Chain tensioners and guides are often used in "extreme" mountain biking such as downhill, freeride, and fourcross. They are used to stop the chain from bouncing around and falling off. However, they are very expensive for a simple item, generally ranging from 30 to over 100 euros. This is a simple way to make one that costs almost nothing  and you probably already have the materials! Also, chain tensioners can usually only be used with one or sometimes two front chain rings. This one works with three!

Step 1: Materials

1) Rear Bike reflector

2) Small piece of garden hose

3) Ziptie(s)

4) Scissors or something else to cut with

5) Phillips Head Screwdriver

<p>just made it ... need to try it now!</p>
Great! I like to see the face of the mechanic when he finds pieces of diy on my bike:-)<br>I can grant that this solution is really robust. I made it on my trek. Pictures with my phone are quite dark...
Love it! Hope it will be OK with my SS project, if not I'm gonna stick it on my xc bike. Thank you
instead of garden hose, i'd like to use inner tube - is it a good idea?
Eh, I would recommend the garden hose for two reasons: <br>1) More durable, and <br>2) More slick. <br>The innertube would probably work, but there would be more friction and it could wear down. So... if you have garden hose, use that. If not, use the innertube.
How do you make chainstay protector?? is that old innertube
Yeah, I just cut open an innertube, wrapped it tightly around the chainstay, then ziptied it on.
when i broke my rear derailleur it was scratched down the protective film :P so i need to make something like this
http://www.mtbtips.com/mountain-bike-maintenance-guides/how-to-make-a-chainstay-protector-guard/ <br> <br>Use this website but you don't need to take the wheel off.