Hello All,

I recently bought Cannondale Supersix 105 bike and athough i like it i am bit confused ont he size. I am between 5'8" and 5'9" so as per cannondale site, 54cm is better for me, however the shop keeper suggested 56 bike for. He said in 56cm, i will be more upright and comfortable..(and that was one of my requirement to have more endurance posture rather than race).because the tube is taller in 56 vs 54. Is that true or just he was trying to sell 56 to me?

Smaller bikes have shorter head tubes, which means the stem and bars are lower, and there's only so much height you can add with spacers. If you go with a larger frame you can still set the saddle at the same height and fore-aft position as on the smaller bike, but the bars will be higher, and you can use a shorter stem to make them the same reach from the saddle.

The other alternative is an endurance bike, like Cannondale's Synapse, which will have a taller head tube in the same size than the SuperSix. It depends on how much saddle-to-bar drop you want.

How comfortably do you straddle the top tube? Too tall could cause injury.

Usually we can fit a range of frames. I have a 32.5" inseam and 54-56 works well for me. Ideal is 54-55 w/55 TT. However, I have a 58 Masi road bike that I can ride pretty well. The problem is that in comparison to a 54-55, the 58 just doesn't feel "right." If it were me I'd get the proper size in an endurance bike as suggested by genejockey. My current ride is a CAAD 12 so I'd go to a Synapse. FWIW don't rely on Cannondale stated sizing. My CAAD 12 is badged a 52 but when measured using a virtual TT it is actually a 54.

It depends on the specific frame in question, but generally a bigger size frame will have a taller head tube and also a longer top tube, which sort of negate each other as far as upright-ness goes.

I would get the 54. You can add more spacers unless they unwisely cut the steerer.

Start with an accurate cycling inseam measurement or well known saddle height. I think the shop is trying to sell a too large bike, unless you have long legs for your height.

As an example, I have a 73cm saddle height. I usually look for a 520-530mm stack height. I'd pick the 48. Most riders of your height have a saddle height that's no higher than mine. A 56 would be way too tall.

If you want to sit upright, get an endurance frame.

There’s a lot of generalities to frame fit; as the other posters above me have pointed out; but to the OP, you are trying to get an endurance fit on a race frame the Six (and the CAAD) are shorter front-to-back, and intended to be ridden in a more aggressive position than an endurance bike like the Synapse.
To get a more upright, stretched out fit on a Six, you’d need to upsize.

Did you go go into the dealer looking for a carbon endurance bike, and they put you on a Six, or did you go in asking for a Six, and ‘make me fit on it?’

Frankly speaking I have been riding Trek FX4 from last 3 yrs and i wanted a bit faster bike. So i was searching for carbon road bike in under 4k CAD range...in entire Toronto there are no road bikes available in this price and size range. This store had 56 and 54 available and I asked for 56 as I "somehow" thought 56 is better for me. I told my history to the shop representative and he gave me 56cm evo. When i reached home and saw the size chart in cannondale website i saw 54 is recommended for my height so i went back and I asked to try 54 but not sure why the representative kept seat height of 54cm bit high and it was really uncomfortable to ride. The reasoning he gave to go with 56 was even though website is suggesting 54, but for more endurance kind of fit, i should go for 56 as there the seat tube is bit taller. He said that If I was looking for more racing kind of needs, then he would have suggested 54cm. So i came back with 56 but i just wanted some expert advice from this forum as didnt wanted to continue using wrong size and hurt my back or shoulders....One other thing I noticed (and I am bit finicky on that) is if I try to press thumb on the top tube, it squeezes a bit...i hope that is normal for carbon top tube?

https://www.cannondale.com/en-us/bik...evo-carbon-105

Look at the geometry chart.
The 54 has 554mm of stack height and 384mm of reach.
The 56 has 574mm of stach height and 390mm of reach.
Additionally, its between the 54 and 56 where front end geometry changes so the frames have very different head tube angles and therefore also different fork rakes to compensate for the change in head tube angle and keep the trail measurement the same(which affects how the bike feels when steering).

Anyways, with the 56 you get 20mm more stack height(bars are higher) and 6mm longer reach(bars are further away). If you want to have the same effective reach, just get a shorter stem- they come in common 10mm sizes and so get one thats 10mm smaller and call it good.

The shop did what you asked- you got the size that will feel more upright. And a stem swap is incredibly common and only known once you ride the bike for a bit(on your own or during a fit session) so its not like they know if you need a longer or shorter stem.
No idea why you bought a race bike when you want a more relaxed endurance fit. The Synapse has another 16mm of stack height and a smidge less reach.
I wouldnt really call either 'upright' though, if that is what you are really after.

What they're telling you is reasonable.

thx for the confirmation

when I went there were no other bikes available. So yeah I kind of asked them to fit me on super six 😞

I can easily straddle the top tube

This^^^

Adding spacers does not affect the steering/handling, unlike shorting a stem too much can. Further, if the OP is looking for a more upright position, they might end up needing to shorten the stem even on the 54.

I am someone who needs a more upright (higher stack to reach ratio) than most, and the best results I get are from going with the bike with the best reach (the smaller size) and using spacers to increase the stack.

Yeah, that makes sense, given the state of bike inventories at the present.

We also see the opposite around here, what I call ‘over-researched’ customers, who are convinced they need a certain model, spec and size, buy sight unseen, then get get the bike home and want to change everything but the paint job.

Nothing wrong at all with the Six, although I prefer my Cannondales in aluminum
You did ok by going with the bigger size, I would, too, if I was trying to get a more relaxed fit on that kind of bike