This article is from the Bicycles FAQ, by Mike Iglesias with numerous contributions by others.
Position the cleat so that it lies on the imaginary line between the
bony knob on the inside of your foot at the base of your big toe and
a similar but smaller knob on the outside of the foot at the base of
the smallest toe. Set azimuth so that the pointed end of the cleat
points directly toward the front of the shoe.
If you're switching from clips and straps, and you are satisfied with
your current alignment, use the following alternate method. Position
your SPD shoe fully in the clip of your old pedal and align the cleat
to the spindle of your old pedal. Center the cleat in the X direction,
leaving room to adjust either way should the need arise.
Some people find pedaling more comfortable if their left and right
feet are closer together. This is sometimes called the "Q-factor".
If you prefer to start with a low Q-factor, then move the cleat so that
it is as close as possible to the outside of the shoe. Tighten both
cleat bolts before engaging the pedal.
Adjust the release tension of the pedals so that it is somewhere in
the low to middle part of the tension adjustment range. The higher
the release tension, the harder it will be for you to disengage the
pedals when dismounting. The lower the release tension, the easier it
will be for you to inadvertently pull out of the pedals, especially
when standing and pedaling. If you stand often to power up hills,
consider setting the initial release tension higher as an unwanted
release under these conditions can result in a painful spill. See
the pedal instructions.
Mount your bike on a trainer, if you have one, to make preliminary
cleat and release tension adjustments. Practice engaging and
disengaging the pedals a few times before you take a real ride.
Soon you will find this easy. If you notice that a shoe rubs a
crank or chainstay, adjust left/right translation and azimuth
until the shoe no longer rubs.
As you pedal, you will probably find the initial azimuth
uncomfortable on one or both legs. Notice how your foot would like
to rotate. Adjust the azimuth of the appropriate cleat in the same
direction your foot wants to rotate. For example, if your foot
wants to rotate clockwise, adjust the azimuth of the cleat (when
looking at the bottom of the shoe) clockwise. Start by making
moderate corrections. If you overshoot the adjustment, correct by
half as much.
As you approach optimum azimuth, you may need to ride longer before
you notice discomfort. Take your bike off the trainer, and go for
a real ride! And bring your 4mm allen key.
You may find very small azimuth adjustments difficult to make. This
happens because the cleat has made an indentation in the stiff sole
material (usually plastic, sometimes with a tacky, glue-like
material where a portion of the sole was removed). When you tighten
the cleat after making a small correction, it will tend to slide back
into the old indentation. Try moving the cleat one millimeter or so
to the side or to the front or back, so the cleat can no longer slip
into the old indentation pattern as it is being tightened.
Pain in the ball of your foot can be relieved. One way is by moving
the cleat rearward. Start by moving the cleat about two to three
millimeters closer to the rear of the shoe. Be careful not to change
the azimuth. When pedaling notice how far your heel is from the
crank. After making a front/rear adjustment, check to make sure the
crank-heel distance has not noticeably changed.
Moving a cleat rearward on the shoe has the effect of raising your seat
by a lesser amount for that leg. The exact expression is messy, but
for an upright bike, the effect is similar to raising your seat by
about y/3 for that leg, where y is the distance you moved the cleat to
the rear. For example, if you move your cleat 6 millimeters to the
rear, you might also want to lower your seat by about 2 millimeters.
Remember, though, that unless both cleats are moved rearward the same
amount, your other leg may feel that the seat is too low.
Another way to relieve pain in the ball of the foot is to use a custom
orthotic and/or a padded insole. Most cycling shoes provide poor arch
support and even poorer padding.
After riding for a while with your aligned cleats if you find yourself
pulling out of the pedals while pedaling, you will need to tighten the
release tension. After tightening the release tension the centering
force of the pedals will be higher, and you may discover that the
azimuth isn't optimum. Adjust the azimuth as described above.
On the other hand, if you find you never pull out of the pedals while
pedaling and if you find it difficult or uncomfortable to disengage
the cleat, try loosening the release tension. People whose knees
like some rotational slop in the cleat may be comfortable with very
loose cleat retension.
As with any modification that affects your fit on the bike, get used
to your pedals gradually. Don't ride a century the day after you
install SPDs. Give your body about two or three weeks of gradually
longer rides to adapt to the new feel and alignment, especially if
you've never ridden with clipless pedals before. Several months after
installing SPDs, I occasionally tinker with the alignment.
After performing the above adjustments if you are still uncomfortable,
seek additional help. Some people can be helped by a FitKit. If
you're lucky enough to have a good bike shop nearby, seek their