There maybe value in having a fitting
before you obtain the new bike; to help you choose the correct size.
The chances are a "pro fitting" will be with someone who has access to fitting jig, many of which work on handle bar X Y, the 462 and 580mm below on a BikeCAD drawing I have made based on the Derosa data you have listed. Although the manufacturer does not list handle bar X Y the fitter should be able guesstimate, from the bike image they can roughly see the upper head stack height, spacer height, stem length and angle, plus handlebar reach and drop (although the latter will be more difficult to visually gauge); all of which will allow them to set their jig so you can compare the bike fit to your current bike.
Referencing your current bike it's advisable to take that to the fitting with you, normally measuring saddle height and set back (730 and 57mm below) then saddle tip to shifter and bar height (684 and 847 below) which is far easier to measure on a current bike than the handlebar and saddle X/Y coordinates. By the same token the fitter will be able to cross reference these same easier to measure set of dimensions across to their jig, taking into consideration saddle length and bar reach-drop differences between your bike and what they may have fitted to their jig; although they will normally have a variety of both they may not have any with the exact same dimensions.
View attachment 403374
Referring to your Kuota Kharma, as was the norm' 8 years ago stack and reach was referenced far less than it is now. They also do not list fork length, but using the same components, forks included as the Derosa which in fairness may not be drastically different, for what it's worth I have used as much of the data as they have listed on another BikeCAD drawing for you.
Although the Kuota top tube is longer, the bike fit reach is actually shorter due to the the extra stack height, as you can see using the same cockpit set up as the Derosa the Kuota bar height is significantly higher. Note I have only used 15mm worth of headset spacers, most will by default initially be supplied with something more like 30mm, especially in these two examples, from the illustrations I found of both on 'Google Images' each appears to have quite a
shallow upper head set stack; many bikes use
far higher in a bid to achieve stealthy additional height.
View attachment 403375
In both cases relating to my drawings I do not know headset stack, stem length, angle and even depth, bar reach-drop and shifter positioning. For both bikes I've had to fill in the gaps where the data is not listed; the Derosa doesn't list fork rake for example so I have had to use the 'front center' at 580mm which alludes to what the fork rake needs to be. I also have to assume that the provided data is correct; you'll be amazed how often I have questioned a manufacturers listed data and been provided with an update; treat both as a starting point only.
Regarding component sizing that directly influences the bike fit, as you'd expect some manufacturers list more than others. Trek for example on their dealer 'b2b' website list for each bike the bar width reach-drop, stem angle-length, plus the headset and spacer stack height they've used for each individual size bike; all of which are of value to the 'fitter' when helping the customer choose a size of a potential new bike as they will have to guesstimate far less. Trek are of course a huge company, I doubt Derosa would provide as much information, plus, they are Italian after all
.
The fitter may not, infact probably not, have all the data they need, like the exact dimensions of bar reach and drop for example, but they should be able to get the sizing fit close enough to advise what should be a viable proposition interms of what size bike you need to choose; then fit you to that choice on collection with the correct component sizes. Not only with headset spacers, stem length and shifter position but bar reach, width and depth, Bontrager alone include
75,
81,
93,
100 mm reach bars and that's
just some of them, other bar manufacturers will also have a variety of sizes to help achieve the desired bike fit.
Well worth making sure the bike you buy is the right size, I fit so many on recently bought bikes that after the fit the conclusion was given the chance they would have chosen a different size.
