Steep seat tube angles?

If they’re comparable measurements (either both effective or actual) then you’ll have more weight on your hands on the steeper seat angled bike and the ett will be shorter for the same reach.

On the flip side it’ll be easier to keep the front of the bike down when climbing steep climbs.

As soon as you ride a steep SA bike up a hill, when you get back on something slack you do notice just how far behind the bottom bracket you sit.

Problem is with a steep SA, it shortens the ETT which means you generally increase reach to compensate. Which can be a good thing of course! 😁

Problem is with a steep SA, it shortens the ETT which means you generally increase reach to compensate.

You’ve got that back to front

OP, naff all difference if you don’t want it to. You can slide the saddle aft to compensate if you want to

OK cheers folks, I get the jist re. reach and ETT and actually the bike in question has very simillar reach to the current bike which is fine with me. As a consequence the ETT is quite a lump shorter which is also good as I feel a bit overstretched when seated on the current bike and have the saddle fully forward to compensate.

So, for that reason I would prefer not to slam the saddle backwards on the new bike but am a bit concerned about what differences I would feel in my legs/knees from sitting further over the BB?

“You’ve got that back to front”

Do you mean back to front or chicken and egg?

You’ve got that back to front

Have I? Unless I'm understanding it wrong...

Effective top tube is horizontal from the head tube to where it intersects the seat tube. Angling the top of the seat tube forwards will shorten this measurement.

Reach is from the same head tube but horizontally to a vertical line from the bottom bracket.

So increasing reach, also increases the ETT.

It's why my new bike is 33mm longer in reach, but with a 79 degree seat angle instead of 76 degrees, the ETT is within a couple of mm.

If it had the 79 degree seat angle but the same reach as my old bike the ETT would be much shorter.

And yes you can compensate with the saddle rails but only to a certain degree.

@ta11pau1
Your second post makes sense, but your first one says you increase reach to counteract a short ETT but the only way you can do that is by increasing the ETT, which is why it was a bit confusing I think.

<span style="font-size: 0.8rem;">Assuming your saddle to bar measurement stays the same on both bikes then the steep STA can feel a little weird at first as you will be positioned far more directly over the bottom bracket than a typical bike with a slacker STA.</span>

None of you move the saddle back an inch. You’ll notice that the back wheel isn’t quite in the same place. If that’s not a big deal. If you want a short wheelbase, Google flying gate.

2 deg change in seat angle is equivalent to moving the saddle on the rails by an inch (the longer your legs the bigger the linear change per degree). It’s easy enough to slide your saddle back or forth and then to extrapolate the change.

I feel that I’m using different leg muscle (or at least a slightly different ratio of quad to hamstring/glute) with a steeper st.

The pedals feel more under you with a steep st compared to in front of you with a slacker one.

I prefer this for pedalling steep climbs.

IME steeper = better for steep climbs but not as good on longer gentler climbs. I also find I’m more sensitive to saddle shape on steeper bikes. The same saddle I’d used for 6 years on previous bike was an implement of torture on my new one. Swapped to one with more of a scoop and difference was night and day. Same model of saddle on my hardtail is still as comfy as ever. I feel like I sit more on my “bum bones” with a steeper SA.

One other thing to bear in mind is that although head tube angles are usually very comparable because they really are what they are (assuming you’re comparing full-sus vs full-sus, not full-sus vs hardtail), seat tube angles vary a lot in how they’re measured because most seat tubes aren’t a straight line from the BB.

seat tube angles vary a lot in how they’re measured because most seat tubes aren’t a straight line from the BB.

Very true. I've taken to measuring my own bikes myself to get accurate measurements (ST angle being a straight line between centre of BB axle and centre of top of seatpost in extended position)

At 187cm I can't believe the improvement moving to a steeper ST-angled bike: mk3 Tallboy to a Geometron - around a 4deg increase in effective ST angle. No longer fighting a lifting front end on climbs. Obviously there's a lot more differences than just ST angle between those particular bikes though.

That's very true when the seat tube is kinked, offset and you then don't run your saddle at head tube height.

I used to ride a MK2 Cotic BFe with about 420mm reach, my current Marino is 510 however because the sta on my Marino is considerably steeper, the saddle to bar distance is virtually the same.

Fwiw, I love the steep (77°) sta on my hardtail as I never get a wandering front wheel on steep climbs (obviously there's more to it than just the sta affecting the climbing ability

Cheers! @Robz and @clubby that's the kind of info I was looking for.