At around 60mph I start to feel a vibration throughout the car that gets stronger at 70mph and real noticeable at 80mph (noticeable as in I can feel it, but it doesn't change the driving characteristics). It feels kinda like 3 thuds, then a break in thuds every 2-3 seconds, then 3 thuds, and so on. The vibration can be felt in both the driver and passenger seat and I've tested it on multiple road surfaces so it's not the road.

Does anyone know what this may be? My thoughts are:

Tires bad? (front and rears are different brands and changed at different times)
Bent rim? (haven't hit any potholes that I can remember)
Alignment? (car doesn't pull to left or right though)

Any feedback is appreciated.

 

Bent wheel.

 

I would have a shop check it out might be the Alignment not balance

 

your wheels just need to be balanced. balance all 4.

incorrect alignment does not cause a vibration, a bent wheel would cause vibration but since you haven't hit anything I would rule that out.

 

Mixed responses here, alignment or balance?

 

wheel alignment is how your wheels are made to be perfectly in line with the car vertically and horizontally and made parallel with each other.
wheel balance or wheel balancing is adding weights to the rim in computer designated spots so that when the wheel spins its perfectly balanced and spins with equal weight on all degrees of the circle

so basically when you car shakes the tires needs balanced. When it pulls to the left or right the tires need aligned.

your case needs to be balanced
worse case is you might need new tires

 

I have/had almost the same exact issue with my IS350. I thought tires might be the culprit but the 2-3 second break where there was no vibration kind of freaked me out. Just like you said, a couple seconds of a vibration and then it would stop for a few seconds, then vibrate again for two seconds or so.

I took it to a dealership I used to work at for years and had one of the techs I knew check my tire balance. Found 2 rears were out of balance 1.0-1.5 ounces and one tire had excessive road force (16 pounds of road force I think).

Rebalanced the two rears and the vibration is much much better. I can still slightly feel it when the tires are cold from the excess road force, but seems to disappear after 5 miles or so. I was really worried for a while I had a drivetrain issue.

In summary, see if you can find a place to do a road force balance.

 

That's what I thought as well............just odd that the weights on the rim would work themselves loose I guess.

Glad to see I'm not the only one. BTW, what differs from a road force balance vice a normal balance? Great 1st post btw.

 

Thanks! Basically a "road force balance" applies a roller to the tire with any wheres from 700-1200 pounds or force while spinning. This simulates what a tire will actually do under load. It can detect radial and lateral tire runout and tread pull and can give an overall better balance and detect if there is a tire/rim issue. Some machines will allow you to do whats called a "match balance or match mounting". This can detect an out of round area on a rim and/or tire and will have you dismount and rotate the tire to a specific position on the rim to basically make it round again. Most shops charge quite a bit for a mount balance just because its a pain in the butt and takes a while, and it isnt often needed. We usually did it on large truck tires when we had issues getting a good spin balance.

 

Tires flat spotting maybe?