I want to run thicker tires for better ride quality

[z4ninja]

Hello I have a 03 z4 sport
I have front 18 8.5 et 35 running 225/40/18 and rear 18 9.5 et 35 running 255/35/18
I kinda want to get a thicker tire because ride quality is bad. I do not want to size down on wheels as this is to my liking. Is there other sizes rear wheels that can fit with no issues?

[grannyknot]

I went up to 245/40 18 front and 275/40 18 rear, it did improve the ride quality, it was noticeable but not a lot.
If you are still on stock shocks and springs you shouldn't have any problems with rubbing.
If you have lowered the car then you may have to increase the neg camber to avoid rubbing.

[Emmrbee]

Try this web page for comparisons

https://tiresize.com/comparison/

[wdb]

Originally Posted by grannyknot

If you are still on stock shocks and springs you shouldn't have any problems with rubbing.

You might also want to consider new shocks and other suspension refresh items on a 2003 car.

One of the biggest things you can do is ditch the runflats if the car still has them. Carry a patch kit or a AAA card and put non-runflat tires on the car. Runflat sidewalls are very stiff compared to non-runflats and really impact ride quality.

[KevinC]

If running runflats, get rid of those turds and you probably won't feel the need for a "thicker" tire. Suggestion to refresh suspension components is also a good idea, assuming they haven't already been addressed at some point since new.

[Rafichicago]

Shocks and ditching run flats are your best bet on your car. If you diy remove the wheel support suspension at the bottom and unbolt the shock. Push it in. If it doesn’t return or doesn’t require significant force to push in its shot.