I had two professional bike fits and the results diverge by a lot.
Hi, I am a beginner without a road bike looking to get the first one. I recently first had a professional bike fit with bike fitter A in order to define my ideal position on the bike and have a guide for choosing the right frame size for me. Although, I wasn't blindly convinced by the recommendations of the bike fitter on bike sizes each time I consulted them, because they seemed to always suggest me a slightly big size for the standard geometries related to my measures.
Assaulted by many doubts, I thought of getting a second opinion booking another bike fit with bike fitter B, moved by the need of having a reassuring further confirmation of those "unusual" recommendations. However, the second bike fit produced very opposing results to the first one.
To start, bike fitter B frame sizes reccommendations were instead in line with the common standards for my proportions, and they actually specified that bike fitter A advices were in their opinion a bit unbalanced for me. For instance, bike fitter A would suggest me a size M, while bike fitter B a size S on the same bike.
Furthermore, though, what alarms me more is that, while body measurements they took about me are essentially the same, the prescribed position on the bike is very different among the two bike fitters.
Measures observed (bike fitter A):
169.7 cm height;
83.2 cm inseam.
Measures observed (bike fitter B):
169.3 cm height;
83.5 cm inseam.
Prescribed position (bike fitter A):
5.4 cm saddle nose setback;
6.4 cm saddle nose-handlebar drop;
73.5 cm saddle height;
143-145 degrees knee extension angle.
Prescribed position (bike fitter B):
3.5 cm saddle nose setback;
7 cm saddle nose-handlebar drop;
71 cm saddle height;
150 degrees knee extension angle.
After reporting my antropometric measures, I'll also include a specific example of their very different views on an ideal frame size for me.
I asked both about a Scott Addict 20 Disc 2020 (
geometries: [https]://99spokes.com/en-EU/bikes/scott/2020/addict-20-disc
remove the brackets around https ).
Bike fitter A told me I'd need a 110 mm stem and 3.5 cm spacers on size S while a 100 mm stem and 1.5 cm spacers on size M. They afterwards told me I could adapt both but the M size would be a little bit more balanced for me.
Bike fitter B told me I'd need a 100 mm stem and 2 cm spacers on size S while a a 80 mm stem on size M. They afterwards told me the correct one for me would be the size S, while the other would be a bit too big.
Among all things, I am the most worried about that difference in saddle height (73.5 cm vs 71 cm) and knee extension angle (143-145 degrees vs 150 degrees) suggested by each of them, I feel a bit lost and cannot determine which would actually be the correct values.
After some thoughts, I decided to go for the S size of the aforementioned Scott Addict 20 Disc 2020 (afraid that the M size would indeed be too long for my height), but I still have to decide which bike fitter I should bring the bike to for the actual set up. Substantially, my choice is between a 110 stem and 100 stem and ESPECIALLY between 73.5 cm saddle height and 71 cm saddle height.
I am undecided because, even though I am following bike fitter B's advice for the choice of the size, bike fitter A's visit was more deep, involved and apparently scientifically-numerically based about body angles on the bike (they accurately considered elbow, feet, pelvis, knee angles through a computer program and database), while bike fitter B's visit was more brief and "essential" (they only considered knee angle) and their opinions and suggestions were based on their instinctive experience on the field. I trusted bike fitter B's instinct on frame size, but should I also entrust them with the full bike set up or instead refer to the more "scientifically precise" bike fitter A?
What do you think on the matter? What would you do in my place?
Thank you all.
Last edited by Surpin; 01-22-23 at 12:52 PM.