Hi all, Encountering some strange grip behaviour on the transition from a dry to wet track, tried some previously fine tyres and they seem to be playing up as well. I haven't yet tested on ISI stock content but hoping maybe someone's noticed similar or can confirm it's fine (and the problem's on my end/mod). Put simply: wet tyres lack grip on a dry track, are quite slippery on a 100% wet track, but are offering dry-tyre-on-dry-track grip on a 50% wet track. There are a few variables at play here: The track has a dry grip value, and a lower wet grip value Tyres have a (dry) starting grip, plus a wet multiplier for a fully damp track There is a lack of some wet parameters and effects that make realistic dry-damp-wet running difficult to simulate The 'normal' approach seems to be having wet tyres with quite low dry grip values, but they gain grip on a damp track. This is offset by the drop in track grip. So a dry tyre might start with a rubber grip value of 2, which on a fully wet track is multiplied (by the track) by 0.85, and then the tyre itself might lose 10% grip because of the wet as well. So the final grip is 2 * 0.85 * 0.90 = 1.53 While a wet tyre might start with 1.7, mult by the track's 0.85, but then mult by the tyre's 1.15 for a wet track. Final grip 1.7 * 0.85 * 1.15 = 1.66 Testing on a dry track, my wets are considerably slower than dry tyres. On a fully wet track, the wets are faster than the dry tyres but both are much slower than in the dry. On a 50% wet track my wet tyres are doing the same times as dry tyres on a dry track. Dry tyres are quite grippy but a little slower than the wets. I'm pretty sure this didn't happen before build 382 (we only did one league race on that build, this potential bug could have gone unnoticed). It's like one side of the transition isn't happening properly - the wet tyres might be gaining their wet grip while the track isn't dropping its grip properly, or something like that. The wetness figures I'm giving are in devmode, where you can set it explicitly, but this strange behaviour was found in multiplayer (just to rule out a devmode-only issue). I'm a bit pushed for time to test ISI content, if anyone could shed some light I'd appreciate it.
Also noticed something similar. With Skip Barber 2000 on slicks at Mills Metro Inner Loop C in multiplayer, during transition from dry to wet, laptime got quicker by 1.5 seconds and the car felt like on rails. This was with build 494. On previous builds, grip level seemed to stay too high as track got very wet, then it finally fell off, but did not gain grip like this.
Wanted to try and test this methodically, but I'm hitting a snag. The theory is simple: grip at any time on a wet track is determined by the tyres and by the track. The tyres have a whole lot going on internally (rubber wear and degradation, which have their own grip loss curves, plus the rubber temperature affects grip) as well. To test the two sides of wetness effects it's best to keep one side constant while varying the other. To start with I set the tyre degradation curves (per wear fraction, and per unit history) to all 1 so grip remains at full. I set groove effects to 0 to make sure I couldn't rubber up the track during testing and gain grip. I then changed the staticcurve (raw grip based on rubber temp) to have all three grip coefficients of 1.0, so running under- or over-temp will have no effect on grip. With the tyres now stable, I set the track tdf dry and wet values to 1.0 (no change). I then set all 4 tyre weteffects values to -0.99. That's a nearly complete loss of grip on a fully wet track. So I did a quick run at the skidpad (Testfacility; I had to change the skidpad to RaceSurface01 to give it wetness in devmode, looks funky because it's not set up graphically but I think it should be ok physically...), starting with 0% track wetness and ramping it up. Holding the inner skidpad curve at an approximate maximum speed: Wetness Speed 0% - - 75 10% - - 68 20% - - 61 30% - - 49 40% - - 35 45% - - 24 49% - - 13 50 - - can't turn at any speed basically That seemed to indicate the tyre weteffects are coming in more quickly than linear. The second part of the test should be to set the tyre weteffects to 0, set the track wet value to 0.01 of the dry value, and see how the results compare (at full wetness the tyres still have full grip, while the track loses 99%; in theory the same final result as above but done the other way round). And this is where I'm hitting a problem. I set those values, put the track on full wet, and could hold the curve at around 62kph. Sensing an issue I put the track's tdf wet value to 1.0 (same as dry), but instead of reaching the same 75kph as in the dry I was sliding at about 67. Set the tdf dry= and wet= values to 2.0 to see if I just had the completely wrong material, but was then able to hold about 104kph in the dry and mid 90s in the wet. Is there another variable determining the effects of wetness on grip? Or is my quick RaceSurface hack causing a problem? (haven't done much in the way of track modding, as you can probably tell) Just to reiterate the main issue here, I had to turn off the chance of rain for our league race (running a custom prog to get random weather) because it was possible to have better than slicks-on-dry-track grip using wet tyres on a damp track, as long as the track didn't get too damp (hard to measure that, hence I'm using devmode for testing). There were enough people getting the same thing to be pretty sure something is going weird, but I'd like to measure what and how much. *Edit: This makes a little more sense with some info provided by ISI. More info here.
