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Climbing, steeper head angle vs steeper seat angle

2K views 24 replies 14 participants last post by  *OneSpeed* 
#1 ·
Which is the bigger factor of the two? I've noticed bikes HA are getting slacker while SA are getting steeper.


Is a steep SA with a slack HA going to climb as good or better than a steeper HA with a slacker SA?
 
#13 ·
Steep STA only climbs well if you are comfortable sitting upright 90 degrees at the hip and spinning fast while sitting on the saddle. Guess the idea is that it puts the weight forward, and keeps the front wheel on the ground. The trade off is that it totally sucks pedaling on flat ground. Personally I like a 71-72 STA with the seat all the way back, but to each his own. To the question of HTA, slacker lengthens the wheel base and helps keep the front end planted.
 
#14 ·
sta definitely agree. i dont spend 90% of my time going straight up. so a more relaxed sta works better. also helps balance the load into the legs.

dont agree a slack front end keeps it planted. proper weight distribution is the answer. so a slack front needs a long rear. see the pole stamina and gnarvanna for examples.

but what do i know....
 
#3 ·
Steep seat tube lets you stay quiet on the seat to maintain smooth power to the rear tire for longer. And that helps with traction to climb higher before you spin out. You still need to control front wheel flop for slacker ht angles. Skill still necessary.
 
#4 ·
Is a steep SA with a slack HA going to climb as good or better than a steeper HA with a slacker SA?
Probably if it's a long travel bike. Depending on what category of bike you're looking at the steeper STA could help a lot or very little. On an XC race bike it's probably not going to make much of a difference because the geo is already puts in a more front weight biased position.
 
#5 ·
+1 on what jeremy3220 said.

A bike could be designed to allow you to leisurely climb steep inclines, due to how it accounts for weight distro.

Blue Slope Colorfulness Line Electric blue


To not tip backwards (AKA prevent front wheel lift), the center-of-mass needs to be forward of the rear contact patch.

Some designs achieve this by having longer chainstays to move the contact patch back, but this compromises handling elsewhere. Refer to early 29ers, and how they were said to handle like a bus and not jump well. Boost and 1X helped to shrink chainstays back to what people were used to, to the point that they discovered 29ers actually can jump and carve well enough for good bike handlers to take the good (better rollover) without compromising on the rest.

A steeper HA leads to a shorter front end, which shifts the CoM closer to the front wheel. Long way of saying that there is naturally more weight on the front. People might feel like this is good for intuitive cornering, due to reduced risk of front wash-out. On the other hand, it isn't a pretty sight to watch XC noobs dragging their rear wheel like an anchor letting it pinball down any steep, just for the sake of conquering what they found scary (which didn't look scary in picture/video).

Long travel bikes are prone to sagging deeply on climbs, so a steep STA naturally counters this. Lengthening the front, with a longer fork and slacker HTA shifts the CoM closer to the rear. The longer wheelbase also offers high speed stability, which synergizes with the long travel. Without lengthening the CS excessively, a rider's position is re-centered between the wheels on a long travel bike by extending the reach and steepening STA.

A side benefit of steepening the STA is how it reduces the difference in suspension feel between sitting and standing. Depending on geo, when sitting, 65% to 75% of your weight is on the rear wheel on level ground; when standing, 55-65% of your weight in on the rear on level ground. When tuning suspension for sag and bottom out, there's a compromise regarding how the susp feels when sitting vs standing, perhaps having to choose between lack of sag and softness up front when sitting vs the front being divey when standing.
 
#6 ·
I think it'll depend on how much speed you can carry uphill. If you're riding a long slack bike slowly uphill...the wheel will be pretty far in front of you. It'll be much harder to control the font end without a lot of weight on the bar. When you're tired or slow grinding up...it'll take more effort to keep the bike straight.

When it comes to steep seat angles...its not the seat angle that "makes climbing easier" its the saddle position relative to the bottom bracket. No? A steep seat tube angle allows you to get the saddle farther forward...but if your slacker seat angle allows you to get your knees into a comfortable climbing position...it don't see where the issue is. Your saddle is not permenately fixed to the seatpost...it can move back and forth. Only time I can see a problem is if a seat tube be too slack so that you can't get your saddle forward enough...or too steep that you can't get the saddle far back enough.
 
#8 ·
Which is the bigger factor of the two? I've noticed bikes HA are getting slacker while SA are getting steeper.

Is a steep SA with a slack HA going to climb as good or better than a steeper HA with a slacker SA?
But would you ant to descend on tha bike? The point of the newer geometry is more stable and confident handling descending and speed while tweaking the seatangle to keep climbing manageable. I take my cyclocross on same trails as mymodern geo FS, i can pretty much climb as well as on it, but theres no way in heck i can go we fast on the descents.
 
#9 ·
For each degree of STA, the saddle clamp moves about 12-13mm fore/aft (for average height adult).

Perhaps the new "norm" of 76-78d STA is due to how people center their pedal axle mid-foot, rather than under the ball of their foot. It cuts the difference between the two, maybe. For me, that's about 2.5" or 63mm. I'd need a STA that's 5 degrees steeper to just offset that difference.
 
#10 ·
Here are the saddle positions on two of my bikes. Both with 50mm stems. The Banshee has a 10mm longer reach...but with the slightly steeper STA...the ETT is a bit shorter than the Evil. This is the saddle position where my body settles at after pedaling for a while on both bikes. If I come to a steep section...I have enough room on the saddle to slide forward. I can't really have the saddle any more forward. I've found that if I do...I feel more pressure on my knees...isolates my quads and it blows out my legs way too fast. In a more neutral position...I can move back and use my glutes and hamstings.

I have short legs too...short femurs actaully. 5'8" ~30in inseam...probaby less than 30in.

I remember that you had a Following a few years ago and you didn't get along with the STA because you couldn't get the saddle forward enough...I did think about that when I got mine since I do have short legs...but I was able to get my saddle forward enough to make my knees happy.

The Following climbs better out of the two bikes...the Following feels better in general when it comes to pedaling the bikes.

Bicycle tire Bicycle frame Tire Wheel Bicycle wheel rim


Bicycle tire Tire Wheel Bicycle frame Bicycle wheel rim


Here's my road bike for comparisons sake.

Bicycle tire Bicycle frame Wheel Tire Bicycle wheel rim
 
#12 ·
I recently went from a ht frame with a 69HT, 74ST and a 440CS to a 65HT, 74ST and 428CS and the the new frame is better in every ways both climbing and descending. So obviously it’s not just a couple numbers that determines the handling characteristics but the whole frame design.
 
#25 ·
Which is the bigger factor of the two? I've noticed bikes HA are getting slacker while SA are getting steeper.

Is a steep SA with a slack HA going to climb as good or better than a steeper HA with a slacker SA?
So when will we get to 90 degree seat angle and 45 degree head angle?
Hmm, Troll? Sock?
 
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