# stack/reach difference between 54 and 56 caad9



## emt8q5 (Jul 20, 2009)

hey folks,

I'm currently riding a 56cm Caad9 but have always felt too stretched out. I'm thinking about buying a 54cm frame off ebay and swapping out the components. Looking at the measurements however on Cannondale's website, It seems to me that the difference is only 1.6cm in reach between teh 54 and the 56. Is this accurate, or are there other factors in the geometry that make the measurement greater?

Am I just not a good fit on the cannondale geometry? I'm currently running an 80mm stem flipped down on my 56 and really feel that I would be most comfortable about 10-20mm shorter. For handling purposes, I'd like to run a 90-100mm stem on my bike, but according to the geometry, a 90mm stem on a 54 would be nearly identical to my current setup. 

What is the relation between stack and reach? If I decrease stack, does that increase reach? or vice-versa? I'm pretty flexible, so a large saddle/bar drop isn't a huge deal to me, but only if I can decrease my reach. 

Thank you!


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## aengbretson (Sep 17, 2009)

emt8q5 said:


> hey folks,
> 
> I'm currently riding a 56cm Caad9 but have always felt too stretched out. I'm thinking about buying a 54cm frame off ebay and swapping out the components. Looking at the measurements however on Cannondale's website, It seems to me that the difference is only 1.6cm in reach between teh 54 and the 56. Is this accurate, or are there other factors in the geometry that make the measurement greater?


There's a reason manufacturers have started to do stack and reach measurements. They do a reasonably good job of representing how a bike fits using fewer variables (think TT length, HT length, ST length, ST angle, HT angle, etc.)



emt8q5 said:


> Am I just not a good fit on the cannondale geometry? I'm currently running an 80mm stem flipped down on my 56 and really feel that I would be most comfortable about 10-20mm shorter. For handling purposes, I'd like to run a 90-100mm stem on my bike, but according to the geometry, a 90mm stem on a 54 would be nearly identical to my current setup.


The caad9 has a relatively aggressive geometry, i.e. short HT and longer TT. Maybe you could size down, as you said you're rather flexible. You could also look into changing your bars to something with less reach to keep your stem size constant.



emt8q5 said:


> What is the relation between stack and reach? If I decrease stack, does that increase reach? or vice-versa? I'm pretty flexible, so a large saddle/bar drop isn't a huge deal to me, but only if I can decrease my reach.


Not quite sure how to answer this one, but here it goes: for a given size of frame, lowering the stem will increase the reach slightly. This can be done using the formula

```
Δr = Δh*cosθ
```
 where Δr is the change in reach, Δh is how far you raised or lowered your stem (lowering is positive, raising is negative), and θ is your head tube angle. Stack and reach measurements quoted on geometry charts show the vertical and horizontal measurements from the center of the BB to the top of the head tube (so it doesn't take into account the headset cap, which adds a few mm to stack and takes a few away from reach).


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## woodys737 (Dec 31, 2005)

emt8q5 said:


> What is the relation between stack and reach? If I decrease stack, does that increase reach? or vice-versa? I'm pretty flexible, so a large saddle/bar drop isn't a huge deal to me, but only if I can decrease my reach. Thank you!


I think THIS should help. Enter the data and it spits out a numeric and visual depiction of different configuations.


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