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MTB Seat Tube Angle Explained | How Does It Affect A Bikes Handling?

MTB Seat Tube Angle Explained | How Does It Affect A Bikes Handling?

– Why is seat angle so important and how can changing the
position of our saddles affect how our whole bike feels when we’re sat down pedalling? Well, I hope to be able to shed some light on that very question today. (whoosh) – There is a huge conversation
going on in regards to our seat tube angles on our
trail and enduro bikes. So, how we ended up on seat tube angle as something to change. Well, as bikes have gotten longer reach, it means that we can get
our weight more central by steepening the seat tube angle, and it makes our seated
position a bit more comfortable on those long bikes. When it moves your weight forward, not only does it position your weight closer to the front wheel, but it can also deliver
more grip on the rear wheel. When we talk about seat tube angle, there are two main
measurements that we discuss. There’s effective and actual. Now effective is the line
from the bottom bracket, the center of it, to the center of your saddle rails. And actual follows the exact angle of the metal tubing there. Now, how do these different
measurements have an effect on the feel of our bike? Well effective is in some
ways the really important one, because that really does
change where your weight sits. But actual is a vital measurement too. People that run lots of seat posts exposed outside of the bike will find that effective seating position
is drastically effected by your actual angle. Because that means the
higher our saddle is, the further it is moving backwards. Now imagine if you had a very, very slack actual seat tube angle, it would mean that your seat post would be coming really far out, so the higher you have your saddle, the slacker the effective
seat tube angle is becoming. I hope that makes sense. So, how would we measure this? How are we going to measure it today? Well, I have measured
between the two extreme marks on this saddle, right in the center of the rails there. And I have positioned that right in the center of the seat post. We measure from the center
of the bottom bracket, straight up through until
it dissects that mark and we take a measurement. Now a way we can drastically
effect our effective seat tube, is by sliding the saddle
forward and back on its rails. Let’s take some measures then and find out the overall
effect we can have on our seat tube angles. So what if you want to
run either a slacker or steeper effective seat tube angle, what can you do? Now you might find yourself
in this position due to a limitation of bike design, or because you have a bike where you run a lot of seat post, and exaggerates some of those angles. Well you can of course
move it on the seat rail, but how much room do we have to play with and what does it effect
in terms of the numbers? So this is actually Blake’s bike and he’s got the saddle at full extension and with the saddle in
its most neutral position, he is running an effective seat tube angle of about 76 degrees. So here I have this saddle
slammed as far forward as it can in its most extreme forward position. That is sitting about 77.5 degrees. So it’s added a huge amount
in terms of the effective, it’s made it a lot lot steeper. Let’s slam it back and
see what the difference is on the other end of the spectrum. (funky music) – There it is, that’s 75.5 in
its most rearward position. So three simple readings there. In its steepest position, it was 77.5, in its most neutral position, it is 76.5, and when this effective seat
tube angle was at its slackest, thanks to slamming it back on the rails, it was 75.5. So that’s really interesting. We talk a lot about frame design and people are up in arms and going crazy because a frame might
have got a degree steeper in the seat tube angle, but we already have a lot of use and a lot of adjustment
in our saddle rail. Now bike fit is something
really, really, really important. And I’m not telling you to
slam your saddle forward on the rails like there’s no tomorrow. What I am suggesting
is have an experiment. It’s also really important to know that having the correct saddle height is always going to be king
to a comfortable ride. I don’t expect you to put up with pain just to be keeping up with the Joneses in terms of effective seat tube. If you’re getting any discomfort, then trust that and change something. I personally find that having
a steeper seat tube angle, it basically alleviates some
of the discomfort I have when riding my bike. But, if I go too steep, it gives me a different set of problems. So it’s a real sweet spot and it’s about getting it just right. In terms of saddle height,
you want to be riding with a slight bend in the knee. And, as you can imagine, as we are effecting where
the saddle position is, it will also have a consequential effect on our effective saddle height because as we’re moving it
more over the bottom bracket, we’re effectively reducing it. So, that’s another thing to think about. Like I said, a slight bend in the knee, and I find in my experience, it’s always better to err
on the side of caution. When you have your saddle a bit too high, you feel so powerful, you feel odd, just so you smash the gears but that doesn’t necessarily mean you’re using your body in the best way. Now, as you can imagine, as we move our saddle
position forward or back, it’s going to have an effect
on all of our contact points. Suddenly, a change in the saddle position, can effect your comfort
if you’re riding clicks. It can also effect
things like your wrists. You’d be amazed at such
a small difference here could potentially be
putting too much pressure on your wrists in your seated position. Which is obviously no good. What I’m trying to get at, it’s really important
to listen to your bodies and understand that a small
change in one part of the bike that effects one particular
area of your body is not isolated to there, and if you changed your saddle position, and then the next day you go riding and your feet hurt like never before, well, they’re quite probably linked. So there we have it guys, there’s over two degrees of movement just in our saddle rails alone. Which is pretty cool
when we’re talking about progressive geometry. Now if you want to stick with geometry, click down here to see
the Dodster’s geometry 101 and click down here to see how we get on when we start messing about with different offsets for our forks. As always, don’t forget
to like and subscribe and we’ll see you next time. Cheers guys!

46 comments on “MTB Seat Tube Angle Explained | How Does It Affect A Bikes Handling?

  1. More content similar to GMBN's on EMBN please? I enjoy EMBN and it is really informative, but feel it is not up to GMBN standards. You all work together, please sort it out. 🙂

  2. Future bike companies:
    90 degree seat angle
    0 degree head angle
    2m reach
    Bike testers, seat angle could be steeper, and it should be lower, longer and slacker

  3. Henry, did you twice say 'how we can effect (sic) our seat tube angle'? Sorry to be that guy, but your high standard of presenting is let down by such a basic mistake and it's a bad example to schoolkids learning English. And it really grates!

  4. Can you please talk about how steep seat tube angles destroy your knees and what the next "remedy" for that will be and how much it will cost?

  5. As far as I can tell, seat tube angle (STA) is meaningless for descending. That makes sense because we get off the saddle for descents. So, is STA only about climbing? When I'm climbing steep and technical, I get off my saddle. The only time I sit is when the trail is easy, and I want to recover before the next challenge. I don’t see STA as being important when I’m relaxing. Am I missing something? Or is STA just another way to drive us to buy new bicycles?

  6. Like the explanation of actual and effective. But there are so many variables and each change affects something somewhere else. Moving the seat forward and back also changes your reach and therefore weight distribution which is also affected by seatpost height. Most important take away is that there are ways to make minor adjustments to get significant changes. Thank you!

  7. I have a theory about how the increasing seat tube angles and reach numbers came about.
    The verdict: we have to thank dropperposts. Because of dropper posts, we can move the saddle out of the way easily. Before that, the seattubeangle had to be shallow, to get it out of the way when stood up. This made longer reach numbers then neccesary. To compensate the loss in toptube length.

    What do you think?

  8. All the big fuss about steeper STA… Apparently a big amount of new frames comes with that. But if it changes anything? Think not because you have still a big margin of adjustment. Of course it will shorten your TT, but yeah old frames still can be up to date

  9. Why aren’t bike frames designed with the bb on the chain stay, the wouldn’t be any chain growth meaning that the suspension would work much better and pedal kickback wouldn’t be an issue why hasn’t this idea hit the mainstream and have any companies tried it and it not worked

  10. So weird I was actually playing with this yesterday… just a leisurely loop with mainly down then mainly up but I ended up slamming the saddle all the way up for the climb back… it’s my silly bike XC HT but with short stem for when I find jumps i can’t resist so very light front end change compared to its design and steep seat tube anyway .. (and dropper routed through BB)

  11. Please stop saying Guys…Guys…Guys. plenty of great female riders out there. Some may be watching ( if not all already turned off by the Guys only thing)

  12. Very clear and vv interesting…never actually thought about saddle impact seat tube angle, tho of course it obvious when u see this.
    Top work

  13. Thanks nice job. I've gone full circle over the course of two years. Needed my saddle slid full forward to put me more upright when I started riding. Now, two years later, my saddle is all the way back to deploy more glutes and hamstrings. The later also removes pressure off my knee

  14. To find a frame size that would fit, How does the seat tube angle effect the reach?  Move the seat forward on the rails, it will put you over the bottom bracket, so the point of the reach measurement and seat tube would be reduced., Would seat tube effect effective top tube?

  15. #askgmbntech Hi Doddy and Henry i'm thinking about getting a hardtail to make my local trail more interesting, but how does geometry compare between hardtail and full sus regarding the feel of the bike? My current bike has a 467mm reach in size L and it feels a bit short, however when looking at hardtails the tend to have a shorter reach even in XL. I'm 182cm tall by the way.

  16. Hate the steep seat tubes. Might be alright if you have a short torso, long limbs and little feet. Makes it impossible to fit for some people. On road bikes, you see those angles on track and TT bikes, and it is compensated with lower bars to keep the same effective hip angle for optimal power output. On a trail bike there is no way to compensate, the bars can not be lower than the fork allows.

  17. I'm 5"4 so I think the new angles will effect taller riders more than it will help me.Still dying to try the new stuff to see what happens though.

  18. It’s so funny when you get a new bike you always play with it and as you go on as a cyclist and keep on making adjustments.

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