Shopping around for my first road bike, and was wondering if a 52 cm frame would fit. I hear that 52 cm Cannondales fit like 54 Treks--is there validity to that? Here's my specs from the Competitive Cyclist sizing calculator:

The Eddy Fit (cm)
Seat Tube Range c–c: 53 - 53.5 cm
Seat Tube Range c–t: 54.6 - 55.1 cm
Top Tube Length: 51.2 - 51.6 cm
Stem Length: 9.1 - 9.7 cm
BB–Saddle Position: 67.6 - 69.6 cm
Saddle Handlebar: 49.7 - 50.3 cm
Saddle Setback: 5.7 - 6.1 cm

The Competitive Fit (cm)
Seat Tube Range c–c: 51.8 - 52.3 cm
Seat Tube Range c–t: 53.4 - 53.9 cm
Top Tube Length: 51.2 - 51.6 cm
Stem Length: 10.2 - 10.8 cm
BB–Saddle Position: 68.4 - 70.4 cm
Saddle Handlebar: 48.9 - 49.5 cm
Saddle Setback: 4.5 - 4.9 cm

The French Fit (cm)
Seat Tube Range c–c: 54.7 - 55.2 cm
Seat Tube Range c–t: 56.3 - 56.8 cm
Top Tube Length: 52.4 - 52.8 cm
Stem Length: 9.3 - 9.9 cm
BB–Saddle Position: 65.9 - 67.9 cm
Saddle Handlebar: 51.4 - 52 cm
Saddle Setback: 5.2 - 5.6 cm

Your Measurements (in)
Inseam: 31.5
Trunk: 22.1
Forearm: 13
Arm: 24.5
Thigh: 23.5
Lower Leg: 21
Sternal Notch: 56
Total Body Height: 69

Thanks for your help! I've tested some 52 cm Cannondales and they felt alright, but I'm coming from a hybrid bike so the posture is completely different and tough to get an accurate feel for. But looking for some validation that 52 cm frame would be a good choice.

Seat tube length is "size" .. Go test ride the bikes , (No C'dale dealers Here)

now get back to work!

Does the measurement usually go based on the c-c or c-t? Looks like it makes a bit of difference..

If your measurements are accurate, and competitivecyclist fit calculator is accurate, then you may wish to look at a Cannondale that has an effective top tube length of 51cm to 53cm in length. You can check the geometry measurements on their website. Which model of Cannondale bike are you considering?

Thanks Ned! Currently looking at a CAAD9

A 2010 CAAD9 in size 52 has an ETT of 53.5cm. According to CompFitCalc and your measurements that may be a bit on the large size but doable. I have a CAAD10 that exceeds my CompFitCalc recommendation for ETT and wish that it was one size smaller, but still ride the heck out of it with a shorter stem. My primary road bike has a 1.5cm shorter ETT and fits perfectly. We are all different obviously, but in the future I will lean toward slightly smaller than slightly bigger for a road bike. Can you test ride both a 52 and 50? If so, pay particular attention to how comfortable you are with the drop of the handlebar. My preference for go fast as I can 35 mile club rides is to have more drop. For 80 to 100 mile rides I prefer less drop.

Thanks again. That's funny because size charts by height alone recommend size 54. Must be the smaller inseam pulling that size recommendation down. But makes me feel better because I'm going to check out a size 52 CAAD9 this morning from a craigslist seller. And as for being my first road bike, maybe a slightly less aggressive fit would be a good place to start?

Just my opinion, but if you are comfortable with the standover then you will be pretty close. CAAD's have a very horizontal top tube compared to more relaxed geometries. I also know that standover isn't what should be considered but makes a difference for me. I agree on less aggressive fit to start. You want to be able to enjoy the bike instead of it being a dust magnet in the garage.

Thanks for all your advice Ned. I went with the CAAD9 size 52 and took it for a quick 20 miler, size felt great! Feeling a little sore in the lower back, but probably just because the posture is completely different from the upright position I'm used to with my hybrid.

I'm 5' 7" with an inseam of 30 inches. I tried a 52 cm Cannondale supersix evo, and the top tube touches my crouch when I stand over it. However, I like the top tube length more on the 52 then the 50.
Anyone have the same issue where their Cannondale is too tall, but the length is perfect?

I believe the standover reco relates to hitting your pubic bone, not your crotch. Is that what you mean? I wouldn't buy a bike that hit my pubic bone again - BTDT, paid for it in pain one bad day, but that's JMO.

@UCDHacker, I just went through comparing the "race" road bike geometries in Cervelo, Canondale, Trek and Specialized
I didn't exactly write down detailed conclusions, but the notes I wrote were that Cervelo and Trek had the highest aspect ratio (relatively tall compared to length). Canondale was a little lower, and specialized was the lowest. Problem is though, I was looking at the larger sizes. Things sometimes get funny in the smaller sizes as they all compromise differently. Just check out the geometry tables and see which ones have lower stack for the same reach in your range.

However, you might have to look at the photos or try the real thing too, because stack doesn't necessarily tell you the standover height, if the top tubes slope differently. My guess is they all slope pretty similarly though.

Hitting the top tube seems pretty wrong to me on a modern style bike, and may just be a size (or two) too big. One thing I've been really realizing, maybe kind of obvious, is you can't tolerate nearly as much saddle to handlebar drop in a fit that's too long. For the same body position, your arms swing in an arc where up means out. Down without coming in will put you in a lower body position, for arms extended on the hoods at least. The problem on those smaller frame sizes though is they don't tend to get shorter in length as they get lower. If you're really right about your problem though, that could be good for you. A size smaller is likely the same length, but lower.

Realize though that length is determined by REACH, not top tube length. The smaller sizes usually do have shorter top tube length, but the reach will often be the same. For the smaller size you need more setback on the saddle post to get the seat in the same position relative to the BB, but once you do that, as you should, the length of the bike is the same. You may just need to adjust the saddle position on the 50. You can of course also add a couple of cm to the stem.

By the way, here is the canondale chart.. oops, link didn't work, well just click geometry from their website listing.

From 52 to 50 the top tube length only decreases 1.2cm, easily an amount correctable by stem length BUT, the number that matters, reach, only decreases by 6mm. So you add 6mm more to the saddle post setback and 6mm more to the stem and you're in the same position with same reach.

However, the standover height only gets 2 cm better.

You can go all the way down to a 48 and the reach only gets 1.2 cm shorter. Still easily correctable with a longer stem. That would get you 3.5 cm of standover clearance which sounds better to me. It's starting to get into altered trail at those sizes and I guess might handle slightly differently.

tl;dr: With very minor adjustments to seat and stem you can get the fit to the same length even in two sizes smaller. With another brand you might also find shorter bikes in the same reach.