RoadBikeReview.com's Forum Archives - Components


Archive Home >> Components(1 2 3 4 5 6 7 8 9 10 )


Help me understand stem rise and rise when a stem is flipped(7 posts)

Help me understand stem rise and rise when a stem is flippedss-nyc
May 8, 2003 11:28 AM
In the old days of quill stems everything seemed so simple, most Head Tube angles were 73 or 74 degrees and stems were -17 or -16 degrees to result in a 90-degree stem or what is now called "0 dgree rise".

Now, I cannot figure out how to calcualte stem angles when you flip an AHEAD stem to get more rise. It should be simple and I hope I am not making it more complicated than it needs to be.

Anyway...
Assuming a 73 degree head angle with a -17 (0 degree rise) stem, what happens when you flip it. Is it as simple as +17 (17 degree rise)?

What would happen if you started with a 10 degree rise (aka 80 degree) stem and then if you flipped it? What would you get in terms or rise?

I hope this makes sense to someone so that they can explain it to me. It has been a long time since High School Geometry class.

Thanks in advance!
re: Help me understand stem rise and rise when a stem is flippedtheweasonator
May 8, 2003 11:51 AM
I just figured it out myself. If you flip a -17 stem, it means it will be 117 degree rise in relation to the Headtube. So this means the stem angle in relation to the ground will be about 30 degrees (degrees above horizontal) instead of 90 degrees. I found a website,

http://www.habcycles.com/fitting.html

That helped me. I have a 100 mm -17 stem that I flipped. I also took it off, printed the chart and plotted on the chart where the center of the HB clamp fell and the center of the steerer in relation to the reach. On the -17 side (parallel to the ground) it was on the bottom with 0 rise. When I flipped it it went to + 30 degrees above horizontal. This means my handlebars were now 5 cm (2 1/2 inches) higher than before. A big difference. It feels good but you might feel it is too high up. I decided to keep it this way until I can get one with like a -6/+6 degree rise that will put me in the middle of where I am now.

Good luck..
More...KEN2
May 8, 2003 12:01 PM
As you can tell from the habcycles site, flipping will also affect your reach to the bars; the more extreme the angle change, the more the reach is affected. In this case, your reach will be about 15 mm shorter after flipping.
Thanks...But...ss-nyc
May 8, 2003 1:33 PM
Do you mean that when you flip a -17 you actually get a 107 degree rise in relation to the headtube which is +30 degrees above horizontal?

I figured this becasue a -17 is also +73 degrees (the same as the headtube) so a +17 should be -73 or 107 degrees which is 180-73.

Let me know if the 117 was a typo or my math is just screwey.

thanks!
You are right.....he was wrong..Rusty Coggs
May 8, 2003 2:42 PM
You add or subtract from 90 degreese. 90-17= 73, 90+17=107. angles are relative to steerer,not ground. The -10 would be 80, or if flipped +10 or 100 degreese.
I had a typotheweasonator
May 8, 2003 6:25 PM
yes, it should be 107. I'm definitely not a mathlete. I do know when I flipped the stem it lined up on the 30 degree angle which increased my rise by 5 cm and decreased my reach by about a 1 1/2 cm. Sorry for the confusion.
re: Help me understand stem rise and rise when a stem is flippedCurtSD
May 8, 2003 2:39 PM
If you start with a -17 degree stem that is level w.r.t. horizontal (for a 73 degree head tube), and you flip it over, then you've now got a 34 degree angle w.r.t. horizontal. So your vertical rize will be stemlength * sin34, and your horizontal distance (reach) will be stemlength * cos34. For example, a 12 cm 17 degree stem will have 12*.56 = 6.7 cm of rise and 12*.83 = 9.96 cm of reach.