Can someone explain to me why comapct frames are supposed to be stiffer? I'm not asking why manufacturers use compact frames today (current style, mountain bikes, less sizes to stock) and I understand the advantage of more standover clearance without a giraffe neck stem and I am not saying compact is better or worse than traditional . But why would a compact frame be stiffer than a traditional frame? That's one of the biggest advantages claimed about compact frames. Supposedly Abraham Lincoln was once asked how long a man's legs should be and he replied, "Long enough to reach from his body to the ground". It's pretty similar with bicycles: the seat tube/seat post/saddle has to be long enough to reach from your buttocks to where your feet touch the pedals right? So if you take a compact frame in isolation, I suppose it is stiffer but if you include the longer seat post, why would it be any stiffer than the traditional frame? We had sloping top tubes back in the day too - we called them "girls' bikes" but we always said that one of the main disadvantages of that frame design was that it flexed too much. So what gives? Can anyone enlighten me? Why would a compact frame plus seat post be stiffer?