You will need the following materials and tools to perform an air-seat
conversion on a Miyata unicycle seat:
(* NOTE: If you want something REALLY luxurious, follow the optional
instructions to also include a gel pad)
- a 12-1/2" x 2-1/4" inner-tube (the type used on scooter tires - available
from your local bicycle shop or toy store)
- a bicycle tire pump (a mini pump or frame pump is ideal; you don't
need much pressure)
- a ratchet wrench with a 10 mm socket and short extension
- a flat blade screwdriver
- some adhesive tape
* optional: A gel pad seat cover. I recommend the Schwinn gel
pad cover that is sized to fit the seat on their exercize bike. It is huge,
and about 1/2" thick.
Before beginning, take a look at how your seat is constructed and make some mental notes about how the various parts fit together. For example, note that the seat bumpers are held in place with acorn style nuts over washers, and the seat post is held in place with open ended nuts with an integral lock washer. You will see that the seat cover is held in place by a series of metal clips around the perimeter of the seat base and also by the front and rear bumpers.
It's easiest if you take the seat off the seat post first. Disassemble the seat from the seat post by removing the four seat post nuts (put the nuts somewhere where you won't lose them) and then pulling the seat off of the post. You may have to spread the sides of the seat apart a little bit to get the seat post bracket past the metal seat-cover clips.
Next, remove the front handle-bumper and the rear bumper. But
before you begin, take a look at the underside of the rear bumper.
See the semi-circular cutout along the edge that is in-between the two
bumper mounting bolts? Take a pencil or crayon and trace along this
semi-circular cutout. You will need this for reference later - we
will be drilling a hole in this area for the inner tube valve stem.
Now remove the nuts, washers, and front / rear bumpers.
Take a minute to examine how the seat cover is held in place. There are eight metal clips around the perimeter of the seat. One end of each clip is riveted to the seat base. The other end of the clip, which is the toothy part that you see, goes over the black "cuff" of the seat cover and is pressed tight against the seam where the cuff is joined to the green cover. When you replace the cover after putting in the air tube you will want to duplicate the way that these clips are in place against the material. You may also notice that there is some thin white padding protruding from underneath the sides of the seat cover. There may also be some adhesive tape in there which was used to hold this material in place while the seat was being assembled.
Okay, take your flat bladed screw-driver and place it underneath a clip and gently pry it away from the seat cover. Just pry it away enough so that you can slip the hem out. Be careful that you don't slip and gouge the cover!
Go all the way around the seat and pry each clip away from the cover.
Remove (just) the cover. Allow the white padding and the seat
cushion to stay on the seat base.
Wow....you are one of the privileged few to see the guts of a Miyata
Seat! Take a minute to look it over and see how the white padding
is arranged and held in place.
Carefully peel off any adhesive tape that is holding the thin white
padding to the seat base and then slowly peel the cushion off of the seat
base. It may be glued down in spots. Go easy so that you don't
destroy the cushion - you may want to use it again sometime. Here's
a picture of the seat base without the padding:
Remove the white padding material from the cushion and put it back
into the seat cover.
If you are going to add a gel pad, take the Miyata foam padding and
lay it on top of the gel. Trace around the padding and then cut this
shape out of the gel. You may want to cut it undersize by about 1/4"
to allow room for the gel to expand as you sit on it.
Then insert the gel pad into the seat cover.
You are now going to drill a hole through the seat base to allow the
inner-tube valve stem to protrude. This is necessary so that you
can easily add air to the seat. The best place for this hole is in
the area that you marked in step 2. You want the hole to be positioned
in the flat area between the cut-out in the rear bumper and the beginning
of the center rib that runs down the seat base. Drill a pilot hole
about 1/8" in diameter and then enlarge it to 11/32". Remove any
burrs. Remove the valve cap and check to see if your tube stem will
fit through this hole. If not, enlarge it as necessary.
Inflate the tube slightly, just enough so that it begins to have a
bit of shape. Push the stem through the hole and arrange the tube
like this. You can use a little tape to hold it in place until you
get the cover back on.
Replace the cover and padding material. Try to get it back exactly in the same place that is was originally. Make sure that the white cushion material is in place correctly. You can tape it back down again as it was before if you wish. Make sure the cover is on straight, and that you are not pulling it down too tightly; you need to leave some slack for inflation. You should be able to see "teeth marks" where the clips were. If you line these back up with the clips you'll be in good shape.
Everything back in place? Good. Now go around and push the clips back into place with your fingers. Then take the flat side of the screwdriver blade and push them home against the seat cover fabric. They should be tight, but not so tight that they are putting holes in the cover.
Replace the bumpers (acorn nuts and washers). If you mis-drilled
the hole location a bit and the rear bumper won't go on because it is against
the valve stem, remove the bumper and take an X-acto knife and enlarge
the semi-circular cut-out as necessary until it fits.
Replace the seat post. If it came off with difficulty it will
be the same thing getting it back on, but you'll do it.
Make sure that the four nuts are tight.
Put the seat assembly back on the unicycle. Pump the tube up
a little so that you expand the cover to its original height.
RIDE! Adjust pressure as needed.
Webmaster: Kevin Gilbertson <gilby@unicycling.org>