Frame flex question

[1beaglebaby]

80 Motobecane touring... fun to ride around town.. Going up grades the top bar really flexs side to side? Is that normal for a light frame? I havent noticed this with old heavy cruiser bikes.

 

[OneHorsePower]

not normal if its aluminum or carbon, it will break due to fatigue ....
normal for a light chromo or steel frame ,specialy girl frame or ,with tall handle bars due to leverage
my peugoet chromo frame scare me .. alot of flex everywhere , but i ride it like a beast since 5 years and still holding , flex did not increace over time at all

 

[1beaglebaby]

Thanks for reply. Ya the frame is steel and the top tube whips side to side under load/ up grades. Great bike and never had a problem.