Bikefitting misunderstanding...

[bobbybrown78]

Hello everybody!
I have a canondale supersix evo 54 that probably is a bit small for me.
I am 1.84cm 89mm in seam measured with bike shoes on.
I did a bikefitting and i post here the measurements.
In the shimano bikefitting program you can choose Racing/sport/confort.
We chose sport.

Based on these mesurements the stem of my current bike was 4cm lower!!!

I tried to understand which measurements are the most important for choosing a bike, and i concluded the most important is the stack followed by reach. Based on my bikefitting program i neen a 590mm stack and a 379mm reach.
Then i checked the geometry of many different manufactures and noticed a controversy.
In most bikes i am about 56/58 or L/XL based on the stack and 50 or S based on the reach....
Anybody can explain the reason of this controversy?

 

[bobbybrown78]

Anybody else has this large deviation on bike fitting? reach 38cm and stack 59cm?

Do you think it could be miscalculated?

 

[jessand]

Don't know if I'd trust that bike fit but Specialized Roubaix reach=376 stack=585, both within 5mm of your figures so small adjustment taken care of with stem. There's far more to bike fit than stack and reach which you need to understand to get the fit right.
Btw, unless you're very flexible a 54 is small for your size. Rule of thumb would be 56 or 58 depending on the type of riding you do, physical make up - small/large torso/legs, we're all different!

 

[cyberknight]

Just a thought,when I looked at a Cannondale a 51 had a 54 TT and the 54 was more like a 56 could this be related to your issue??

 

[T.M.H.N.E.T]

View: https://youtu.be/9tsuKmFAm0Y

 

[SkipdiverJohn]

Stack height is closely related to leg length. If you've got long legs you need a high saddle. If the saddle is high the bars also need to go high enough to be comfortable.
It's easy to fit a long seatpost in a small frame but it's not so easy to get much increase in bar height.
I have got long legs so I favour big frames, since lugged steel bikes have horizontal top tubes. Reach I can deal with by stem swapping but I can't change the length of my legs, so the most critical dimension for me is how high the bars will go.

 

[jessand]

The Supersix Evo is a 'race' bike, Canondale's Synapse is their 'sports' bike (now usually called 'endurance').
This explains different geometry as 'sports' bike are more upright for longer rides, 'race' bikes lower for aero sprinting. The other thing is that Canondale suggest a 56cm for your height - which obviously comes with a lower stack. The 56cm Synapse is 59 stack 38.6 reach. Good opportunity to get a new bike!!!

 

[bobbybrown78]

I understand your point ... but when i go cycling i really enjoy riding an agressive stiff bike. I enjoy the acceleration and the feeling you get. I had a less racing bike in the past and i can describe riding on it boring.... The disadvantage of a racing bike is that you may get tired from the position in longer rides.
I prefer to risk and get another bike with racing profile and slightly bigger, than get an endurance bike that i won't find interesting to ride. I don't say what i do is right, but this is personal and nobody is perfect

 

[bobbybrown78]

Skipdiver that's exactly my case i have long legs so i need to get a bigger bike beacause when i adjust the heght of my sadle the upper part of my body needs to go down to reach the stem...

I ll try an adjustement in my current bike . I ll change the potence trying to gain those 4cm in height. I am curious to see the result in bike handling....

 

[SkipdiverJohn]

Unfortunately modern road bikes with threadless steerers do not have a very big range of bar height adjustment. You have a "choice" of low or very low bars. The only way you can get a decent increase is to fit alternative stems with a lot of rise angle, which can then look rather odd. That's just one of the many reasons I avoid modern road bikes and stick to the old-fashioned steel variety with quill stems. However I like the comfortable relaxed handling that you might consider boring to ride.

 

[MichaelW2]

Most production bikes are made for riders of average proportion regarding arm, torso and leg dimensions.
If you are outside the norm, a fitting should suggest a bike outside the norm which may be long reach for its height or short reach for its height.
In addition, a non norm ratio of upper leg to lower leg will suggest the fore-aft position of the saddle in a non normal position.

In the olden days, you would accomodate these special requirements through a local custom frame builder.
Modern factory bikes can often be made to fit by selecting approprite style eg conventional or compact style, picking make/model with frame geometry closest to requirement, and fine tuning with selection of bar/stem/seatpost layback/ crank length.

The fit is a different issue to the bike stiffness/handling but they can interact.

If you want a sporty style bike with a high bar then you will have to stop someone cutting the steerer down before the bike or fork reaches you

 

[bobbybrown78]

View:

View: https://youtu.be/9tsuKmFAm0Y

Thanks for the video very well made for understanding the basics on bikefitting, still complicated to totally understand

 

[bobbybrown78]

Unfortunately modern road bikes with threadless steerers do not have a very big range of bar height adjustment. You have a "choice" of low or very low bars. The only way you can get a decent increase is to fit alternative stems with a lot of rise angle, which can then look rather odd. That's just one of the many reasons I avoid modern road bikes and stick to the old-fashioned steel variety with quill stems. However I like the comfortable relaxed handling that you might consider boring to ride.

I ll put this adjustable potence to raise stack...it should be 4cm higher. I am not sure about the result. I ll text pics and impressions after the change.

I think racing bikes with higher stack would be a good idea for bike makers, you can always get more aero position by adjusting your body and elbow angle on a bike with higher stack that keeps all the other characteristics of a racing bike.

 

[T4tomo]

I think racing bikes with higher stack would be a good idea for bike makers, you can always get more aero position by adjusting your body and elbow angle on a bike with higher stack that keeps all the other characteristics of a racing bike.

They do, they are called endurance bikes / sportive bikes etc.. that is the fundamental difference between the two, achieved via a taller headtube.
the "other characteristics of a racing bike" are all there still.

 

[alicat]

I'm not sure what the problem is, @bobbybrown78. Is your bike uncomfortable as it is? Are you looking to buy a new bike and wondering what size to buy?