency. Many years ago someone in a parking lot backed into the passenger side of the car, but everything was repaired. Beyond that it's just a daily driver vehicle. I appreciate any insight into what might be causing the problem, and how I get it fixed.
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Nov 6, 2021 07:05
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| # ? Apr 29, 2024 01:47 |
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Go out to the car and look at the tires. Are they worn? I have a feeling you may not be a car expert and that is fine. When was the last time you got new tires? If I had to bet one of the tires on the rear is more worn than the other. You need to probably get a new set of tires AFTER going and getting an alignment. But…the tires there are going to cost a lot more than a new set from online. Take some pics of your tires and I’d be happy to let you know if you need some. I had a bad wobble at low speeds and vibration over 90 in an import and I was worried I’d need a control arm at least but it was just a worn tire and out of alignment. Parts are cheap and plentiful for your Scion. It is probably not a big deal.
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Nov 6, 2021 20:23
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You are correct that I am not a car expert. I am an engineer, I have a couple of degrees in nuclear engineering that included some mechanical adjacent education for power plant operations. In theory I should be able to understand most of what makes a car go, but having an education in the fundamentals doesn't translate to actual working knowledge of the system very well. I've worked on my vehicles before, but nothing more involved than replacing rotors/pads. This may have been around longer than a year? Time has been weird since the pandemic started. I know that I've had the car aligned, front and rear, and the tires on the rear replaced since the problem showed up. At one point in time there was a seriously uneven wear on the rear passenger tire but it's been "addressed" before. The current wear seems slightly asymmetrical? I can't actually tell. Rear tires:   I don't know if the car came with a sway bar, but I considered installing one to address the symptoms but that won't solve the actual issue and I'd rather do that.
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Nov 6, 2021 21:18
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Your tires look fine, certainly not what is causing your problem. Next step would be an alignment shop. Nothing on those tires shows me a cause. Before you add anything I’d get an alignment and go from there
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Nov 6, 2021 22:07
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Are your lug nuts on tight? An alignment and an inspection of the rear suspension should pinpoint the issue.
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Nov 6, 2021 22:48
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Might also ask the shop to check the wheel balance. May have lost a weight on them. Sounds like something is loose in the rear suspension or wheel nuts though. Might have several things going on back there.
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Nov 26, 2021 18:36
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Olothreutes posted:Many years ago someone in a parking lot backed into the passenger side of the car, but everything was repaired. Alignment and wheel balance are the first steps, as others have said. The speed bump comments made me think of possible bushing issues, and then I got to the passenger side accident comment. There's a chance there were bushings damaged back then that took a while to fully degrade. The alignment shop should be able to check for that, too.
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Nov 27, 2021 00:02
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EVERYWHERE 
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Thank you for all your help, I was able to begin this whole investigatory process much better informed than I otherwise would have been. Bushings and joints are all fine. Turns out that both the struts and shocks were totally gone and the oscillation was probably because the suspension wasn't able to damp any of the road issues. This was combined with a pretty rough front alignment, which seemed to be pushing everything around even though it felt very much like it was the rear of the car that was haunted. Replacing the suspension bits with the help of a coworker and getting new tires and an alignment has resulted in a 99.95% reduction in ghosts haunting the car, and the remaining 0.05% is probably just regular road induced movement that I'm hyper-vigilant to and would ignore in any other car. It's much nicer to drive now. I'm not certain what caused the front alignment to be so bad in the first place, but that's an issue for another day. E: Holy cow this was from a year ago wtf.
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Nov 27, 2022 23:29
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Olothreutes posted:Turns out that both the struts and shocks were totally gone and the oscillation was probably because the suspension wasn't able to damp any of the road issues. That could certainly cause it, congratulations! quote:E: Holy cow this was from a year ago wtf. It's okay, we're all friends here.
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Nov 28, 2022 00:20
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Olothreutes posted:the suspension wasn't able to damp any of the road issue I just wanted to thank you for your correct usage of "damp" in this situation, rather than "dampen". Also a year to the day+1. impressive.
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Nov 29, 2022 06:50
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A twist, the car is still haunted. But only a little. Normal driving has no issues, and several locations that used to be problematic are not. But the OG location for the ghosts to appear still causes problems. A flyover from one highway to another, a left turn that both ascends and descends in elevation. And I generally drive pretty aggressively anyway. Those signs about 40 mph are bullshit, you can easily do 60 and not even load up the suspension very much. My coworker thinks it might be pillow ball joint problems in the rear of the car.
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Feb 4, 2023 17:45
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Odds are if the front struts were shot the rear ones are too, might wanna start there. New struts in the front with blown shocks in the rear are gonna make for a weird handling car
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Feb 4, 2023 19:51
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Applebees Appetizer posted:Odds are if the front struts were shot the rear ones are too, might wanna start there. New struts in the front with blown shocks in the rear are gonna make for a weird handling car The rear ones were replaced at the same time as the front. We did the whole coilover in the front and the shock in the back, the old springs are still back there though. You are correct, they were all absolutely shot.
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Feb 5, 2023 02:02
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| # ? Apr 29, 2024 01:47 |
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Maybe check on some model specific forums for the same symptoms. On Volvo R forums the cars had a thing that got labeled "side hop" where if you had the shocks on a soft setting, and you hit a bump during a curve, the rear toe would change just enough to passively steer the car a little. This made it feel like the back of the car was hopping over to the side which required some steering input to correct. I experienced it on my own car when one shock got ruined so it wasn't damping properly, so when I hit a bump the one tire was leaving the ground so the other was able to steer it in an unexpected way. The solution for most people was to put in alternate alignment specs like less toe in or something. Might see if others have that problem.
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Feb 8, 2023 01:09
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