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The right size(6 posts)

The right sizeHappyguy24
Jun 8, 2003 11:54 AM
Hi, I am new to road bikes. I am planning to buy a road bike soon. My hieght is 5'4", what frame should I get?
re: The right sizejtolleson
Jun 8, 2003 12:27 PM
I thought about not even trying to answer this thread since it defies answering. But... the true answer is... (drum roll please) ... IT DEPENDS.

What kind of riding do you want to do?
How much do you want to spend?
What is your cycling inseam, torso length, arm length, flexibility, back/ab strength...

If your question is truly that wide open, then get thee to a good road-oriented bike shop and spend some time with a sales person. Talk about frame materials (steel, aluminum, carbon fiber, titanium) and about the varying levels of components, as well as the variations in geometry between different bikes. Then if you get some general direction but want some real life feedback, come back and ask.

There is no "right" answer to your question.
oh sure theres a right answer...collinsc
Jun 8, 2003 12:42 PM
and it is "search"
re: The right sizeHappyguy24
Jun 8, 2003 3:47 PM
I got I need a 49cm, that's all the answer I need
I'm glad you think that is all you needjtolleson
Jun 9, 2003 5:44 AM
and it may be just fine for you, particularly if you are just looking to tool around 200-500 miles a year.

I had read your question of "what frame should I buy" to also encompass frame materials, etc. I guess you are just curious about sizing. But even then, assuming all you need is a 49 cm is not accurate.

Manufacturers measure differently. Is that 49 cm measured center to center or center to top?

What length top tube and stem is best for you? If you are all legs, you can wind up with a reach problem and if you are short legged you'll be too scrunched.

At 49 cm, should you consider a bike with a 650 cc wheelset? Do you have a risk of substantial toe overlap?

At your height, anything from a 47 cm to a 51 cm could be in the ballpark, depending on what manufacturer and how you are built.
It's not nearly that simpleKerry
Jun 8, 2003 4:35 PM
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) and see if you adapt to the 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.