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  1. #1
    I'm just sayin'... Raven87's Avatar
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    Question about frame size, standover, and comfort...

    Ok... I've looked at several bikes and I swear, each LBS has different theories about what actually 'fits' me when it comes to frame size. Although most fall in the "Buy a medium (17"-19") size frame, some have said it doesn't really matter how the frame is labeled as long as it fits comfortably.

    Now, I know that S/O height is important. But, I've read that there are varieties of measuring that too and that using inseam length is really an incorrect way; that you should measure your pubic bone height and go from there. Ok... no problem.

    But my question is really about what is wrong with buying a shorter frame than what it may appear you need? For example, the Jamis Boss Cruiser 7 I rode was a 19.5" frame. It was up against my crotch but not uncomfortably so and nowhere near the pubic bone.

    Yet, I had my eye also on another bike that had a 16" frame but the LBS said I should not buy a frame that short. It FELT fine and had more S/O clearance so what is the problem? Is it the leverage imposed upon the seat post by having more of the post itself exposed outside of the tube to get correct saddle height?

    I did not see a problem at first glance. Should I go by numbers only? Or, by what fits/feels the best?

  2. #2
    His Brain is Gone! Tom Bombadil's Avatar
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    A smaller bike will usually have a lower head tube and shorter top tube, along with a shorter seat tube.

    This can result in you being unable to extend proper (too short of a cockpit) and the handlebars can be too low relative to your seat - which will have a lot of seatpost showing from where you had to extend it to get the correct length for your legs.

    You can try to address this by getting long stems and/or stem extenders to get back to your correct handlebar position. Or use set-back seat posts to get your seat further back - although that will mess with your seat to pedal angle. It can be done, but can be difficult to get right and even then your overall balance may not be optimal.

    You should know that not all bikes are measured in the same way or configured in the same way. Some bikes have longer top tubes and thus may make it easier to use a smaller size. I have found reasonably good fits on 16", 17", 18" and 19" bikes from different manufacturers.

    Standover is important, but being able to get into the correct riding position is more important.
    "Too often I would hear men boast of the miles covered that day, rarely of what they had seen." Louis L'Amour

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  3. #3
    His Brain is Gone! Tom Bombadil's Avatar
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    An example, which I've shared here before.

    On most bike models, I fit a 17" to 17.5" frame. I test rode (multiple times) a Trek 7.6FX and a Gary Fisher Mendota. Both were good fits in their 17.5" sizes. Then I rode a Fuji Absolute 1.0 in their 17" size. I liked a lot about the bike, except I couldn't get comfortable on it. It rode and handled beautifully.

    The LBS suggested I try the 19", so I did and it was immediately obvious that it was a better fit.

    When I checked the geometry specs, I found that the 19" Fuji had an effective top tube measurement of 555mm. The 17.5" Mendota was 563mm. The 17.5" Trek was around 550mm. But the 17" Fuji wsa only 540mm. Also the head tube on the 17" was 20mm shorter.

    Thus the 17" Fuji was too small, and even the 19" was smaller in some dimensions than the 17.5" Gary Fisher.
    "Too often I would hear men boast of the miles covered that day, rarely of what they had seen." Louis L'Amour

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  4. #4
    I'm just sayin'... Raven87's Avatar
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    Quote Originally Posted by Tom Bombadil View Post
    An example, which I've shared here before.

    On most bike models, I fit a 17" to 17.5" frame. I test rode (multiple times) a Trek 7.6FX and a Gary Fisher Mendota. Both were good fits in their 17.5" sizes. Then I rode a Fuji Absolute 1.0 in their 17" size. I liked a lot about the bike, except I couldn't get comfortable on it. It rode and handled beautifully.

    The LBS suggested I try the 19", so I did and it was immediately obvious that it was a better fit.

    When I checked the geometry specs, I found that the 19" Fuji had an effective top tube measurement of 555mm. The 17.5" Mendota was 563mm. The 17.5" Trek was around 550mm. But the 17" Fuji wsa only 540mm. Also the head tube on the 17" was 20mm shorter.

    Thus the 17" Fuji was too small, and even the 19" was smaller in some dimensions than the 17.5" Gary Fisher.

    That's what I have been wondering... if some sales people get hung up too much on particular numbers and end up discouraging buyers from bikes that, if they actually test ride them, MIGHT find they feel/fit better than the 'recommended' size.

    Thank you for your replies - you've been helpful. I'm going to ride the 'smaller' bike tomorrow hopefully. Just standing over it in the LBS, it felt really great and actually more comfortable than the other, 'taller' bike.

    But, I know that I need to ride it to know for sure of course.

  5. #5
    Small Member maddmaxx's Avatar
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    As Tom has pointed out, Effective Top Tube Length is probably the most important number on a bike. Think of effective top tube length as being the great equalizer between frame designs. It is the top tube your bike would have if it was horizontal to the ground. This length sets how much you are going to reach out for your handlebars and establishes how much of your weight is going to be supported by your hands and how much by your..........saddle. If the bike is too long, you are going to have too much weight on your hands, your arms will get tired etc. If it is too short, you are going to be crowded, the bars will seem too close. This is the abbreviated version as there are many other factors that go into the proper fitting of a bike.

    Standover height is the most abused number used in fitting a bike. For many it will turn out to be a meaningless number. Standover "clearance" is important to mountain bikers and freeride trick artists who ride places where they are easily knocked off the saddle and may suffer sudden and painful contact with the top tube. Bicycle designs and sizes for these folks reflect this need. For the rest of the world...........once you begin to ride, you will not be standing over the bike with both feet on the ground. You will eventually come to a stop, still sitting on the saddle with the bike leaning over and one foot on the ground.

    To make a long story short, it is more important to fit the bike to your riding position than your standing position................unless you stand more than you ride in which case this is all moot...


    Edit: Don't get me wrong, standover is nice......it is just not the first, second or third etc thing that I start with when sizing a bike. It is one of those numbers that can be fudged to make the other important ones come out right.
    Last edited by maddmaxx; 09-19-08 at 06:38 AM.

  6. #6
    Senior Member dguest's Avatar
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    Tom and Max
    That is the first time I have ever heard fitting broke down and explained that way. I think it is great and makes a lot of sense. I just wish a lot more people would read and investigate what the need in a bike, I think a lot more would enjoy riding if they just learned the correct way to buy and fit a bike.

  7. #7
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    As others have indicate, you can't tell much by a seat tube dimension. It's the virtual top tube that's the most important. One might also consider frame angles. A steep seat tube angle will rotate the bike (and the virtual top tube) forward of the bottom bracket/pedals. Since one will sit at the same position relative to the pedals irrespective of the seat tube angle you'll have to reach further for the handlebars with a bike that has a steeper seat tube angle.

    For example, the difference in reach for a given virtual top tube dimension between 68 and 71 deg seat tube angles for a seat height of 28" (above the BB center) is about 1.5".

    I like my knee over pedal spindle about 1.5" (behind) for my road bike in N Florida. I used the same for my mountain bike until I started riding almost half-time in the N Georgia mountains. Then I found I did better on the climbs with it moved forward about an inch (and reduced the saddle tilt angle a couple of degrees) due to the climbs. I had to change to a longer stem to compensate.

    Now I slide further back on the seat in Florida, but it's not a problem as I use a long narrow flat-topped saddle. A dished saddle wouldn't work well.

    My point of all this is that where you like to sit relative to the pedals and the seat tube angle can have a big impact on the proper virtual top tube length. You can compensate with stem length, but keep in mind that longer stem lengths slows steering response and shorter stem lengths increases it. Normally not an issue, but if you have an aggressive head tube angle like 71 deg or way relaxed angle, the result might not be to ones liking.

    I personally set up my bikes for about a 50 deg. back angle relative to horizontal. Forty five is considered optimal for mountain biking, but it's a little to low for me.

    Al

  8. #8
    Time for a change. stapfam's Avatar
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    Mountain bikes are generally fitted so that you use a smaller frame than you think you should need. As Mad Max pointed out- It is effective top tube length that is more critical on any frame and I have found that Mountain bikes that should fit me on standover height- are too long in the reach to the bars. Hence I ride a 15" mountain bike frame with a long seat post

    Now going to the Extreme- I ride an Offroad Mountain Tandem. The sizing on this is very unusual and it is basically a large frame. But top tube length is short on tandems so it feels comfortable.

    And road bikes. Whether By luck or carefull selection- I finished up with both the New road bikes having a top tube within 5mm of each other. They are both comfortable on reach but one is a compact frame and the other is conventional sizing.

    But it does not matter which of these bikes I ride. Critical part to set up within the variables is the saddle. Fore and aft position- Height and slope of the saddle. All the bikes are set up for me but when seated- I cannot touch the ground on any of my bikes. My legs are 2" too short.

    Problem is that as you get into understanding bikes- You get to know what works for you. But we'll leave that till you get on your 3rd new bike next year.

    There are variables you can adjust on a bike- but MAD MAX has a Scale that although I did not use on the selection of my bikes- Came spot on to the sizing I have. But be warned- Sizing is only approximate and BIG mistakes can occur if you get it wrong.
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    Bikes are comfortable to ride if the highest portion of the bars are level with the top of the saddle. A tall frame makes it easier to get the bars that high. If comfort is your FIRST priority, buy the tallest frame possible. The frames that fit me best are very tall (a size 60, a size 61 or a size 62) although I am less than 5'10" tall.

    That means that the top tube will brush against my jeans when I standover the bike flat-footed. Do NOT buy a frame that is so tall that the top tube presses painfully against your crotch when standing over the bike. If the top tube is just brushing your jeans, that is the correct size.

    Folks assume that because a taller frame has a longer top tube, that buying a taller frame increases the distance between the saddle and bars. Not true. As the bars get higher, they move both UP and BACK, closer to the saddle. As a result, the cockpit length on my size 56 bike is 31 inches, identical to the cockpit length on my size 61 bike (measured from the back edge of the saddle to the front edge of the stem).

    I've learned from experience that the bikes that fit me best have a cockpit length of 31 inches, a saddle height of 30 inches, and ZERO bar drop. I ignore the manufacturer's advertised size and buy the bike that yields a result of 31/30/zero.

    Of course, folks who race want a super-small frame, that way they can have the bars four or five inches lower than their saddle.
    Last edited by alanbikehouston; 09-19-08 at 11:51 AM.

  10. #10
    Time for a change. stapfam's Avatar
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    Quote Originally Posted by alanbikehouston View Post
    Bikes are comfortable to ride if the highest portion of the bars are level with the top of the saddle.


    Of course, folks who race want a super-small frame, that way they can have the bars four or five inches lower than their saddle.
    I don't want to race and when I get back into riding I go out for milage.

    First road bike I got was a "Performance" frame. A Giant OCR and have to admit that the headtube is high and I even got a Riser stem to put the Bars at the same height as the Saddle. Second bike was a Race frame and the LBS put the bars at 3" below the saddle. I had my doubts but that Bike is comfortable- Fine for 60 or so miles before I have to think about taking a stretch. Might cause a problem for a 100 miler but I haven't done one of those recently.

    Then I got the TCR-C. Another Race frame and The bars are 2" below the saddle. Most of my fit problems on this is down to the bar height- But on this Bike I have done a couple of Centuries and a 120 in the Spring. For that extra milage- This bike is comfortable.

    Still say that bike comfort is down to the fit. If I were to put the bikes in order of comfort (Most comfortable first) It would be difficult between Boreas and The TCR- but The OCR with the high bars is not even in the same class.

    Every one is different- but I prefer that stretched out feel that the Later bikes give me- And the bars being lower do not cause me a problem- In fact it is the reverse.

    Attachments of the 3 bikes showing the Different bar heights- Saddle position is the same on each of them
    Attached Images Attached Images
    How long was I in the army? Five foot seven.


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  11. #11
    I'm just sayin'... Raven87's Avatar
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    Excellent and very informative replies by everyone. Being out of the market so long, I wasn't sure - all I have been hearing from all the LBS's that frame length and particularly standover height is the key measuring tool. Thus, I have been assuming this is the most important factor.

    Obviously, this is wrong - or at least, incomplete information. Top Tube length is the vital piece.

    I'm glad I asked this because you guys have given me a wealth of info. I do know what fits/feels right - now I know WHY/HOW and this will help me fit the right bike to me.

    Greatly appreciated!!!
    Last edited by Raven87; 09-19-08 at 04:40 PM.

  12. #12
    Sarcastic Bastid mastronaut's Avatar
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    I'm no expert by any means, I am 5'-10.5" the recommended frame size for me is a 23".
    I was not happy with that size because it looked really small (to me). I ride a 26" frame
    and I like how high up I sit on the bike. Sure I can't stand over the top tube, but I just
    learned to lean to one side or the other when stopping. I guess my point is is it's a personal
    preference. I don't race obviously, but I do like to be seen by traffic.
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  13. #13
    His Brain is Gone! Tom Bombadil's Avatar
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    Quote Originally Posted by mastronaut View Post
    I'm no expert by any means, I am 5'-10.5" the recommended frame size for me is a 23".
    I was not happy with that size because it looked really small (to me). I ride a 26" frame
    and I like how high up I sit on the bike.
    If you are talking road bike sizing, that's a different chart than mountain bike sizing, which we've been quoting in this thread.

    On a mountain bike, someone who is 5' 10.5" would normally ride a 19"-20" frame. On a road bike, you'd probably be started on a 56-58cm, which converted to inches is 22"-23". Mountain bike sizes are usually 8-10cm smaller for the equivalent fit.

    It would be unusual for someone of your height to be on a bike larger than 58, unless you have long legs and long arms for your size. As people's proportions vary all over the place, as well as their fitness level, you can't fit a bike size to someone's height.

    I see in your bike pics that you have your seat posts all the way down. That's a sign that the bike's frame is too big for you. But if you are comfy, then that's all that matters.
    "Too often I would hear men boast of the miles covered that day, rarely of what they had seen." Louis L'Amour

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  14. #14
    Sarcastic Bastid mastronaut's Avatar
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    "I see in your bike pics that you have your seat posts all the way down. That's a sign that the bike's frame is too big for you. But if you are comfy, then that's all that matters." Tom Bombadil

    The springer seat is an added few inches, if I had the original saddle the post would be up more. I've been riding for many years, you are correct about the comfort factor. Cheers!
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  15. #15
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    Quote Originally Posted by stapfam View Post

    Then I got the TCR-C. Another Race frame and The bars are 2" below the saddle. Most of my fit problems on this is down to the bar height- But on this Bike I have done a couple of Centuries and a 120 in the Spring. For that extra milage- This bike is comfortable.

    Still say that bike comfort is down to the fit. If I were to put the bikes in order of comfort (Most comfortable first) It would be difficult between Boreas and The TCR- but The OCR with the high bars is not even in the same class.

    Every one is different- but I prefer that stretched out feel that the Later bikes give me- And the bars being lower do not cause me a problem- In fact it is the reverse.
    Both my bikes provide pretty equal comfort for 4 or 5 hours in the saddle if I ride that long regularly. The road bike has the flats (drop bars) about the same height as the saddle. For the mountain bike, the hand-grips are about 2 1/4" below the saddle. My back angle is about the same at 50 degrees. One can get the same back angle by adjusting height and distance from the seat of course.

    After some experimentation, I found I had better control on fast, tight turns and climbing was aided by the lower bars on the mountain bike. It seems easier too to pull-up on the bars too when just out of the saddle on steep climbs. I may have to experiment with the road bike if I ever get back to that much.

    Comparing road and mountain bike comfort is probably a stretch though as the riding is so totally different.

    Al

  16. #16
    Sarcastic Bastid mastronaut's Avatar
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    My bad, I was out of my element there....
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  17. #17
    His Brain is Gone! Tom Bombadil's Avatar
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    Technically the size of your frame doesn't change how high you sit off of the ground. The bottom bracket height makes a difference, as the higher the BB is off of the ground then the higher the "starting" point is for determining your seat height. The seat angle can make a difference, as the lower the angle, the closer to the ground you will be. And, oddly enought, the crank arm length makes a difference too ... with shorter crank arms resulting in higher seat positions.

    Otherwise the distance between the top of your seat to your maximum pedal extension should always be the same, as it is a function of how long your leg is.

    Thus within a specific model line, where all of the bottom brackets are at the same height, the distance from your seat to the ground will be close to the same whether you are on a 16", 19", or 22" frame, providing that you can find a seat post long enough on the 16" or lower it far enough on the 22". But that distance will actually be higher on the 16" by a small amount, because the larger frames will almost always have a lower seat angle.

    Thus going to a larger frame does not get one higher off of the ground, and in some cases, could move you a bit closer to the ground. Unless you purposefully select frames that have a high bottom bracket height.

    The extreme case of very high seats can be seen on circus bikes, where the bottom brackets are moved several feet off of the ground.
    "Too often I would hear men boast of the miles covered that day, rarely of what they had seen." Louis L'Amour

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