Seat Tube Angle?

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2/9/2014 3:18 PM

What does it all affect?

I was looking at a couple frames on dans and some of them had different angles, like the WTP Clash had a 70* and the BS WZA had a 71*, not that 1 degree would make a difference in general, but what does the ST angle affect?

I know that the headtube angle, top tube length, bottom bracket height, rear end length, etc. can determine the "twitchiness" of the bike

and the seat tube/standover height as well with the bottom bracket height effects clearance in some instances, but that also has to do with the sprocket most of the time.

so all in all what does the seat tube angle affect? does having a steeper one give a chance of having a shorter rear end? or is it something else?

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2/9/2014 3:23 PM

It effects the "twitchyness" as well it also makes your top tube feel longer or shorter. 71 is the standard most bikes have and I don't know of any frames with lower than 69. and a degree will make a difference, just like a degree in your headtube will make a difference. I've never ridden a frame with anything but a 71 sta, but I've heard some dudes say 70 or 69 is easier to manual.

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2/9/2014 3:27 PM

Collin_McClenahan wrote:

It effects the "twitchyness" as well it also makes your top tube feel longer or shorter. 71 is the standard most bikes have ...more

oh, alright thanks. I just never really payed any attention to that part of the frame haha.

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2/9/2014 4:14 PM

mellower (less than the norm, 71) will make a frame feel a little bit shorter. for example, a 21" frame with a 69" will feel like a 20.75" (i dunno the exact measurement, just an example) while still maintaining the front end room of a 21". thats what i found when i was reading up on it a while ago anyway

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2/9/2014 4:55 PM

tr1x wrote:

mellower (less than the norm, 71) will make a frame feel a little bit shorter. for example, a 21" frame with a 69" will feel ...more

This.

IMO a 69 degree seat tube angle makes the bike feel soooooo much roomier and comfy.

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2/9/2014 4:58 PM
Edited Date/Time: 2/9/2014 5:34 PM

Just to throw a wrench into this discussion...the Subrosa Balum has a seat tube angle that starts at 74* and goes to 69*. When they first released this frame I asked them what the reason was for the offset. They said the 74 allows for a shorter rear end with a longer top tube. Now, that doesn't mean it was necessary to do the offset seat tube to achieve this - the Balum just has a 13.5" chain stay slammed like most of their frames, and the longest TT is 21". Honestly, I think it was just something neat that they wanted to try. Although I am not sure if the 74* affected the position of the BB horizontally.

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2/9/2014 5:00 PM

^^ Thats interesting I would def like to ride one aand see what it feels like

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2/9/2014 6:09 PM

It doesn't effect twitchiness, it just gives a different amount of room. So a 21" with a 69degree seattube will feel and ride exactly like a 21" but if you measure the tube itself it will measure out to like 21.2". So for tricks like barspins where you clamp the seat, or when youre simply sitting down, youll have more room.

You can get a similar feel by using an Èclat Torch 15offset, Subrosa Layback, or Odyssey Convertible seat post with a 71degree seattube.

The only difference you can feel is the seat sitting back just a tiny amount.

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2/9/2014 11:35 PM

Fondue wrote:

Just to throw a wrench into this discussion...the Subrosa Balum has a seat tube angle that starts at 74* and goes to 69*. When ...more

The Fly Tierra Frame had/has (I'm not sure if it's still made) a similar thing. it had a 71 degree seattube angle all the way through but it was offset on the BB 0.4" back.

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2/10/2014 7:24 AM

Fondue wrote:

Just to throw a wrench into this discussion...the Subrosa Balum has a seat tube angle that starts at 74* and goes to 69*. When ...more

BMX_Forever wrote:

The Fly Tierra Frame had/has (I'm not sure if it's still made) a similar thing. it had a 71 degree seattube angle all the way ...more

Never knew that. With the Balum there's a bend in the tube near the BB shell.

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