Iride01 

Yes.
If you don't have any experience with bikes that you know fit you well and you liked the position they gave you, then buying any bike you haven't first tried out will be a chance.

IMO, in some models of bike, their geometry in any size might not be comfortable for you. And in other models of bike several different sizes might fit you well.

eduskator

At 6'1'' (185cm), 56cm is my ideal ''aggressive'' size while 58cm is the ''recommended'' one.

At 5'6'', I'd say you are between a small (52cm) and a medium (54cm). Scott will probably recommend a medium when using their sizing tool? Remember that a proper bike fit AND how you feel on the bike is what's important here.

Also, be careful of LBSs that wants to sell the bikes that are on their floor at all cost. If you got a neutral / objective opinion by a third party, that's great.

delbiker1 

Neither is right , or wrong. A fitters suggestions are just that. They are opinions based on, I hope, experience and knowledge they have gained, and stats/measurements they have come up with. I have never been to one, never will be. IMO, no one can fit a bike to me better than I can. I would really like to see some stats on percentage of fit users that abandoned, or disregarded the changes suggested by the fitter. Nothing against the fitters or those that use them.

DaveSSS 

The larger frame would force a more upright fit for a beginner, but wouldn't be ideal for a more accomplished rider. If you're overweight and can't bend over very far, maybe the 54 is what you need now, but a fit rider would do better on the 52. You can always start with the full stack of spacers that comes with a new bike and remove some of them later. The 52 needs a 10mm longer stem than the 54, with the reach corrected to the same stack on both. I'd believe the person who recognized the 54 as being too large.

​​​​​ I made a change from an 8cm saddle to bar drop to 10cm when I had been riding for 25 years. That much saddle to bar drop is not unusual. All it took was a change from a -6 degree stem to a -17. I've never felt the need to go back to less. FWIW, I'm a retired mechanical engineer. I weigh 60-62kg. I'm still riding over 9,000km per year in Northern Colorado. I'm turning 70 this year.

eduskator

I agree with you. Most of us can ride 2 sizes. One being more aggressive, the other one being the recommended or normal size.

DaveSSS 

Here's another item that's not been mentioned - saddle setback. An initial fit might be done using the traditional KOP method, but that doesn't mean it's ideal. I tend to place my saddle up to 20mm further back. When I do that, it helps with climbing and takes weight off my hands, which is important when using a 10cm saddle to bar drop. It also increases the total reach to the bars, so suddenly my supposedly too small frame has as much reach as a bike that's two sizes larger, with the saddle set by KOP.

The frame size that I ride might seem too small at first glance, but isn't, once you know all of the facts. Even with my short torso, I use a 110mm stem and have no knee to elbow overlap when pedaling in the drops. My current frames have the smallest stack height I've ever used, at 505mm, but I've got 20mm of headset top cover and spacer, plus a -7 stem, so it comes out with the desired saddle to bar drop. This was all planned carefully before ordering Yoeleo frames with integrated bar/stem. You can't change the stem angle. There were no surprises.

DaveSSS 

I can usually pick between two sizes and still get the same fit too. Usually it only takes a little change to spacers or stem angle and one size difference in stem length. With integrated bar/stems the stem angle is fixed, so spacers have to be used. I see a lot of these bikes with a big stack of spacers, but the pics are usually of a new bike that hasn't had any fit tuning done.

PeteHski

I usually find myself caught right between 2 sizes in any brand of road bike. I could easily make both sizes fit, so it comes down to whether or not I would prefer the slightly longer wheelbase and higher stack of the larger frame. The general rule is to size up for comfort and stability or size down for a more aggressive fit and more nimble handling. A lot of personal preference in the end. No right or wrong answer unless you are so far out that you can't achieve the appropriate stack and reach or run out of seatpost adjustment.

ClydeClydeson

Comments above that most people fit two sizes is not entirely correct, in my opinion. Most people can fit THREE sizes - an 'ideal' size, one size larger and one size smaller. The reason for this is that, if you accept that there exists the 'ideal' size, the difference in any dimension between the 'ideal size' and the next size up or down is small (generally ~2cm or less) so can be compensated for with adjustments (seat height, position, or angle) or parts swaps (stems, bars, crank arms).

My experience has been, generally speaking, if you need to swap parts to some non-standard parts, like extra long or extra short stem or seatpost, to get the bike to fit, then the frame is the wrong size. Most people can find a size in most bikes that the can fit one size up or one size down without extra long or short parts needed to make it fit.

DaveSSS 

Three size cross compatibility for me, depends on the ability to use two stem angles, like -6 and -17 and then it's a maybe. If the bike uses an integrated stem/bar, then it's likely only two, unless I reduce the saddle to bar drop on the largest size.

I have one frame that uses a 30mm headset top cover and no spacers with a -17 stem. I could get the same fit with a 15mm top cover and a -6 stem, but then the steerer would be cut to the minimum, which reduces resale potential. I set up two Colnago C-RS frames slammed with -17 stems. I still got the frames sold a couple of years later without too much trouble.

Surpin

I reported above that the first bike fitter recommends a 100mm stem and 15mm spacers for the size 54. Are these normal or unusual (extra long or extra short) adjustments?
How would an 'ideal size' bike compare to a 'size up' bike that can be adjusted to fit? Would they be equivalent or even just provide the same ride experience?
Or should I always prefer the 'ideal size' bike?

I ask this because exactly today I asked to the first bike fitter for an evaluation of a Cannondale Synapse Carbon Disc 105 2020, in size 51 (geometries: [https]://99spokes.com/en-EU/bikes/cannondale/2020/synapse-carbon-disc-105
remove the [] brackets around https), and he said it would be more balanced (I suppose my 'ideal size'?), recommending a 110mm stem and 35mm spacers on it.

Between the Scott and the Cannondale, I prefer the former for look, price, and components, but I don't how much the adjusted 'size up' vs 'ideal size' matter should come into play for my choice between the two.

Thank you all for any further feedback in advance!

ClydeClydeson

Surpin
100mm stem with 15mm spacers is 100% normal, no need for concern. That's probably close to how 99% of bikes are set up at the factory. 110mm stem and 25mm of spacers are also totally normal.

Your body only 'sees' three points of contact - the saddle, the pedals and the bars. If you can get these three points in relation to each other such that you can ride comfortably without maxing out any adjustments or using oddball parts then I don't think there is an advantage to use a bit shorter stem or a bit longer stem, as long as the end result is a well-fitted bike. If you needed to use an extra long like 160mm stem, there could be some concern that this will put your weight a bit further forward than the manufacturer intended and the handling of the bike might not be ideal. And there might be other considerations depending on your intended use of the bike - for instance, a mountain bike used for very rough terrain often has a smaller frame to allow the rider more room to move around to balance and position the bike on the trail and overcome obstacles. But this is less important with road bikes as you are often sitting relatively still and cranking on the pedals, and the shape of the frame connecting the saddle, pedals and bars is less important.

SoSmellyAir

I recently bought a Stigmata CC and in the process came across this explanation of why I always seem to prefer the smaller of the two sizes:Stigmata - Gravel Bike | Santa Cruz Bicycles

It is not because I want to be in a race position; it is because, while I am not super model material, I have long legs for my height.

Kontact

If you have any misgivings at all about it being too big, just get the 52. You'll need roughly 35mm of spacers and a 110mm stem to get the exact same position. And if you start to ride more aggressively, you have more spacers to remove to get lower.

But 15 is plenty to remove as well. So buy whichever with confidence!

Kontact

Folks with different proportions are living in a golden era. It used to be that level top tubes meant that bar height was dictated by frame size. Now a particular top tube length can be found with a wide variety of head tube lengths, so creating a bike with a short top tube and high saddle and bars is no issue (Cervelo). Nor is it hard for someone with shorter legs to get adequate standover and a reasonably long stretch to the bars by going with a bike that has a low front end for its size (Cannondale).

PeteHski

That's kind of saying the same thing framed in a different context. If you specifically wanted a race position you might well size down again from your preferred nominal size.

Ultimately there are many valid reasons why someone might choose to size up or down. With most road bikes I generally find myself right on the cusp between M and L in stock sizes. I have always gone with the larger size for several reasons, including relatively long arms, naturally limited back flexibility and my overall focus on endurance riding.

eduskator

+1. And unfortunately, regardless of the amount of experts consulted and advice provided when you first start cycling, I strongly believe that you can't ''get it right the first time''. The more you ride, the better you become but the ''pickier'' you become as well in terms of what specific dimensions you like. It took me 3 seasons with 2 different frame sizes and 2 professional fit to figure out which specs (frame size, stem length, bar width, saddle height, saddle to bar drop) my body liked, and I still make small modifications from time to time today depending on how flexible (or not) my body gets.

himespau 

If you're not sure what size you need and are new to cycling, try going used if at all possible. You get more bang for the buck, it's easier to recoup most of that if it doesn't work for you, and it doesn't hurt so much when you learn what you really want/need and "have" to buy something new.

PeteHski

There are actually two aspects to this conundrum:-

1. The actual bike fit i.e. the positional relationship between the contact points (saddle, bars and pedals).
2. Bike handling - which is related to the specific bike model and size geometry i.e. head angle, trail, wheelbase, chain stay length, BB height, stiffness etc

Unfortunately, the stationary fitting bike doesn't tell you anything about the second aspect. So you can have multiple bikes that fit you identically, but handle quite differently out on the road. One might have a much longer wheelbase or a steeper head angle or different stiffness/compliance characteristics. But the thing is, you are a beginner so you don't know what you would prefer at this point.

One thing you could say is that a larger frame of the same bike model will tend to be a little more stable handling as it will have a longer wheelbase. A bike model with a slacker head angle will also tend to be more stable. These are things you could discuss with your fitter when comparing the Scott vs Cannondale. Both these bikes are "endurance" road bikes, so likely to be pretty similar overall. It's anyone's guess which one you would actually prefer! If the fit is good (i.e. point 1 above) I suspect you would be fine on both these bikes (assuming an endurance road bike is the best type of bike for your riding).

Another extreme way of putting this is to imagine 2 different cars with exactly the same driving position relative to the steering wheel and pedals. But one is very low to the ground with a short wheelbase and the other much higher and longer. Despite having an identical fit, they will handle completely differently. In your case it will be more subtle as you are comparing two quite similar bike models. It's like saying do you prefer a BMW 5 series to an Audi A6?

Iride01 

Scott shows in their geometry for the M/54 size bike that it has a stem length of 103 mm. So pretty much on par with the fitters recommendation. The bike has what looks like 2 5mm and one 2.5 mm of spacers under the stem in the picture for 12.5mm of height. So very close already to what the fitter is saying. And unless it's changed for Scotts, the bike will probably come with the stem cut a little longer to allow for more spacers. But check with the people that are receiving the bike for you and putting it together.

https://www.scott-sports.com/us/en/p...icle=286425054

If you aren't really certain what bike you need and in what size, do you really want to pay this much for a bike? Get some experience on less expensive bikes if you don't have much. Unless this is inexpensive for your situation.

bblair

Not to mention that many bikes have a slopping top tube, so there is lots of room to slide your seat up or down.

I would think that reach, meaning top tube angle, stem length, angles, etc. would be at least as important and down tube length.

FWIW, I am about same height and my Trek is a 52cm, I think. My newer Lynskey is listed as a medium, or small/medium....I think. Best to ride the darn thing.

Iride01 

Also, reading back I never saw that you said what your preferences are for how you sit. The Scott Adict while not as aggressive a fit as my Tarmac is certainly not the most relaxed fit bike out there either. So if you aren't use to riding with your head out front you might resort to making the bike ugly by putting weirdly angled stems and steerer tube extenders on it. And that might be difficult as all the wires and hose are routed through the stem on that bike which will further reduce your choices if there really are any for changing up the stem on the Addict.

If you are picking the bikes by their aesthetics when you look at them, then you might well get a bike isn't really the bike for the way you intend to ride. So decide if you really want the sports car. You might be better off with a luxury sedan.

Surpin

The bike is the model from 2020 and is second-hand, they asked 1400 pounds for it! I found it a very good deal.

But, just about anybody I am hearing from (I got that second biomechanist opinion and many many opinions online) says that the size 54 would be too big and clunky for me. Even if I was precise to indicate my very long legs and long arms. Multiple times, I heard long legs would even aggraviate the matter.
Only the first biomechanist confirmed two times (after the visit and when I called him back) that I could ride the bike without problems.

Now, I resigned myself to give up on the said 54 sized Scott, even though it was a convenient purchase for me and I was truly eager to start riding. I really, really hope I didn't let myself fall into an internet rabbit hole and that the bike fitter was truly superficial about the matter. If the Scott would have instead worked out without major problems for me, it would be a pity!

Now, though, the real problem is I don't know which bike, brand or size to consider, I am very confused! I am looking forward to ride a bike and I feel in a stalemate position!

I looked at a Cannondale Synapse Carbon Disc 105 2020, size 51, and, again, the first biomechanist said it would be "very well balanced" but when I referred my ride set up to the bike retailer (especially, saddle height) they told me it would have a drastic saddle-handlebar drop and they would advise against it. They also sent me a picture of the bike with the given saddle height (of 73.5 cm) to show me the issue. I am totally unexperienced but I let them convince me it was too extreme.
Although, the geometries of the said Cannondale seemed quite right to me after a conscientious read, just the saddle tube lenght seemed a bit short, if you check them out.
(geometries of the Cannondale: [https]://99spokes.com/en-EU/bikes/cannondale/2020/synapse-carbon-disc-105
remove the brackets around https)

Basically, I'd take any bike that would be good for me right now, but I don't know a safe way to determine it. After these two episodes, I lost my faith in the first bike fitter so I don't know who to ask to for a reliable opinion.

Surpin

I'd love the luxury sedan! But how to find in a reliable way?

Iride01 

If you look in the geometry spec's for the bikes, then pay attention to the stack and reach. Stack is the frame stack and is measure as the vertical distance from the BB to the top of the head tube. Reach is the horizontal distance from the BB to the top of the head tube center. Other things like seat post angle and seat post setback, stem length and handlebar reach can make frame reach figures mislead you at times.

As a general quick reference frame reach and stack get you to quickly seeing bikes you should or shouldn't put on your radar. Things like stem length you'll find are usually the same for similar sized new bikes. Used bikes you should double check as I've bought some used bikes where the owner put a really long stem on them. If you are looking at them in person, just put them side by side and then look at them from one side and see which has the higher head tube and how far the hoods on the handle bars are to each bike.

Here are some of the geometry specs of the bikes that have been talked about in this thread along with the Specialized Roubaix that is one of the most relaxed fit road bikes. Others exist, but that's for others to recommend or you to find if relaxed fit is what you decide you want. I left my Tarmac in there just to show that you can find bikes with much lower stack height if you wish to have a race fit or aggressive fit.

https://geometrygeeks.bike/compare/s...lr-2021-54-cm/

push the radio button underneath the Scott Addict and it will show the differences in the other bikes relative to the Addict.