Whether you’re coming from the oval or road course world of sim racing, the new tire model (NTM) –even in its early state — is going to be a game-changer. The most intense focus in testing thus far has been targeted towards oval racing, since the first car planned for release is the NASCAR Nationwide series COT. At the same time, we’ve all kept our finger on the handling of several road course cars in order to keep the developers up to speed on how core changes to the tire model are affecting all cars.
My first time out on the new tire model was in the Sprint Cup COT; at that point the Nationwide car had not been released for testing yet. The most obvious difference was how much more solid the force feedback (FFB) effects were. It was a much deeper feeling compared to simply increasing the force of the effects. I could tell from the FFB feel how loaded the front tires were in the corner compared to the straight. It was really noticeable at highly-banked super speedways. The very next thing I tried was tossing the car down onto the apron, as many of us know “dewedging” many of the iRacing cars on an apron, curb or otherwise sharply angled surface is viciously unsettling. A large smile crossed my face when I took the Sprint cup COT down onto the apron in the middle of turns 1 and 2 at Charlotte and didn’t immediately spinout.
As concepts were added into the tires (eg how wear affects heating) I got to feel how the cars performance changes over a run. Overdriving the tires in the Nationwide COT now has a subtle but compounding effect on handling. Pushing the car deep into the corners at a short track such as Richmond begins to build heat and pressure into the RF in addition to increasing wear .Those changes pile-up and make a much bigger impact on handling relative to the old tire model. Put yourself into a comfortable rhythm at a short track and you’ll be able to run 10 lap segments with consistent times within a tenth where falloff is manageable. Constantly overdrive the car into the turns and you’ll quickly see how that abuse tightens the car as the RF loses significant amounts of grip and lap times increase several tenths of a second. But backoff and run conservatively for a short stint and the heat and pressures will bleed off. While the handling won’t be as good as on fresh tires, you can recover from overdriving.
Whether you’re coming from the oval or road course world of sim racing, the new tire model (NTM) –even in its early state — is going to be a game-changer.
The DWC drivers have all been wondering if they’ll still be running as slipped-out and sideways as they currently do. Thus far the answer to that is “no”. It’s a concern on several testers minds and something we’ve been paying attention to, hoping that we don’t suddenly find ourselves running on as sharp an edge as possible turning right constantly. The amount of yaw the Nationwide COT currently tolerates is significantly lower than everyone is used to running, so much so that many testers are having trouble visually recognizing when the car is getting out from under them. It’s taken some tweaking but also some relearning as a driver how to deal with a loose car. The first problem with a loose car is how early you need to recognize that the rear end is getting away from you. As you increase your slip angle, heat builds faster in the rears in addition to aerodynamic side-force. These all act together to compound the situation much faster than we see in the old tire. An early reaction usually takes the form of reducing the amount of steering input, along with a slight lift as one would expect. Too late a reaction (when the car begins to exceed as little as 8-10 degrees of slip) will see you full-on countersteer combined with throttle modulation. Once you’ve made a successful save, you still have to deal with the built up heat in the rear tires. On a speedway like Charlotte you’ll definitely notice the car will be looser in the following corner after heating-up the rears. The quicker onset of a slide and effects of heat buildup have made having a comfortable setup much more important.
The group races we’ve done testing the Nationwide COT are some of the most true to reality replays I’ve seen. We recently ran at Michigan and, looking back, all the cars appear to be running with the appropriate amount of crab angle through the corners. The cars ride over bumps and slip and slide in the corners when overdriven at one end or the other much the way I see on TV every weekend. It’s a subtle but impressive difference when you have the chance to compare testing replays on the NTM with actual iRacing replays on the old tires. But more than that is the feeling you get driving the car in traffic at a place where you can take advantage of multiple lines. I’ve always been more of a tactician style driver.I’m really enjoying trying to push people into overdriving their cars and then taking advantage as they go into a corner too hot and push into the grey or have to chase the rear end up the hill. The effect of trying to run a race purely as a series of hotlaps is so detrimental that I’ve seen cases where you can kill your times by over a half second at both large and small tracks inside of 5 laps of overdriving. The way your particular setup is built will also have a big impact on how it handles over a run; in many cases the fastest setup I’ve found does not do nearly so well over a long run due to uneven tire wear.
For the road course cars many of the same improvements apply. Driving over curbs is a different experience in the new tire model — which for me is huge. I’ve always hated having to avoid what appear to be relatively benign curbs at the edge of the road because of how quickly it upsets the car. Overdriving the new tires builds heat and increases wear in much the same way it does for the oval cars. A loose setup is also slower at this point as the cars don’t tolerate abusing the rear tires for long: Slide a few corners heavily in a row and you’ll be babying it through the remainder of the lap in order to keep it under control.
Most of my testing has been done in the Spec Racer Ford. My opinion of the road cars on the old tire model isn’t nearly as critical as it was of the oval cars. The old tire model handles light cars much better than heavy ones, especially the lower powered cars that don’t see as wide a variety of speeds and loads. But the differences are clearly noticeable, particularly more stability over curbing. The new tire model is more sensitive to loading, so a car with a very rearward weight distribution like the Spec Racer Ford has a much higher intolerance now towards abusive trail-braking. Since we don’t feel the effects of g-forces in the sim it was very hard for me to get used to that at first. But going back and looking over my replays, many of my initial spins in the car were due to driving it hard into the corner and putting a ton of weight on the front tires and then proceeding to turn-in. With that much momentum in the rear of the car and no loading on the rear tires, it comes around quite quickly. On exit sliding the rear out under power doesn’t translate to forward acceleration the way it currently does on the old tire model. You really feel the diff working differently with these tires particularly through a cambered corner such as the keyhole at Mid-Ohio. You can quickly spin-up the inside wheel, get loose and correct the wheelspin but still be sliding too much to get proper forward traction. That, combined with the fact that you build up so much heat in the rears that by the time you get to the esses you have to brake much earlier to deal with cornering the car, really reflects on how much differently you need to approach driving it fast..
I hope this will give everyone a taste of some of the differences we’re experiencing in the new tire model from a drivers perspective. I’m sure there are a ton of questions left unanswered. But they will have to wait until the release. For certain many of us who are testing are hugely excited to see this released into the wild: It’s really going to make a big splash when that first practice session gets joined!