The Deda Dog Fang is a small plastic accessory known as a ‘chain keeper‘ which attaches to your bicycle to prevent your chain falling off the inside of your smallest chain ring. Many pro mechanics are now fitting them to team bikes.
The chain can fall off the inside chain ring on even the best adjusted bike. It may not happen often, but when it does happen, it always seems to be at the worst possible moment, for example on a steep hill. You have to stop to put the chain back on, you get oil stains on your fingers and then you struggle to get moving again.
How much better would it be to be able to power your way into the hill in a high gear, confident that you could safely change to your small chain ring when you needed to?
The chain keepers are available in three sizes and you must make sure that you get the right one for your bike. Measure the diameter of your seat tube (if you don’t know it and can’t look it up on the bike manufacturer’s website). I found the size of my seat tube by closing a big adjustable spanner on it and then measuring across the jaws of the spanner. Crafty, huh? NB This measurement is the outside of the tube – your seat post fits inside the tube so that is not the diameter that you want!
The Fang is fitted to the bottom of your seat tube, below your front derailleur.
If you have a bike with a non-circular tube, or one that is an unconventional size, then you are out of luck. The devices are available in 3 sizes: 28.6 mm, 31.8 mm, and 34.9 mm.
I dropped my chain 3 times in one ride recently, each time on a steep hill. Result: dirty hands and frustration! I fitted a Dog Fang to my bike after that. Since I fitted the device, I haven’t fluffed a chain ring change. I’ve looked at the Fang after riding and I can see oily marks on it, so the chain definitely falls onto it from time to time, but it then obviously slides back onto the chain ring where it should be.
The devices don’t cost much, they don’t weigh much, they aren’t particularly noticeable unless you look for them so they don’t spoil the appearance of your bike and they do what they are supposed to do. They get my 100% recommendation!