The following tweak might be of use to people, I'm on a less than state of the art set-up and it seems to help.
First off create the following file if it doesn't exist
[INDENT][Steam Directory]\steamapps\common\rage\base\rageconfig.cfg[/INDENT]
Then provide the following settings to it:
[INDENT]vt_pageimagesizeuniquediffuseonly2 8192
vt_pageimagesizeuniquediffuseonly 8192
vt_pageimagesizeunique 8192
vt_pageimagesizevmtr 8192
vt_maxaniso 4
vt_restart
image_anisotropy 4[/INDENT]