By Coach Steve
You can't do anything to change the dimensions of your body, but
there's a lot you can do to custom fit your bike to you. Not everyone
can afford to have a bike custom built, but there are probably more
ways than you realize to modify the bike you already have. With
a few minor adjustments, and perhaps a new part or two, your "ride"
can fit like that bike your buddy just paid four-thousand bucks
for. Here's a list of possible adjustments to your bike: Seat height,
seat front-to-back adjustment, seat tilt, stem height, handlebar
angle, brake lever positioning, and last but certainly not least,
the cleat position on your cycling shoes. Here are some items that
can be replaced to make major changes to your bike's fit: a different
seat, longer seat post, longer or shorter stem, stem that angles
up or down different type or width of handlebar, different type
or size of aero bar, and longer or shorter cranks.
Setting a proper seat height is the first step. The correct height
is quite easy to define since there's a widely accepted rule that
works well for everyone. Generally, the optimal position is to set
your seat height at the highest possible level, while still maintaining
a smooth spin with absolutely no rocking of the hips, or feet reaching
excessively to make full extension of the pedal stroke. There are
all sorts of measurements and numerical computations to try, but
by far the easiest and most sensible way to determine seat height
is as follows: Get dressed in your biking outfit and sit on the
bike with bike shoes on and clicked into the pedals. Then, extend
your leg to the farthest reach of the crank on either side (crank
arm about 5 degrees forward of vertical, in-line with your seatube).
Lock your knee back, putting your leg at full extension and check
the angle of your foot relative to the ground. Your foot should
be parallel to the ground, with both your heel and ball of foot
at the same level. It's as easy as that. You can do this by yourself
while coasting past a reflecting plate-glass window or you can lean
against something solid and have someone else take a look. Check
and double check on both sides, and make sure you aren't rocking
your hips while over stretching to the bottom. Your foot angle from
the side should look like the ideal seat height/foot position in
Figure 1. When you examine Figure 1, this simple technique of seat
height determination makes perfect sense. We know that as you pedal
and your leg is at the fullest extension of the stroke, we want
just a very slight downward angle of the foot. This slight pointing
down of the foot shortens your effective leg length just enough
to give a few degrees of knee bend at the bottom of the pedal stroke.
When compared to the foot flat, knee locked, leg fully extended
position, which we used as our reference to set the seat height,
the foot tipped slightly down with the knee slightly bent relationship
makes sense. Also, different brands of shoes or cleat/pedal designs
can make as much as a 1.5 centimeter height difference. Changing
bike saddles can cause a substantial height change as well. I always
recommend that you take careful measurements before and after changing
any parts an your bike to limit the chance of unexpected or unwanted
If you ride with your seat too low, you lose power. This is because
the amount of power your quadriceps can develop increases proportionally
to leg extension (Your leg can push progressively harder as it becomes
straighter). This was thoroughly discussed in the energy transfer/pedaling
force article (check it out). Also, some experts contend that a
seat position which is too low may cause excessive knee joint stress,
and therefore, long term wear on your precious knee joints.
Years ago, The United States Cycling Federation did some in depth
sports science research on optimal seat height. The researchers
found that power output kept increasing as the seat height was raised
in small increments, but at a certain critical height, oxygen consumption
increased abruptly. It was determined that the higher oxygen need
negated the benefits of potential power increase from anymore leg
extension above the optimal height. This seat height was at the
point where the pedaling technique became sloppy, perhaps with rocking
hips, or feet angled too far downward in order to make the stretch
to the pedal. The exact height where energy consumption becomes
disproportional to energy output takes place just above the proper
seat height I described above.
Figure 1. Proper angle of foot with leg fully extended (knee
joint locked back), at lowest point of pedal stroke.
There is an ongoing debate about how to best utilize the well developed
musculature of runners for multisport competition. The origin of
the "forward" seat positioning, as accepted by many multisport
athletes, is an attempt to reproduce the motion of running on the
bicycle. We know that running is a much more hamstring-powered movement
than cycling which is traditionally a quadriceps powered activity.
Much of the runners movement is "behind" the runners center
of gravity as the leg moves back Also it's believed, that during
the cycling portion of a multisport event, if you're using similar
muscle movements to running, the difficult transition from bike
to run will be easier. Personally, I believe the latter to be correct,
especially in "sprint" distance events. Over the last five
years though, the thought on seat positioning seems to be shifting
away from this forward positioning. The latest thinking is that
the great amount of potential force lost from the quadriceps muscle
group outweighs the intrinsic gains of the seat forward position.
You see, we do know, through basic physiology, that as the seat
position moves forward, the hamstring muscle must deliver proportionally
more of our pedaling force. But, the hamstring muscles are significantly
weaker than the quadriceps, which work in unison with the gluteus-maximus
on the downstroke. The "quad" muscles which favor pushing
from farther behind the bottom bracket, also have the additional
advantage of their own weight working with gravity's downward pull.
The hamstrings pull backwards with neutral gravity, and then upwards,
fighting gravity. Also, as a riders position moves progressively
farther forward, the down force initiating motion of pushing forward
over the top of the pedal stroke becomes virtually impossible to
supply, because of the lower legs' angle relative to the crank arm.
With the seat forward-position, it becomes increasingly difficult
to climb out of the saddle effectively since the nose of the saddle
interferes with the bike's natural rocking motion while climbing,
as it hits your inner thighs.
The foundation for fore-aft seat positioning is your frame's seat
tube angle, which can either tip you forward or backward as measured
in degrees from horizontal. There are many seat-tube angle choices
to consider when buying a new bike (assuming a new bike is an option).
The typical range is from about 72.5 to 78 degrees. The former is
a traditional "laid back" road bike configuration for
a tall rider, and the latter is a "radical" forward angle,
suitable for multisport athletes only. In my opinion a mid-range
choice is best because it allows an optimal quadriceps power stroke
with no off-the-saddle climbing restrictions. This range of about
74.5 degrees for the tallest riders, to about 76 degrees for the
shortest riders is typically used by elite cyclists for time trial
The fore aft seat position has another strong effect on bike positioning
that should be mentioned. This is your hip/lower back angle. You
see, as your body moves forward in relation to the bike's bottom
bracket, the angle between your hip and thigh area and torso "opens
up." When this angle opens up, your lower back is spared some
of the stress required making the tight radius of an aerodynamic
position. For riders with a history of tightness through the lower
back, or with chronic low back injury, the forward position can
afford some relief.
If your bike's frame does not have the seat tube angle you think
best for your body and riding style, there am ways to make small
changes. A typical saddle has rails clamped down by the seat post
which allow it to slide forward at back (depending where it started,
of course). Special seat posts are available with a forward angle
that can shift your position as much as 4 centimeters. On a medium
size frame, each centimeter of fore or aft seat movement equals
roughly 1 degree of seat-tube angle. Of course, if you make this
change of your seat position, you must alter the stem length accordingly.
Often keeping the stem length reasonable can be the limiting factor
on your original frame. One caveat regarding making these changes
on an already existing frame is that you can radically change
the overall balance of the bike for the worse. Especially risky
is shifting too much weight to the front of the bike. This can make
the handling very twitchy and unpredictable.
The next step after choosing a seat height and fore aft position
is to find the optimum stem length and height. And stem positioning,
in turn, must be determined by how well you can flatten your back
while bringing it as close as possible to horizontal. As with most
adjustments on your bicycle, the position of your upper body is
a fine balance speed and comfort. The ultimate position is the one
that offers the least drag coefficient through the wind. Consider,
Chris Boardman's, (former World Pursuit Champion and current Olympic
Individual Time Trial bronze medallist) position. Chris' shoulders
are actually lower than his hips. Perhaps Chris should wear a sign
that says: "Don't try this at home, it could be hazardous to
your health." Boardman's position goes to the extreme, but
he shows us what's possible. I've found that the vast majority of
even moderately flexible riders, can maintain a horizontal back
for the duration of an international distance event. There's nothing
wrong with raising your stem a centimeter or two for any event over
international distance, and on up to an Ironman event.
Figure 2. Effects of hip rotation on lower back and
Figure 2 shows three slightly different versions of bike positioning
based on various angles of "hip rotation." Rider (A) shows
a typical position for a rider who's not comfortable with rotating
his or her hips forward on the saddle. This is easily recognizable
when a rider shows a significant hump in their back. An overly long
stretch of the arms in making the reach to the handlebars, on a
bike that is in fact the proper size, is another visual clue. This
type of positioning problem can also be caused by an overly tight
lower back and hamstring combination.
A tight lower back and/or hamstrings, can only be relieved by
stretching, and perhaps learning to relax more effectively on the
bike. As you rotate your hips forward, the pressure on your saddle
moves from where the pelvic bones more contact at the wider rearward
part of the saddle, to fleshy areas which rest on the front of your
saddle. Tipping the saddle downward a few degrees is totally acceptable,
and may relieve some of the pressure caused by this forward hip
rotation. Notice the angle of the darkened hip bone area in the
three variations of Figure 2. As the hips tip forward, the lower
back does not have to make as tight of a radius to accommodate the
horizontal aerodynamic position. The area between the arrows is
the span of the spine where muscular stress originates, potentially
causing problems. Rider (B) has an acceptable but not fantastic
position. Rider (C) is as low and aerodynamic on the bike as anyone
can be, with a flat back and very low drag coefficient (not much
frontal area to catch wind). If you're not sure you have achieved
this type of forward hip rotation with a flat back, try this: Sit
on the bike with your hands on the drops or aerobars. While either
motionless or riding (don't crash into each other), have a friend
push down on your lower back. Try to accommodate this pressure by
flattening this area of your back. It's almost impossible to do
without tipping your hips forward. So this is what you must do to
be like Rider (C), It's not a natural body position, or easy to
perfect, but well worth the extra speed you'll gain.
The next step is to zero-in on the proper stem length. With regular
"drop style" handlebars, I can give a general rule for
sizing. While sitting on the bike, preferably riding relaxed, look
down at your front hub. When your hands are at the drop position,
you should see the hub just ahead of the handlebar where its held
by the stem. With your hands on the upper part of the bars, the
view of the front hub should be blocked out by the handlebar. This
is a very general guideline for stem length, but it should give
a measurement "in the ballpark." With "bull horn"
or "time trial" style bars, there's no easy rule for fit.
With the same top tube length as we used with the drop style bar,
the stem must be approximately 2 centimeters shorter. And, for the
rider's position to be aerodynamic, the stem must be significantly
lower. Because of this, a slightly undersize frame is often required.
If it's not possible to move the bars low enough in relation to
the seat, it will be difficult to set up a proper areo bar position.
Aerodynamics is everything if you're attempting to maximize cycling
speed. The weight of your bike is really of no consequence unless
you are accelerating, climbing, or having a hard time lifting it
to your roof rack! In multisport racing, which is predominantly
flat steady speed time trialing, we don't do much sprinting or climbing.
Mechanical resistance is also remarkably insignificant in comparison
to aerodynamic losses or gains. Aerobar position is another subjective
positioning consideration that's difficult to define. From aviation
aerodynamics and the hydrodynamics of water craft, we know that
to increase length without increasing girth (frontal area) improves
air/water flow characteristics. So, this would lead us to believe
that the more stretched out we are on our aero bars the better.
But, another consideration is our power output and stress to our
lower back muscles. I find that a rider given a trial and error
session with a variety of aero bar adjustments, can always find
a good compromise between comfort and speed. An example of this
is wind tunnel testing results, versus the consensus among aero
bar users. The wind tunnel trials found unequivocal evidence that
the aero bar position with least drag is when they are tipped-up
about 30 degrees. Not a single elite cyclist or triathlete uses
this position though. Having your forearms level just feels right,
and that's what we all gravitate to eventually. If you've have found
a proper handlebar height, then aero bar height positioning must
come from that. With regular drop style bars, the aero bar should
be mounted as low as possible on the top of the drop bar with no
additional spacing for height. On time trial style ban, the area
bars do need some sort of spacing to increase height. This height
adjustment must be modified by experimentation and observation of
one's position while riding the bike. The spacing width of the aero
bar armrests should be set for comfort in proportion to shoulder
width. I feel that the benefits of a very narrow arm position are
over-rated, it reduces steering control, and perhaps in extreme
narrow settings, lung expansion. The aero bar length I recommend
should give you a upper arm position similar to that which appears
in either Figure 1 or 2 (upper arm angled forward 10 to 15 degrees).
I've found that this arm position is achieved with one size shorter
aero bar then the manufacturers recommend.
This leaves cleat position, and this can literally make or break
- your knees. There are so many options for the foot/pedal relationship
that there are rarely any reasons for unwanted stress here. Several
pedal types allow for lateral rotation and that's the key to healthy
knees. In the old days, we had to nail cleats to leather shoes.
What a pain. Once those cleats were nailed we were committed! But,
now for the front to back adjustment you should just find a spot
somewhere in the middle of the range and make sure both shoes are
the same. Make sure there is minimal yet adequate clearance between
crank arm and your shoe. Too far away is awkward, and if the shoe
touches the crank it will eventually wear a grove there, and the
crank may break at that spot. If your pedal system has no "floating"
capability then you must take some time to get then initial cleat
setting just right. Analyze the natural positioning of your feet.
Do they toe in or out? Set your cleats appropriately. Some types
of pedal systems are capable of accepting an increase or reduction
of "height," which is invaluable for people with leg length
discrepancies. Take advantage of this opportunity if you need it.
It works well for me!