Adding spacers is going to effective shorten your reach so if you have two bikes with the same reach on the geo charts but one has 620mm stack height and you add 30mm of spacers, it is going to end up have a shorter effective reach then the 650mm stack height with no spacers. Riser bars shouldn't shorten your reach. Stack height is a bit of personal preference. So people prefer tall stack heights others short. Generally a taller stack height is going to make easier to lift the front wheel but harder to weight the front of the bike while climbing.

 

Riser bars shouldn't shorten your reach.

It depends on how you roll them. Coming from BMX I was surprised to find mountain bikers usually run their bars with no roll back as this increases your effective stem length as you increase bar height. I've always kept bar roll inline with the steering axis. Either way keep in mind you can't cheat frame sizing; you can only move your bars around and it doesn't matter how you do it.

 

Spacers under the stem move the bar closer to you as the fork is tilted back towards you. The slacker the head tube angle the closer it gets.

High rise bars, if rolled correctly don’t really end up close to you. Some people really like the look of them. If they are rolled back you lose distance quickly.

Wider bars feel farther from you than narrower bars do. Depending on your terrain (gaps between trees etc) this might not be realistic option to go wider.

Ideal stem length amongst most of the pro race types seems to be 50mm plus or minus 10mm.

Ergonomics plays a massive role here. Do you have oddly long arms? Do you suffer from back pain? Do you have a weak core strength. Shoulder problems? Neck problems? Weak hand grip strength. How do you ride? Where?

 

Stack isn't really about bar height. How big a bike feels out of the saddle is mostly determined by how far the steering axis is from the BB. To simplify things we use the top of the head tube as a common reference point along the steering axis. So the distance between the top of the head tube and BB is what determines your frame fit and this point is located with X,Y coordinates or as we call them in the bike world "reach" and "stack". So reach and stack on their own mean little because you need both to determine how big the bike will feel. Let's say you have two bikes with 470mm of reach but one has 620mm of stack and the other 650mm of stack. The bike with 650mm of stack is actually 24mm longer between the BB and top of the head tube. The bike with 470mm of reach and 650mm of stack would be as big as a bike with 510mm of reach and 620mm of stack.

It's also nice to have stack in the right ball park so you don't have to run 80mm rise bars or a negative degree stem but that's really secondary to frame sizing.

 

I've always struggled with the concept of stack, and why, within reason it even matters.

In the example you've given, simply having 30mm taller bars (not rolled back obviously) on the 620mm stack makes the bikes identical in BB to the handlebar (effective stack maybe?) dimension.

Now I can see if stack is so absurdly off that you cannot buy a modern bar in a height to compensate, but that seems unlikely.

Please correct me if I'm missing something, but I keep hearing stack discussed but just don't see what the big deal is.

 

Thanks guys. Very insightful and helps a lot.

 

double post

 

Eventually you find a minimum reach and stack number YOU need to be comfortable on a bike. It's different for everyone... I have extremely long legs, frames with stack too low kill me as I end up with a seat towering over the bars.

 

This is my problem and why I put forth the question here.

 

Stack will be more critical for a hard tail than a full squish bike as your weight on the bike drops only the front. I've been on FS bikes for years and just got a new hard tail. The bike is spec'd at a 140mm fork. However, I later went to 160mm which seemed to normalize the bike under my 220lbs.

 

Most modern XL bikes I try feel too low at the front for me with the usual 35-40mm stem, 25-30mm riser stock setup. Great for climbing and cornering but downright scary to ride down steeps. If you're anything like me then you spend the vast majority of your time in the saddle actually getting to the descents, so seated position is really important too. If stack is too low it puts extra weight on your hands and strain on your neck and shoulders. With experience you can feel that just sitting on a bike, but as a beginner maybe not.

Generally I like the grips roughly aligned with the saddle, so that's an easy thing to look for if you get the chance to sit on a few bikes. Set the saddle height - I like the heels on pedals method for a quick result - and then have a look at the height difference. If it's like 20-30mm then you can generally fix it with a riser bar - just add the difference to whatever size bars are on that bike. That's just me though. Some people like a higher/lower position.

 

As an XL rider (1.93m) with very long legs, I find stack to be a significant part of the fit equation for me.

Spacers and riser bars will solve most of it but I often over fork the bike too by up to 20mm (within manufacturer guidelines) which helps raise the nose too.
Of course that affects HTA and STA so one can't go too crazy.

I've ridden bikes with <630mm stack and don't seem to get on as well with them as bikes with a taller stack measurement.

Having loads of spacers and goofy looking riser bars feels like too much of a workaround.

Some brands are finally getting around to considering this properly for taller riders / larger frames.

 

Currently on a Trek Stache 18.5"running a 35mm stem.I just got a 30mm riser bar but haven't switched it over yet. Slightly over 6', long legs (35"inseam) long arms, short torso.I'm going to put some official measurements together so I know exactly what's what. The Stache feels good for an hour or so but having had 5 rotator cuff surgeries in the past fatigue starts to set in. I'm looking for something a little lighter and more aggressive without going full all mountain HT.I think a taller stack and maybe a shorter reach will keep me from being too over the bars with my higher saddle. I'm also thinking I will feel a little more planted in the bike.
Maybe I just need to go with a little slacker HTA. The Stache is 68.9 deg.

 

The 18.5 size is a M/L with a 645mm stack 430mm rich, that doesn't seem like a low stack at all but the reach sounds pretty short. (thats about the same reach the many of the small sized bikes I was looking at for my 5'5" wife) Reeb, YT, Salsa....

 

Sorry.I actually have the 19.5" which is listed as 18.5"virtual and 19.5" actual. It's a 2016 and the stack is listed as 630mm. It's not bad but I would like something a little more modern geo wise with taller stack and shorter reach. Think Sherpa Ti+ with a slacker HT insert.

 

I might be drunk but, did you just write, "I would like something a little more modern geo wise with taller stack and shorter reach".?

 

I was thinking the same. At over 6' tall, riding a bike with 436mm reach you'll be over the bars in no time. If not, you'll be hitting your knees on the handlebars whilst climbing.

That bike is too small. At your height I'd be aiming for 480mm reach as a minimum.

 

Thanks.Maybe I've been looking at this all wrong and need to re-think this.

 

Stack is just a by product of more important numbers. It cracks me up when a so called expert says he likes 29 ers with 65 Deg Head angle and 130 travel forks and high stack. Most 65 HA 130 travel 29er bikes will have similar stack. Only way to make stack higher is lower the Bottom bracket or have an overly long head tube. Stack isn’t a number I consider when designing a frame or searching for a bike.

 

Hey guys,
I came across this thread when researching stack height on new bike geometry.
Im roughly 6 foot, and was used to riding a "large".
Im used to measuring my bikes by effective top tube length. I knew for me, the ideal top tube center to center (ttc-c) was about 23.5 inches.

Ive street tested a few modern trail bikes, and cant get used to the new sizing metrics.
The new large bikes are effectively XL (24-25" ttcc), and cant be ridden while seated. I find im leaning too far forward, and arms too out wide.
The mediums fit better. But the bike shop sales people try to talk me out of getting the mediums, saying theyre too small for me.

Ive started using\liking shorter stems (50-70mm) but cant get used to the ultra wide 780-800 bars. At most i like maybe a 700-720" bar on a 70mm stem.

Now with people primarily looking at "reach" and stack heights, im out of my element. Especially when you tell people that "with a 436mm reach you'll be over the bars in no time''


Advice appreciated