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Picked up my ‘11 IS350C a couple months ago. Loving the ride and the quiet. PO barely drove it..24k in 8 yrs. I’ve searched the posts and didn’t see what I’m experiencing. Various speeds I get a reoccurring vibration...sort of cyclical. I’ve had the alignment done, new front tires, and balanced twice. It’s still there. Mostly only noticeable with the top down. Any suggestions or is this just cowl shake? My previous convertibles were an ‘84 Alfa Spider and an ‘03 MR2 Spyder and neither had this sort of vibration.
Do you have the light grey or dark grey leather? I’ve only seen one other Tungsten Pearl with light grey leather but really don’t remember if the hoops were matched or not. Maybe it was an option? Or maybe a change in 2012?
Do you drive it daily or go long intervals without driving it?
we bought our 11’ with 68k miles in November and as soon as I got it I put some winter tires on it since we live in Seattle (not going to use it in the snow or plan too, however, often mornings when its clear, there can be ice on the hills and while not a daily driver just taking precautions). I noticed that after the car sat for more than one day that leaving the house there was (from what I consider) an excess amount of vibration shaking the whole car (especially with the top down). So I started my investigation:
checked the motor mounts (non-issue).
Air pressure (non-issue)
tire balance (new tires, had them re balanced - not the issue)
here is what I found: it turns out our street close to home actually has a lot of almost invisible grooves from studded tires. When the tires are cold it almost felt like the whole the whole car was shaking through the rumbles. I finally realized it because my wife’s GX was doing the same (my 00’land cruiser is so heavy that it was felt nothing). So this didn’t prove my theory just yet, but when spring came around I put some summer tires on and it hasn’t done it since (or much more reduced). Winter tires are a little bit heavier. I feel like the issues could be similar based on the description and it may be that since the tires may be original because of the low mileage and since the car sat for so long that they could be out of round (in the rear) - this doesn’t get detected by a regular balance (may want to look at “road force balance”).
Also, to describe my vibration - it felt like the rear and windshield shook enough to make the rear view mirror not be clear looking backwards.
Thanks for your reply. I’ve been thinking along those same lines. The front tires are new but the backs are possibly original. And it does sit all week in the garage and only used on the weekends. Can you get flat spots that don’t go away just from sitting a week? The vibration I get comes and goes like sort of a cycle. On. Off. On. Off. And it’s much more pronounced with the top down. It noticeably shakes the steering wheel and dash plus I keep my phone on a vent holder and really see it with the reflection bouncing everywhere. I’m glad you’ve experienced something similar and were able to solve it with new tires. Maybe I will push that right pedal a bit harder around corners and green lights and force myself to by a new set for the rear!
I’m not necessarily saying the the tires are for sure the issue, but it can be a combination of things. In my case, it was the road, with tires that where not up to temperature. It could also be the shocks not up to temperature. That may depend on where in the country owners are. If you are in the south, I don’t expect anything like this to be an issue, however, if you are in any area where people use chains or studs and roads are exposed to adverse conditions - all factors can contribute.
The main thing for me was that it wasn’t anything structural like the motor mounts, drive shaft or engine vibrations. I even considered the carbon build up as a possibility but the engine runs pretty smooth.
I did make a video checking the motor mounts as it was the only way I could see if the engine had any movement while I was trying to force the movement (press brake, step on gas while on drive and reverse). It barely moved. Happy to share but it is 1:30 long.
Update: just before winter I had all four tires replaced, aligned, and balanced. Even road force balanced as the shake continued. Put the car away for the winter. Then spring hit with bad weather and then Covid. Just finally took it for a 500 mile round trip. Still have the same issues: Top up, it’s smooth as silk. Top down, it’s like driving on a rough road even when I know it’s smooth...but not all the time and not just at certain speeds. The dealer has gone thru this car several times and says everything is tight and correct. I know these cars have lots of chassis bracing and aero panels...I’ve honestly been doing along smoothly and changed wind directions and felt the shake....could an aero panel be bad..(or missing) cause this? It goes back in tomorrow for an oil change and run thru again. I’d love to have something More specific for them to check.
06-05-19, 05:35 PM
New ISC owner with a vibration question
