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Another "fit" question(4 posts)

Another "fit" questionEngerSal
Jan 31, 2003 12:57 PM
Hey all:

I am shopping for a Trek 5200. This will be my first road bike purchase in years (since a 57cm steel Basso in the late 80s). I am 5-11, w/ about a 33inch inseam. Historically, I have always had problems with too long a reach and back pain on road bikes. I have tried both the 56 and the 58 in the trek, and both seem fine on test rides. I would like some opinions -- am I better off on a frame that could be a little big or a little small. Also, when it comes to later modifications: is it preferable to increase seat hight, stem length etc to make a roomier fit on a smaller frame, or better to decrease the components to make a tighter fit on a larger frame.
re: Another "fit" questionNo_sprint
Jan 31, 2003 1:26 PM
It is my opinion and certainly not universal in every situation and others will likely disagree some, however, in my experience, I will almost always opt to go a touch on the small side rather than the large side. I have slightly short legs. It's likely easier to go a little larger if you've got long legs for your height rather than short. Many Italian makes along with Mercx will favor this scenario a bit more. I recommend you shop for a bike that fits and is in your budget, not shop for a make and model and make it fit you.
Another thing to considerandydave
Jan 31, 2003 8:51 PM
I don't think I can answer your question directly, but wanted to share some of my own recent experiences in this area. I too am in the mist middle of purchasing a bike after 20 years of riding an old Ciocc. I too tend to fall between even bike sizes (54 and 56). An important consideration (that I neglected initially) was elevation drop between seat and handle bars. Yes, a larger frame will result in leaning out further (and a longer reach) due to the larger top tube. Obviously, this can be controlled to a degree by shortening the stem length. But smaller frames can also cause one to bend over further due to a larger elevation drop between seat and bars. Since the frame is smaller, the seat must be raised in order to keep the proper distance between the saddle and pedals. But the handle bars remain lower. Now this latest problem can be remedied in newer bikes by stacking spacers under the stem and/or a positive elevation in the stem. Some folks, as you may discover however, find this remedy distasteful. I have yet to come across a good discussion on the relative merits of the two conditions. Good luck.
Think through the whole pictureKerry
Feb 1, 2003 9:00 AM
You need to get more precise than "about a 33 inch inseam." Have a look at some of these sizing sites.

http://www.bsn.com/cycling/ergobike.html
http://www.coloradocyclist.com/BikeFit/index.cfm
http://www.sheldonbrown.com/harart-frames.html
http://www.rivendellbicycles.com/frameinfo/Frame_Sizing.htm
http://www.peterwhitecycles.com/fitting.htm

For adjusting the fit of the bike, there are roughly five starting points:

1. Seat height (top of saddle to center of pedal axle) at 108-110% of inseam.
2. Saddle parallel to ground.
3. Saddle fore/aft adjusted so that a plumb bob from the bony protrusion just below the kneecap passes through the pedal axle when the cranks are horizontal. This is known as KOPS (Knee Over Pedal Spindle)
4. Front hub axle obscured by the handlebars when riding in your "regular" position (drops, hoods, or tops).
5. Top of handlebars 1 to 4.5+ inches below the top of the saddle depending on your flexibility and size.

These are all starting points for "average" proportioned people, and many folks like to move away from these starting points as they learn what makes them more comfortable, powerful, or efficient. You want to get the fit of the frame as close as you can, then do minor adjustments with the stem, seat post, saddle position, etc.

A lot of this is personal comfort, and we all tend to adapt to a given position over time. For example, a given stem length may be right for you, but it may feel long at first. I use the "handle bar obscures the front hub" rule for my fit, but others claim better position (for them) with the hub in front of or behind the bar. I'm 6' tall and ride with 11.5 cm drop from saddle to bar, probably more than most people would like but fine for me. Some are suggesting zero drop from saddle to bars - it's about comfort, efficiency, and aerodynamics. The ERGOBIKE calculator is pretty good, but it is not infallible. I would suggest riding some miles (over 100 total, and over 500 would be better) to see if you adapt to a given position. There are no hard and fast rules, just general guidelines, when it comes to these things.

Just as important as your size is your flexibility. If you have a stiff lower back, you may not be able to lean over and stretch out as much. If you are very flexible, you may get away with a longer top tube, with the stem in a lower position. Over time on the bike, too, you may become more limber, or at least become accustomed to being lower and stretched out. So, your first 'real' bike may not be anything like what you will want 5 years from now.

Someone new to road riding is highly unlikely to find their ultimate position on the first go. As they become accustomed to the riding position and get some miles in, sometimes over several seasons, people often find their desired position changing. What was "stretched out" now feels OK, or what was "just right" now feels cramped. With time, if you are working on your position along with all your other riding stuff, seat position tends to rise, handlebars tend to be farther below the saddle, saddles tend to move rearward, and handlebars tend to be farther forward from the saddle. You simply cannot say "this is the right position for someone of your body dimensions" because there are too many variables and things that change with time. Get used to your position, and then occasionally make small changes: raise/lower your saddle, move your saddle forward/backward. Ride a while with the changes (a few 100 miles, anyway) and decide if it is better or worse. If it is better, keep moving in that direction. If it is worse, try moving the other direction. If you don't try, you won't find out, but it is a long term process, often taking years, to really dial in your position. And since your strength and flexibility are changing with time, it is reasonable that your position would need to change also.