measuring STA

[Miranda]

What's the best way to do this? With something like my kid's protractor tool for geometry math homework? lol

Yes, I know geometry is published by the bike brand maker. But, I'm going to a bike yard sale swap meet event that my club is hosting. I've carried my tape measure with me before bike shopping odd places. But, the STA is very important to fit as well.

TYIA.

[OakLeaf]

Just thinking "out loud" here ... the challenge in directly measuring the angle is turning those cylinders of the tubes into straight lines that you can line anything up on accurately.

What about an indirect method using a plumb line, a level and a couple of rulers? What I might do is first set the seatpost so that it's the right height for you. Set the bike in a trainer (with the front and rear wheels level), take the plumb line from the center of the seatpost clamp and measure horizontally from the center of the BB to the plumb line. Would that give you the fit information you need?

[Miranda]

Thanks for responding... you know that might do it. I'm gonna try to measure my current bike I think to verify I can do it correctly. It is already set up in the trainer atm.

Bike fit... live and learn...
My first road bike was an ill fitting mess. I know from the pro fits I've had that about 73.5degrees-ish is ideal for me. My Orbea Onix dama is a 49cm w-51TT and the STA is 74.5. With the saddle (Terry tri gel) set back at the last "stop" mark, I achieve a good KOP. Many brands of smaller size bikes the STA just gets too steep, like 75-76degrees. I know if the STA is any steeper than my Orbea, I will be past the "stop mark" and need a set back set post... which starts to throw off your center of gravity etc. I can also ride a guys size 48cm if the TT is not TOO long. I'm all torso, and short legs build. Which we all know the more you hafta push back the seat, the TT virtually gets longer and longer. Gheez, it's really hard to find smaller bikes with slacker STAs!

This bike is going to be like a "back up bike" to my good carbon roadie. Looking for good used, or lower end new bici price range.

EDIT ADD: Just going to throw this in here if someone has any brilliant brainstorms on other choices of bikes that work geometry wise... my "if I'm buying new" choices are:
1) a 2nd Orbea 49cm dama Aqua T23 (comes either flat or drop bar same price) geo size 49cm ST43 TT51
HT110 STA74.5 http://www.orbea.com/us-us/bicis/mod...ama_flat_t23/#
2) Cannodale women's Sunapse alloy 7 geo size 48cm ST44 TT51 HT113 STA74.5 http://www.cannondale.com/bikes/wome...s-alloy-7-sora
3) REI brand flat bar roadie Novara women's Express XX size "extra small" geo ST43 TT53.5 STA http://www.rei.com/product/807244
*while the TT is longer on this bike, it's about like my hard trail mtb, Trek wsd 4300 size 16" (ST40.7) TT53.4 STA74... I think it works ok because I'm not stretching out to the hoods or drops like on a roadie*

Just thinking "out loud" here ... the challenge in directly measuring the angle is turning those cylinders of the tubes into straight lines that you can line anything up on accurately.

What about an indirect method using a plumb line, a level and a couple of rulers? What I might do is first set the seatpost so that it's the right height for you. Set the bike in a trainer (with the front and rear wheels level), take the plumb line from the center of the seatpost clamp and measure horizontally from the center of the BB to the plumb line. Would that give you the fit information you need?

[Triskeliongirl]

My 48 cm cervelo RS has a 73 degree STA, and I love it. I have long femurs and need a 73 degree or less STA to get set up properly. Saddle matters too. I use a selle italia diva gel flow which has nice long rails.

While you could try to measure it with a protracter, I think it will be hard to get an accurate measurement. Perhaps if it was immobolized in an instrument like you might find in a frame shop. But maybe bringing your saddle seatpost with you, dropping a plumb line and measuring where it falls relative to your bottom bracket would work (but make sure bike is perfectly level, perhaps put in a stand and then be sure both wheels are same distance to ground.)

[laura*]

If you are willing to spend some real money on an electronic tool, then consider this:

http://www.amazon.com/M-D-Building-P.../dp/B0000225AL

It will measure angles to a tenth of a degree. As a bonus, it can also measure the steepness of hills with a readout in percent grade.

[DebW]

Thanks for that tip. I've got a mechanical angle-finder similar to this but it's only good to 1 degree resolution, and
probably 2 degrees precision.

This one at Amazon looks good to for $30.

[Cataboo]

My litespeed terramo probably has a geometry that you can work with. I need about a 73 degree seat tube angle as well.

[emily_in_nc]

Older Terry bikes with the smaller front wheel have a 73-degree STA. My Bike Friday Pocket Crusoe does as well. Both are obviously very different compromises because of the small wheels, but that allows the slacker STA and no toe overlap even with shorter top tubes.

I used to have a Terry Isis with that configuration and liked it very much; and now I really enjoy the fit of my Bike Friday.

[Miranda]

Cool... didn't know there was even such a tool made to measure like that... the things I learn here on TE lol... ok, good ads on bike brands too with similiar geometry, that helps my search, thx.

[alimey]

We use an iphone. Useful for measuring STA & also saddle angle. Just download one of the spirit level apps. Don't forget to make sure the bike is standing level - a long something balanced/held on the top of the axles/QRs w/ the phone on top will tell you this.

[OakLeaf]

Oh duh, why didn't I think of that? Good call Alimey!