I have the following system:
OS: Windows 7 64x
Graphic: ATI Radeon HD 6850
RAM: 4GB
Processor: AMD Athlon 64 X2 6000+ 3GHz

Every time when i starting a game, the intro run normal but when I come in the game, it lags extremly. For the first 5 seconds it lags, then 1 second it runs normal and then it lags 5 seconds agains. This is going so on. I have the latest patch and graphic driver. I have copied a Rageconfig.cfg to my Rage/base folder but it doesn't help too.

Have anyone the same problem or better a solution for this problem?

I had this exact same problem, I got it working somehow by uninstalling whole graphics driver from system, then I installed the drivers what have been thrown around on these forums too, so I think it took all info out concerning "the old" driver this way or something.
Then I rebooted and went to ctrl+alt+del and processes and shut down CCC.exe and MOM.exe I think. After this it worked, tho its bit choppy still now and then... also textures are popping still. Guess it'll have to do for now since we get something better.

Win 7 64bit
AMD Radeon HD 6850 Series
4GB RAM ddr2
Intel Core 2 Duo CPU E8500 3.16GHz

some have said that antialiasing 4x would work better than 8x with the popping on these forums but havent really had time to test it out.
Hope this helps, atleast it got me into game what is smooth now and then but choppy on some parts.

I had tried your solution. Now it run a bit faster but it lags again hardly when the chamber open.