Bob, the combination of of art that is pre-existing to get a patent must be something that is not apparent / obvious to a layman.

AKA no patents for the obvious.

That says.. If bigger brakes came on an 89 its not considered an invention to put them on an 87.

Good point on prior art, since everything we do in one way or another is based on prior knowledge and existing designs.

Putting helical gears into a differential to produce a traction device is a good example of a combination of prior art being patentable (torsen diff).

Basicly I was going for... You cant get a valid patent for cylindrical device with a hole in the center rotating on a shaft used to reduce friction of a horse drawn sled. <img src="/forums/images/graemlins/smile.gif" alt="" />

I'm named on a few patents and have three more in process. I got one less then two weeks ago, I should have done a better job of explaining what I was trying to say.

Kevin