Big difference between 17.5 & 20" Trek 7.3 frame?

Hi: Sorry if this is an idiotic question. Am new to biking. Plan on getting a Trek 7.3 FX. I am 5'7" tall & a bit longer in the torso than in the legs. Have been told by two bike shops that I'm between a 17.5" & 20" frame.

Tried a 17.5 inch in the 7.3 and a 20" in the 7.2 (they didn't have the 20" in the 7.3). Neither felt dramatically different. Both were comfortable, but the 20" may have felt a bit more comfortable.

My dilemma is that I can get a great deal a on a barely used 17.5", but will have to pay full price for the 20".

Is there that great a difference given that they both seemed pretty comfortable with the edge to the 20"? Don't want to end up being cheap & regretting the used bike purchase.

Will not be riding more than 30 or so miles a week. At least that's the plan for now. Thanks so much for any advice.

Denise, I'm also about 5'7" with more torso than legs. What I got recently was a 49cm Lemond which is considerably more comfortable to me than our son's 50cm Trek Pilot. It's a function of vertical height (legs) and cross bar length (torso comfort).

If I remember the conversion correctly, the 20in frame is about 50 cm.

Get the best you can afford. But for me, I'd go with the "best fit" for your body because you're going to enjoy it so much that you'll be riding it more than you think. 6 months ago, I couldn't do 10 miles without heaving and now I'm averaging 70 to 100 miles/week and shooting for my first century tomorrow.

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Originally Posted by Denise147

Hi: Sorry if this is an idiotic question. Am new to biking. Plan on getting a Trek 7.3 FX. I am 5'7" tall & a bit longer in the torso than in the legs. Have been told by two bike shops that I'm between a 17.5" & 20" frame.

Tried a 17.5 inch in the 7.3 and a 20" in the 7.2 (they didn't have the 20" in the 7.3). Neither felt dramatically different. Both were comfortable, but the 20" may have felt a bit more comfortable.

My dilemma is that I can get a great deal a on a barely used 17.5", but will have to pay full price for the 20".

Is there that great a difference given that they both seemed pretty comfortable with the edge to the 20"? Don't want to end up being cheap & regretting the used bike purchase.

Will not be riding more than 30 or so miles a week. At least that's the plan for now. Thanks so much for any advice.

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My Trek hybrid is a 17.5 and I'm 5'8' and long legged- the 20 was too big for me- I'd lean toward the 17.5 if I were you and get the best deal you can. Good Luck. Jenn

I'm also 5'7", with long arms and a long torso. When I was bike shopping recently, I tried both Treks. The 17.5 felt all wrong to me - I felt all scrunched up and kept wanting to scoot off the back of the saddle. The 20" was much better.

I didn't end up with either bike, but I'd be hesitant to buy the smaller size without spending more time comparing the two, if I were you.

Thanks so much to everyone for the replies! Really appreciate the advice and plan to head back to the bike shop to give both another shot. Thanks again!