What type of plastic is the K75S bodywork made of?

[nh7robmw]

Anyone know what kind of plastic the K75S fairings and bodywork are made of? I've heard that they are a fiberglass-plastic "mixture" but not 100% sure. Need to know before I attempt some minor repairs.:bikes

[BuddingGeezer]

Fiberglass reinforced plastic.

I used an epoxy putty to repair several cracked and broken places on a K100LT fairing with great success.

On the hairline cracks I used a Dremmel to make a v or u shaped channel along the crack. Applied the epoxy putty, let cure and then made the same channel on the backside of the crack and puttied. Sanded and finished with body filler.

I have used fiberglass cloth to reinforce larger broken parts, but a auto body buddy put me on to fiberglass drywall tape. Much easier to work with and very strong.

Ralph Sims

[nh7robmw]

Thanks, Ralph; looks like I'm good to go. I already have some epoxy putty formulated for fiberglass and I just wanted to make sure...:clap

[Gilly]

"expensive" plastic;)

[nh7robmw]

:laugh Good one, Gilly!

[2old2rockNroll]

"Fibron" was BMW's name for their proprietary Fiberglass, it is a very high density sandwich of polyester resins, stranded fiberglass and fillers(usually marble dust). These parts were molded in two piece metal molds under heat and pressure, making a very strong composite.

Ordinary fiberglass is usually shot or laid into a one-side mold and can suffer from voids or differences in density. You can see the glass strands on the back of inexpensive parts...BMW's approach to plastic, like everything else, was to engineer the best part possible. These parts are expensive because they are expensive to make. I think it's amazing how much abuse fairing panels will take and hang together. The flexible ABS plastics on most sport bikes disintegrate on even a minor fall.

You can repair your Fibron parts easily. Road rash can just be filled if it's not deep. Bondo has a bad rep because it is usually applied badly...build up two or three coats rather than one lumpy blob. Cracks should be repaired with good epoxy. WEST systems is high quality. I fix breaks or cracks like this:
*wipe down the repair area with acetone.
*spread the crack with a liberal coat of epoxy, then put a piece of Saran wrap over it.
*clamp it tightly ... overnight cure.
*rough sand both sides w/ #60
*lay up two layers of fiberglass mesh (self adhesive/auto parts house) and saturate with epoxy resin...I only epoxy the back of the part unless it is really busted.
*if needed,repeat the glass/resin when the first layer is still tacky. squeegee off the excess.
*sand out and fill the front surface with a good catalyzed filler, prime and paint


jb
If you are obsessive :^) you can fill and sand the inside too.

[nh7robmw]

Thanks for the highly informative post, JB.

Marble dust, eh? No wonder my fairing and rear cowl are relatively heavy.

I think the AquaMend epoxy putty (formulated for fiberglass) will work just fine for my several small/tiny areas that need to be filled. Thanks for mentioning acetone, though---a good degreaser for sure.

I'll let you know how it turns out soon ( I plan to do the bodywork early next week when I have four days off in a row):whistle:drink:dance