Frame dimension questions

[Digi]

I've got a few questions about frame dimension:

Have yall found the listed frame dimensions to be accurate?  Do some deviate from their listed specs or are most true?

Are the listed head tube angles from the various manufacturers based on a 100mm fork?

I've noticed that most of the China frames have short effective top tubes compared to their seat tube lengths...this brings me to the final questions:  Is the standover height also higher with these bikes (when matched with a longer seat tube)?  Does anyone know the standover height of the Orion 29er 15" & 17" (with 100mm fork)?

[Carbon_Dude]

Yes, I laser measure all my frames and they are within +/- 0.000005mm of the advertised specs.

[seat_boy]

Every dimension I've checked on my IP-106 has been spot on, at least as closely as I can measure with a tape measure.

Most of the frames' drawings have a fork length indicated for the given head tube angle.

[Digi]

I'm going to blame it on information overload but I never really paid attention to that measurement.  I started looking at that measurement and this is what I came up with...bear with me if I'm all over the place.

For sake of ease, I'll use the 19"(483mm) 056/057 geometry since this seems to be one of the most popular frames.  So I just measured my fork just now, from the top of the crown, to the middle of the thru axle and it's 550mm.  Now looking at the 19" 056/057, it has a head tube angle of 69.5, measured with a 506mm fork, and wheel base of 1118.8.  After finding this calculator:

http://bikegeo.muha.cc/

...I entered in the measurements and it spits out a calculation of 67.42.  So does this mean that the longer fork would decrease the head tube angle, creating more slack with a difference of -2.08?  Then I picked the "Reba 29 - 100mm" fork from the drop down list in the calculator and it shows the fork only measuring 510mm, which then gives me 69.31.  This seems like I'm missing something here.  Giving the general rule of "20mm fork difference = 1 degree head tube angle", it seems like I'm measuring my fork wrong.  Has anyone measured their head tube angle (starting off with 69.5 degrees) with a 100mm fork?

[adym]

What length fork are you thinking of using? And does the calculator account for any initial sag of the fork, the longer the fork, the more sag you'll get, and decrease the HA difference.

[Digi]

I have a 100mm fork.  I'm assuming the calculator measures an unweighted, fully extended fork.

[Digi]

Anyone have more input on this?  I want to make sure I have this head tube angle thing down before ordering the next frame....just not sure what the final angle is on these frames when paired with a 100mm fork.

[carbonazza]

You need to look at the crown to axle distance, and the offset at the axle.
Then compare it to the geometry file.

If it is shorter, your bike is less stable but easier to turn.
If it is longer, your bike keeps better its curse, but harder to turn.

I do not remember exactly but I think I'm 10 or 20mm off the geo length with my 100mm Lefty.
I don't know your level,  I ride around 60-70km per week. But can't feel anything wrong.
The bike is incredibly easy to ride.

[Digi]

Okay, so I used Carbon_Dude's template and created a spreadsheet for my potential frames.  It has several popular bike manufacturer frames along with 4 Chiner frames at the bottom.  For anyone that might be looking for the same, here are my measurements:

Height: 5' 8.5"
Weight: 165 lbs
Inseam: 30"
Purpose: XC race

For the "Head Tube Angle", I listed the given specs as "Head Tube Angle/Fork Length/Fork Rake".  For the "Effective Head Tube" measurement, I calculated what the ending head tube angle would be with a Reba 100mm 29er fork.  Someone correct me if these calculations wrong.

[rrrrxx]

Digi
Can't see the big pic...

[Carbon_Dude]

The chart looks good to me on my Mac using Safari.

[Digi]

I can see it fine in Windows7 with Chrome, FireFox, IE10.  Try right clicking the chart and opening the link in a new tab/window.  That should send you directly to the chart.

*I uploaded a corrected chart. It now contains the standover height for the "Orion 29er S" and corrected "Effective Head Tube Angles".