I'm not that familiar with AI in any game as I tend to just go straight to the online portion of every racing game. I wonder though, if anyone has ever tried to design a game with adaptive AI. And by adaptive I mean that you show up to a race event and qualify and then you set up the AI based on a percentage of your qualifying time, meaning that the fastest of them will be capable of that percentage of your last time period so you qualify at 1 minutes and 40 seconds for example, and then you set the AI at 100 + 1% of that meaning that their best lap time is going to be one second behind you. A minimum qualifying or practice time would be required so that the AI could run the track in the conditions that you set up an adapt to get to that lap time. To me that would make much more sense than having to guess at setting up the AI before you race and would allow for all kinds of variables that happened with a I'm moving from track to track, different weather conditions, different track conditions Etc.
One problem with doing it that way is that you probably won't have the AI actually driving to the best of their ability (minus whatever they are set below 100% potential) based on their version of the physics and their driving line and "racing algorithm." Pretty much the only way to have them be based off of your speed is to have them simply cheat and get dragged around the track at a set pace -- particularly if you can drive faster than their own "natural" ability. Then they drive like classic NFS or GT6 style rubberbanding(even if you can't see it changing within each session. Unless you can get really, really clever at having them match player line and inputs without running into problems with the simplified physics they all seem to use to improve game performance. Adapting like that could also of course introduce the possibilty of cheating the system, but that's always there one way or another.
I prefer to have bots that drive as lifelike as is possible under the circumstances, although I know fast people tend to be faster than any bots can be. It bugs me when I see AI cars that can clearly dramatically exceed their cars' top speed or cornering capabilty. I guess you can make some exceptions if intentionally overpowering them because of a super-fast player, like the artificial straight-line boost they got in rFactor at 120%. I also like to see them make some small mistakes now and then. Making small mistakes is actually something else that seems very difficult to do; you usually wind up with bots that either drive perfect or miss corners by 100 feet.
I guess I've just sort of grown accustomed over the years to expecting to do some testing to see how they drive on a particular track and tweak difficulty as necessary so I don't mind it. Spending time recording their pace in text files can be a little dull, but with a decent sim I'm usually making those files for notes on my own performance anyway since no game ever tracks all the info you might want. It would be nice if they could at least be fairly consistent, pCARS 1 had horrible problems with variable AI pace track-to-track and I guess the sequel does too. I've only seen a little so far, they are monsters at Dubai even at low skill but much less so at the other tracks I've raced.
Another thing with pCARS 1 that may carry over is that they could be WIDELY variable even at the same setting, you'd re-load the same track and almost the same conditions and they would be a couple seconds faster or slower. That probably contributed to why it sometimes seems like you slow them down 15% and they drop 4 tenths, then slow them 5% more and they're 2 seconds slower. Both pCARS games also seem to have it designed so that at high settings they are all within a few tenths of each other, but as you lower their skill the field fans out dramatically so the top cars only go 1 second slower while the backmarkers are 5-6 seconds slower. An interesting idea I don't hate in principle, but it seemed a bit exaggerated at least in the first game.
I only had a very small demo run with Raceroom(didn't love it enough to warrant spending 60 bucks for the whole game, buying any less than that felt like throwing money on a campfire with their price structure) so I didn't see much of how their bots adapted. My experience with them mostly involved them slamming on the brakes way too hard right in front of me and either plowing me out of the way or cutting the corners by 20 feet when behind me.
Dammit, I was going to keep this brief and make a quick point and it ballooned into another monster post again.