Hello Everybody from Canary Islands in Spain!
This is my first post and i need your help please!!
I´m going to buy a 2009 Cannondale Synapse Carbon, but i doubt about what size to choose with my measures (height=183 cm and inseam=87cm), a 56 or a 58.
What do you think??
Thank you very much!!!

I'm 1 inch shorter than you with a 3.5 inch shorter inseam and I was fit for a 56 Carbon Synapse.

Sounds like a 58 would do you well

I am just under 6'2" and have a 59cm HI-MOD Synapse frame that I had built for me. It fits me perfectly. I traded my old 60cm frame in for the new one. The old one was too big. Too much of a stretch.

You have picked a great bike.

The answer is not simple. If that 87cm inseam is an accurate cycling inseam, a 54cm would be the smallest size to fit your legs, which are on the short side for your height. A 56cm is probably the best compromise between too small and too large.

The Synapse has a tall head tube for comfort. It's not designed for a racy fit with the bars low.

While I understand what you are trying to say, I really would not worry about that.

I can easily take a bike like this and "make it racy".

Liquigas rode the Synapse SL throughout the Spring Classic season.

You can use the minmum height headset top, no spacers and a 73 degree stem, but the bars still won't be very low if you buy a frame that's too large.

For example, the 51cm would fit me properly, but I only use a 145mm total stack length with a 73 degree stem. You couldn't get the stack height that low on a Synapse. I could also make the 54cm fit, but the HT would then be way too tall.

oops, double post.

My point is that it really does not matter.

These Liquigas guys went from Super Sixes, to Synapse SL's, back to Super Sixes without issue.

A professional that puts, oh, 30,000+ miles a year on the road would, indeed, be interested in setup.

It may not work for you. It did for all of them.

I have a a 5mm shorter inseam than you, and ride a size 58 Synapse. It's a perfect fit. I have slightly short arms, and still run a 110 stem. I'm 6' -1.5" tall. If you are close to my height, I would say no to the size 56. Oh, and that is my true inseam, not a pant inseam, make sure you use the same.

From the factory, the Syn bar position makes you a bit of a sail. I've flipped the stem, and removed two spacers. Seems much better now for fighting the spring winds, but is still 1.5 inches higher than my Caad.

Here are some sizing and fitting tips.

I have to admit I get kind of annoyed when people say things like this. If you have a long torso, the Synapse is pretty upright, but for those of us with long legs and short torsos, the Synapse gives a pretty "normal" fit. I think I am running 5-6 cm of saddle to bar drop with four spacers under my stem.

For The_Flo, assuming the measurements you gave are correct, I think a 58 would be about the right size. I'm a few cm shorter than you with an 88.5 cm inseam and ride a 56.

EDIT: I just looked at the geometry charts and it looks like the new Synapse geometry is quite a bit different from my older one, but I think the longer top tube of the 58 is still what you need.

Why does this "annoy" you? The Synapse has a taller head tube for a given size than typical racing frames. That's obvious from the geometry chart. If that's what you need, it's a fine choice, but is wouldn't work for me.

I've got a very short torso at 169cm tall with an 83cm inseam. I don't need the tall head tube, a bunch of spacers or a riser stem because I use a drop in the 10-12cm range. To get 11-12cm I use a 73 degree stem and to get only about 9-10cm of drop I can use an 84 degree stem. I have one 5mm spacer under the stem.