Help! Slight vertical bounce with new wheels/tires

[SilverTipp]

My problem:

I upgraded my stock wheels to 18x9 +35 with 255/35 Bridgestone Driveguards. At first this was really wobbly and bouncy. It turns out they forgot to get hubcentric rings to put on the car. A few days later these were put on. This helped quite a bit, but there is still a little bit of bounce that turns into vibration at high speeds.

Does everyone deal with this going this wide? Could the Driveguards just have really stiff sidewalls?

I'm still at stock height. Could I possibly be rubbing slightly on my springs/struts?

If anyone could point me in the right direction for my next step, that would be awesome ...

Bridgestone has a 30 day Buy and Try policy so I'm contemplating getting rid of the tires for something else if that will solve the problem.

Thanks!

[KidRed]

After a quick search, I found this

https://m.reddit.com/r/BMW/comments/...lats_but_what/

In my case, it was unsprung weight. The fat sidewalls made the tires about 2x the weight of non-runflats. With a light car on a road with potholes (my daily route at the time) the extra mass was a challenge for the suspension to manage. Traction was so screwed, it felt like the tires were bouncing off the road.

On a smooth autocross course, they were fine. And the stiff sidewalls helped turn in. But the world isn't an autocross.

I've heard runflats have gotten lighter since then (2007), so maybe the problem isn't as bad.