Wheels fall off really easily now.

With the 4.5 update, it seems wheels aren't connected very well to the beams. Around 30m/s (~100km/h), if you go into a turn, you'll shed wheels like they were attached with duct tape. Occasionally, I'll end up having a perfectly intact car without any wheels. I like my cars to flip or skid or spin out when the wheels fail, not snap an axle. The game does, however, run faster.