perceived differences in the NextGen car and other vehicles + clueless physics blabbering below
Tyre: lower sidewall -> narrower slip angle, i.e. 'peakier' grip
Wheel hop under braking / tyre chatter seems to be reduced as well; there just is less rubber to expand and contract. If the tyre surface slips, it slips, and off you go.
Steering: rack and pinion instead of pitman arm -> less feel
(I think of it as a 'law of the lever' thing, but maybe I'm wrong. This is the part I understand the least.)
Earnhardt explained: "The rack and pinion steering is probably the one thing that that would be the most difficult to get used to. It’s so much different than the old style. The car steers very fast. Where you would turn the wheel quite a bit to get around the corner or try to get to a car to side draft, you’re very almost surgical with the steering now.
"Very small movements to make the car do a lot and so you can’t get real crazy with the steering wheel because the car is just going to take off (and) start darting around. That’s one of the things that I think would be most difficult to get used to. The rack and pinion steering and how fast it is."
Although it presents a new challenge at superspeedways like Daytona and Talladega, Earnhardt believes drivers will 'love' how quick the steering reacts at more technical circuits like road courses and short tracks.
Reddick concluded, “It’s really hard to turn the wheel. Just because of how much load is getting sent through all that stuff.”
Working power steering does fix that, of course. The other thing is that when you feel so much of how the car is sucked down to the road or pushed into the track, you may struggle to feel how the rear swings out. That kind of information could get drowned. But I won't complain; people on iRacing and at VO have been quick without any FFB or with steering wheels that have less detailed FFB. Still, to me, and if it was all about knowing which way is up, the Truck at Mid Ohio is like a pendulum and the Next Gen at Loudon is more like a clock hand. The "upside" is that it's not a compass needle.
The web says rack-and-pinion is more compact, lighter, easier to maintain - anything you or an engineer could want.
Having been listening to the #43 radio every race this year - it seems pretty common that not being able to feel the car is a common complaint.
Aero: diffuser instead of side force -> stability worsens with increasing angle of attack
Dirty air behind the car is narrower, supposedly. Looked awful at the first RL tests when the cars were in line. Short Tracks / single groove tracks suffer, also from not having much tyre degradation that would lead to searching around on different lines for grip.
I read somewhere that RL drivers have changed their approach to setting up a pass, i.e. whether to get clean air onto the left side or the right side, whether to get to the left rear or the right rear.
It has always been beneficial to run a car low, but the NextGen seems to be run with harder suspension than Gen6; the rub blocks on the underbody can hit the ground fairly hard, but I can't recall that it unsettles the car.
The iRacing car is very sensitive to transitions in banking (e.g. onto the apron) that shift the weight on the wheels (or even unseal the underbody aero?). Seams in the racing surface and painted apron lines have had bad impact as well.
Brake modeling in iRacing: brakes start off cold -> brakes don't grab (at first)
Brakes on the Class B & C vehicle are better than in real life, and should be worse than those on the NextGen.
In iRacing NASCAR, it can and often does pay to brake less as long as it doesn't mean scrubbing the tyres; if/how/when this translates to picking larger or smaller brake cylinders in the NextGen, I don't know.
Sometimes, for qualy on some tracks (Road America in Class B comes to mind), you want a soft tyre (through brake heat) and a low tyre surface temperature (by going slow). Over time, within a few miles of racing while keeping sliding low, the heat from the brakes and rim goes into the tyre sidewall, then into the tyre surface, at which time cooler brakes could become beneficial.
Off off a tangent, I found this comment by Christian Budd on tyre wear/saving to be interesting and concise: https://forums.iracing.com/dis…nt/238952/#Comment_238952
Gearbox: sequential 5-speed instead of 4-speed H-pattern, over-rev downshift protection -> giving the driver more options, except when the computer says no
A lower gear usually gives better engine braking, turning, sometimes better torque, but the NextGen requires to blip the throttle on downshifts / lift off the throttle on upshifts. Flatshifting using the clutch has caused drivers to spin.
Car body and chassis: less prone to taking dents, wheel suspension easier to break -> self explanatory