It has long been known that an aluminum skidplate reflects an awful lot of engine racket up to the rider. Alternatives to an aluminum plate include plastic (not a great option in rock country) and carbon fiber (expensive). There are several possible solutions for quieting down an alloy plate, including closed cell skidplate foam, Dynamat acoustic foam, roofing ice-guard material, and spray-on pickup bedliner. I chose the latter, since it is inexpensive, extremely durable, easy to apply, and is claimed to deaden sound transmission. It also shouldn't require any attention after a few years like the other options. According to Rhino Liner's FAQ, it is good to 175 degrees F, so hopefully (!) it won't melt on under my hot engine. (I couldn't find any temperature data for the product I used.)
My local auto parts store carries Duplicolor bed liner. It is available in liquid form by the quart, but I like the aerosol for ease of application on a complicated shape like a skidplate. I wasn't sure how much I would need , so I bought two 16.5 ounce cans for $17. This stuff contains MEK, toluene, acetone, ether and other nasty solvents, so it is very important to use good ventilation. It _really_ stinks up the area for over a day, so don't take your work into the kitchen!
My Enduro Engineering skidplate is
fairly new and has a very rough surface texture, so I skipped the recommended
sanding steps and just cleaned all the surfaces thoroughly with lacquer thinner.
I masked the underside of the plate, leaving the top and edges unmasked. I used
a hobby knife to cut the tape cleanly around the perimeter and holes.
I sprayed multiple layers of the
coating , waiting several minutes between coats for the stuff to skin-over, to
prevent runs. Holding the can further away gives a pebbled texture, and moving
in close gets you a smoother one. I built it up layer after layer until I had a
thick, even pebbled coating. I used one full can plus a little of the second. I
was concerned because the plate seemed to be getting really heavy, but after
reading the MSD for the coating I realized that 87% of the weight of the coating
was solvents, and they would soon evaporate away.
After waiting several hours for the
plastic to harden enough to handle, I carefully cut along the edges and holes
with the hobby knife to prevent the tape from pulling off the soft plastic, and
I then removed all the tape and let the plate sit overnight to cure. After 24
hours the coating was hard enough to allow me to install the plate onto the bike
- it wasn't fully cured, but I wanted to let the plastic conform to the shape of
the frame tubes and mounting areas. I was pleased to see that the four holes on
the EE plate did not need to be elongated - the plate fit perfectly without any
modifying.
So, how well does it work?
I went for a 100 mile ride and was pleased with the result - there is definitely less racket from the engine. It is especially noticeable at highway speeds. I suspect that I could improve the sound reduction by adding foam or dynamat on top of the bed liner, but I don't want the complication or added weight. The bedliner is pretty much maintenance free, lightweight (once all the solvents have evaporated away), and looks great. I didn't get the engine blistering hot, but so far I haven't seen any sign of distress near the exhaust header tubes. I give the mod 4 stars out of 5.
I have about 3/4 of a can left, and I may just add some more material in front to quiet the sound of gravel pinging onto the aluminum.
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