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Stack To Reach Ratio how good is it

Fitting Your Bike Are you confused about how you should fit a bike to your particular body dimensions? Have you been reading, found the terms Merxx or French Fit, and don’t know what you need? Every style of riding is different- in how you fit the bike to you, and the sizing of the bike itself. It’s more than just measuring your height, reach and inseam. With the help of Bike Fitting, you’ll be able to find the right fit for your frame size, style of riding, and your particular dimensions. Here ya’ go…..the location for everything fit related.

Stack To Reach Ratio how good is it

Old 08-27-19, 12:16 PM
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Stack To Reach Ratio how good is it

I'm in the process of buying a new bike. For me this process is awful. I am 6' 3" with a long inseam so typically the size bike I need according to sizing charts is a 62 / 63 (when using numbers) and a XL (when using letters). The difficulty I have is that no LBS stocks a bike this large ever, NONE, NADA that's it. So for me I am essentially buying sight unseen / sat on / test driven all not possible.

I have to look at geometry charts comparing new bikes I"m interested in to my current bike which from a geometry and size perspective has me in the right position (back a little lower than 45 degrees toward the handle bar). My current bike (Kestrel RT 1000) has a Stack to reach ratio of 1.57 and I put a 17 degree 110mm stem on it. The stem effectively increases the S/R however it's hard to say how much. Anyway this setup is just fine for me and I have built a chart of bikes based on head tube length and angle, top tube length etc. along with S/R.

How much can I rely on the S/R when finding a bike? The Trek Domane in my size has a S/R of 1.7 while a Canyon Endurace has a S/R of 1.54. Oddly enough the racy Trek Emonda has a S/R of 1.59 and the Bianchi Infinito is a 1.58. One would think that a correct position (not too low / aggressive) would be had on any bike that has a S/R greater than 1.57 (my current bike). Is this the S/R figure worth looking at or does one need to look at all the measurements in concert? The bikes I have charted are as follows, with corresponding Stack To Reach Ratio in my size:
Canyon Endurace: 1.54
Ridley Fenix: 1.55
Giant Defy: 1.57
Bianchi Infinito: 1.58
Emonda; 1.59
Domane 1.7
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Old 08-29-19, 11:07 AM
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I would say that S/R ratio is a pretty good metric. But I think you should mainly focus on reach, since the stack can mostly be altered using spacers - you don't have to slam the stem. See if you can find a bike with a very similar reach, and can modify the stack to meet the effective stack measurement on your old bike.

Most of the geometry figures on a bike determine handling and such. You don't need to worry about standover since you have long legs. You may need to worry about seat tube angle, though. Long legs means a lot of seatpost extension. You could end up with a saddle that is too far back this way. Similarly, look at the seatpost setback on the new bike. If the seatpost is very setback, and the seat tube angle is slacker, you're going to have a harder time getting the saddle as forward as you like.

Also have a look at crank length since the optimal fit around a shorter crank will increase reach and reduce stack (decrease S/R ratio). It will also move your center of mass higher and further back.

Stem length is obvious, but handlebars that are wider or narrower than "just right" will significantly increase your reach. I went from 42 to 38cm bars and I would say that felt like a 10- 15mm increase in stem length.

EDIT: unfortunately, there is a lot that goes into how a bike *rides* that cannot be determined from S/R. Two frames could have identical stack, reach and components but ride differently. Generally, though, shorter wheelbase, steeper head tube angle, higher BB (less drop) and less trail means more "twitchy".

Last edited by smashndash; 08-29-19 at 11:18 AM.
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