Am I measuring my frame size correctly?
 

For some reason my original post in the MTB forum went away. Mods can move this if need be.

I have a Trek 3700 mountain bike. I want to make sure I am measuring the frame right.
Based on what I'm seeing, it looks like either a 16" or 17" frame.

Is that correct? Is this how you measure all frames, including MTB frames with the slanted cross bar?

Here is a photo with tape measure for reference:

[IMG]http://i.imgur.com/rA6qoWA.jpg[/IMG]

Thanks so much!

For what purpose?

The way to tell would be to find the Trek catalog for the model year of your bike (it should be online) and find their spec chart for the frame. From there, you should be able to compare measurements like that one and easily be able to tell which size Trek called it.

Center of BB to top of seat tube is the length of the seat tube, itself..

Stand-over OTOH is mid point of top tube to the ground..

The purpose is that this bike fits me well and I want to know the frame size for when I get something new.

Finding an old Trek catalog can't be the only way to measure my frame size...can it?

So how do I know the frame size?

https://www.google.com/search?q=how+...ih=887#imgrc=_

Look at those pictures...
You want to measure from the center of the bottom bracket (the middle of the crank arm, basically) to the top of the seat tube - for the seat tube measurement.

For the top tube measurement - Measure from the center of the seat tube to the center of the headtube.

For the stand over measurement - measure from the ground to the top of the toptube, near the middle section.

Your bike looks like maybe 15-15.5, but its hard to tell since its not lined up correctly.
Below are some pics from the search. You can also watch youtube videos (just search "how to measure a bike frame").

Like the other poster said, it's typically measured from the center of the bottom bracket to the top of the seat tube. Looking at Trek's catalogs back to 2007 or so, they list 16" and 18" frames among the sizes for the 3700. You can be fairly certain that's a 16.

More importantly, from Trek's specs you could find other (more) important dimensions, such as effective top tube length and reach.

yes, but... some modern sloping top tubed frames are measured to the top of a virtual horizontal top tube.

Thanks!
My photo is the same measurement as the photo you posted on the right, or am I missing something?

Thanks!
How did you find that catalog?

if you do not want to measure everything yourself - best bet is to find the catalogue.
Aside from seat tube length (which is pretty meaningless on MTB with modern sloping TT) - there are reach, stack, effective TT, standover height (and SO height can be affected by how tall are your tires). Moreover - if you get the exact same bike which was fitted for someone else it may have longer/shorter stem, stem angle could be different, your bars may have additional rise, they also may have setback and may have different setback angle.

Look at the pictures of frame geometries from different manufacturers (I recommend Surly, they have very detailed sizing info) and replicate the measurements on your bike.
here is an example to get you started, Karate Monkey 27.5+ | Bikes | Surly Bikes
http://surlybikes.com/uploads/bikes/geo-gusset.gif

Well it appears that the end of the tape measure is too low in the photo you posted. If you moved the end to the middle of the crank arm/bottom bracket, then it would measure about 16". But, i know its hard to take a photo while trying to hold everything in the correct space, so that could be it.