Hi everyone. I'm working on some tyre updates for our NGMT BTCC mod and trying to reduce the speed at which tyres heat up. I've read a number of post on the matter but still a little baffled..normally I just paint the skins Ive been able to reduce the wear rate of the tyre but im also trying to reduce the speed the heat in the tyre builds and in particular when its sliding. Tyre should take around two laps to build temp but can hit 150 degrees plus on lap 1. I know it can be done by increasing the SlidingBaseCoefficient vaule but tyre grip in itself it at the right level, it just spikes massively as soon as the tyre is pushed. Is there a simple way or setting in the TGM to help manage or reduce these temperature spikes?
This same defect also tends to destroy drive ability on many of the open wheel cars rear tires under acceleration. Oddly enough it doesn't have near the effect under locking tires under braking. I suspect the thermodynamics algorithms are flawed to a point where correcting them in the algorithm (or state machine) level would require updating all the existing TGM files published to date to adapt; if thats the case rF2 may not be able to keep up with other sims on the realism front. As realism is the key asset of rF2 over other sims I'm disappointed to see this defect fester as its probably going to impact the longevity of S397.
Remember that there are core temps and tread temps. It's not hard to overheat the tread on any tire in just a few seconds. Overdriving a fwd car and understeering will overheat the tread on the front tires very quickly - which is true to real life. The outer temps figure is an average - locking the brakes is only going to heat up a small portion of the tread whilst the rest stays relatively cool. Power oversteer heats the entire circumference, hence the high average reading. Last thing to remember is that in RF2, the track temprature, as far as I know, is always 27°c - which is quite warm.
Sort of.... Surface temps are the thinner outer layer with very little mass. As the temps reach over about 275° F the volatile begin evaporating off, by 350° they boil away. Factoring in the latent heat energy it drops temp a lot faster than one might expect. The heat is also transferred to the pavement, and vice versa. None of this heating is accounted for in rF2. Have a look at what tire thermodynamics look like to a FLIR camera. (FWIW, one of my customers uses 6 FLIR ISC1202 SWIR image sensors 2 rear, 4 front) to monitor tire surface temps in real time.) Stop it at 33 seconds to see the heat the tire surface exchanges with the pavement.
Real time section: DryTerrainEffect=(0,1,1) /// third variable specifies the fraction of sliding power applied to the tyre as heat energy You can also try increasing specific heat value on every node of your tyre. Temperature will not spike while cornering, but side effect is it will refrigerate slower, then probably it will accumulate more and more rolling heat after some laps: TreadMaterial=( , , , , , X, )
Good info, thanks. If only there there was a proper Developer's Manual that provided the effects of the physics variables in each of the files... I put something like that together years ago for rF1 as full remarks on each line. No longer have those files as the DDU crashed and I had no backup. Tire physics in rF2 are exceptional overall, but lacking proper thermodynamics. But rF2 is the only generally available sim where a car can be structured with identical geometry and force values where the setups pretty closely match those on track on a fairly smooth track. Harsh tracks like S397 version of Sebring are a challenge but I'm beginning to suspect thats due to the latency of the programmatic calculated response of motion in tire deformation and suspension motion.
Nice footage. I like thermal images. I think tarmac and tire rubber heats together as tire is at great stresses such as insane spin there, or locking up when braking and sliding at great speed. I have read one study that stated about almost complete loss of adhesion of tire with the tarmac as it goes past its melting point, and it was said that these temps aren't even that crazy high, just around 100C. The very surface of the place where super overheated tire touches tarmac melts it at very instant at surfaces very top layer. I think it was also said that this is why skidmarks appear, materials exchange or something. IDK. Well.... I suppose thats kind of how the theory is, if I recall it correctly. It kinda reminds me how ice produces instantaneously melting at the contact when great pressure is applied.
There is thermal conduction, between tyre and track surface in rF2. You can check this if you take a car with pre heated tyres, for example the Formula ISI. Just stand still for a while, lets say 20 sec., then move very slowly forward until the contact patch, which was in contact of the tharmac pass the thermal sensors. You should be able to see the difference in temp on the tyre page of the HUD for example.
That's not heat exchange, it's rubber. The shots of the car rolling in the pits with relatively hot tyres, and at low speed which would increase heat transfer, show no visible heat exchange to the track (though of course it's safe to say there is some). rF2 has heat exchange to air and track, with realtime parameters commented in the devmode skip barber files. What it doesn't have is variable track temp or other heat exchange (such as brakes).
Mostly rubber (along with particles pickup up off the track) but there is some heat laid down to the pavement which is speed dependent at a linear rate. While higher velocities diminish the heat conduction to the pavement it also increases the convection to the air at a non-linear rate. What makes velocity-convection rate non-linear is through penetrating the Boundary Layer of air around a solid object moving through the air. Typically the convection rate on a tire will quadruple between 60-80 MPH as the Boundary Layer is penetrated; the convection rate is closer to linear with velocity above that point, but not below that point. Then there is the effect of thermal convection transfer from the wheel itself. Highest for aluminum, less for magnesium and steel. Not a big deal for street compounded rubber with a thick tread, huge for thin carcass racing rubber loaded with volatile oil bearing compounds like Isobutylene and Isoprene. Both of these compounds are released as the tire heats (thats that funky "curing rubber" smell you find in a tire store with new tires). So why is that important? As the rubber decomposes it involves a endothermic chemical reaction and as a big bonus the latent heat of transformation to changes these from a liquid to a gas sucks a lot more BTU's of heat out of the tire. OK so I've gone into a few physics and chemistry lessons beyond what you were looking for. The bottom line is the thermodynamic effects of tires is very complex and is probably the most difficult to model - OK I get that from having a pretty good understanding of the effects. But in the end, the tire surfaces cool a lot more quickly than rF2 code can currently manage. And they will never see temps over about 600° F without the volitiles igniting and quickly turning the tire into a burning inferno. Nor will they reach over about 250° by spinning on moist grass alone.
Thats some deep stuff there. Not commenting on rF2 being right or wrong on that matter, though didn't notice any problems yet, at least nothing obvious to me. Perhaps for not driving modern high performance models too much. Tires of the cars I drive cools relatively great while in straights, as far as I have noticed. I just read there that asphalt ignites at over 500 degs of Celsius, and rubber ignites bellow 300. Source: http://www.tcforensic.com.au/docs/article10.html
Really shows how quickly the heat goes away on straights. Wish i could watch several laps in FLIR/thermal.
