Rhythmic Vibration and Shimmy at highway speeds

Nissan 350z / Nissan 370z technical discussion forum: Maintenance, performance, installations, modifications, how-to's and troubleshooting.
JenzToy
Posts: 2
Joined: Wed Aug 02, 2017 9:59 am
Car: 2007 350Z convertible

Post

HELP! I've searched on here and not found anything addressing the problem I've been having now for the past year. When I drive at speeds between 72 and 75 there is a noticeable rhythmic vibration and shimmy that can be felt primarily in the seat but also in the steering wheel of my 350Z. It's only in that speed range. Drive faster it goes away, slow down it goes away. I've had new tires put on, I've had alignment and balancing done TWICE and still the vibration. When I say rhythmic it's because it's not a constant thing. It feels like the vibration starts at the front of the car and moves through the car, stops for about 2 seconds then starts all over again, constantly while I'm driving at those above reference speeds. It's driving me INSANE. I want a nice smooth ride in ALL speeds but cannot seem to get my mechanics to understand what I'm experiencing. Anyone out there have any suggestions???


amc49
Posts: 1183
Joined: Mon Jun 19, 2017 7:24 pm
Car: '11 Nissan Versa
'17 Nissan Altima

Post

If talking about a vibration that seems to increase to hit a high then drop back off over and over look at your mounts, may be engine instead. A harmonic that lines up just right in the unibody to show up at a very tight speed and spread. If you can drop a gear for just a few seconds and check same speed it might tell you something, tires still going same speed but engine not then. Would then point at engine.

Start seeing if any different throttle inputs can affect it too.

Often aftermarket mounts can make things like that worse, the aftermarket in no way makes the diverse numbers of rubber compounds they used to like the OEMs, commonly they are rock hard now and new mounts can be as bad or even worse than old original ones. What we got with things Chinese. Like the utterly crap alternators and starters we get now. The companies have a stranglehold on things like that now and crap is all you can get period.

Look at tire trueness by spinning them, out-of-round can do it too and no balancing on the planet can touch that. A slightly bent wheel could do it.

If anyone has used like Fix-a-Flat in the tires that can do it too, the extra fluid moves around to balance then unbalance the tires in a recurring harmonic and I've seen it be very speed related in a tight pattern before.

User avatar
evildky
Posts: 14713
Joined: Sat Jan 31, 2004 9:23 pm
Car: 71 240ZT, 87 300ZXN/A-T, 06 350Z GT, Tundra TRD RW
Location: Louisville, KY
Contact:

Post

What you describe sounds most like a Wheel and ro tire issue. Just because they balance doesn't mean they will be vibration free at every rpm. I'd start by rotating the fronts to the back and backs to the front unless you have access to a spare set. if you have a factory staggered setup yes you can do this and yes it will clear, I don't recommend leaving this way for any period of time beyond testing. See if the issue moves. Next suspect would eb the wheel bearings, they are pretty inexpensive and pretty simple to change and are a wear item.

amc49
Posts: 1183
Joined: Mon Jun 19, 2017 7:24 pm
Car: '11 Nissan Versa
'17 Nissan Altima

Post

Look at the 2 second thing if true, that says much. Normal worn parts do not commonly wear to make a frequency issue that slow, that's a timed stackup of some sort. Something plus something else have to both occur to do it. Why it's timed.

JenzToy
Posts: 2
Joined: Wed Aug 02, 2017 9:59 am
Car: 2007 350Z convertible

Post

Thanks for the suggestions....as to rotating tires, front and rear tires are different sizes so that won't work. I may have my mechanic check the wheel bearings next.

nsvihra
Posts: 1
Joined: Sat Jun 01, 2019 12:59 pm
Car: 2003 Nissan 350Z (Touring 6-Speed)

Post

Did you end up getting this fixed? I'm now having similar symptoms with my Z after new tires and trying to track it down. Curious what you found out... My new tires are balanced and true, alignment done. I didn't have this issue immediately prior to the new tires, and that set was very worn/bald, chopped up and alignment 6+ months old.

I'm having the front driver's side rim straightened this week after they pointed out there may be a slight issue there. But like I said, prior to the new tires I did not have any of these symptoms. Hoping this fixes it, but if not I'm curious what to check next.


Return to “350z / 370z Technical”