If either is the case, your saddle is too high. Straightening your knee during the pedal’s rotation limits how fast you can smoothly rotate the pedals, and causes you to want to use a higher gear than that which would be most efficient.
By limiting the extension of your legs you smooth out your pedaling and make higher RPMs possible. That’s better for your muscles and joints. If the saddle is too low you’ll quickly feel a burning sensation in your quadriceps or thigh muscles.
So what does all this mean when it comes to picking a frame size down at your local bike shop? Stems and seat posts come in lots of different configurations. That means you can choose from several different frame sizes and still get the same good fit.
All other things being equal, a longer top tube will give you a bike with a longer wheelbase, less twitchy handing, better shock absorption, and require a shorter reach stem. Since the down tube, (which connects the bottom bracket with the head tube) will be longer, it can twist a bit more making the frame somewhat less stiff while accelerating, so there is a performance penalty.
A longer seat tube will allow for a higher handlebar position with the same stem and give more room for pumps and water bottles. It can also prevent you from getting as low a handlebar position as you may want. Most importantly though, the longer seat tube raises the top tube and decreases stand-over clearance, something you should give careful consideration to.
Notice that in most of this there is no mention of measuring body parts. The Fit Kit and other marketed fitting systems are based on the measurements of lots of different riders and their bikes. It assumes that the averages of those measurements are somehow going to result in a good fit for you.
But take the case of two riders; Rider A, and Rider B. Rider A has very little upper body muscle but very strong legs. Rider B is identical to Rider A but has been working out at Ralph’s Gym and looks like a body builder. The fore aft position of the saddle will be slightly different for the two riders. The extra upper body mass of Rider B will require a slightly further back saddle position to give the same balance.
But that doesn’t necessarily mean that Rider B should have his saddle further back. He may prefer the more forward position. Only he knows what his preference is. It is recommendable to find out what you’re size is and what measurements you may be able to ride comfortably and longer.
Somewhere between the fit of the track racer’s bike and the long distance tourer’s bike is where most of us want to be. But each of us has to find that point for ourselves. Remember, there is only one expert when it comes to fitting your bike. Only you know how you feel on your bike. Only you know what compromises you are willing to make while riding. You’re the expert.
