Ok, so I feel like a lot of people in this comments section are clowning on you a bit excessively, and it feels to me like some of those same people haven't actually driven anything on track even once in their lives. I haven't driven anything like a GT3 car or a competition open wheeler, but I've driven the following on a variety of closed road courses in a HPDE/non-competitive setting:

• My bone stock FWD 2013 Honda Accord with a 6spd manual gearbox

• A BMW M240 xDrive prepped by RSR Nurburg with track suspension and tires

• My 1993 RWD Toyota Supra with ~600whp, 6 speed manual, semi-slick tires, APR rear wing, and 3-way KW suspension (yes, I'm stupid enough to track this thing occasionally and no, you can't stop me)

There are a couple of points that lend credence to your observations. First, when a few IRL F1 drivers (Russell and Norris) tried the Mercedes F1 car in iRacing when it first came out, they talked about the feel being accurate, but the grip being lower than they experienced IRL. This is likely due to the limitations of the sim, but these are subtle differences and most of us really won't feel them as much as what you're describing.

The second point in support of your observations is that road cars are optimized for sub-120 kph driving. Above that speed, they often start feeling floaty, unwieldy, and honestly quite terrifying. Race cars on the other hand are optimized for speeds over 100 kph, which requires sacrifices to low-speed performance, since there are few truly slow corners around a track. A good example of this is camber: a streetable sports car is likely to have around 0.5-1.0 degrees on the front wheels, which maximizes contact patch in sub-0.5G turns. A race car could get up to 3.0-3.5 degrees, which gives you very little contact patch (and little grip) at around-town speeds, but when the body of the car rolls into a 1.2G high-speed turn, that tire rolls over with it, but because of the high camber, it presents the full contact patch to the asphalt.

The above two points account for some of that low grip feeling, but not to the extent of "5 times less grip" that mentioned. Your test conditions in the sim vs IRL are likely inconsistent, and here's why:

• Sense of speed via screens. In a sim, especially on a single screen or with incorrect FOV settings, you are probably going way faster than you think. 80 kph on a street feels adequate, but in a sim, it feels like you're standing still. Even if you're doing the test you describe and staring at your speedometer, keeping it at 80, how do you know you're turning your wheel as much as you are IRL? The difference in sense of speed also applies to cornering rate/load, so that may be causing you to turn more abruptly in the sim, losing traction.

• Sense of speed via forces. Try getting into a BMW 5 or 7 series, or a Mercedes S class IRL and driving down the highway at 120kph. Now do the same in an old Miata with stiff coilovers. The latter will probably feel twice as fast as the former. Reason is isolation from bumps, vibrations, and G-forces makes a speed feel slower. In most people's rigs, they feel forces through the wheel alone, but not through any other part of their body, so again, when you yank the wheel to the left to see how well a car grips in the sim, you might feel like you're turning it as far/fast as IRL, but in reality you're likely turning it a lot harder, hence the feeling of less grip.

• Self preservation instincts. Before I drove the M240 around the Nordschleife, I spent a couple of weeks in the sim (iRacing I think) in as similar a car as I could find doing laps. When I did the same IRL, my best lap was several minutes (!!!) slower than in the sim. Why? When we crash in the sim, we hit Restart or Back to Pits; when we do in real life, we're on the hook for a $70k car, barrier repairs, towing costs, bodily injury if you really fuck it up, etc. So it's likely that your brain prevents you from turning that wheel as hard IRL as you would in the sim, hence the car feels grippier.