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Discussion Starter · #1 ·
TLDR: What stack height do you like, and why? Are stacks measured consistently across manufacturers?

I searched this topic and primarily found convo's from 4 years ago. Much has changed in geo since then, so I wanted to get some updated opinions. I found this thread on VitalMTB that's semi-recent, and everyone basically disagrees on the topic whilst also disagreeing on how comparable Motocross was to MTB in this regard...

I have a spreadsheet of bikes I'm interested in with all of the geo measurements. I also have bikes I've ridden (rode?) on the sheet so I can start to formulate what I think I like and don't like, similarities, differences, etc. The state of buying bikes these days has forced this sort of approach. Dealers don't have bikes to sit on, and a few of these bikes aren't even offered around me anyway.

I've spent time obsessing over certain measurements, but typically only when they stand out with all else mostly equal. One such measurement is stack height. Most of the bikes I'm looking at have somewhat comparable stack heights, within 20mm of one another. Close enough that you could use spacers or bars to make them even. However sometimes I come across a bike that has a stack that's WAY different.

One such example is the Esker Japhy, which lists a 614 stack height (size Large). Now, Esker says on their geo chart that their numbers are at 30% sag, so that number is likely a little taller at static height, but still...This also calls into question if all manufacturers measure stack the same way? I emailed Esker on the subject and their response started out like this:

"Take your fork A-C and add the head tube length to get stack height."

That's not at all how stack height has been explained to me before. What I expect stack height to mean is the vertical distance from the bottom bracket plane to the head tube plane (top of HT). Now, if I do some triangle calculations, I come up closer to the 650's with the Marzocchi fork the Japhy build is spec'd with.

So I pressed Esker (reply actually came from Krueger Outdoors?) further and they said, "Just talked to our tech guy who said stack is the distance from the tire tread (assuming he means contact patch?) to the top of the steerer stem cap. I just measured my J1 Large and came up with 44.5 inches."

Again, not accurate from what I have seen. When I do this calc (taking off tire radius and assumed extra steerer length above top of HT) I again come out at a more typical stack compared to other bikes.

So we have a number of items here:
  1. Low/High/Rider specific stack height...implications on handling (first) and comfort (second). TLDR: old guys want high bars, young guys disagree but many want low bars.
  2. Is stack measured consistently across manufacturers?
  3. What the Helsinki is the dang stack height of the Esker Japhy, in terms that are comparable to other models?!?
 

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Answer the TLDR,
My preferred stack for 5'6.5 rider:
road: 520mm, -17 degree stem. I stay in drop 40% of the time. Drop is 125mm lower than bar top.
gravel: 540mm, -6 degree stem. Drop of gravel bike is about half way between top and drop of road bike. And it's top is tall and comfy.
29er MTB: lowest possible given the fork height. It's never low enough. For example, if the bike has 600mm stack then I have to use -25 degree stem, or maybe Syntace Drop Force, or some -30 degree stem. MTB riding position is quite dynamic so I'm not quite precise in measuring it correctly with sag. All I know is, I can't get low enough using flat bar unless I got to around 560mm stack. Which is not seen on 29" wheel MTB with suspension fork.
 

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Discussion Starter · #3 ·
29er MTB: lowest possible given the fork height. It's never low enough...All I know is, I can't get low enough using flat bar unless I got to around 560mm stack. Which is not seen on 29" wheel MTB with suspension fork.
Curious, do you feel this has to do with front wheel handling/traction?
 

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No, just proper ergonomics with RAAD around 56 degree. I have long torso for my height and use quite low saddle height. My low-ish stack height doesn't look impressive anymore when consider as saddle to bar drop. Low saddle, then the bar have to be low too.
See, on road, stack scale with frame size. But on MTB, it's already too tall with smallest sizes. But then become a bit too low on large,XL (which require raiser bar etc.).
I trained from road and only pedal well with my torso lean a bit forward. That make my shoulder socket lowered, and thus if the bar is high, then I have to bend the elbow a lot to keep my torso where I want and my hand on the bar.
 

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Discussion Starter · #5 ·
No, just proper ergonomics with RAAD around 56 degree. I have long torso for my height and use quite low saddle height. My low-ish stack height doesn't look impressive anymore when consider as saddle to bar drop. Low saddle, then the bar have to be low too.
See, on road, stack scale with frame size. But on MTB, it's already too tall with smallest sizes. But then become a bit too low on large,XL (which require raiser bar etc.).
I trained from road and only pedal well with my torso lean a bit forward. That make my shoulder socket lowered, and thus if the bar is high, then I have to bend the elbow a lot to keep my torso where I want and my hand on the bar.
when seated pedaling on flat ground are your hands weighting the bars? In other words heavy hands? My current bike (likely too large) feels that way and it's painful on flat, semi-smooth courses. I'm fine on descents (out of saddle) and in/out of saddle climbs, though. Still, since I may end up ordering my next bike without the luxury of getting to try it first (due to bike shortages), I'd like to have an idea on stack height.
 

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I'm 6' with a +2 ape index. I like tall stack. IIRC my bike has a stack of 624mm, with 6mm of spacers and bars with 38mm of rise. Though I suspect part of my preference is affected by flexibility, core strength and confidence to lean forward to attack downhills that could all use some improvement.
 

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Discussion Starter · #7 ·
I'm 6' with a +2 ape index. I like tall stack. IIRC my bike has a stack of 624mm, with 6mm of spacers and bars with 38mm of rise. Though I suspect part of my preference is affected by flexibility, core strength and confidence to lean forward to attack downhills that could all use some improvement.
I'm about the same ape as you. What's your inseam, if you don't mind me asking, haha? Mine is 32". Are you heavy handed seated on flat ground?
 

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when seated pedaling on flat ground are your hands weighting the bars? In other words heavy hands? My current bike (likely too large) feels that way and it's painful on flat, semi-smooth courses. I'm fine on descents (out of saddle) and in/out of saddle climbs, though. Still, since I may end up ordering my next bike without the luxury of getting to try it first (due to bike shortages), I'd like to have an idea on stack height.
Most people think low stack alway cause weight on the hands. That's true if lowered bar force your torso to lean at a steeper angle.
In my case, it's opposite. My torso want to lean at a certain angle regardless of the bar height. If the bar is too high, I bend elbow and rest too much weight with my hand. But if the bar height is lowered, then I use less hand support and more of core muscle support. So, for me, tall bar cause heavy hands. Low enough bar (just right, not too low that it force me to lean more than I want) reduce weight from my hands.

To combat weight on hands, I might try to pull saddle more rearward on your current bike first though.
 

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Discussion Starter · #9 ·
Most people think low stack alway cause weight on the hands. That's true if lowered bar force your torso to lean at a steeper angle.
In my case, it's opposite. My torso want to lean at a certain angle regardless of the bar height. If the bar is too high, I bend elbow and rest too much weight with my hand. But if the bar height is lowered, then I use less hand support and more of core muscle support. So, for me, tall bar cause heavy hands. Low enough bar (just right, not too low that it force me to lean more than I want) reduce weight from my hands.
it's an interesting point. And I probably do need to work on my core. To be clear, I'm heavy on the hands only seated on flat ground. I saw another member say the same but that they got used to it because in every other situation they felt good. Wondering if that's my fate as well.
 

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Large/19" 2017 Jamis DragonSlayer. It has a short reach (426mm) but slightly longish ett (~630mm?). I have a 60mm stem and 780mm bars. But I also have a -2° Works Components angleset, which drops the front end a bit, and a 10mm Reverse Angle spacer in place of the crownrace, which raises it back up a little.

Back on the topic of stem and bars, they also affect how you load your hands. Wider bars pull you forward, shorter stems let you sit back. My bike came with 720mm flat bars and an 80mm stem which I ran for about 6 months. Then I put 800/20mm risers and the 60mm stem on, also for about 6 months, but they still felt too low, and I was unsure about the width. Finally I put on the 780/38mm risers (still with the 60mm stem) and it feels perfect.
 

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Discussion Starter · #13 ·
Large/19" 2017 Jamis DragonSlayer. It has a short reach (426mm) but slightly longish ett (~630mm?). I have a 60mm stem and 780mm bars. But I also have a -2° Works Components angleset, which drops the front end a bit, and a 10mm Reverse Angle spacer in place of the crownrace, which raises it back up a little.
My bike is a Fuji Nevada 1.7 XL. 459 reach, 653 ETT, 635 stack (at 69* HTA, 73* STA). I have a 40mm stem and 780 bars with 25mm rise. I started with 60mm stem and flat bars with just a little backsweep. My stem is all the way up, probably 25mm spacers.
 

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Discussion Starter · #14 ·
Doing the math on the Japhy, I think the 614 stack is at 30% fork sag - which Esker has a little note at the bottom of their geo chart that says
Hardtail geometry based on 30% fork sag.
Actual stack by my rough calculations (size Large) should be more like 645ish. Not horribly low at all :)

Wondering if any Japhy owners can confirm?
 

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i find dramatic increase with hand pressure after tipping my seat down.

stack height???

the whole bike geometry comes into question i guess. depends on what you want the bike to do? a bike set to 63 degree hta meant for going down the steep gnarly stuff will setup diff than one for general trail riding w 130mm fork. or you should want it to be.
 

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Discussion Starter · #16 ·
i find dramatic increase with hand pressure after tipping my seat down.

stack height???

the whole bike geometry comes into question i guess. depends on what you want the bike to do? a bike set to 63 degree hta meant for going down the steep gnarly stuff will setup diff than one for general trail riding w 130mm fork. or you should want it to be.
I want an all a rounder. There aren’t many downhill parks here. No lifts. No sustained long runs. Flow, tech, some occasional bike park stuff, maybe a trip to a more DH oriented park every few months.

Seems like the bike in question doesn’t have a criminally low stack height as I previously thought. They just list all their geo at 30% sag, so it can be odd to see the numbers up next to other manufacturers who don’t.
 

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I want an all a rounder. There aren’t many downhill parks here. No lifts. No sustained long runs. Flow, tech, some occasional bike park stuff, maybe a trip to a more DH oriented park every few months.

Seems like the bike in question doesn’t have a criminally low stack height as I previously thought. They just list all their geo at 30% sag, so it can be odd to see the numbers up next to other manufacturers who don’t.

it makes it hard to compare diff bikes if others dont list the same

assume 64 degree hta unloaded and figure out the stack/opposite length increase by using 36mm for the hypotenuse.
 
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