Update: One the elements of the treadmill belt that attracted me--toughness-- is also a problem. Because it does not stretch, when the shoe flexes the glue on the toe is pulling the glue on the heel. Walking is fine, but I don't think it will hold. My suggestion is to put one patch on the front half and a second on the heel. Or, use a tire or other rubber slab. I continue to experiment.
I have a pair of Keen shoes, nicely broken in after four years of wear, but with soles worn thin. Friends told me that Keen would replace the soles, free, but their website says there is only a one year guarantee. It was off to the cobbler or DIY.
The first material I thought of was a tire tread. Since I was a child I read about making tire tread sandals, and a few sites have instructions on how to use a tire tread to resole a shoe. Most tires are steel-belted, making them tough and rough for my purpose. Some leads have suggested motorcycle tires, wide bicycle tires and I had thought of a wheelbarrow tire (they show up in our dump) but I needed my shoes fixed sooner and did not have time to research or gather these materials.
While at the dump looking for older tires to use, I saw an abandoned treadmill. Having tried to replace the belt on my old treadmill I knew a) they were tough and b) they gripped well enough. With my pocket blade I cut it off and experimented.
Step 1: Materials
Pair of shoes with sole firmly attached to upper, but thin and in need a another layer. Remember, this only covers worn soles; it does not replace the sole entirely.
Tin-snips, cutting blade or other such tool. You will be trimming, so I found the snips quite helpful.
Shoe-goo. This is rubber cement designed for greater wear. I have read of people using bicycle repair glue or rubber cement for such repairs. My tube cost about $5.00, and I used half of it. Do two shoes at once!
Sharpie or other marker. You will trace your shoe before you cut.
Duct Tape. This will hold the tread to the sole while the glue dries.
Cardboard. The Goo is messy, so save yourself some clean-up.
Vaseline. Put it on parts of the sole you don't want the glue to stick to (i.e., the sides).
Treadmill belt. It is woven and layered and tough. I preferred a tire because of the tread, but for everyday-wear the grip of the belt is fine.
Step 2: Trace Sole
Cut outline with tin-snips or blade.
Repeat with other shoe.
Remember that the black side of the tread faces down. This is your gripping surface. You should have two outlines that fit the bottom of your shoes.
Update: As mentioned in the introduction, think about using one patch in the front and a second on the heel. Leave the arch alone to allow more flex overall, or it might pull apart.
Step 3: Glue Belt Onto Shoe
Take sandpaper and rough-up the side of the belt that will get glue on it, and the bottom of the shoe. Of course, clean it up afterward or it will not stick.
Open the Shoe-Goo and cover the belt with it.
I made the mistake of going light on the Goo and had to redo bits later. More is better. Your shoe bottom has treads, so there is not much surface where a light coating will stick and take long term abuse. Surfaces should be clean, and use lots of glue.
You may want to put Vaseline on the sides of the sole, where no tread will be and that you will want to keep clean. I did not because my shoes are pretty beat already. And, if you get oil or Vaseline anywhere else the glue will not stick. So, it's best if you don't use it.
Place the glue covered belt onto the bottom of the shoe.
Lay a piece of cardboard on the floor. Carefully, put your hand in the shoe and "walk" it. You should use enough pressure to spread the glue, but not so much to push it all out the sides. The cardboard will keep the glue off of the floor.
Step 4: Duct Tape
I taped the arch first to pull it up. Then I worked my way to the toe and heel to keep it tight to the sole.
Shoe Goo recommends 48 and 72 hours to set.
As the Goo squirted out the sides, it glued some of the tape to the shoe. You can clean that up later, or put some Vaseline on the sides of the old shoe sole prior to gluing so no Goo sticks. You may not need tape all the way around (I went a little crazy).
Step 5: Trim Sole
If you look at the arch you will notice I trimmed quite a bit. The arch of the Keen is such that I almost felt a separate piece for the ball and heel was needed. Not only would the arch not stick, it was not even close to touching. I used a blade and snips to cut out the wedge.
After trimming you can see where the sole did not attach to the belt. I was able to shovel some more Goo in those spots with a toothpick. Let dry.
Update: I have cut out my arch, leaving a patch on the front and a second on the heel.
Step 6: Wear and Enjoy
The treadmill belt does not slip on the floor, but it also does not stick like a rubber sole. It does take some getting used to.
After a day of wear, check to see if it coming up anywhere and glue again where needed.