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steep seat tube angles and Endurance / XC riding

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FishMan473

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Discussion starter · #1 ·
TLDR: Am I the only one who thinks these 'modern' seat tube angles of 75°+ are too steep for comfort and knee health?

A couple years ago I got a professional fit on my road bike. The fit focused heavily on biomechanics and power output, neither of which I'd want to compromise. So I fit my MTB saddle position the same and then fit the rest of the cockpit around that. I end up with the saddle mounted about 2/3rds of the way back on the rails on a bike with a 73° STA. To fit my newer bike with a 75° STA I had to get a 9point8 dropper post with a 25mm setback seat clamp. And STA's only seem to be getting steeper on newer bikes.

The story is that the steeper HTA on "modern" bikes makes for more power/efficiency for climbing. But I've always been warmed about how if your seat is too far forward you could wreck you knees. Maybe that steeper STA is going to make it easier to get back to the top of the hill for your next enduro run, but what's it going to do to your knees after mile after mile pedaling the bike? Or does a fit for a road bike somehow not apply to a mountain bike? Am I missing something?
 
Discussion starter · #3 ·
Well, it ranges from dead flat to so steep I have to get off and walk up... just like everyplace else.
 
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#5 ·
I've raced courses where the bulk of the elapsed race time was spent going up or down pretty solid grades. For those courses, a more progressive geo would have been great. I've raced other courses where an old-school slacker seat tube and slightly sharper head tube would have been more appropriate. It seems like insular thinking to suggest that either is objectively right or wrong as a universal statement that applies in all cases. There's only what's best for you.
 
#6 ·
Seems like people would be talking about knee issues if it was a thing. Steep ST has been a thing for nearly a decade now. All I know is the steeper the better. I slide my saddle all the way up regardless of how steep the ST is. That said, I've yet to own a super steep frame. 75 is what I'm on with saddle as forward as possible.
 
#7 · (Edited)
I recently got a bike with a 76.5 STA. With the saddle centered...it feels like I'm sitting on a barstool. All the load on my legs are put into my quads. My rear keeps wanting to slide off the back of the saddle. My saddle is slammed all the way back. On the flip side...I have another bike with a 74 degree STA (seems slacker than the advertised 74) and thats almost slammed all the way forward.

I was also fit on my road bike. The pedaling position really works for me.
 
#8 ·
FishMan473 said:
TLDR: Am I the only one who thinks these 'modern' seat tube angles of 75°+ are too steep for comfort and knee health?

A couple years ago I got a professional fit on my road bike. The fit focused heavily on biomechanics and power output, neither of which I'd want to compromise. So I fit my MTB saddle position the same and then fit the rest of the cockpit around that. I end up with the saddle mounted about 2/3rds of the way back on the rails on a bike with a 73° STA. To fit my newer bike with a 75° STA I had to get a 9point8 dropper post with a 25mm setback seat clamp. And STA's only seem to be getting steeper on newer bikes.

The story is that the steeper HTA on "modern" bikes makes for more power/efficiency for climbing. But I've always been warmed about how if your seat is too far forward you could wreck you knees. Maybe that steeper STA is going to make it easier to get back to the top of the hill for your next enduro run, but what's it going to do to your knees after mile after mile pedaling the bike? Or does a fit for a road bike somehow not apply to a mountain bike? Am I missing something?
Click to expand...
Super steep seat tube is uncomfortable on the flat. Add tri bars and you'd be set for Ironman. Without them, knees or not, it is awkward. Look for an older frame, like five or seven years ago for a balanced ride. There are NOS full carbon bargains waiting for you.

Put that LLS with steep seat tube to work on up / down trails and you'll not have it easier, no perching on the nose, no seat in the way with dropper down.
 
#9 ·
In short, yes. I had a steeper ST bike I took on the Iditarod trail 2 years in a row and it was pretty horrible, too much pressure on the wrists and forward-rotated riding position for long-endurance riding. I changed it out the 3rd year for my favorite fat bike, which was much slacker and it was much better. I think the steeper ST is decent on steep climbs and then it doesn't really matter for dropped seats on the DH...but that's a lot of straight up and down that in reality most riding is not, even when you still have big climbs and descents. Reduces versatility to go too steep IME.
 
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#10 ·
The steep angle does keep your weight forward. Otherwise I’m out of saddle to stay on the front for turning. But I’m out of saddle already for turns so it doesn’t matter.

I really don’t understand why the sta are so steep now, for me it isn’t comfortable for long rides. Are the steep sta people the same ones that complain about wheelie-ing out?

Ive got a Chromag trailmaster on my singlespeed which is a long lounge saddle and I can scootch up on the steeps if it’s not so steep that I must stand.
 
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#11 ·
The answer is complicated and simple at the same time.

All these changes began with trail/enduro/AM bikes. Steep STA came about primarily because of slack HTA.

Slack HTA alone was tried first (to improve downhill handing in steep terrain). It turns (no pun intended) out that a slack HTA with a traditional STA makes climbing difficult - the front end wanders everywhere. Similar issues with flat or off-camber turns - insufficient weight on the front contact patch = understeer and blowing through turns. So a slack HTA necessitates a steep STA, from a handling perspective.

These evolutions were eventually tried on XC bikes as well, with similar (though less extreme) angle changes being settled on.

The problem with XC bikes is that the compromise between power output, comfort, and handling is very much terrain dependent. Here, in the foothills, you have short (and occasionally steep, but not usually) climbs and descents. Modern geometry gives very little handling advantage here over traditional bikes (talking 2015-2018 as "traditional", not 1996, obviously). On the other hand, power output and comfort are worse - too much weight on the hands, too little glute and hamstring (as a hip extensor, not a knee flexor) involvement in the pedal stroke on flat terrain with constant pedaling as we see locally.

Here, a RM Element would be a poor choice for many for XC or marathon, as would a Spur or similar. The previous generation of 67.5-68 HTA and 74-ish STA bikes were better. The even earlier bikes of 68-69 HTA and 73-ish STA were great, too.

Now go 2 hours west of here and the most modern bikes are better - sustained steep climbs and descents.

So no, you're not crazy.
 
Discussion starter · #12 ·
As I'm thinking about this more -- stimulated by mikesee's comment despite my glib response -- when I was fit, the bike was on a level surface, so the fit's goal was to get my maximum power output on level ground. This may not carry over to when I'm pedaling uphill.
Is there a difference in the average grade when I'm pedaling on the mountain bike or when putting the power down on the mountain bike matters compared to when I'm putting the power down on the road bike? I think there is.
Is this difference in grade enough to justify moving the saddle an inch or two further forward? No way.
But I'm inspired by this line of thinking and I'm going to try an experiment. I have a "Spring Break" trip coming up where I'm going to be putting in a lot of miles over a 2 week period. I'm going to move the saddle forward on the bike I'm taking by 10mm, and put a 10mm longer stem on it too.
Like others here have stated, when my saddle is too far forward, I just feel like I want to schooch back further. But we'll see how it goes as my only option for 10 consecutive rides in largely steeper terrain.
 
#13 ·
Super steep STA for big travel bikes was created when the quest for shorter and shorter chainstays forced the seat tube to be moved forward and out of the way, riders then noticed they weren't falling off the back on steep climbs. A bigger travel bike will gain a lot of sag as the trail tilts up so moving the weight forward helps offset this, especially with shorter chainstays compounding the saggyness. Of course moving the rider forward helped weight the front wheel. At roughly the same time, the trend went from clipped in to flat pedals, allowing riders feet to naturally find an acceptable place for knee comfort, so for many, there were no drawbacks. For trail riders there were no drawbacks. Keep in mind these trends were largely on longer travel full suspension bikes with squishy suspension, soooom much less applicable to the short travel, firm/locked or hardtail bikes we train and race on. Horses for courses! This is the XC/endurance forum, if super steep enduro bike STA don't feel right, use an offset seat post to get the hip/knee/foot angles working for you, the XC rider.

DT
 
#14 ·
turnerbikes said:
Super steep STA for big travel bikes was created when the quest for shorter and shorter chainstays forced the seat tube to be moved forward and out of the way, riders then noticed they weren't falling off the back on steep climbs. A bigger travel bike will gain a lot of sag as the trail tilts up so moving the weight forward helps offset this, especially with shorter chainstays compounding the saggyness. Of course moving the rider forward helped weight the front wheel. At roughly the same time, the trend went from clipped in to flat pedals, allowing riders feet to naturally find an acceptable place for knee comfort, so for many, there were no drawbacks. For trail riders there were no drawbacks. Keep in mind these trends were largely on longer travel full suspension bikes with squishy suspension, soooom much less applicable to the short travel, firm/locked or hardtail bikes we train and race on. Horses for courses! This is the XC/endurance forum, if super steep enduro bike STA don't feel right, use an offset seat post to get the hip/knee/foot angles working for you, the XC rider.

DT
Click to expand...
Yes! I buy this argument.

with rear sag the effective sta goes back to a more normal place.

the steep sta hardtails are what makes no sense to me. If youre having trouble weighting the front for grip you should already be out of the saddle.

Is the fix for this conversation to only discuss sagged sta?
 
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#15 ·
eri said:
the steep sta hardtails are what makes no sense to me. If youre having trouble weighting the front for grip you should already be out of the saddle.
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Seems no one talks about seat tube flex on hardtails much either.
Compared to the seat tube the rest of the frame hardly has any compliance at all.
A slack STA will allow more flex as you go over small bumps. So it makes for a more comfortable hardtail.
 
#16 ·
Jayem said:
In short, yes. I had a steeper ST bike I took on the Iditarod trail 2 years in a row and it was pretty horrible, too much pressure on the wrists and forward-rotated riding position for long-endurance riding. I changed it out the 3rd year for my favorite fat bike, which was much slacker and it was much better. I think the steeper ST is decent on steep climbs and then it doesn't really matter for dropped seats on the DH...but that's a lot of straight up and down that in reality most riding is not, even when you still have big climbs and descents. Reduces versatility to go too steep IME.
Click to expand...

That's one of the flattest routes around -- of course a steep STA put too much weight on your hands.
 
#17 ·
I have knee issues nothing horrible but they are there occasionally bothersome, surgery on one of them many years ago now. Those knee issues all came before modern geo bikes (which I love and am a believer in) I am confident the geo for me is not related

Things to remember:
  • Everyone is Different, so you really gotta be in tune with yourself, what you ride, where your ride and learn from experience
  • If feasible having options is good I have bikes anywhere from 74.5 degree STA to 77 plus, how the saddle is positioned also going to vary on those bike.
  • For me what is important is I actually get ride time on all those options and if I want to do some sort of event or just personal challenge it is important to me to train on the bike I plan to use for said event (or at least something similar). So I I would not train on a road bike with super slack STA and low stack than expect to spend all day on a trail bike with super steep STA. That would throw me off, train like gonna "fight"
  • Play with the position and geo on your bikes, adjust only a little at a time eventually you will know what works for you
 
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#18 ·
Well im not xc anymore but do a lot of riding for hours.

My ebike has a stupid sta of 80°. That is just fucked for anything other than stupid steep uphill and downhill. Pedalling on the flat is uncomfortable. Because its an e-bike you dont need to be as efficient so you get away with it.

On my mtb I need to be more efficient.

Essentially you want to understand what your ideal reach and effective TT is then that give you the required seat angle to achieve those measurements.

I like a reach of 450 and a effective e TT of 600. That equates to a slacker sta of 76-77 ish.
 
#19 ·
eri said:
Is the fix for this conversation to only discuss sagged sta?
Click to expand...
There isn't a metric to where frame manufactures go by. They basically just draw a straight line up from the center of the bottom bracket to the back of the seat tube...some draw to the center of the ST. If you measure the actual STA vs the effective...the numbers can vary widely. I have two bikes advertised with a "74" degree STA...but one has an actual of 66 and the other 71. Mt friend had a Trek Slash from ~2018. It has an advertised 75 deg effective STA...but the actual number is like 65.5.

I'm noticing that a lot of the XCO riders have their saddle slammed all the way back.

There has to be a tipping point? Especially on XC bikes. I mean we're seeing 77 eSTAs on short travel bikes.

I think there are bike companies out there that straight misrepresent their numbers.
 
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