Show me proper bike fit

I'm interested in the answer to this question as it pertains to road bikes. My LBS (stands for lousy bike shop) didn't fit me AT ALL and I don't have the cash to do it. I was thinking about taking a series of photos and seeing what I could do from that.

My physical therapist, who's an avid cyclist, told me that as far as the legs are concerned, with the ball of your toe over the axis of the pedal and with your foot level, you're looking for a 9-13^o bend in the knee. So that's really all I know.

Here is one article from Bikesport.  http://www.bikesportmichigan.com/features/exisitingfit.shtml Poke around the site they have a bunch of bike fit articles that are good.  This link was just the first one I saw this morning.

Oh, go to your LBS and get fit.

My coach is a certified bike fitter and I've gotten my tri bike professionally fit so the knowledge I express here stems directly from these two sources.  Additionally, these are merely the BASICS of bike fitting and by no means replace proper bike fitting from a professional as there are many other things that are involved in bike fitting such as your flexibility in your hamstrings and lower back, your neck flexibility, and your wattage in a given aero position.

1. I will assume that your cleats are correctly positioned on your shoes, as this is an advanced concept that can't really be adjusted accurately w/o seeing a pro bike fitter.  Start with putting your right crank parallel to the ground (3 o'clock position). With your foot clipped into the pedal, your kneed should be DIRECTLY over the spindel of the pedal.  If it is not, adjust your seat fore/aft for this to occur.  This is now the position of your seat and this should NOT be moved from here on out (unless you adjust your seatpost height...to be discussed later).
   
2. Now place your elbows on your aerobar pads so that your weight is being held up skeletally and NOT muscularly.  Have someone observe your body position.  Two things should occur in a "perfectly" fit bike.  (a) your back is parallel to the ground (quite rare in most setups...but obviously the ideal aero position) and (b) the angle created by your femur and lower back (negating any natural curvature of the lower spine) as well as the angle created by your chest and humerus (negating any curvature in your chest from your lungs) should be at 90 degrees.  This typically means that your elbows are either directly below your ears (drawing a perpendicular line to the ground through both) or just SLIGHTLY fore of your ears.
   
3. The only way to adjust the angle of your humerous/chest to equal 90 degrees is from a stem length change since, as previously stated, your seat can not be moved fore/aft due to the correct relationship it now has with your "knee above foot placement."  However, if you have to go to a 80cm stem or shorter to effectuate this angle, your bike frame is too large for you.  A "forward" seat post can not correct a too long top tube as your knee will then be forward of your pedal spindle.
   
4. Now, with all that adjusted, you can adjust the comfort level of your neck by increasing/decreasing the stem angle allowing your back a non-parallel relationship to the ground.  This is typically done by most people because (a) it's more comfortable for longer rides and (b) you are not constricting airflow to your diaphram as much by the less parallel your back is to the ground.  The other way to adjust the comfort level of your neck is by simply adding spacers to your fork (assuming you didn't cut your for too much prior to getting your bike fit) above or below your stem.
   
5. Seatpost height is more of an adjustment depending on your hamstring flexibility than a "general" rule of thumb adjustment but to make it work without seeing a professional bike fitting and having him/her measure the angle of your knee flexation, the best way to determine how high your bike seat should be is to raise it just high enough so that when you pedal at 90rpm you buttocks does NOT move side to side on the saddle when someone observes you from the rear.  If it does, lower the bike seatpost a little bit until this stops.  PLEASE NOTE: if you do have to change your bike seatpost height, be sure to recheck #1-#3 above as the seat height will affect these positions.

The two most common things that are adjusted in a bike fitting are the stem length/angle as well as the cleat positioning on the bike shoe.  After that seatpost adjustment and seat fore/aft adjustment are the 3rd and 4th most common because most people naturally gravitate to the correct seat height and fore/aft adjustment and these are the easiest things to adjust as well.

Keep in mind that these points above are just things you can do at home to get a "general" bike fit.  If you plan to train for a 1/2 IM, I strongly advise against fitting your own bike and then training an entire season on it because injury can quite easily occur when training on an improperly fit bike.  And if you want my opinion, I would GLADLY pay $150 for a pro bike fit to avoid an injury.....any day!

Hope this helps you a bit.

I don't know the answer to this question.  This is a very advanced concept and something only a pro bike fitter could explain and fit you for.

The main jist of it, however, is that proper cleat positioning is determined by how much you pronate/supronate, if you are naturally toe in/or toe out, if your right leg naturally steps "wider" (further from your body) than your left, etc, etc, and so forth.  It's quite complicated and not as simple as just getting the cleat positioned on your shoe so that the ball of your foot is on top of your pedal.  there's MUCH more too it than that.

yes, upper arm.

also, if you shorten/lengthen you're aerobar extensions too much your elbows will no longer be skeletally supported...but will be muscularly supported.  you can do this for a few centimeteres, but that's about it.  the rest must be done with stem length.

Additionally, remember that with your elbows skeletally supported, they should land nicely in line with (or just SLIGHLTY fore) of the perpendicuarly plane drawn from your ears through your elbows to the ground.

Of course, there are many positions that "work" for people, but the bike positioning I'm advocating is one that is most energy efficient and transfers the highest ratio of energy into wattage that makes the bike go forward.  If your elbows are supported by your forearms (aka muscularly supported as in Norman's Kona winning position) then the average athlete (aka NOT norman) will be using energy to stabilize their upperbody on each pedal stroke by firing their shoulder stabilizer muscles....try it out and you'll see.  What you want is a position on the bike that when you pedal; your shoulders, biceps, forearms are not firing on each pedal stroke...this wastes energy...but this will occur when your elbows are muscularly supported or your elbow pads are too close together or too far apart (something I didn't get into in my discussion for this thread).

Edited by Steve- 2005-02-25 11:49 AM