3ds Max :: Enhancing Grain Pattern Without Increasing The Texture?

I'm fairly new to using bump maps and have a question about a wood grain bump map.

I am using a bmp file in the material editor for the wood grain, along with a UVW modifier to make the grain run differently on the different pieces of the furniture. I was hoping to "enhance" the appearance of the grain on the wood, so I thought I would try a bump map by using the same bmp file and set it to 30%. While there is much more texture to the grain than wanted, I'm wondering why the vertical instances of the wood do not seem to have the map applied?

Aside from that question, is there a better way of enhancing the grain pattern without necessarily increasing the texture?