Currently ride a colnago V3 at 54s with a 120mm stem. I am looking into a more relaxed geometry as N+1 and specifically into Basso Astra. Here lies the issue. I dont know whether 56 or a 58 in Basso would suit me better. Recently I tested a BMC Roadmachine at 56cm and that was great fit too. Speaking to the shop, before ordering, they are telling me to go with a 58cm BUT this to me looks BIG (on paper). I tried to run the bikes on bike insights but Basso does not show as an overlay so I can only go by numbers and the numbers look BIG. Hoping someone can chime in and provide some insight for my decision.
Colnago 54s vs Basso 58

Stack 578mm 625.4mm +47.4mm
Reach 390mm 384.4mm -5.6mm
Stack to Reach Ratio 1.48:1 1.63:1

https://bikeinsights.com/compare?geo...57a4001d95e561,

Depends on 'You' and how you want to interpret 'Relaxed position' - and your general Body dimensions...
Here's a link to a comparo of a 2020 V3 - 54 & 2023 Basso Astra in 56 & 58 - which seem to match your numbers...
... on the 56 a .5cm shorter reach for me is not a huge consideration - could be compensated by a longer stem, unless the integrated cockpit/stem/headset thing is complicated ... the very slightly steeper seattube angle combined with shorter stock stem length might make it 1 cm 'shorter' reach.... a big deal ?
AND the reach for the Astra 56 & 58 is only 2+mm different - then the stem length difference makes up whatever the actual reach might be - frame difference seems negligible...
The 58 have a 4.7 higher stack would be a sizeable increase - depending on what you want...
Since neither lists a standover height & Both the V3 and the Astra have a 'Seattube Length' listed, but not as 'Effective Seattube Length - I have to assume the standover on a 58 is quite a bit higher than the V3 and Astra 56....
so what your cycling inseam is, might be a consideration... or not...
...maybe the shop has a 58 in stock ? or can;t get a 56 ? or this is how they interpret your desire ?
... I could say what I prefer... but that shouldn't impact on your decision...
.... if you can replace the stem on your V3 - buy a cheap +17 deg. stem, and you'll get a feel for the difference +40 mm stack will be....
//yojimg.net/bike/web_tools/stem.php (I put in numbers: 73.5 angle, 120 length & --7 deg for V3 & 73.5, 110 & +17 for the Basso...

Ride On
Yuri

A long inseam for your height might suggest the smaller size frame. However without trying them out for real and riding them in the conditions you normally ride, the best thing you can do is accept that you won't know for sure. However neither size will be so detrimental to you that you can make it work. What will be detrimental, is if the bike isn't made in the geometry for the position you wish to be in.

Relaxed geometry doesn't mean you will be relaxed and comfortable on the bike. It just means you'll be more upright than you would on a race fit geometry bike. More upright isn't a guaranty of comfort for everyone. A person that likes to ride with a all out adrenaline rush 90 minutes to 3 or 4 hours and on a unloaded bike, might be more comfortable on a race fit bike than if they were on a relaxed fit bike. Conversely, one that is having to carry a load of camping gear and stuff for a extended trip will probably be riding at a much slower pace and therefore might be more comfortable on that relaxed fit bike.

So my inseam is 89cm at 188cm tall. On the Colnago I have an agressive setup with only 2 spacers.
What I would want is a geometry that will be close to the Roadmachine 56cm frame and maybe even slightly more upright, just not much longer (so that I can slam that stem lol )
But really that 58 in Basso just looks to me like I will be riding a MTB frame. The store doesnt have any in stock for me to ride and has to be ordered in.

so, if you add the BMC Road Machine into the geometry geeks comparison engine :
https://geometrygeeks.bike/compare/c...chine-2024-56/

in the geometry specs which can be compared, the Basso Astra 56 comes closest to the Roadmachine 56...
Ride On
Yuri

Man I so wish I could plot both frames against eachother in the bike insights website. Weird that they dont have that.

Bike Insights will allow you to input the geometry yourself, won't they? You might have to create a account with them to be able to do so. But I think that is free.

Just change the fit on the Colnago. What's going to be better than that ?

Because I love the fit of the Colnago and want another bike. Not a replacement.

Craigslist is a great source for test rides

If your goal is to have a new bike that fits like the old one except the handlebars are 2 inches higher, the Basso 58 sounds perfect.

Why would you want a new bike fits like the old one except the handlebars are 2 inches higher?

Well, it goes to 11 dunnit ?

With age and arthritis I have gone through this and experimented by buying and temporarily using ugly/goofy looking stems/bars until I got what felt good and then knew what I was looking for in the frame. Worked out well.

Aggressive fit vs relaxed fit?

I don't know what that means, and I'm a fitter.

Those terms are thrown out without any context. Sitting straight up isn't "relaxing", and I doubt your current fit is all that "aggressive" compared to a pro's.

It would be good information to share your height and inseam.

A 54cm Colnago is equivalent to 58cm / XL on most other brands if I remember correctly. therefore, 56cm may be too small.

I totally understand that you mean by ''a 58cm would feel like a mountain bike''. Components size increases when going from 56cm to 58cm (wider bars, longer stem, longer crankarms). I'm 6'1'' and need a 58cm frameset (Giant & Specialized), but 54-56cm components. I owned both a 56cm TCR and a 56cm Propel and they felt too small although I was in their recommended range. I didn't like the extra seat post sticking out & spacers between the stem and headset neither.

Aggressive and relaxed are relative terms. And context depend very much on whether talking about you and the bike or comparing two or more bikes to each other.

Right or wrong, it's common for many of us to refer to a bike with a really low stack height that gives a lot of saddle to bar drop as a aggressive fit bike. Conversely, a bike that has a high frame stack where the bars and saddle will be more even will be considered a relaxed fit bike. There is a little more to it and sometimes seat tube angle plays a part too.

The relaxed part is not talking about your comfort. It's just means the geometry of the bike from a design standpoint is relaxed. Many people seem to confuse that relaxed term as meaning their comfort. But actually it doesn't. Depending on what type cycling you do, you could be more comfortable on a aggressive fit bike, also known as race fit, than you would be a relaxed fit bike. And for other types of cycling, a bike with a more relaxed geometry will be more comfortable.

But you haven't expressed anything that tells us what type cycling you do. If your longest ride is less than 60 minutes, then anything might fit you comfortably. Comfort changes with the demands of your type cycling and the time of your rides.

You're really not making any sense. "Relaxed geometry" is geometry. "Relaxed fit" is fit, and that can happen regardless of the bike's geometry. If "relaxed fit" isn't about being more comfortable, I can't imagine what else it would be. "Fit" has nothing to do with the way the bike rides.

He explained it well. Relaxed fit would be more upright, aggressive fit more drop to the bar. I’ve heard and read these descriptions many times and it’s easy to understand.

I am in the exact same boat. I went from a ML Defy to the Colnago. The Colnago fits more like 57cm size, a bit smaller than a Large TCR. On the Defy I was just like you, the seat post up to the max and 130mm stem and still felt a bit cramped. This colnago just fits me like a glove, but the itch for N+1 remains. But I also dont want to get a new bike and spend another few 100$ replacing cranks, stem, bar etc.
Honestly, I companies would start to allow buyer to custom the contact points. Its not much work to throw in cranks and bar/stem of choosing.

Didn't I say that?
Sure, it's relative. I said that too. And it's important to know what it is relative to when using it.
I suppose you must be using that relative to how a person is set up to fit a particular bike. But when talking broadly about two different bikes a person is looking at, I can say that a Specialized Roubaix will give a more relaxed fit than a Specialized Tarmac. However on either I can be fit either aggressively to give better performance or relaxed to give more comfort. But the aggressive position on a Roubaix is will never be as aggressive a position as can be had on a Tarmac. And vise-versa.
I don't think I said it did. The geometry of a bike can suggest whether that bike will lend itself better for touring and loaded up with stuff you need to take along. Or whether it's more for one days fast riding unloaded. But don't take that to mean they can only do that one thing.