I think the game is simply hardcoded with a sensitivity curve and deadzone specific for the Dualshock 2 pressure buttons on a regular PS2. Some third-party controls aren't too great to use with PS2 GT games, too.
replyPatching that is possible I guess, but it would also require setting up some sort of calibration in the game.
Most people I know use the DualShock 4 for PS2 emulation. All you need is to write a mapping for the DS3, 4 and 5 to the DS2 curve and you can cover a big part of the users.
replyGeneric PS2-to-USB adapters ignore that part of the spec, so the PC doesn't receive these inputs at all. You'd need to build your own adapter out of Arduino or something.
replyThere are two types of generic PS2 to usb adapters, the one designed for pc (usually has two ports) and the one designed for PS3. The PS2 to PS3 controller adapters work perfectly with the right drivers (DSHidMini on Windows).
replyCool, didn't know that. I thought they've got rid of pressure sensitive buttons in PS3 already, not PS4. Thanks!
replySo apparently, to make pressure sensitive PS2 controller work in PCSX2, you need ShanWan PS2-to-PS3 adapter (or equivalent), DSHidMini, and set input mode to SDL. Since I lack both pieces of hardware, I can't test it myself. Or skip the middleman and get a PS3 controller, which is a better option anyway for several reasons.