Advice on Gluing Rubber
To glue rubber, the first thing you'll need is rubber cement. Because you are working with a flexible material, you should avoid glues that are not flexible. The process may be difficult if you do not have the correct materials, so be sure to purchase the correct glue. Rubber cement is available in most hardware stores and from many on-line retailers.
To start, put the rubber under the same conditions under which it will be once glued. That may mean stretching the rubber and putting it under the appropriate amount of stress. Wet the area being glued and clean it with soap. Rinse off the soap and make sure the rubber is thoroughly dried before proceeding.
Use sandpaper to sand the surface so that the rubber is rough enough for the glue to adhere. Avoid making dimples or indentations in the rubber. Once that is complete, apply a thin layer of rubber cement to the area being glued. Avoid using too much glue and press together both surfaces, removing any excess. Air bubbles may be forced out by applying pressure on one edge of the rubber. Refer to the instructions on the cement tube for appropriate drying times.