I faced the same question since I had gotten all the cars and finally wanted to start testing them all with fairly consistent results.
I finally settled on 4 different tracks to test:
1) SSR7: Top speed test track. I opted for this over Le Mans, because Le Mans is very bumpy and a lot of the lap-time is influenced by how much you're going over the curbs.
2) Eifel Kart Track: I was looking for a narrow twisty circuit with low speed corners. I fiddled around with the track creator for a while until I was reasonably happy. It has 5 corners <90 km/h, at about 1 minute lap times.
3) Top Gear Test Track: Mixture of slow and fast corners. And, well...it's THE test track.
4) Nürburgring 24h: The ultimate test. And I disagree with previous posts: It DOES produce consistent benchmarks, exactly because it's so long. Small mistakes will not affect lap-times in relation as much as on shorter circuits.
So, now I'm testing all cars in stock condition. I started with non-race cars, from smallest PP in ascending order. From the lap-times I will calculate new PP numbers, which should represent a car's performance a little better than PD's. (Some of them are way off) I'm not the world's fastest driver or anywhere near the top WRS guys, but at least I'm division 2, and consistently so, so the results should have some merit.
Will post either the full results when I'm finished (that will take a while) or maybe intermediate ones before, if people are interested.
