I've imported Sketchup vehicles into Blender, some good ones with lots of polies which as Harey said are a bit dificult to work with. Some are publicly shared and they are all free to download.
Importing sketchup to Blender links:
https://sites.google.com/site/alexvaqp/
Import a Sketchup object into Blender
Some people may find it easier to create a basic car mesh in Sketchup then finish it off in Blender, or create buildings for a track, etc.
However there is a plugin for Blender that will allow you to import objects, and this is how you do it:
In Sketchup once you are happy with your model go to:
file>export>3D model
Select Google Earth (*).kmz as the export type (not Google Earth 4)
Click export.
Download the Blender Import Script kmz_ImportWithMesh_Z019 (right click save as):
"
http://jmsoler.free.fr/util/blenderfile/py/kmz_ImportWithMesh_Z019k.py"
or go to this page and download it:
"
http://jmsoler.free.fr/didacticiel/blender/tutor/py_import_kml-kmz_en.htm"
save it in your blender \Blender Foundation\Blender\.blender\scripts folder as "kmz_ImportWithMesh.py"
It's a python script so you need to have pyton installed. You can get it from "
http://www.python.org/download"
Load up Blender.
In the File > Import menu item there will now be an Google Earth 3 kmx option
Select that and load the .kmz file you exported from sketchup.
The object will probably need to be scaled.
Thats all folks. I tried this with a couple of cars from the Blender 3D warehouse, Use Google to find the 3dwarehouse which is now Trimble 3Dwarehouse.
If you read the terms of service, any objects in the 3D warehouse are free to use and modify:
Which means you could take an object, such as a car or building, and modify it for use in racer.