Decisions, Decisions, Frame Geo. Help
 

Well long story short I test road a Caad9 and a Synapse. I liked the ride on both. I have a really old/vintage road bike late 80's maybe that I've been riding that is far to big for me . To be brief my inseam is 29.5-30" (74.9-76.2cm) and I'm 5'6". I know I'm not going to get a pro-fit from the feedback I'm just trying to educate myself as to which frame geometry measurements are most important.

I took some measurements as best I could of the current bike I'm riding and am trying to compared frame geometry of the Caad9 , Synapse and the current bike. One dimension in question is the Stand Over Height. As I am on the shorter side it seems that I will not clear the stand over height on any of these frames.

Stand Over Height
Caad9 (50cm) = 74
Synapse (51cm) = 74.4
Caad9 (52cm) = 76.5
Synapse (54cm) = 77.1
Caad9 (54cm) = 78.5
Current Bike = 81.3

The Caad9 (50cm) and the Synapse (51cm) are the only two that I will actually clear buy 0.5-1.0cm.

But then looking at other dimensions as far as TT length they seem to be on the small side compared to the current bike I'm on and I actually feel ok on it. Although I have noticed on rides ~15mi I get numbness in my left foot outer toes and I think that is entirely related to saddle, saddle position, and Seat Tube length which there isn't much I can do about on this old frame.

TT Lengths
Caad9 (50cm) = 52.5
Synapse (51cm) = 52.5
Caad9 (52cm) = 53.5
Synapse (54cm) = 54
Caad9 (54cm) = 54.5
Current bike = 54.6

I actually feel ok well at least I think I do with my current bike.

Measured Size (BB – TT, measured from Center Line of BB to top of Tob Tube)
Synapse (51cm) = 45
Caad9 (50cm) = 48
Synapse (54cm) = 48
Caad9 (52cm) = 50
Caad9 (54cm) = 52
Current bike = 58.4

My current bike has virtually now seat post exposed. The issue I have with the 54cm frames is that there is only about 1.8-4cm of seat post exposed. Just seems like the 54cm would be to big of a bike for me. Yet the on-line fit calc suggests a 54cm to be the right size for me.

I could list every and all dimensions instead I made a spreadsheet with them. Would anyone care to comment on them and help me out. Am I looking at the correct dimensions to decide on the best geometry for me?? or should I be looking elsewhere to establish a baseline geometry for me?

Then there's the question of do I go with the Caad9 or the Synapse ?

Thanks in advance

what's important: top tube length + seat tube angle + head tube angle.
the 50cm and 52cm of the caad9 aren't that different in terms of geometry.
The end result is a whooping 0.5cm 'cockpit reach' size difference between the 50cm and 52cm.

cockpit reach is nose of saddle to center of bar clamp length.


CAAD9 is more racing oriented and puts you in a more aggressive position
synapse is more recreation/comfort oriented (not that you can't do the opposite with either)

Yes, you should be looking elsewhere ...go to a shop that knows what they're doing, will fit you and will remove the guess work from your side of the process.

The LBS I have chosen will do a proper fit, I'm just trying to educate myself.

You're digging WAY too deep into this. If you were dropping $5G on a custom frameset, then there would be some relevance ...and we'd need to know a lot more than just your inseam and height.

If I gave you my measurements, you'd probbaly tell me to ride a bike bigger than what I'm on. I like a more compact fit. I run a 130cm stem to make up the difference. I have longer arms and it lets me get lower (flattens out my back), handles better and it just makes the bike feel snappier. I was professionally fit on my current bike and I'm no more/less efficient than I was on my last bike which was even smaller than what I'm on now.

Go ride them - you'll get nowhere with this thread.

Three things define the fit. The TT length, the STA and head tube length. The TT length and STA work together to define the reach. It's rare when the HTA has enough of an effect to worry about.

If you measured your inseam to saddle like crotch contact in bare feet, I can't imagine how you're riding a frame with a standover that's 5cm greater than your inseam. What's your actual saddle height? Mine's 73cm, for example.

I'm only a half inch taller, but my inseam is 83cm, so standover is never an issue. Too much reach is a greater concern for me.

The big difference with the Synapse is the much taller head tube. If you don't want much saddle to bar drop, that may be OK, but the head tubes are too long to suit me.

I'd compare the 50cm CAAD9 and the 51cm Synapse. The CAAD9 would have only about 4mm more reach and a 30mm shorter head tube.

DaveSSS your feedback is exactly what I was looking for thank you. The current bike that is 5cm greater than my inseam was given to me for free so I can't complain about the issues with that. I've learned to lean to the side when coming to a stop. I think to help me explain to my LBS how I'm comfortable with certain aspects of the bike I have now I'll have to take it with me.