Hi everyone. I just wanted to get someone else's opinion on an opportunity I was presented with. I currently ride a 2016 giant tcr small. I have changed out the 90mm stem and put a 100mm stem since purchase. I was presented with an opportunity from a family member to be given a 2014 giant propel isp size medium. I looked up the geometry for the giant propel and it says its a size 52 frame with a 55.5cm length top tube. My current giant tcr has a 53.5 top tube length. In short would the 2014 giant propel in medium be ok for me if i shortened the stem some? I feel pretty comfortable on my giant tcr small but i was wondering if i could just use a shorter stem on the propel if i got it. I forgot to add that my inseam is 78cm and my height is 167cm.

Hi I am about the same size. You can ride the larger bike. I do not recommend it. Not only is the top tube longer, the headtube is taller as well.I do not know about your riding style, but try it out. I think your standover will be erased and it will be really upright.

I am 167 cm as well, 783 mm inseam.
Used and use a bunch of bikes with top tubes ranging between 515 and 535 mm, with the exception of one bike measuring 545 mm top tube.
That one bike with the longer top tube was a challenge for me to set up comfortably, although I mastered it, having had 40+ years of riding and bike fitting under my belt at the time. Rode it for 9 years, until the frame (Al) cracked near the Bottom Bracket.
Lately, all my bikes have the TT within 530-535.

I suspect that the 555 mm top tube on the Giant Propel you mentioned would be too much for you.
Playing with stem lengths is a secondary thing, it serves only to position your handlebars where you feel most comfortable once you have properly positioned your butt on the bike, and has no bearing on the selected frame size and fit.
It is the location of your butt in relation to the Bottom Bracket that you should be concerned with while choosing a frame size.

It would not hurt to set up the bike and test-ride it and see how it feels, however keep in mind that riding goals evolve and if today you like fast 25-mi group rides, tomorrow you may want to shift focus on centuries, for which the same bike setup won't do...

thank you guys for your input. i skipped out on it and im looking into an aero frame elsewhere. again appreciate your opinions. thanks.