Hybrid Bicycles - What size frame do I need?

I've been looking at the Trek FX 7.5, but don't know which size frame to get. I went to the LBS last week and got on a 17.5" and a 20". I didn't ride either since it was raining that day. The salesman said it looked like I was in between the two. I really felt more comfortable on the 17.5". I am 5'11" and leg length from crotch to floor is 30".

I am 5'9 with a 30 inch inseam and ride a 17.5 of the same model. I have the seat post up about 5 inches . Best thing to do for yourself is to take both size bikes for a test ride to see what fits you best. Stand over height is important, but also horizontal reach from the seat to the stem.

I would take a hard look at the 20" frame. At least try and get in a test ride before deciding. One of my early mistakes with bikes was to buy toward the lower of the possible sizes that I could fit. Too small a size results in a seat too high relative to the bars, and then in too much weight on your wrists.

I'm not saying that 20" is right for you. I'm just saying not to dismiss it out of hand.

You might also look at other brands and models. Another brand may have a similar bike sized at 19".

I am 5'11" and leg length from crotch to floor is 30".

I'm about the same size as you. My Trek 7.3FX is a 20" frame, and fits me perfectly. When I was trying it out at the LBS I did also try the 17.5" frame, and opted for the 20.

Overall I agree with the others....try them both, see which fits you better.

And, when you test the two different sizes, make sure that both are the same.

Check tires for the same pressure, same seat height from the ground, seat as level as possible, and as close as possible the handlebars should match. If there is anything wrong with brakes or shifters, have them adjust them right away.

Take them for as long a test ride as they will allow.

That way, you will be comparing apples to apples.... and you will find out if the longer reach is better for you, or not.

[QUOTE=jacksbike;9932594]I am 5'9 with a 30 inch inseam and ride a 17.5 of the same model. I have the seat post...

That is about the height I am. Now my quandry is a listed 7.5fx Trek, "52 cm" as posted. Now are we talking top tube? My guess thus far: he has a 20". But I recall once a LBS telling me 54 cm is about right for me. WTF.

Oh yes. Does Trek size their bikes small?

--confused here

I like frames on the larger side.Like my saddle as low into frame as i can get within reason.Stems can be changed for reach,so reach doesnt affect my decision too much.Bikes ride a little smoother the larger the frame i think.Just my preference.
Check the Rivendel site,whether you agree or not theres quite a bit of info on sizing there you might enjoy checking out.Just saying is all,dont need flack from those of you who dont agree with Lemond French style of fitting,as found on Riv site.