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  1. #1
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    Need advice on sizing a bike....

    So I think I am confused on how to properly size a bike. I know the best way is to go get on the bike, but I am trying to get a feel of what I want to look at based on specs. I have a Trek 7200 in a 25" frame right now. It has a stand over height of 34" and an effective top tube of 23.3". Overall this bike fits me well, when riding on the road that is. I tried taking it on the trails, and it didn't handle wells for many of reason. One of my biggest complaints was that it had too much stand over height. This really sucked because I felt like I couldn't stand up to pedal when needed.

    I am 6'8" and have a 36" pants inseam. I tried measuring true inseam and got about 37". this wasn't with shoes on, but I was wearing sandals. Standing over my 7200, it feels tight on. I am guessing I need at least 1-2" more of clearance. I read a few places that you should have at least 3-5" of clearance between your inseam and stand over height. I am not sure exactly how stand over height is measured. Is it fairly consistent. The top bar of my 7200 is parallel to the ground, does that change anything?

    Anyway, I am looking at a few bikes...

    Gary Fisher Cobia 29er
    25.3" effective top tube, 31.7" standover


    Trek 6000 21.5"

    25.2" Effective Top Tube, 32.1 Standover

    Trek 4500 24"
    24.2" Effective Top Tube, 35" Standover

    Specialized Rock Hopper 29er 23"
    26.4" Effective Top Tube, 34.4" Standover


    I worry that the Trek 4500 and Specialized Rockhopper have too much stand over height. Are they measured differently than my 7200 or is stand over, stand over? The Specialized seems to have the best top tube length for me, but it has .4" more stand over height. Seems like the Trek 21.5" size has the most "ideal" top tube length to stand over height. I think the Gary fisher would work too.

    I sat on a Gary Fisher 26er 21" and it wasn't bad. The stand over height is only .2" of a difference between the 26er and 29er, so it was a close approximation. The guy at the bike shop thought the handle bars were too close to me, and it wasn't the best fit. He suggested the 24" Trek 4500, but looking at the specs, it does have a shorter top tube length.

    Looking at the Specialized 21" specs, it has a 32.9" stand over height, and a 25.6" effective top tube length. So that might be more ideal than the 23". Although, I like Treks a lot, and I am really starting to like what I see from Gary Fisher.

    I guess my question is, am I looking at this right? Is 34" of stand over height on mountain bike geometry the same as 34" of stand over on my parallel top tube hybrid? My thought is that if the handlebars are a little short on the fisher, I can extend them out a bit. The guy at the bike shop recommended against it saying that I would have less control over the bike. So not really sure what is ideal. Any advice would be appreciated.

  2. #2
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    Standover is measured from the ground up and lets lets you know (on paper) how much clearance there is between the top-tube and "the boys" should you need to put both feet on the ground with the bike between your legs. You get back 4 to 5 inches of clearance while on the bike because your pedals at their lowest are that high above the ground.

    I think the difficulty you had with standing up to pedal is that your handlebars are in the wrong place for it on the 7200. Hybrids are a PITA to stand up on while riding (for me anyway and that's true even on a bike that's two sizes too small). Also, if your seat height is set so that your legs are fully extended while sitting, it will be hard/impossible to stand and mash as your already at maximum extension.

    If it helps, I'm 6'0" have a 33" inseam and would ride a 21" Specialized as my 19 is actually a little too small for me.

  3. #3
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    I know the concept of stand over height, however my 7200 has a bar parallel to the ground. It does not look like that on Trek's site, but the 24" has a parallel top tube. So where the confusion comes in, is where is the actual stand over height measure on bikes without parallel top tubes? Is it measure in the middle, or at the highest point of the top tube? I guess I am curious if a 34" stand over height on a bike with a parallel top tube is different than 34" of stand over height on a bike that does not have that.

    Riding my 7200 on the trails was more than just the stand up ride, as I realize the bars are too far back giving a more upright position. It just overall felt to big. I sometimes couldn't stand over it on uneven ground. I felt like I had too big of a bike for the trails. Although I literally could not stand up and pedal at all. I kept feeling like I was going to crash into the bar and I couldn't gain momentum. Maybe it was just me, and the geometry, but I felt like my bike needed to be smaller.


    I don't understand how you can ride a specialized where the stand over is the same as your inseam. Everything I have read says 2-5 or 3-5 inches of clearance. Also, its my understanding that its better to have a frame that is a little too small, because you can adjust the seat and handle bars. Where if it too tight of a fit, or too large, you cannot make it fit smaller.

  4. #4
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    I think they measure standover vertically through the bottom bracket to the top of the top tube. I know it is NOT to the highest point of the toptube.

    As for standover, I don't worry too much about it. As long as I can stand on level ground with the bike b/w my legs without hurting myself I'm ok. My bike shoes have cleats, so I think I'm up to 34" inseam with them on. When riding on uneven ground (on the trails) it is either a spontaneous dismount (crash) or I just put one foot down and lean the bike over for clearance.

    Seriously though, the best way to figure out what you like is by test riding. I don't like my current bike because it is too small, I have the seat all the way back, the 400mm seat post just about at maximum extension, and I really need another inch or so of toptube length.

    Also, on a MTB vs. hybrid the standover may be a bit taller (for frame size) because of the bigger tires. If you can find an LBS that allows demos, go for it. I think you'll find the change in seating position and hb height will make a huge difference to your off road confidence.

    Edit: For the life of me I can't figure out how people ride an MTB with 3 to 5 inches of TT clearance unless their top tubes are very sloped.

  5. #5
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    Stand over should be measured with the tires on, otherwise what is the point. So the measurement accounts for the tire size. While my hybrid tires (700x35c) are bigger than a 26" wheel bike, they sure aren't bigger than 29er wheels.

    I do know that when I looked at the fisher 26er, putting the seat at maximum extension was way too tall for me. So that wasn't an issue at all. I had more than enough to work with. The guy just said he didn't think the handle bars are far enough forward, and I shouldn't extend the stem because I will loose some of the steering control. The bike he recommended ordering though has an inch smaller effective top tube length, it also has about an inch longer stem. So in reality, its probably about the same, which I do not get.

    He was insisting I didn't fit on the bike, but I thought I could. I thought if anything I would maybe need to raise the handle bars up a bit by getting a stem with a steeper rise angle. So I am not sure. I didn't ride the bike, nor did I get a good feel for it. I just adjusted the seat really quick and sat on it. First maxing the seat height, then lowering it to where I could actually get on the bike.

    I found some formula online, and I am not sure how accurate it is. But it suggested that when looking for a mountain bike you should take your measured inseam and multiply it by .59. If I do this I get 21.83". That would leave me to believe that I should be able to swing these 21 and 21.5" frame bikes. It also makes sense to me, since standing over my 7200 on the driveway I barely clear the bar of the 25" frame bike. I calculated that using my inseam at 37". Even if I call my inseam 38" that would give me a 22.42" frame.

    I am not sure how accurate or realistic that is. I realize all frame sizes are different, and all of the geometry will be slightly off. What I do know, is regardless of how my 7200 is built, its bigger than what I want for a trail. I constantly felt like the frame was too huge. I would want something where I had a little more crotch clearance, and also something I could jump over things with. Pretty much impossible on the huge 7200 to do anything but pop the front tire, which is part of the reason I bent the smallest chain ring while out on the trails.


    Also, this is something I found on Specialized's site....
    Be aware that there are typically going to be two different frame sizes that will fit you. The main deciding factor will be what riding style. People who are more aggressive riders, or with a BMX background typically prefer a frame that is slightly smaller where as riders more interested in comfort or a long, aerodynamic position typically do better with a frame that is slightly longer than an aggressive riders would use.
    I think this is true for the trails I was on. Also maybe because I rode BMX bikes throughout my youth, even at my current height. I just weighed a lot less than. I have never had issue with my Trek on the roads. IT worked fine, but I always pedaled from a sitting position and went on longer rides. When on the trails I needed to stand up a lot, try and jump some minor obstacles, and maneuver quicker. I felt like I couldn't do it, and for the most part I couldn't.


    I really wish I could go try all these bikes next to each other, but I can't. Seems like the bike shops mostly carry 15"/17"/19" with the occasionally 21"+ bike sizes. I would love to compare a Trek 21.5" to a Gary Fisher 21" 29er and a Specialized 29er 23" vs. 21". Its not easy finding all that in store, especially right now when they are clearing out the 09's for 10's.
    Last edited by DarkKnight369; 07-28-2009 at 09:54 AM.

  6. #6
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    Standover height is to the lowest part of the frame in front of the seat. Most 29er frames have the top tube sloped upward from the seat.

    Best test is to stand over the bike in front of the seat, feet flat on the ground. Lift the front wheel off the ground until the top tube comes in contact with your family jewels. Depending on your riding style and comfort level, you should be able to lift the front wheel about 2 to 4 inches off the ground, or have about an inch to 2 between you and the top tube.

    But really, this is all academic. The real answer is to test ride, sit on, and get help from a good LBS.

  7. #7
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    Try running your numbers using the fit calculator at competitivecyclist.com.

    I am going through the same process right now trying to figure out the geometry differences between 29ers.

    The advice I see over and over is fit the top tube first, and then worry about the standover.

    With your measurements, it sounds as if you have a long trunk/torso, so I can see standover being an issue. You'll want at least 2" from the tob tube to your crotch, where you dismount..

    When I was comparing geometries, the longest top tube I saw was the Specialized 23. Gunnar also makes a very large steel framed 29er.

    Remember too that the geometries really seem to vary at lot with 29ers, depending on things like seat angle and fork travel. Look at the bikes on the Felt, Rocky Mountain, and Niner web sites and you'll see a lot of distance between the seat and the top tube.

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