Here's a quick fix for anyone interested in fixing an old vinyl or leather bike saddle that is scuffed and torn. This instructable came about because I did not want to replace a torn and scuffed saddle since it was original equipment on a somewhat rare retro mountain bike. The results are far more pleasing to look at and ride than before.
Step 1: Clean All Oils, Dirt and Grease
Prepare the surface by cleaning the area to be fixed of oils, dirt and grease. Use a mild cleaner that does not leave any residue.
Step 2: Hot Glue or Contact Cement
This part you'll want to glue down the frayed edges or cut off any really stringy bits. I used hot glue because it sets quickly and fills holes but you could use contact cement.
At this point after gluing you should be able to take the saddle for a ride and not have the vinyl spread apart. If there is nothing under the vinyl to glue down to you should think about placing some material underneath and glue the vinyl down to it like a patch underneath.
The reasoning here is that you should not rely on the Sugru to act like glue to hold two pieces of vinyl together. If the sugru simply acts like a filler that is not under tension I believe it should last quite well.
Step 3: Knead the Sugru Into a Thin Roll
About four small sachets of Sugru is what my saddle took to fix the rear edge. Roll pieces of Sugru into thin rolls and place around the area to be covered. Knead and shape them with your fingers. Wet fingertips occasionally to help you work it to the right shape. Wrap under the edge with the Sugru to help keep it stuck there better. Don't mess to much with it. Get it done quickly. The longer you take the more you'll start to feel the Sugru becoming unworkable.
Step 4: Wet Fingers Whilst Smoothing
Keep a trickle of water running whilst you smooth out the surface so you can wet fingers and get it smooth quickly. Once done you can either leave it smooth or use a texture stamp to leave a slight grain or texture on the surface. I tried to do this a little bit the Sugru was already starting to resist being worked any further so the leather grain did not end up noticeable. It did not detract from the end result though.
Step 5: Give It a Day to Cure and Re-fit
It will need time to cure before you ride on it. I did not use it for a couple of days after applying the Sugru. I'm very happy with the results. Four sachets of Sugru cost me about $15 but the saddle was not easy to replace since it was made around 1989 so I think the cost was worth it.