Vibration at speed

Hey all! I’m curious if anyone can help me troubleshoot this oddity. Coming home from vacation, I noticed a cyclical vibration in my '96 Volvo 960. The cycle shortens with increased speed, and specifically at 85 mph it would swell to a peak and then smooth out to disappear over ten seconds. It’s not real noticeable, steering wheel slightly shakes and you can feel it in your feet. At 80 mph it was about a 15 second cycle. Any thoughts? And thanks!

  1. Check tire pressure 2. Have wheels balanced 3. Why are you driving 85 in a vehicle that has steering wheel vibration ?

Could be tires. The tires on opposite sides of the drive axle could each have a belt shifted a bit, a road force variation or a small imbalance that sets off a vibration that comes and goes as the tires go into phase and then back out. Some cars are very sensitive to this, not sure about a Volvo 960

If it bugs you, have the tire balance checked. I may be OK. I currently have a tire that vibrates a bit at times but the balance is just fine.