My draw lenght is 25.5, but I bought my first bow with a 27 inches. How does one know when the bow is too long or too short?

If you had your DL measured and that's what it is your bow is too long. However, besides measuring your draw length you can draw the bow back and if the string is not touching the tip of your nosewith your brace arm bent the draw length is too long.

You can also take a picture with you at full draw and post it here. There are a lot of good guys that can tell you right away what's wrong.

I tend to pay more attention to where the nock falls at full draw in relation to your eye as opposed to the string touching the nose, because today's shorter a-to-a brace heights can severely throw that relationship off.

Most people seem to agree that the nock should be in line (directly under) with your eye at full draw.

- let me add that I would certainly like my string to touch my nose as DaveC said, I just know that if that's all I go by, my draw length would change considerably between, say... my Tribute and my Constitution -- or at least my anchor would, and I'd prefer that stay constant.

For draw length I prefer to look at rear elbow position. I believe this is the best indicator of draw length personally. From a side view I like to see a rear elbow that is at least level or slightly higher than therelease wrist and bow hand, and from behind I like to see a rear elbow that ishorizontally levelor slightly outside (right) of the and release wrist and bow hand (assuming right handed shooter)For hunting purposes higher and/or outside can bebetter to allow you have enough range of motion to stay behind it when shooting at odd angles or from less than ideal footing. For target, I personally do best shooting a bow that has me almost level both horizontally and vertically at full draw with that rear elbow.

I really couldn't care less about nock position to be honest, that has little to do with the overall geometry of your form as a shooter. String position can also beon the tip of the nose with nearly any ATA length of bow by tweaking loop length for most average draw length shooters. Make the true draw of the bow (string to throat of grip @ full draw) shorter, and increase loop length for a longer ATA bow, or for a shorter ATA bow make true draw longer and shorten the loop. You can accomodate most any bow out there tojust touch the nose onpeople under 30" draw length or so most of the time this way. My personal opinion is that if you can't get your nose on the string by tweaking loop length, you are probably too long of a DL for that short of a bow. At over 30" of draw length, I can get my nose on the string with a 32" bow pretty easily by extending true draw and using a short loop, but not everyone could do this.

Here is a quick video of me that shows my rear elbow position on a target bow at full draw. My hunting rig will be 1/2" shorter and will have that rear elbow a bit higher to help me stay behind it when shooting with bad footing or odd angles.

http://smg.photobucket.com/albums/v283/ringostar40/Archery%20Competition%20and%20Form%20Pics/?action=view¤t=24958d05.flv

I agree. I've found great variance in what draw length I need, depending on my loop and my release aid. I've mad great efforts getting a release that allows me to use a longer draw length and yet keep my elbow in the same position. Things like adjustable barrel lengths, short jaws, proper fitting wrist straps,forward triggers and the shortest possible loops can allow longer draw lengths with the elbow remaining in the same position.