ive clocked my bike at 36.7 mph by gps, and it felt fine. if you have a bicycle that is manufactured poorly or the design simply isnt good for a bicycle than i could see there being issues, however with a bicycle that is well made you should be fine. if your wheels arent straight you might have a problem, if theirs play in the steering for some reason or your tires are messed up, you might have a problem. if i had front shocks it would work even better, that could help with stability issues, getting a better handlebar could even help. not to mention theirs a video online of someone with a chinese grubee crankcase and a puch cylinder speeding along at over 45mph, he was actually passing people. so its definitely possible if you do it properly. depending on the bike though it might be more challenging than its worth to do it. i keep up with traffic decently when im riding and the speed limit where i ride is 30. consider looking into either a better bike or higher quality parts.