Another geo thread - this time, related to stack height

Yes but on a moto, much like a DH bike or dirt jump bike or trials bike, the seat is just for resting. Not for having fun on. Motos have pretty high peg heights relative to BB heights. So I doubt that the relative angle of you on moto standing on pegs vs your MTB angle is really that far off.

I'm MTB having dabbled briefly in moto with an XR 100 and have never seat bounced in my life. But I certainly didn't find myself with more vision on a moto.

And I should add that I'm 6'7"/2M so my angle on life is a bit different than most. I love the Deity dirt jump bars for their high-rise, but again being tall I match it to a longer 65mm Deity stem to get more hight with the proper roll and no shorter reach. And my XR has a crazy block of a bar riser and Pro Tapers.

just buy those 80mm rise protaper bars and test it

https://nsmb.com/articles/fit-before-fashion-protapers-76mm-riser-bar/

I wish I was enough of an expert to know the answer to this question. What would actually happen if the handlebars were like 5"-6" higher up, all else remaining equal? All my time reading reviews and comment sections tells me something about the front-end not being weighted enough for traction, but I have no idea if that's true. I'm not anywhere near skilled enough to be pushing the limits of my current, relatively normal setup, much less to be able to judge if a dramatic change like that would ultimately be a help or a hindrance.

My first DH bike, back when DH bikes didn't really exist but DH races did, was a 22" (XL) Santa Cruz Heckler with a Z! Bomber fork and Formula front disk. I think I had one of those brand new Azonic/World Force DH riser bars for general trail riding but ended up switching them out for a seven or eight inch (180-200mm) rise pair of GT BMX cruiser bars for DH racing. It was pretty eye opening. I raced that bike for a season and eventually cracked it with no handling complaints. For a replacement I got a Medium from Willy at Santa Cruz in Orange to match my Z1 Bommer fork. What a bike that was. basically a 100mm by 100mm BMX bike for a giant. Eventually Santa Cruz came out with the Super 8 and I went back to the Azonics and eventually went lower and lower as my bikes got longer to lower my center of gravity.

So I guess what I'm getting at is... Do what YOU like. Trends are just that, temporary trends and not rules. A higher bar and slightly longer stem are cheeper than a new fork or crown and steerer assembly. So just try it out. If it doesn't work out just build a dirt jumper or "Pump track bike." around your new bars!

spoon_ wrote:

just buy those 80mm rise protaper bars and test it

https://nsmb.com/articles/fit-before-fashion-protapers-76mm-riser-bar/

Oh doode!

I really might try those.

Jakeepooh wrote:

I wish I was enough of an expert to know the answer to this question. What would actually happen if the handlebars were like 5"-6" higher up, all else remaining equal? All my time reading reviews and comment sections tells me something about the front-end not being weighted enough for traction, but I have no idea if that's true. I'm not anywhere near skilled enough to be pushing the limits of my current, relatively normal setup, much less to be able to judge if a dramatic change like that would ultimately be a help or a hindrance.

My guess is that without any body-english changes, you'd have a slightly lighter front wheel. You'd wheelie a little more under pedal power and have a little less front wheel grip in the corners. I think adjusting your form would fix it all. (Plus, manuals would likely be easier!)

Falcon wrote:

My guess is that without any body-english changes, you'd have a slightly lighter front wheel. You'd wheelie a little more under pedal power and have a little less front wheel grip in the corners. I think adjusting your form would fix it all. (Plus, manuals would likely be easier!)

That makes sense, hombre. Thanks

Jakeepooh wrote:

I wish I was enough of an expert to know the answer to this question. What would actually happen if the handlebars were like 5"-6" higher up, all else remaining equal? All my time reading reviews and comment sections tells me something about the front-end not being weighted enough for traction, but I have no idea if that's true. I'm not anywhere near skilled enough to be pushing the limits of my current, relatively normal setup, much less to be able to judge if a dramatic change like that would ultimately be a help or a hindrance.

I'm in no way an expert but *have* spent the last 4 months messing around with riser height, stem length, bar width and headset spacers.

tl;dr is pretty much what @Falcon said. Climbing steep stuff would be trickier, a little (or a lot) less grip in corners and a more upright position overall.

Some of it you can adjust for w/ body position but that can lead to other issues.

I ended up going from a 130mm fork w/ 35mm stem and 780 bars to a 150mm fork w/ a 50mm stem and 740mm bars to get the position and bike handling I wanted.

I've read the book "Dialed" by Lee McCormack and have taken what he details there and his website https://www.llbmtb.com/ to compare bike geometry/set ups to find what bikes will fit me the best. At 6'0" (but with dimensions that make me fit bikes more like I'm 5'10",) I have found that the majority of frames lack enough stack. Most bikes will need to have a lot of spacers under the stem and a high rise handlebar to get the grips the right distance and angle from the BB to fit me and my riding preference.

I remember a number of years ago it was common to see large, machined spacers under the stem and high rise bars on the pro's bikes in the World Cup bike checks. Then it became the cool thing to put the bars as low as possible with the argument that it puts you into an aggressive, attack position. But I don't believe there was much if any data used to make that claim. Then again, I no longer believe that there is much experimentation/data used for anything in mountain bike design, just trend chasing that sometimes takes bike design in the right direction, but quite by accident.

Bar height is something that's worth playing around with, and comes down to personal preference. It's a balance between being able to weight the front wheel enough in corners but being upright enough that you can relax in a neutral position with centered weight on the bike, without feeling like you're being pulled forward. As bikes are getting longer, higher rise bars make more and more sense to avoid being pulled forward.

I don't know much about moto. Is there a need to shift weight forward to get the front wheel to bite in corners? Or is such body english futile relative to the weight and power of the bike?

taldfind wrote:

I've read the book "Dialed" by Lee McCormack and have taken what he details there and his website https://www.llbmtb.com/ to compare bike geometry/set ups to find what bikes will fit me the best. At 6'0" (but with dimensions that make me fit bikes more like I'm 5'10",) I have found that the majority of frames lack enough stack. Most bikes will need to have a lot of spacers under the stem and a high rise handlebar to get the grips the right distance and angle from the BB to fit me and my riding preference.

I remember a number of years ago it was common to see large, machined spacers under the stem and high rise bars on the pro's bikes in the World Cup bike checks. Then it became the cool thing to put the bars as low as possible with the argument that it puts you into an aggressive, attack position. But I don't believe there was much if any data used to make that claim. Then again, I no longer believe that there is much experimentation/data used for anything in mountain bike design, just trend chasing that sometimes takes bike design in the right direction, but quite by accident.

Wc riders are pretty good at figuring out what works and doesn’t on a bike. As reach got longer and suspension got better front ends got shorter. Guys are riding with very central positions and basically moving bike under them as opposed to getting off the back and using their legs and arms to drive bike into ground and keep a bit of traction. (Obviously they are still doing this but it’s more like piloting these days then jockeying a iron horse.). There are definitely guys who prefer a setup and feel somewhat closer to what they started on rather than commiting to riding like Troy or loic.

Personally I prefer something somewhere in between. I can ride a bike with pretty much any height stack and get used to it though. Stand over on the other hand needs to be lower on so many bikes. I get that suspension and seat tube angles limit a lot of peoples designs but I absolutely will never buy a bike with anything but super low standover again. I never realized my seat was in the way till I rode a transition and I can’t go back now.

I'm not actually sure the bars are that low compared to a moto. They seem low sitting there in the garage, but a moto's peg height is a lot higher than a mountain bike's BB height.

Can someone do the math here?

So there are a few answers here that could help solve the mystery.
1) the higher the handlebars are, the farther you have to effectively lean over when cornering. The only way you would really be able to have bars at a similar height to your moto’s is if you rode it like a moto and lean more with your body, and less with the bike. This would require trails to be quite a lot different than they mostly are.
2) Fitting and body measurements. There is a whole other side of science that I don’t know enough to teach about but know enough to get me in trouble. There is an optimal position unique to you that your body can function best in. From working with a bike fitter your handlebar height usually depends on your lower back and neck flexibility, as well as your proper saddle height. All I can say is have your pedaling position looked at by an expert in bike fitting and they can definitely help you look farther ahead. From your description you might be a little on the tall side for a large meta depending on the year.

3) maneuverability. Bikes are designed to be good at both going uphill, and downhill. If you look at modern DH bikes, they are not meant to climb at all so the bars can be a little bit higher to help you go downhill with more confidence. While on the other end of the scale, XC bikes have much lower bar heights to help keep weight on the front wheel so that you don’t wheelie or loop out as soon as the trail points up. The Meta sits almost exactly in the middle so does require a lower bar height, but when the seat is dropped, the bars effectively feel higher.

Yes, while climbing I tend to look a lot closer to my wheel than I do descending, but that is only because I am leaned farther forward due to the increased saddle height.

jeff.brines wrote:

I'm not actually sure the bars are that low compared to a moto. They seem low sitting there in the garage, but a moto's peg height is a lot higher than a mountain bike's BB height.

Can someone do the math here?

If you have both in the garage just measure reach and stack and report :D

jeff.brines wrote:

I'm not actually sure the bars are that low compared to a moto. They seem low sitting there in the garage, but a moto's peg height is a lot higher than a mountain bike's BB height.

Can someone do the math here?

Karabuka wrote:

If you have both in the garage just measure reach and stack and report :D

I do. And am feeling lazy. I'll get on it soon enough.

taldfind wrote:

I've read the book "Dialed" by Lee McCormack and have taken what he details there and his website https://www.llbmtb.com/ to compare bike geometry/set ups to find what bikes will fit me the best. At 6'0" (but with dimensions that make me fit bikes more like I'm 5'10",) I have found that the majority of frames lack enough stack. Most bikes will need to have a lot of spacers under the stem and a high rise handlebar to get the grips the right distance and angle from the BB to fit me and my riding preference.

I remember a number of years ago it was common to see large, machined spacers under the stem and high rise bars on the pro's bikes in the World Cup bike checks. Then it became the cool thing to put the bars as low as possible with the argument that it puts you into an aggressive, attack position. But I don't believe there was much if any data used to make that claim. Then again, I no longer believe that there is much experimentation/data used for anything in mountain bike design, just trend chasing that sometimes takes bike design in the right direction, but quite by accident.

I can tell you that I cut my steer tube longer and use about as many spacers as I can, and I often over fork a bike just to get the bars a bit higher. I have neck injury’s and it really helps to get those grips higher. I do notice that I tend to raise the bb and make the bike a bit floppy(at least from the design intention), but I can still shred a bit and the climbing impact is more or less negligible. For example I have a new Stumpjumper 130 rear 140 front stock, but mine is 160 up front with a long steer tube and stem all the way up with 40mm riser bars. Bike rides rad!

I've long been in the higher rise camp, but even 50mm rise bars are more rare these days. You can still get them from Spank and a couple of others. In addition to always being a fan of being a bit more upright, I wore out my hips through years of riding and arthritis and a torn labrum really got me upright.

I use 1.25-1.5 inches of spacers(depending on bike) as well as 50mm rise bars and it feels great.

On my size M Timberjack hardtail, I overforked it from 120mm to 160mm and use 1.25" of spacers and 50mm rise bars. I had to switch from a 50mm stem to a 10x70 stem and slide the seat most of the way forward to compensate for the weight shift to the rear on all of that. It still climbs well, but it's no CC race bike.

On my size L FS (Ripmo), I'm running a 35mm DMR Defy stem, so that lifts up the bars a lot and it has 1.5" spacers and 50mm rise bars. The seat is in pretty neutral position.

Both of my bikes climb well, but both require a little bit of body positioning on really steep climbs in order to keep the front end planted...the hardtail more so than the FS due to the overforking.

You have to be very careful about the front end getting too light for climbing. There's a lot of mass in your upper body and how much you lean forward or sit up shifts the weight around significantly.

Jakeepooh wrote:

I wish I was enough of an expert to know the answer to this question. What would actually happen if the handlebars were like 5"-6" higher up, all else remaining equal? All my time reading reviews and comment sections tells me something about the front-end not being weighted enough for traction, but I have no idea if that's true. I'm not anywhere near skilled enough to be pushing the limits of my current, relatively normal setup, much less to be able to judge if a dramatic change like that would ultimately be a help or a hindrance.

You would not have enough weight on your front wheel and you would crash.

Falcon wrote:

OK, weird MX guy asking a bicycle question here. Why do all MTBs have neck-breakingly low handlebar heights? Even with 30-35mm riser bars, I feel like I'm craning my neck to see more than 3 feet ahead of my front tire. I am 6'1" on a large Commencal Meta. I feel like the bike is the right size for me. Even if it isn't, all bikes I ride feel similar, from this complaint's perspective.

When I ride my MX motorcycle, a seated position puts my grips about on the level with my ribs. On a bike, they are at my hips or lower. I could, in all honesty, benefit from about 4-5" more handlebar height, just for neck comfort. (Not to mention descending capability.)

I get that MTB has sort of grown organically from road bikes to XC to what we have now, but at least in the disciplines of Enduro and Downhill, wouldn't it be OK to sit more upright? I'm surprised the MTB geometry evolution hasn't gone in that direction.

Can somebody please design and test an enduro bike with about the same geo, but a much taller stack height, please???

Try and get your handle bars and saddle the same height and go from there. I like mine similar heights. Peddling a bike with the bars 6” above your seat will probably be very tedious on a decent climb.

I have about 20mm of spacers under my stem and the One Up bars in the 35mm rise. I have shoulder issues and find a higher bar height is less stress on them. I will get on friends bikes that have minimal rise and I feel like I am going over the handlebars. I have tried moving a 5mm spacer from under the stem to above it once in a while, but I am comfortable where I am.

I've been playing around with bar height, and think two things are worth pointing out: 1. The vast majority of mtb instructors will tell you not to weight the bars with your hands (front end weighting should occur through all of your weight running through the bottom bracket in a line parallel to gravitational force, with slight adjustments to compensate for acceleration and deceleration), so you really shouldn't see a difference in front-wheel weighting if you have proper form. This doesn't necessarily hold for seated technical climbing, so I agree with the points about a wandering front wheel in those instances. 2. I think someone mentioned this above, but stack height makes a huge difference in how easily you can manipulate the bike (bike-body separation). If your stack height is too high, you'll find it very cumbersome to lean the bike properly in corners as there won't be enough room between your chest and the bars. This was the first thing I noticed when testing a high stack height. Overall, I've settled on a stack height that keeps bike manipulation from feeling cumbersome when I'm in the attack position, while also keeping the bars high enough that I'm not struggling to keep myself from being pitched into the bars/over the front. I have learned from World Cup pros that the stack height that balances those two things does vary with the steepness of the terrain, and plan to run a higher stack when I ride places such as Windrock and Shephard Mountain.

hd4rider wrote:

I've been playing around with bar height, and think two things are worth pointing out: 1. The vast majority of mtb instructors will tell you not to weight the bars with your hands (front end weighting should occur through all of your weight running through the bottom bracket in a line parallel to gravitational force, with slight adjustments to compensate for acceleration and deceleration), so you really shouldn't see a difference in front-wheel weighting if you have proper form. This doesn't necessarily hold for seated technical climbing, so I agree with the points about a wandering front wheel in those instances. 2. I think someone mentioned this above, but stack height makes a huge difference in how easily you can manipulate the bike (bike-body separation). If your stack height is too high, you'll find it very cumbersome to lean the bike properly in corners as there won't be enough room between your chest and the bars. This was the first thing I noticed when testing a high stack height. Overall, I've settled on a stack height that keeps bike manipulation from feeling cumbersome when I'm in the attack position, while also keeping the bars high enough that I'm not struggling to keep myself from being pitched into the bars/over the front. I have learned from World Cup pros that the stack height that balances those two things does vary with the steepness of the terrain, and plan to run a higher stack when I ride places such as Windrock and Shephard Mountain.

Just to call out the obvious here, longer reaches require different weighting than shorter reaches.

I never really think about pushing into the bars in a corner on my moto. I always think about it on my mtn bike. YMMV (based on reach/CSs etc)

jeff.brines wrote:

Just to call out the obvious here, longer reaches require different weighting than shorter reaches.

I never really think about pushing into the bars in a corner on my moto. I always think about it on my mtn bike. YMMV (based on reach/CSs etc)

The trend toward longer reaches concerns me for that reason. Bike companies are pushing for a change in rider style as they make longer bikes, but I haven't heard a single instructor agree with that push. Humans are bipeds, not quadripeds. I think this is a reason we are seeing so many pros size down/run narrower bars. I have have yet to see a downhill pro who isn't applying "light hands" for the majority of their run.

hd4rider wrote:

The trend toward longer reaches concerns me for that reason. Bike companies are pushing for a change in rider style as they make longer bikes, but I haven't heard a single instructor agree with that push. Humans are bipeds, not quadripeds. I think this is a reason we are seeing so many pros size down/run narrower bars. I have have yet to see a downhill pro who isn't applying "light hands" for the majority of their run.

I can go find a bazillion videos showing the opposite if you like...

I also have put my bike on scales to prove this point. The only way to properly weight the bike when the reach/CS measurement is a certain ratio is by weighting your hands. I've posted a bazillion times about this.

See Also: The internet was wrong, short chainstays suck.

jeff.brines wrote:

I can go find a bazillion videos showing the opposite if you like...

I also have put my bike on scales to prove this point. The only way to properly weight the bike when the reach/CS measurement is a certain ratio is by weighting your hands. I've posted a bazillion times about this.

See Also: The internet was wrong, short chainstays suck.

I think we are on the same page, but coming at it from different angles. I think we need longer chainstays for the current reach values so that we don't have to weight the bikes with our hands, and think pros may be sizing down and running narrower bars because they secretly agree. That could also be why people like Minnaar are running longer chainstays.

I also acknowledge that weighting in a corner is different from weighting on a straight, but wonder if we would be better off with bikes balanced so that's not necessary. Interested to hear your thoughts!

jeff.brines wrote:

I'm not actually sure the bars are that low compared to a moto. They seem low sitting there in the garage, but a moto's peg height is a lot higher than a mountain bike's BB height.

Can someone do the math here?

Karabuka wrote:

If you have both in the garage just measure reach and stack and report :D

Was about to tell him to go in the garage and measure for us, haha. Out of everyone on this thread, he's probably the one sitting closest to both a moto and mtb.

Some additional thoughts that I haven't heard yet:

1. 29ers have taller front ends. Someone mentioned that as reach lengths got longer, WC pro's started lowering their handlebars. That's actually not true. It might look like pro's front ends are coming down because we see lower rise bars and fewer stem spacers, but that's because with 27.5 & 29" wheels, frame stack heights have gotten higher. A 29" front wheel and fork is 2" higher than a 26" frame and fork. That's part of the reason why a lot of companies are speccing stupid short head tubes on their 29er frames. There was a trend in the mid-2000's for WC pro's to run low bars (Sam Hill famously took the top cap off his headset to minimize cockpit height), but bars went up in the pro ranks around 2010 and they haven't gone down since. Going downhill, taller really is better. Modern 29er downhill bikes might look like their bars are lower, but they're actually as high or higher.

2. Good descending position depends on where you ride. As discussed above, the steeper your trails are, the taller your bars need to be for descending and you'll just need to put up with steep bars on your way back up the hill. But the inverse is that, the flatter your trails are, the lower you need your bars to be to weight the front wheel and give you a reasonable range of motion over the front of the bike. To answer the OP, if trail/enduro/all mountain bikes were only made for gnarly riders in Squamish, BC, the stack heights would be higher. But bike companies also sell aggressive full-suspension bikes to Jerry's in Indiana and to old/slow/ignorant riders in my neck of the woods who choose to compromise their descending position to get better pedaling characteristics. For a local example, if you're selling a 160mm travel enduro bike to someone who only rides at Duthie, they're going to be pissed about a high stack height because... Duthie is flat.

3. Inseam height affects bar height. Riders with tall legs and short torsos will need higher bars. For instance, Jack Moir runs short frames with really tall bars, and so do I. I'm 6'3" with long legs and I chose the 490mm reach XL Megatower over the 515mm reach XXL frame. I'm happy as a clam with that decision. Riders hinge at the hips to reach the bars, and the higher your hips, the higher your bars need to be. The opposite is true for riders with short legs and long torsos- they will need lower bar heights. Our recent senior men's world champion is a great example of this body type, and as a result Reece Wilson runs low rise bars and no stem spacers on his Trek. If you're a frame manufacturer, is your size large frame designed for 6'2" riders with long legs and short torsos who want a long head tube, or is it designed for 5'10" riders with long torsos and short legs who need a short head tube? It's made for both, so frame manufacturers play it safe and spec a shorter head tube. That means guys like me and Jack Moir end up running tall bars and a grip of stem spacers.

I know nothing about Motos, so I have nothing to contribute to that side of the discussion.

its definitely a balance, but for me is has been getting a little ridiculous, I am 5'8", my old bike, a 2012 Medium v10 had a reach of around 400, it felt perfect. got it stolen, then bought a 2020 medium v10 29er. reach = 437. with the new bike I would say I definitely feel like its harder to get the weight off of my hands on steep terrain, a feeling I really don't like. when the rear of the bike is to stiff it makes this problem even worse.