So here is my bike that I bought as a replacement for my old Cannondale R1000 after a car hit me on a training ride...payed less for this bike than I did for my old one...

Its full Campy Record
FSA OS-115 stem
FSA K-force carbon bars
Mavic SSC Sl wheels
Cannondale Si Hollowgram Crankset
Thomson Elite seatpost
Fizik Arione saddle
Apparently the frame was extremely light for six13's and the bike shop where this bike was maintained apparently weighed it and found it was a little less than 1000g... so that would mean that this bike and this build would be getting close to 15.5lbs

No pedals as of yet, but am debating between Look Keo Carbon CroMo or new Shimano Dura Ace, you can give some opinions if you like.
(Dont mind the other comments, those were to help me decide if I was going to buy the bike)

I am about your size and always rode a 58 C'dale. THe only qualm I have is the length of the headtube. Best bet? Ride it and see.

I'm your height. I've ridden 56, 58, and 59cm cannondales. All were made to fit somehow. My favorite setup is the 58 with 120 stem with no spacers and a no setback seatpost. I like the way the bigger bike handles.

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The Chronic

see I would test ride the bike but the problem is I was hit by a car and had knee surgery just over a month ago but I am going to go tomorrow and look at the bike to see if I can make it work

There is over a half cm in the difference between 73.5 and 73 seat angles, so the bike is maybe 1cm more stretched out and 2cm taller. Get a 1cm shorter stem and that takes care of the length. If you had spacers under your stem before ditch them... and get a horizontal stem if necessary. You can probably make it exactly the same position as your old bike without doing anything strange.

At your size the 58 is right. The bike will handle better and be more stable (less twitchy) than the smaller 56 frame. I agree with the Dude. Follow rruff's advice and experiment, you'll get within acceptable fit tolerances and have your dream bike.

Your previous 56cm frame was also a Cannondale? Did it fit? If it did then I can't imagine a different size frame can also fit.
Of course if your 56 meant you were using a 14 stem with spacers under it and a seatpin up to its max (or beyond) then you may have scope to go up a size.

With the measurements you have supplied, I would say that you were riding a frame that was too small for you at 56.
I'm 5'10 with a long inseam and was bike fitted for a 56 dale.
58 should be your frame size anyway, buy it and get some photos on here.

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Pedalling Law Student.

If you were using spacers and a relatively flat or a riser stem on the 56, then you should fit a 58 without a problem.

It does depend on your torso length and flexibility as to how long a bike you need... I'm 5'11 and am on a 56 'dale, but would be better on a 58 with my long torso, but my short legs won't give me enough standover. So I use a 56 with spacers and a 120mm -8 stem. With your height and inseam you shouldn't have a problem with standover on a 58.

So the only issue is if you had the 56 with no spacers and a flat stem, then you'll have reach issues with a 58.

give us a pic of your old bike and we can see
tikka

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All we need to know is your current setup.
By the way, arm length of 45cm seems a bit short. 65 is more likely

Im 181cm and ride a 56 system six with a 130 stem, and it fits great. I was originally set to get a 58 but it didnt feel as good to me.

wash it at 90 degrees. Don't use bleach. It will shrink...

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Bianchi EV3, Master Olympic, Pinarello Asolo

Is it possible to put the bike on a stand or trainer and just sit on it to see how it fits? That said I agree with most of the others that at your height the bike should fit.

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"Really fast people are frustrating, but they make you faster. When you get faster, you might frustrate someone else."

2009 Trek Madone 5.5 Project One SRAM Force 16.4 lbs w/pedals and cages.
2007 Bianchi 928 Carbon Lugged- SRAM Rival-17 lbs.

Like I said, a 1cm shorter stem is all he needs to get exactly the same reach. In fact 1cm is so little he may not even notice it.

99% of bike fitting is getting the seat in the right place relative to the bottom bracket and putting the bars at the right place relative to the seat. I'm 6ft tall and I can easily do this with pretty much any 52-60cm frame, using normal components. The reach on bike frames doesn't really vary that much. The top tube lengths change, but smaller frames also have steeper seat angles which erases some of the difference.

On a Six13 the 52cm size has a 74deg SA, an 12.1cm HT, and a 53.5cm TT. The 60 has a 72.5deg SA, a 19.2cm HT, and a 59cm TT. The difference in seat angle is eq to ~1.5cm in TT length, so I still have 4cm real difference in reach.

On a 52 I'd need a pretty long stem (~130mm) tilted up (18+6deg) with maybe 20mm in spacers, and a seatpost with some setback. On the 60 I'd want a shorter horizontal stem (~90mm), no spacers, and the seat a little farther (1.5cm) forward on the rails. Note that I'm getting the seat and bars in *exactly* the same position, so the fit will be identical. Beyond that it is mostly esthetics... and yes I prefer a 55-56cm frame for that reason.