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  1. #1
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    What Trek 7.1 FX frame size do I get?

    Hi all,

    I'm new to this community and am really excited to be purchasing my first hybrid bike for commuting (I previously used a cruiser bike but quickly outgrew it). I want to buy a Trek 7.1 fx bike as it's in my price range and exactly the kind of bike I'm looking for, however, I'm very confused as to what frame size I should get.

    I've gone to look at and test ride the bike on a few different occasions and I found that every time I went the employee would tell me I needed a different size than the last time I was there. Sometimes I was recommended the 17.5" size frame, and sometimes they would tell me I needed the 20" size frame. I'm only 5'9, 155lbs but apparently my legs and arms are proportionally longer than most people which is why I'm always recommended something different. My height tells the staff that at 17.5" would be ideal, but my leg/arm length tells the staff that I need a 20" frame.

    As this is my first hybrid/commuting bike I don't really know how it's supposed to fit me. While both frame sizes are comfortable they affect the way I sit on the bike and I'm not sure which is best. While I ride more comfortably upright on the 17.5" frame my legs feel a bit squished even though they don't hit the handle bars or anything - is it normal for them to feel this way? The 20" frame feels beter on my legs but makes me feel like I might be leaning over more than I should be. In the end the staff say that the decision is up to me - whatever I find most comfortable and it's a tough decision for me to make as their both comfortable in different ways. I want to make sure I pick a bike that I won't start to feel really uncomfortable riding after a few months.

    Does anyone have any suggestions for me as to which frame size I should get?

    Thanks!

    Paul

  2. #2
    Senior Member EsoxLucius's Avatar
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    I believe you should have 2" below your crotch at standover for a hybrid. Adjusting the seat and the handlebars should help you get comfortable after that.

  3. #3
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    I have a 7.3FX in the 17.5" size. I'm about 5' 11" and the ride is fine for me. Had to raise the seat up but I'm mostly comfortable. You would probably be fine with either but you say you are comfortable on the smaller frame so that should give you your answer right there....probably raise the seat up like what I did. A word of advice on the smaller frame, it only has mounts for 1 bottle cage (on downtube). I believe that the 20" frame will have 2 - downtube and seattube mounts.

  4. #4
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    I was in almost the same place. 5'9" is right on the cusp between the two sizes. It's really a matter of what works best for you. I went with a 17.5" 7100 (not the same bike, but but the issue is the same). The bigger frame felt too stretched out and I was able to adjust the seat on the smaller frame for a comfortable balance. Chances are the seat on the smaller frame is lower than it should be. I ended up raising the seat more than I thought I would.

    See if you could take some more extended test rides, since the real fit issues won't show up for a few miles.

  5. #5
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    Thanks for the tips guys.

  6. #6
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    right off the bat i'd tell you to get a 20". i'm 5'9" too and will buy a 20" 7.2 fx tomorrow. just like you, i have long legs for my height. i have a 33.5" cycling inseam. these days its fashionable to buy bikes that are too small but don't fall for it.

    if you buy a bike that is too small you're going to have a ton of seat post showing and the handlebars are going to be low. that's a recipe for back pain.

    hop on a bike, pedal backwards with your heel, and keep raising the saddle until there is no bend in your knee when you do a full backward stroke. now you've got a rough idea of saddle height. then check to make sure that the seat post is not higher than 7-9". i personally make sure that handlebar is even if not higher than my saddle at proper height. it's my preference for comfort.

    the above are pointers on what to look for when doing a test ride. there is absolutely no substitute (and better way) than to go to a shop, do a test ride, see how you feel and get professional feedback. some shops are dishonest and they just want to get rid of whatever they have...so go to several if you are unsure. don't go based on what others think are comfortable or what they ride...they can be same height yet very different in proportions...they may have different riding styles.

  7. #7
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    Quote Originally Posted by Free_style View Post
    While I ride more comfortably upright on the 17.5" frame my legs feel a bit squished even though they don't hit the handle bars or anything - is it normal for them to feel this way?
    for me this is an indicator that you should be on the 20". too bad a slow, brief parking lot ride doesn't tell us as much as a 10 mile ride.

    Quote Originally Posted by Free_style View Post
    The 20" frame feels beter on my legs but makes me feel like I might be leaning over more than I should be. Paul
    do you know the length of the stem you were riding? if it was 120 mm, change it to 100 mm. a longer stem like 120 mm will shift more of your weight forward. a shorter stem like 100 mm with the longer TT of the 20" will keep your weight back and you won't feel like you are leaning over more than you should be. if the bike already had a 100 mm stem, then consider an 80 mm although some people claim that causes twitchy handling (which you DON'T want when riding around traffic). i haven't noticed the difference but then again i don't ride near traffic.

  8. #8
    aka Phil Jungels Wanderer's Avatar
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    I say go for the 20, and adjust the reach with a shorter stem, and "maybe" sliding the seat forward a tiny bit. I like to ride stretched out, so the bigger one always feels better to me.

    "Retirement is the best job I ever had!" Me, 2009


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  9. #9
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    I am the same height. I tried a 17.5" and felt too cramped on it. Went with the 20". A few tweaks here and there and I'm real happy with it.

  10. #10
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    Buy the 20" I ride a Trek FX 7.9 in 17.5 and I'm about 5'7" with a really short inseam. I'd think a 17.5 is not enough bike for you.

  11. #11
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    Thanks for all the feedback! I ended up taking the 20" frame 7.1 for a good 20 minute test ride yesterday and ended up going with it without even trying the 17.5" again. I think I made the right decision but I suppose only time will tell. I'm really excited to get going on it, I'm new to owning a commuter bike and am really excited to learn a lot more about biking. Thanks again everyone.

  12. #12
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    I'd take a glance over Sheldon Brown's website:

    http://www.sheldonbrown.com/

    I've benefited from taking his advice when I had knee pain, and his articles on bike sizing/fitting were what I used to select my current one.

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