Originally Posted by
stapfam
32" inseam at your height seems long but then I am 5'6" and have short legs. Frame size of 53cm is a good starting point but that is all it is-A starting point.
I take it you have not ridden a Road bike for some length of time so do not know bike set up yet. The main point about that is that it "Must Fit"- obvious- but must be comfortable.
Top tube length is normally the measurement to go by as this is a fixed size on a bike. Standover height will not affect fit until you get off the saddle and stand up so is not that imortant. Saddle and bar position can be altered.
Choosing the right size bike is an art that takes several bikes to get right and is relatively easy. What is not is finding your Local Bike shop (LBS) that will give you all the help possible to get somewhere near the right bike first time out---So first find your LBS.
Sorry to throw a few more problems at you- but only one person can get the right bike for you-- and that is you-----But hopefully with the help of a good bike shop.
And I ride several bikes- all different sizes but they do fit me- Some fitted off the shelf and some had to have a few parts changed to get right. And you cannot rely on a 53cm frame fitting you as good as another manufacturers 53cm frame- you might need a 51 or even a 54.
I think 32 inches is not a bad measurement. I'm 5'5 1/2" and mine is 81.4 cm. 32 inches, if exact, is 81.3 cm.
Standover height is no longer really accepted as the best way to size a frame, but there is such a think as a top tube that is too high for you. On a big enough bike you will make painful and perhaps harmful hard contact, unless you have developed a special skill to dismount fast, or to stop on one foot with a leg raised. Not recommended for a new returning cyclist, and really, why would you? I think the absolute upper limit is as follows: assume the thickness of your shoe heel is 1 cm. Add your inseam, in your case this gets 82.3 cm, again if 32 is exact. If its not, you want to round this number DOWN to 82 cm. If you straddle a bike with a top tube including the rear brake cable routing at this height off the ground, your body (ahem) will make contact, but not a hard bruising contact against hard parts of your body, such as pelvic bones.
Tob tube length is significant, but so is seat tube angle, and the position of the top of the headset above the ground, relative to the top of the saddle when set, from the ground. There's a lot more flexibility in adjusting the saddle height than the handlebar height, so some say that top tube length is much more critical than seat tube length. Too long and your bars will not be low enough. Too short and your bars will be too far below the saddle for you.
Seat tube angle places you farther behind the pedals, interacting with the seat post setback and to some degree with saddle design. Here we bridge into opinion: do you place your saddle the same distance behind the bottom bracket for all of your bikes, regardless of purpose or style? My opinion for my riding is yes, but others do not agree. But with a more laid back seat tube, I want a longer top tube for my style.
This degree of interaction says one of two things: buy and set up a bike, even a used one, with the aid of an LBS who will fit you to the bike during and after purchase. Or, it says, get something somewhere has a seat tube or effective seat tube around (in your case) 53 cm center to center, and maybe a cm or two more if you can stand over it and if you need a higher head tube end, AND get assistance to fit it to you. Our old joints need all the help they can get to remain healthy and allow you to turn and turn and turn those pedals.
Go too tall and you'll be uncomfortable when you straddle and may be stretched out too far. Go too short and you won't be able to get the handlebars up high enough without solutions that might be ugly on such a small bike, or even detrimental.