The other possible problem is that by default, P7 uses high texture filtering on all your texture maps - this can lead to blurred details, such as the writing on the tyre's sidewall. Whilst it can be a pain to go through each and every texture in your scene and switch the texture filtering from quality to none, there is a handy script available by stewer (look up 'texture filtering script' in the forum search, and you'll find it), which allows you to reset the filtering for any given element, figure or the whole scene if you desire. Well worth getting.

JonTheCelt