Safe. I have and know lots of guys & girls that have used them on the track. Lots of times its because its a quick & cheap fix. Nothing wrong with that. On the other hand Ive seen the whole arm changed for lowering & weight purposes.
Thanks for the info guys. The only reason it even came to mind is that I saw an advertisement for a set of extensions that included the phrase "for show use only". Perhaps I will steer clear of that particular brand.
Jamie, I am located in Australia. If you are willing to ship, please PM me the details of the extensions.
I had 8 inch bolt-on extensions on my 06 ZX10R until Sunday night. I ended up rear ending a Mercury Cougar and somehow the extension on the side of my bike that didn't hit the ground broke. I'm not sure how it broke without contacting the ground, but it split straight in half at the end of the swing arm.
I'll get some pics up in a day or two, I had faith in them until I saw this. I'd say go with a custom swing arm as it isn't that much more expensive and looks a lot better in my opinion