Confused about the stack/reach ratio
10-30-18, 03:01 PM
#1
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Confused about the stack/reach ratio
So I have started looking at the stack/reach ratio and look at frames that are more comfortable as I am not as flexible as I once was. I got rid of my SS EVO last year and got a Slate. When I test rode the Slate I was definitely more upright than my EVO so I bought it and now I started to look at the numbers and something is not adding up:
All numbers in CM
SS EVO - Size 56
Stack 56.7
Reach 39.3
Ratio 1.44
Slate - Size XL
Stack 58.2
Reach 41.2
Ratio 1.41
So based on this the Slate would have me in a more aggressive position but that is clearly not the case.
Now another bike I am thinking about getting the new Nukeproof Digger Pro
Digger Pro - Size L
Stack 58.127
Reach 40.33
Ratio 1.44
This is a gravel bike that can take some massive tires, so there's no way it's as aggressive as a race road bike.
Plus the ratio on the Medium size is even crazier at 1.39.
All numbers in CM
SS EVO - Size 56
Stack 56.7
Reach 39.3
Ratio 1.44
Slate - Size XL
Stack 58.2
Reach 41.2
Ratio 1.41
So based on this the Slate would have me in a more aggressive position but that is clearly not the case.
Now another bike I am thinking about getting the new Nukeproof Digger Pro
Digger Pro - Size L
Stack 58.127
Reach 40.33
Ratio 1.44
This is a gravel bike that can take some massive tires, so there's no way it's as aggressive as a race road bike.
Plus the ratio on the Medium size is even crazier at 1.39.
10-30-18, 03:14 PM
#2
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Depends on how the bikes are actually set up. Stack and reach doesn't tell you how high your stem is above the headset, what stem is being used and which way it's flipped, what handlebars are being used and what angle they're at, what brake levers are being used and where they're positioned on the bars, what your saddle height and fore-aft is, etc.
10-30-18, 03:28 PM
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Depends on how the bikes are actually set up. Stack and reach doesn't tell you how high your stem is above the headset, what stem is being used and which way it's flipped, what handlebars are being used and what angle they're at, what brake levers are being used and where they're positioned on the bars, what your saddle height and fore-aft is, etc.
10-30-18, 03:34 PM
#4
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All things equal, the higher the stack the more upright riding position the bike can accommodate. The reach has a lot to do with how stretched out on the bike you can expect to be if you take the saddle position is fairly fixed with knees over the pedal spindle at 3 o[clock position and leg mostly extended when the pedal is at 6 o'clock (it oftentimes has a lot to do with things that cannot be changed, e.g., a combination of the length of the top bar and the angle of the headtube).
10-30-18, 03:50 PM
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why did you buy an xl slate? a large would have had a similar reach figure to your SS Evo. Stack isn't really that helpful of a measure unless you are trying to slam the stem or need something with a huge stack and can't pile on the spacers. The effective stack and possibly the effective reach on the slate could have given you a different ratio depending on the stem length etc. Assuming seat setback is the a good way to compare would be nose of saddle to hoods.
10-30-18, 03:53 PM
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All things equal, the higher the stack the more upright riding position the bike can accommodate. The reach has a lot to do with how stretched out on the bike you can expect to be if you take the saddle position is fairly fixed with knees over the pedal spindle at 3 o[clock position and leg mostly extended when the pedal is at 6 o'clock (it oftentimes has a lot to do with things that cannot be changed, e.g., a combination of the length of the top bar and the angle of the headtube).
There is a solution though which is not exactly cheap but actually fixes two annoyances. Project321 makes an assembly that replaces the entire 1.5 inch steerer tube with a 1-1/8 one and because it's much taller you can increase the stack by up to 2 inches. Adding 1 inch of stack to the XL puts the numbers where they should be for the ratio to make sense. Plus then I wouldn't be stuck with the expensive 1.5 inch cannondale stems anymore.
10-30-18, 03:55 PM
#7
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(Then there's the matter of saddle position and cranks...)
Maybe there is a difference of 1cm of extra stack on steerer tube because of the spacers but would that make a huge of a difference?
10-30-18, 03:57 PM
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why did you buy an xl slate? a large would have had a similar reach figure to your SS Evo. Stack isn't really that helpful of a measure unless you are trying to slam the stem or need something with a huge stack and can't pile on the spacers. The effective stack and possibly the effective reach on the slate could have given you a different ratio depending on the stem length etc. Assuming seat setback is the a good way to compare would be nose of saddle to hoods.
10-30-18, 03:59 PM
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But you just said yourself that the headtube is the same length on the large and xl, so a shorter toptube(ie reach) would make you more upright assuming they were set up the same
10-30-18, 04:07 PM
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There are still a whole lot of unknowns in this description. Are the stems the same length? Are the handlebars the same shape? If yes, do you have the cockpit components positioned identically on the bars?
(Then there's the matter of saddle position and cranks...)
In the terms you're concerning yourself over, yes. It would effectively cancel out the difference in stack:reach ratio by itself.
(Then there's the matter of saddle position and cranks...)
In the terms you're concerning yourself over, yes. It would effectively cancel out the difference in stack:reach ratio by itself.
10-30-18, 04:12 PM
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thats not how stack and reach work, they are measured from the BB, the seat distance from the BB should be the same. If the bars were lower on the L then the bikes weren't set up with the same effective stack either with less spacers or different stem
10-30-18, 04:26 PM
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Don't pro's do this all the time? They use a smaller frame so their saddle to handlebar height is taller so they can get more aero?
Last edited by gus6464; 10-30-18 at 04:29 PM.
10-30-18, 04:30 PM
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Don't know what to tell you but the steerer tube on the L and the XL is the same part so spacers are the same. As far as the front end goes (spacers, stem, bars) they are the exact same. The main thing I noticed immediately was that the saddle to handlebar height was bigger on the L.
10-30-18, 04:31 PM
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They do this because the stack(headtube length) is generally lower on smaller frames, but that isn't true for the slate so the saddle to bar drop would be the same
10-30-18, 08:52 PM
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stack and reach aren't affected by the seat tube at all and the head tube angle doesn't really play either. They are the x and y coordinates of the top of the head tube with the bb as the zero of the coordinate system. It's really more of a lower limit on sizing. A taller/longer person should be able to make things work.
I don't understand why you would look at ratios.
I don't understand why you would look at ratios.
10-31-18, 04:21 AM
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I agree with Unterhausen on the ratio thing. As another person who builds frames, I don't even know what the ratio is supposed to tell you. Stack and Reach numbers, as presented by the manufacturers, reference the frame only and are only a means to compare one frame to another.
The stack and reach of the handlebars is a completely different thing, though it could be related if you use the same bars, spacers and stem on each bike.
The stack and reach of the handlebars is a completely different thing, though it could be related if you use the same bars, spacers and stem on each bike.
10-31-18, 06:52 AM
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When setting different bikes for myself, I use "handlebar" stack and reach and "seat" stack and reach. Take a bike that is comfortable to you. Push it up to a wall so the front wheel is touching the wall and the bike is level on a hard floor. Then measure from the wall to the BB and from the wall to the center of the handlebars next to the stem. Subtract the second number from the first and you have a number to replicate on another bike. Do the same thing from floor to bb and floor to handlebars.
Then do do the same thing to the nose of the seat. Once everything is set up exactly the same on another bike, you won't be able to tell a difference in fit. Getting everything dialed in may require adding spacers (don't let the shop cut the steerer until you are sure), changing stems, or seat posts.
Don't worry about the ratio between them. Both numbers have to right for you. Measuring stack and reach at the bars and the seat puts all of your contact points in the right place relative to one another.
Then do do the same thing to the nose of the seat. Once everything is set up exactly the same on another bike, you won't be able to tell a difference in fit. Getting everything dialed in may require adding spacers (don't let the shop cut the steerer until you are sure), changing stems, or seat posts.
Don't worry about the ratio between them. Both numbers have to right for you. Measuring stack and reach at the bars and the seat puts all of your contact points in the right place relative to one another.
10-31-18, 07:23 AM
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The ~1cm difference in frame stack and reach you are describing can easily be overshadowed by differences in cockpit.
Are the stems the same length? Are the two bars the same shape and are the levers the same and positioned exactly the same? these can both effect your “effective” stack and reach (from the bb to where you grip the bars)
Also, while it does not effect stack and reach, saddle position will effect how stretched out you are. Are you sure the saddles are in identical position (including fore-aft) relative to the bb and bars?
Are the stems the same length? Are the two bars the same shape and are the levers the same and positioned exactly the same? these can both effect your “effective” stack and reach (from the bb to where you grip the bars)
Also, while it does not effect stack and reach, saddle position will effect how stretched out you are. Are you sure the saddles are in identical position (including fore-aft) relative to the bb and bars?
Last edited by Kapusta; 10-31-18 at 03:28 PM.
10-31-18, 07:25 AM
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People have been using "reach" to mean the distance between some (probably nebulous) points on the saddle and the handlebars for as long as I have been riding. And then someone comes along and tries to change the meaning. I don't know if this is why it has been so slow to take off as a sizing metric, but ignoring the saddle position also seems to be a mistake. Granted, using a virtual top tube position is problematic too, but most of us know our size using that. If someone told me the stack and reach of a bike, I would have to go to bikecad to figure out if it fit me.
10-31-18, 07:37 AM
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I’ve only ever used reach to refer to bb to headtube, thus seat tube angle is a relevant value to know. Saddle to bar is a different measurement, I no longer use as the differences in saddle type and position on the saddle preclude repeatable and transferable measurements.
Sorry for any confusion. This graphic is basically my understanding - as seat tube angle changes, the frame reach from bb to head tube can stay the same while real saddle to bar would actually change due to the uncounted “reach” from bb back to saddle clamp.
https://c1.staticflickr.com/7/6033/6...a5a1c0da_b.jpg
I am also not a fan of stack/reach ratio as using one value to determine fit is nonsensical. It’s great to have a high level discussion of frame types over a range of sizes but that’s it.
Sorry for any confusion. This graphic is basically my understanding - as seat tube angle changes, the frame reach from bb to head tube can stay the same while real saddle to bar would actually change due to the uncounted “reach” from bb back to saddle clamp.
https://c1.staticflickr.com/7/6033/6...a5a1c0da_b.jpg
I am also not a fan of stack/reach ratio as using one value to determine fit is nonsensical. It’s great to have a high level discussion of frame types over a range of sizes but that’s it.
10-31-18, 07:45 AM
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What does the ratio between stack and reach have to do with anything? Is that a thing? If so, I didnt realize.
I think a poster in this forum used the same ratio a couple months ago as I vaguely remember being confused about it before now.
Im really confused as to what its supposed to show.
I think a poster in this forum used the same ratio a couple months ago as I vaguely remember being confused about it before now.
Im really confused as to what its supposed to show.
10-31-18, 09:13 AM
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I’ve only ever used reach to refer to bb to headtube, thus seat tube angle is a relevant value to know. Saddle to bar is a different measurement, I no longer use as the differences in saddle type and position on the saddle preclude repeatable and transferable measurements.
Sorry for any confusion. This graphic is basically my understanding - as seat tube angle changes, the frame reach from bb to head tube can stay the same while real saddle to bar would actually change due to the uncounted “reach” from bb back to saddle clamp.
https://c1.staticflickr.com/7/6033/6...a5a1c0da_b.jpg
Sorry for any confusion. This graphic is basically my understanding - as seat tube angle changes, the frame reach from bb to head tube can stay the same while real saddle to bar would actually change due to the uncounted “reach” from bb back to saddle clamp.
https://c1.staticflickr.com/7/6033/6...a5a1c0da_b.jpg
10-31-18, 09:22 AM
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Stack/reach ratio is kinda helpful when you are trying to get a significantly different fit, ie race vs endurance geometry but it's more useful to look at the actual numbers if you have a certain reach you are aiming for and comparing stack between different frames