JoeOxfordCT

Currently own a CAAD9 56cm. I am 5' 10", normal proportions. I am thinking of upgrading my frame to a 2011 CAAD10. The mechanic at my LBS is the same height as me about about 20lbs lighter. He also has a CAAD9 but in 52cm with a longer stem. I am wondering if I could get away with maybe downsizing to a 54cm with a longer stem to get my frame a little smaller & stiffer. Check the geometry chart below. I am most concerned about changes to pedaling position. In general, as frames get smaller does just the front of the bike move closer to you with little to no change in pedaling position ? I see that when you move from the 54cm to a 52cm that the seat tube angle changes from 74 to 73.5. I have heard of pro riders riding really small frames and just using long stems and setback seatposts. Is there a consensus on this ?
I think I could go from a 56 to a 54 without changing pedaling position but if I tried to go to a 52cm I would probably need a setback seatpost in order to maintain my current pedaling position.

??

CAAD10 Sizing Chart

Triguy

Cannondale is great in that they use stack and reach. It makes comparing sizes really easy, if you went with a 54 you would need 1.4cm longer stem and a 1cm of spacers.

A 52cm has almost the same reach as a 54 but another 1.7cm lower in headtube height(and as you pointed out, about .5cm less setback).

So I guess I would say, are you comfy on the 56cm? How many spacers do you have under your stem and is it turned down? What are you looking to get out of changing to a smaller size? At 5'10" you are borderline between a 54 and 56cm. I'm about 5'8.5 and I would fall sqaurely between a 52 and 54 I think. As there reach is the same, I would probably go with the 54 for the extra headtube height.

JoeOxfordCT

Thanks Triguy,
I am really only looking to get a smaller, stiffer frame....I am currently running a 95mm stem down from the 110mm that came with the bike. I feel like I could even run a 90mm if I took the time to order one. I am also running a straight seatpost with my seat pushed all the way back. I had thought at one point that I might gain more power by running a setback seatpost with a more rearward position and purchased and ran one for a bit but ended up in the same position as my straight post with the seat pushed all the way back so I went back to the straight post. I am hoping I can continue to run a straight (and lighter) seatpost with a 54cm. A 52 might call for the setback seatpost.

max power

if you have a ton of spacers on your current bike going to a smaller one might not be feasible due to the decrease in head tube length

cs1

If you're looking for longer stems and more setback on your seatpost why would you want a smaller frame? Your problems are going to be exaggerated in the smaller size. It's really a myth that super small frames are noticeably stiffer. I guarantee you can't feel the difference between a 56 and 54. Ride the bike that's comfortable on you. Good luck

bradtx

JoeOxfordCT, You may shave a few grams with a smaller frame, you may end up using a longer steerer stem which may cause the steering to feel negatively different and you may spend bucks for something that's not quite right for you. If you're really just wanting a CAAD10 frame, buy one that you already know fits.

I think stiffness between two adjacent frame sizes would be unnoticeable. I ride 58 cm Cannondales, but I have a 56 cm crit Cannondale. The difference between the two is down to the head tube angle, crit bike is 1 degree steeper, wheelbase is shorter and it turns on a dime. The top tubes are within 1/2 cm between the two sizes, which allows it to fit me. A standard 56 cm frame's TT is too short... I've tried.

Brad

DaveSSS 

The reach of the 52 and 54cm frames is not the same. There is a bit of a flaw in the reach and stack concept. To make a proper comparision, the reach must be measured at the SAME stack height on both frames. My doing that, you are then getting the real difference in the stem length required, using the same handlebar height and saddle position on both frames. Changing frames sizes should never force a rider to adopt a different position, so comparisons are always made with the assumption of a single bar height and saddle setback.

To make the correction for the 17mm difference in the stack height, you have to add 5mm to the difference in reach to get a total of 6mm. The 5mm amount is the cosine of the head tube angle times the difference in stack height.

https://www.cannondale.com/usa/usaeng...D10-1-Dura-Ace

Using a person's height as a guide to selecting frame size is also not wise. I'm only 5'-6.5" tall, but have a leg length as long as some people that are 4-5 inches taller. You need to know if the rider has short, average or long legs and how much saddle to bar drop the rider can tolerate.