I have a 2007 Jamis Aurora and beneath the seat on the frame there is a sticker that says "50 size" I assume that is referring to part of the frame (centimeters?)? Is that size considered small medium or large? I am 6' and the bike seems to fit me OK and is comfortable to ride.

...50cm would have been 19.6" frame (I never got metrasized) and would have been for shorter riders, say 5'6" or below and I can't imagine it being comfortable for a 6 footer! I'm 6' and ride a 23" frame (58.4 cm) comfortably.

Today, however there are many different styles of frames and the "old system" of measuring is no longer applicable in many cases.

What's more important is how the fit feels to you. I want my knee to be slightly bent at the bottom of the "stroke" (and not hitting the bar at the top), otherwise my knees get very painful in short order.

Does it really make a difference what that measurement is as long as I can adjust the saddle to get proper leg extension? Thanks

If raising the saddle could deliver a proper fit, Jamis would not have offered that bike in 6 different frame sizes. A taller person doesn't only have longer legs, torso length and arm length would also be different. A larger frame grows in more than the length of the seat tube. The top tube is also longer as is the head tube so that the handlebars are both farther away from the saddle as well as being higher to accommodate the higher saddle needed by a taller rider. A 50 cm frame would only fit a taller rider if the frame had the newer style sloping top tube along with a top tube length designed for a taller rider. The Aurora is a touring bike designed for comfort during very long rides. If your rides are relatively short you might never notice discomfort that would happen after 4-5 hours in the saddle

Remember that proper leg extension is to the pedal at 6 O'clock. Not to the ground.

Also, if the seat is raised too high, you can have too much flex in the seat post area. And it's possible that it could cause damage to the seat tube. Sometimes a seatpost will have something on it that says not to raise it over a certain height (or to lower it too far).

GH

I'm 6'2" and have always been most comfortable on a 58cm frame with a short(er) stem. A 56 will work for me as well. I couldn't even begin to handle a 50. That's about what my 5'3" wife rides and my post maintenance checkouts on it are are....painful. If it really does work for you, however, it's all good.

50 sounds a little small for a six footer. I started riding when I was 5'10" and rode a 54. At 6'3" I'm on a 62 and never been more comfortable. I mostly rode a 58 once I topped out and I think I now know the source of my back problems I had. Too small a bike.

I suspect that pro racers ride with the smallest frame they can to save weight. They make up the fit with longer stems and seat posts.

They don't do it to save weight, taller riders ride smaller frames to improve aerodynamics at the expense of comfort and better handling that a properly sized frame would provide. There is no need to save weight, even the biggest bike frames ridden by pros can easily be built up to go under the UCI weight limit

Maybe, maybe not.

I HATE the concept of using the seat tube length as the primary sizing guide. It's really stupid!

First of all, saddle height is the easiest adjustment to make on a bicycle. Worrying about seat tube length is like fretting over the neck dimension of an open collar shirt.
Second is today's popularity with sloping top tubes. The actual seat tube length means NOTHING if you're trying to compare one brand of bike with another.

Since you feel the bike seems to fit and is comfortable to ride, I'd just go with it.

Except that the OP's bike is a traditional horizontal top tube steel touring frame where top and seat tube measurements are easy to take