Mountain Bike Reviews Forum banner

1 - 20 of 38 Posts

·
Registered
Joined
·
396 Posts
Discussion Starter · #1 ·
Curious about this, the primary explanation I've heard for STA in the 77-78d range is how much it helps with climbing, and that it makes pedaling "easier and more efficient". I've never ridden a bike that steep, I have a trail bike with 75d angle, but I was just noticing that a lot of manufacturers are still using slacker angles on more-XC oriented bikes that are presumably better designed for climbing and to "ride all day".

Couple of examples, Kona uses steeper angles on the Process but the 120mm Hei Hei is at 75d. This bike in particular is said to pedal and climb very well … "fantastic pedaling behavior... the bike levitates uphill like a homesick angel.”
Another example, the 115mm Giant Trance Advanced 29 has a 74.5d STA, while their bigger travel bikes get steeper.

Why is that? Is it possible that really steep ST angles are used to compensate somehow for how poorly a big bike would climb without it? If steep STA helped with climbing and pedaling in every case, you'd think we'd see it on the XC/light trail bikes too. Thoughts?
 

·
Trail Ninja
Joined
·
6,167 Posts
When they stretch the bike's wheelbase out, they have to re-center the rider.

They are pushing the front out by a lot with extra reach, slacker HA, and longer fork. The further the front wheel is, the less weight is on it.

Moving the rider's seated position forward about 12mm is equivalent to steepening the STA by 1 degree.

---

The marketing is just there to "educate" stubbornly ignorant consumers into being a little more open to such an idea. They might be skeptical like you are, familiar with ETT or other numbers like a shorter reach. They want you to give it a demo to find out for yourself. They gotta "innovate" somehow and they're hoping that you agree that the new bike feels better overall, enough for you to consider replacing an older one. Without it, people would be creating pitchfork mobs for changing things.
 

·
Registered
Joined
·
3,447 Posts
It's more nuanced than steeper = better. STA is used to balance weight distribution while seated. An XC bike with a low front end, steeper hta, less travel, etc puts more weight on the front wheel when climbing. A long travel enduro bike squats down in the rear a lot more when pointed up hill, plus the bars are typically a bit higher and the front wheel is further out. So the enduro bike needs a steeper STA than an XC bike. You also have to balance reach and STA too. An XC bike typically has a longer stem and needs to be nimble so you can't just increase the STA 5 degrees without compensating with reach.
 

·
Trail Ninja
Joined
·
6,167 Posts
The alternative to steepening the STA is to lengthen the CS length.

If CS is too long, the front wheel becomes too planted, making the rider adopt a rearward position to lighten it. The bike's front is reluctant to get airborne and feels like it dangerously sucks down to the ground on drops and jumps. People who like that kind of riding generally associate bikes with slacker HA and shorter CS as being more their style.

There's a sweet spot for great handling. XC bikes sacrifice that sweet spot for the sake of saving weight. The trend of "downcountry" bikes are XC bikes that seemingly don't sacrifice this. They bring gravity-inspired geo to XC bikes.
 

·
Registered
Joined
·
228 Posts
It's more nuanced than steeper = better. STA is used to balance weight distribution while seated. An XC bike with a low front end, steeper hta, less travel, etc puts more weight on the front wheel when climbing. A long travel enduro bike squats down in the rear a lot more when pointed up hill, plus the bars are typically a bit higher and the front wheel is further out. So the enduro bike needs a steeper STA than an XC bike. You also have to balance reach and STA too. An XC bike typically has a longer stem and needs to be nimble so you can't just increase the STA 5 degrees without compensating with reach.
I think this is right on.

Effectively, the Enduro bike needs the steep seat angle to improve seated climbing performance since the rest of the bike works against that, i.e. long travel, slack front end. The rider is standing during long descents so it doesn’t affect anything there.

For long days in the saddle on flatter trails a steeper seat tube can be counter productive. On flatter trails it will shift the rider weight too far forward when seated and pedaling for prolonged periods and creat hand pain, saddle discomfort, etc. In theory, an XC bike is ridden on flatter more rolling trails where the seated position needs to be correct when the trail is flat, not pointed up so a slacker seat tube is preferred.
 

·
Registered
Joined
·
224 Posts
The steep STA on a trail bike does more than allow for better climbing. Moving the tube more upright gives more room for the rear travel with short chain stays. It also allow for a shorter effective top tube length on a long reach frame. With a slacker angle and long reach the TT would be very long for seated riding. Most medium bikes have a tt around the 600mm length (+- a few mm). My bike has 436 reach with a 74.5 STA and 603 for the TT, a 455 reach bike with a 77 STA has about the same TT, both will have a similar seated reach but the latter will be more trail oriented while mine is more XC. As far as climbing goes. The steeper angle is part of the entire package that determines the ability of the bike to climb. My ‘21 Epic Evo with the slack 74.5 STA climbs like a goat because the STA is balanced with all the other geo numbers.
 

·
Trail Ninja
Joined
·
6,167 Posts
As an aside, a little CS length makes a huge difference in weight distro. I found from testing that 5mm of additional CS length is worth close to 15mm of length added to the front.

I find a lot of difference between a weight distro of 60% rear and 40% front, and a distro of 57:43 (with me in a centered standing position). The EBB set full forward and rearward on my Niner ROS9 achieved this difference. 3% might seem like not a big deal, but I had an undoubtedly strong preference for the more rearward distro. It climbed better out of the saddle and I was more calm/composed through tech, taking corners much faster and feeling more comfortable with pushing traction to the absolute limit. I was running Ikons F&R, it felt like the front tire broke loose at the same as the rear without me needing to purposely weight the front or rear--if there were any way to validate the sweet spot, I felt that these magically effortless two-wheeled drifts were it.

One might say that there a no bad bikes, but there's a lot of performance left on the table with geo tweaks. Brands aren't trying hard enough to earn their sales if they're not going after this low-hanging fruit. It's enough to determine what bike in the quiver is a favorite and a clear deciding factor in judging which are bike-of-the-year contenders. To me, the better geo made me waaaaaay more willing to ride a much heavier bike.

The ROS9 didn't have a steep STA, but it was a hardtail that gets steeper as its susp compressed. Its WB was ~1150mm. I think that was the last XCish bike I owned. Good geo makes the rider's comfort zone much wider. There's only so much room to grow into 120mm HT, and I was feeling like I was riding it above what it was designed for. I get the feeling that downcountry bikes would give the same vibes.

I've ridden up to 83 degree STA. I still pushed my saddle all the way forward on that bike (super long WB). I've ridden an enduro bike with 75 STA ('18 Jekyll 27.5) and its sitting position was so rearward that it was almost a deal killer. It sagged and slackened so much on seated climbs that it wasn't worth sitting. Luckily it climbed really well out-of-the-saddle.

Long CS and slack STA short-travel bikes are what I associate with the riding style that plops into the saddle, only reluctantly getting out for steep DH and to unweight the front and brace for fork compression. That's how it goes for size medium bikes at least. I prefer to be more out-of-the-saddle. That long CS might seem like just the right length for size XXL bikes, considering how much extra reach and WB their size gets.
 

·
Formerly of Kent
Joined
·
12,344 Posts
Because a longer travel, higher sag (>30%) bike sinks further into its travel than a 100-120mm bike at 20% sag.


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
6,590 Posts
Trail bikes tend to have a shorter cockpit and sit you more up-right. This position, combined with increased suspension sag, makes steep climbs difficult. Steepening that seat angle really helped trails bikes climbing characteristics.

Also, there is a hell of a lot of marketing going on. A 75-76 degree seat angle is a huge improvement over a 72 or 73. But IMHO 77-78d offers no improvements, well it does offer marketing opportunities.
 

·
Registered
Joined
·
10,014 Posts
Running up a tame fire road as fast as possible (XC) requires a different setup than climbing up steep technical terrain. Theres not too much slow and seated technical climbing in an xc race.
 

·
Registered
Joined
·
5,302 Posts
I have a hard time taking any single design parameter particularly seriously from the standpoint of dramatically driving performance. Manufacturers combine numerous characteristics to arrive at a final product.
 

·
Registered
Joined
·
396 Posts
Discussion Starter · #14 ·
Ok I think I get it, sounds like due to the slackening of HTA and the longer reach on modern trail bikes, the STA gets steeper to keep riders balanced in the bike. So, a steeper STA would probably not make a bike like the Hei Hei climb better, but does help a long, slack bike get up the hill. Seems to undercut the "pedaling is always better when you are sitting on top of the bottom bracket" argument tho.
 

·
Rippin da fAt
Joined
·
8,567 Posts
Curious about this, the primary explanation I've heard for STA in the 77-78d range is how much it helps with climbing, and that it makes pedaling "easier and more efficient". I've never ridden a bike that steep, I have a trail bike with 75d angle, but I was just noticing that a lot of manufacturers are still using slacker angles on more-XC oriented bikes that are presumably better designed for climbing and to "ride all day".

Couple of examples, Kona uses steeper angles on the Process but the 120mm Hei Hei is at 75d. This bike in particular is said to pedal and climb very well … "fantastic pedaling behavior... the bike levitates uphill like a homesick angel.”
Another example, the 115mm Giant Trance Advanced 29 has a 74.5d STA, while their bigger travel bikes get steeper.

Why is that? Is it possible that really steep ST angles are used to compensate somehow for how poorly a big bike would climb without it? If steep STA helped with climbing and pedaling in every case, you'd think we'd see it on the XC/light trail bikes too. Thoughts?
Why the steeper STA's?? So I can order frames consistent with the DWG file I send to Waltworks, that's why!
 

·
Formerly of Kent
Joined
·
12,344 Posts
Running up a tame fire road as fast as possible (XC) requires a different setup than climbing up steep technical terrain. Theres not too much slow and seated technical climbing in an xc race.
Where are these XC races with fire road climbs? That bears no resemblance to any XC race I’ve done in the last decade.


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
5,302 Posts
Ok I think I get it, sounds like due to the slackening of HTA and the longer reach on modern trail bikes, the STA gets steeper to keep riders balanced in the bike. So, a steeper STA would probably not make a bike like the Hei Hei climb better, but does help a long, slack bike get up the hill. Seems to undercut the "pedaling is always better when you are sitting on top of the bottom bracket" argument tho.
I suppose it depends on where you are that places your center of gravity over the bottom bracket. Going up a hill that would be more forward than on the flats.
 

·
Trail Ninja
Joined
·
6,167 Posts
Ok I think I get it, sounds like due to the slackening of HTA and the longer reach on modern trail bikes, the STA gets steeper to keep riders balanced in the bike. So, a steeper STA would probably not make a bike like the Hei Hei climb better, but does help a long, slack bike get up the hill.
I can't argue with what you said.

Seems to undercut the "pedaling is always better when you are sitting on top of the bottom bracket" argument tho.
Unicyclists vs recumbent cyclists... hahaha.

Pedaling in a different position utilizes different muscle groups. That's partly why climbing is hard. You have to train your efficiency for multiple positions. Someone who is super fit at flats and moderate climbs will be out of their comfort zone on steeper climbs that demand a different position. You only get more efficient with that position by spending training in it (training specificity).

A recumbent rider wouldn't be able to transfer much of their pedaling fitness to a mountain bike, similar to how a mountain biker can't transfer much of their fitness to running, despite similar motions. The same goes for transferring pedaling fitness from a 73 STA bike to a 77 STA bike. Maybe 90% of the fitness might carry over--I'm pulling this # out of my ass, but just trying to make a point that even seemingly small changes make very noticeable differences. Like tweaks to your back posture or pelvic tilt...

The marketing isn't lying if it's merely saying that the steep STA is better than the same bike designed with less steep STA. It's just one geometry figure to juggle with so many others, so hard to judge its pros and cons by itself. It can be difficult to switch from slack to steep, but the other beneficial changes that accompany the STA change can ease the pain. Once you get used to steep it'll be even harder to switch back to slack. There are likely some steep STA bikes out there that are bad that might make you want to go back though.
 

·
Registered
Joined
·
6,590 Posts
Running up a tame fire road as fast as possible (XC) requires a different setup than climbing up steep technical terrain. Theres not too much slow and seated technical climbing in an xc race.
Depends where you are. But in most places your statement isn’t true.
 
  • Like
Reactions: goldsbar

·
furker
Joined
·
224 Posts
"fantastic pedaling behavior... the bike levitates uphill like a homesick angel.”
I think over-exaggerated climbing marketing hype has been the norm for decades. It dates back to when suspension forks first came out. When "serious" riders/racers said their Rigid/Rigid steel bikes were better climbers than those new-fangled toy forks with those pencil erasers in them. Every year since then, suspensions companies have been saying how this year's model of suspension fork, or rear shock, or suspension stem, or suspension seatpost is great for climbing (unlike that crap that they built last year that didn't work).
 
1 - 20 of 38 Posts
Top