I'm looking for a very strong glue to stick the sole onto the bottom of a running shoe without destroying anything. I know some strong glues can be quite destructive. The shoes are Salomon SpeedCross 4's, the soles are rubber and the base is a hard rubbery-foam but I'm not sure of the actual composition.
There are a number of good glues for this. Among the highly rated products, I'm not sure there will be a huge difference in results. The specifics of the repair probably have a bigger effect than the particular glue. You might find that a particular glue doesn't hold up well on your shoes. In that case, try again with a different type of glue (not just a different brand of the same type of glue).
- I've had the best luck in general with glues that are basically some type of rubber in a solvent. These dry to a tough, very flexible joint. These include: E6000 (my usual go-to adhesive for this stuff), and Shoe Goo. They're both usually among the top choices in reviews for adhesives for this purpose. Barge is another popular one of this type.
- There are versions of Superglue (cyanoacrylate) that contain a suspension of rubber particles. These are strong and remain flexible. Boot-Fix Shoe Glue is a popular example, as is their similar Shoe-Fix Glue. Loctite makes a similar product. I've never tried these. I'm hesitant to use Superglue on some repairs because it does attack some materials.
- Loctite Stik n' Seal Extreme Conditions Adhesive gets high marks (another one I've never tried, and not sure what the adhesive contains). Loctite also makes a shoe glue that is often mentioned in reviews (not sure if it is the same stuff).
- Some people have good luck with polyurethane adhesive (like Gorilla Glue). I wouldn't use the original type that expands as it cures because it can make an absolute mess of your shoes, but there is a clear, non-expanding type identified as "Clear", "No-Foam Formula".
Note: all product links above are just to identify the products; they aren't endorsing a particular retailer.
Some important considerations for a long-lasting repair:
- The surfaces to be joined need to be very clean. For some types of glue, they also need to be completely dry. For cyanoacrylate (like Superglue) and polyurethane (like Gorilla glue), a little residual moisture will speed and strengthen bonding (which may not be a good thing because it won't provide an opportunity to align or realign things).
- Most glues set, at which point everything will seem firm, but they don't achieve full strength until the glue fully cures. That is typically at least hours, and in some cases, several days. If you don't wait for the cure to be complete, the bond won't last.
- Some glues require clamping to keep pressure on the glue joint until the glue is set or cured. If you don't do that, the joint will be much weaker. Some glues require coating both surfaces and then letting the glue bond with that surface and dry a bit before joining the pieces. Bottom line, a strong glue joint requires following the instructions for the glue you select.
- The bond is only as strong as the material it is holding. If things separated only because the original adhesive failed, new glue can do a good job of repairing it. But sometimes the bond fails because the material, itself, fatigues or deteriorates. The original glue may still be intact, but some of the surface material separated and went with the glue. Once the material starts to deteriorate, a glue joint won't last long, as more material will pull off with the new glue.
I've had both successes and failures repairing shoes with hot glue.
It's good at filling gaps, reasonably flexible, and bonds well to many of the materials used (in fact it's very similar in composition to some), but it needs to be held securely for quite some time as it cools slowly, and if the surface is damp or has got dirty since the gap opened, bonding is less certain. It also becomes less flexible in very cold weather.