This is a much quicker, simpler studding process than the nut/bolt described below. I used #8 x 3/8"self-drilling screws made from 410 stainless steel. This grade of stainless is a harder (but less corrosion-resistant) alloy than standard 18-8 stainless. The harder steel should result in a longer lifespan for the studs.
I used a thin nail pounded through a small piece of wood to poke a hole through the knobs from the outside of the tire; this told me where to install the screws on the interior of the tire. Then it's just a matter of installing the studs. It went fairly quickly by hand, but I'm guessing an electric screwdriver would work too. I ended up with 156 in the front, and 104 in the rear tire.
From this point I used the same process as before... clean the inside of the tire, and add some silicone to cover the screw head.
Once the silicone is set up, add plenty of talc and mount it up. The pressure from the tube will flatten out the silicone. Be sure to let the silicone set up sufficiently, I got impatient with the rear tire and after about 20 miles the screw heads started showing though the silicone. The tube never punctured, but it could be enough to eventually wear through and cause a flat.
Nut/Bolt Type Stud
In an attempt to give the Endomorph a bit more bite, I put a row of DIY studs down each side of the tire. This tire will only be used in the snow (with very little pavement time) and on frozen lakes/creeks. Pavement riding will wear the screws down quickly and/or cause the nuts to loosen and come off. If pavement is in the tire's future, be sure and loctite or super glue the nuts in place.
Materials I used: a scrap wood jig to hold the tire upright and at a height that didn't break my back, a drill with 3/16" bit, #6-32 x 1/2" machine screws w/ nuts, white-out, a socket wrench, latex sealant, an electric screwdriver, a thick work glove, and bolt cutter (glove and bolt cutter not pictured). And beer... preferably something dark.
Latex sealant that's made to retain its flexibility should add to the durability of the tires. I marked the knobs that would get studs with white-out so I didn't make any drilling mistakes...
Once the knobs were marked, I drilled holes into the desired knobs from the outside of the tire. After the holes were drilled I installed the screws. This is where the thick work glove and electric screwdriver came in handy. With the glove to protect my thumb I pushed the screw into the hole from the inside of the tire. Once I got the first few threads in, I used the electric driver to get the screws the rest of the way in. Next step was to install and tighten the nuts on the outside with the socket wrench...
I wiped the inside of the tire with a damp rag, let it dry, and then started putting latex over the screw heads. The first picture below is the Endo with fresh latex. The second pic below is a tire from last winter. You can see that after some ride time and pressure from the tube, the latex ends up forming nice little protective 'pancakes' over the screw heads...
The 1/2" screws ended up being pretty long, so I cut the screws to about 1/8" above the nut using the bolt cutter...
