How To Make Silicone Sponge Tires
Author: Trek Lawler
Ever wondered if you could make your own silicone sponge tires and save some
of the expense plus create custom sizes?
Well, thanks to Trek Lawler you might be able to.
“OK here go some instructions on how the tires are made now.
You'll need to go down to your local O'Reilly auto parts and get some flowable
silicone, it's made by Versa Chem and is type 750 made for windshield and glass
sealer. You will also need some Pliobond contact cement; this is industrial
grade and should be available from most hardware stores.
You'll then need to find some foam rubber that is comparable to the kind used in
the Wizzard tires. Since I don't know anything about this I simply took off a
foam rubber from a Wizzard tire that was no longer any good and took it to my
local rubber and foam dealer. In my case it was to a place here in K.C. called
Hanna Rubber. These guys looked at it and we found a comparable match. After you
get good at this you can experiment with softer or harder compounds of foam
rubber. Okay now that we have some of the vital components. You will need to
make a tool to cut out a circle in the foam. In my case since I have a lathe I
simply turned down a piece of tubing that was approximately .250 of an inch and
put a knife edge on it. I then chuck this up in a dremel (everyone has a dremel
tool don't they) and cut out the inner circle that the wheel will go into. I
also made a tool to cut out the outer circle to complete the tire donut, but I
suppose you could just cut it out and true it up later after mounting it on the
wheel. I then take the wheel (in most cases I re-use Wizzard wheels, and in some
cases will use flanged .250 wheels with the flanges turned down) coat it and the
inside of the rubber donut with the Pliobond, this doesn't need to be excessive
just a little will do, and press the wheel inside the donut. I usually wait
overnight to provide a good tight glue bond.
Once this crude donut and wheel are made I mount it squarely in an old T-jet
axle (see these are still good for something) using a JW's tire press, I then
chuck it up in my Dremel tool. You'll need to turn this at a fairly high rate of
speed around 20,000 RPM. Take an exacto knife and trim the outer edges of the
tire so that they are close to the edge of the wheel (don't cut them to close as
you'll be able to sand them true later). Use a piece of sandpaper around 200
grit (in my case I simply got some of the stiff finger nail sanding files, I'm
sorry I don't know exactly what they are called but they work very well and
provide a stiff support and are some what flat). I then start sanding the tires
down, you'll want to sand the tires down to around .010 of an inch smaller then
what you want the finished product to be (the silicone will add the remaining
diameter to the tire). Be sure you make it as square as you can. After getting
it to the diameter you want I then sand the outer and inner edges to the wheel.
Now get an adult beverage and clean up all the foam dust you have all over you.
OK now you've got the wheel and tire blown off and you're ready to apply the
silicone. Chuck the wheel and tire in the dremel, and add just a little of the
flowable silicone (just a word of advise, this silicone is FLOWABLE and will
drip so don't do it over your wife's good carpeting or counter, yes, I learned
by mistake). Work this into the foam and around the outer edges, (don't worry if
it's not flat, and just rub it into the foam).
Once the first coat of silicone is rubbed in, hold the tire assembly inside a
Dixie cup or some other disposable cup and turn the dremel on as fast as it will
go. I have an adjustable one and it will turn up to 30,000 RPM. Please do this
inside something that will catch the excess silicone flying off of the wheel
(yes, I also learned this by mistake. I also have a very understanding track
manager. This silicone will eventually dry and peel off of the wall but it's
hard to get off of the dog). You'll notice that the silicone will look rough,
this is OK. Carefully take the wheel and axle combination and either leave it in
the dremel and stand it up right or carefully take it out of the dremel and
mount it in something that will support it upright (in my case I took a block of
wood and drilled holes in it for the axle/tire assemblies. This silicone takes
around 15 minutes to start to gel, I usually wait around 30 minutes and then add
another coat. After each coat check the diameter until you achieve the size you
want. If you spin the tire at the speed I indicated the silicone will add about
.003" of silicone with each coat (I know this doesn't sound like much but 3 or 4
coats will usually get you in the ball park). If you've done everything
correctly you shouldn't even need to true the tire up after it dries. The
silicone will dry very flat at that thin of a coat.
Please be patient when trying this, it's not something you're going to master
immediately, as a matter of fact I ruined 2 pairs of tires just the other night
because I got to zealous with the sanding block and made the tires to small.
I've been running these tires for quite some time now and have been doing very
well in our MAHOR races here in K.C. I hope this helps, it's quite a bit of work
but very satisfying after you achieve the final goal."
Reprinted with permission of the author, Trek Lawler. Thanks again Trek!