Till a week ago, I would have generally said that stay under 35 for sure but my new ZIPP 303 Firecrests are as unaffected as my 30mm shadow alloy Easton R90 SLs. I'm 175 lbs and have ridden in some seriously windy Springs here. The ENVE Foundation 45s are not as stable. I am still a bit surprised and am thinking of using a second set of ZIPP 303 Firecrests on my gravel bike. I'm in Colorado. In general though, under 30 is perfect. My DT 411s were around 21mm in height and unaffected by wind plus very comfy!!