MNiceGuy

I've been on a quest to be healthier and today I chose to upgrade my Specialized Sirrus Carbon to a Bianchi Infinito.

I've had a fair number of Specialized bikes in the past and in each case I was either medium (MTB or Fitness) or 54cm (Roubaix). Each bike fit well and my current medium Sirrus fits like a glove. I'm 5'8" by the way with more torso than leg. When I started looking to Bianchi I had to choose either 53 or 55cm. My LBS thoroughly sized me and determined that the 55cm would suffice as long as I swapped the factory stem for an 80mm alternative. They performed the swap and the test ride felt pretty good.

Tonight I put a quick 20 miles on the bike and general impressions are good. The only general sizing problem I'm noticing is my standover is not quite where it should be. When I stand flat footed over the top tube the bike is just barely touching my groin. Looking through a few forum posts it seems like a 55cm in the Infinito is abnormally large for someone my height. I'm also wondering what the implications are, if any, of riding a large'ish frame with the reduced stem length like that? Would 53cm have been the smarter move? I ask because it's not too late to correct this if need be.

jideta

Bicycle fit is all about you and only you.
If it fits, it fits. If it doesn't go back and ride the 53 again.
Just remember, you can make a small bicycle bigger, but you can't make a bigger bicycle smaller.

Standover sounds okay...where do you want it to be?
Stem is a bit short for a frame of that size but could be your dimensions and/or the type of bars on the bicycle. Shorter stems may make the steering twitchy but I run one 85 and I live with it.
Hows the seat post? Way up? or way down?

I don't really go by seat tube anymore; I size a frame by top tube. It affects how stretched out I'm gonna be.
Maybe check the Sirrus dimensions and get the frame with the closest TT length.

Which ever frame you choose just make sure it's Celeste.

Wilmingtech

I'd go with the 53. Always better to go smaller if between sizes. 80mm stem is pretty short. Better to go with a 53 and have a 110 or 120mm stem or longer if you have a long torso.

Check your reach and stack on both Bianchi sizes and compare with your specialized. You'll have more room with a 53 to hit where you want to be.

Plus a 53 is lighter than a 55.

Nice bike though. Hope its Celeste

-Sean

Ironfish653

Sounds like they sized you more in the classic 'French Fit' where you have a longer, higher top tube, and ride a little more stretched out. Some Italian marques, and pre-TREK LeMond road bikes are designed this way.

I'm of similar proportions to you (short legs for height) and while most of my 'modern' rides are 56's, I do have a '76 Bridgestone that's a 57-58cm. I'm not much of a sprinter, and to heavy to be a pure climber, so I like my bikes long and low.

For a road bike that's intended for long miles, rather than an MTB or commuter, you're going to spend far more time in the saddle, than standing over the TT.

FrenchFit 

Modern Bianchis are a bit tough to fit me, most have a short stack height. I am now apparently 5'10.5" accordingly to my doctors, I've been shrinking. I definitely opt for larger frames, though charts put me on a 56cm. That said, I think stand over is pretty much irrelevant unless you like to jump on the top tube groin first. Proof of concept, I had hard stop into road barrier on a 60cm Bianchi, smacked into the fork stem and top tube, my injuries were limited to wrists and fingers, no groin injuries. Way too much is made over top tube clearance imho. I ride a 90mm stems on two 59-60cm frames, not ideal but I have no complaints about the handling. Smaller frames, I feel cramped, compressed. Larger frames I get to stretch out and the higher stack height means no spacers or risers. Over the years I have gotten rid of all my smaller frames and am happy with 58-60cm bikes, stand over be damned.

Always go bigger if you are between sizes.

puma1552

I'd say if you're more torso than leg, and still need to go down to an 80mm stem on a 55cm bike, the 53 would probably be a better fit.

For reference, I'm 5'5" on a 52cm bike, evenly proportioned, and I am on an 80cm stem (bike came with a 90mm stem).

jadocs

An 80mm stem tells me that frame is too large. I would go 53.

bruce19

Measure your inseam. Mine is 32 1/2" and I can ride 54-55 perfectly. This assumes that the virtual TT is around 55 which they usually are close to. Adjust reach with stem size. Back in the day racers would use .665 of inseam to find frame size. And, as has been mentioned a slightly smaller (if workable) frame is lighter.