OK so the New Tire Model (NTM) preview has been released and will be across all cars in the August 2011 iRacing release.
It’s about time that we tackle how the new tire works and how to get the best out of the car.
Things have changed significantly for the better and there is a lot that can be done.
Lap times drop off over the run, tires get hot and greasy and it’s easy to abuse them.
OK, so what do tires do for us? (Yes this is a traction circle discussion)
The tires are responsible for acceleration, braking, and turning the car. While it’s doing one of these, the effectiveness of the tire doing something else is reduced and there is only so much traction budget. ie if you are too hot into a corner and cranking on the wheel to get the thing turned the front tires are trying to slow and turn the car and if you are going too fast that will lead to an understeer condition and most likely a fast heating of the tires as they are over worked.
I’m going to run through a tire test/ setup session with the Nationwide COT car at Texas, which is the next intermediate oval on the 2011 Season 2 schedule.
First off we take the default Advanced setup and run 10 laps to get a base line.
LF 22.0 100 100 100
RF 47.0 100 100 100
LR 27.0 100 100 100
RR 47.0 100 100 100
The car didn’t feel good to me out of the box but I ran 10 laps as consistently as I could. At the beginning of the run the car was pushy/ loose. After backing up the corners a couple of laps I was having to brush the brakes on entry to get any sort of forward bight and get the car into the corner, but it didn’t feel too bad center off.
Tire Starting Pressure Finished Pressure Wear Temps
LF 22.0 26.3 88% 90% 97% 200 179 149
RF 47.0 58.3 76% 79% 82% 245 229 216
LR 27.0 32.7 93% 93% 95% 198 188 177
RR 47.0 56.7 89% 88% 90% 211 206 202
Interesting results that show that what I was feeling in the car is being reflected in the tire wear. The push into the corner is over using the cornering power and causing the tire to both heat up and wear faster than the rear. It also looks like the camber maybe off as there is little to no wear on the outer part of the tire.
Rather than change the cambers at this stage I want to make the car handle a little better and see what that does to the tire wear.
I look up my trusty cheat sheet to see what changes I can make to make the car better into the corner and we’ll go try again.
So we lower the front ARB (2.250 -> 2.125) and added 2 clicks of RR Trackbar (8750 -> 9.250) to help with loosening the car up into and through the corner. To help with feel of the car in the corner I dropped the RR Spring a click to 1150lbs/in
Typically speaking you should only change one thing at a time so that you know how that change affects the car and in general that’s what I do. I just happened to have a setup I’d started tweaking and those are the changes between the Texas Advanced and that one when I started.
Tweaked setup results
LF 22 26.3 198 177 148 89% 91% 98%
RF 47 58 238 221 212 76% 79% 83%
LR 27.5 33.3 202 191 179 91% 91% 93%
RR 47 57.1 217 212 209 84% 83% 86%
The car started off a lot better into the corner but that only lasted a few laps. An easy throttle let the car roll through the center and thing could get a little dicey center off. Lap times were 31.1 for the best and were pushing 32 by the end of the run of 10 laps.
Ok … it looks like we definitely have right front wear issues so let’s try something there first.
To try something I stood the RF tire up changing camber (1.9 -> 1.4)
The car immediately felt better and i ran a 30.7 as my first hot lap. The car tended to oversteer more over the run getting progressively looser while still be hard to get into the corner
LF 22 26.2 198 177 147 90% 92% 98%
RF 47 57.7 232 219 215 82% 83% 84%
LR 27.5 33.3 202 192 180 92% 91% 94%
RR 47 57 217 213 210 86% 84% 86%
Much better wear rates and the RR is now much closer to the RF which has almost even tire wear now. So far so good.
But i still want the car to turn better without killing exit which is the trick. I’ll increase the RR track bar a click and then work with the bump/ rebound as per the cheat sheet to try and dial in a better behaviour. I did the following.
+10 Clicks LF Bump
-12 clicks RF Rebound
+10 Clicks LR Rebound
-12 Clicks RR Bump
+1 Click RR Track bar.
The car feels a lot better although you have to be careful the first few laps as it is still a little loose off. I hope this gives a bit of understanding on how i go about setups and if you have any questions please let me know.
I also kept ATLAS traces of all my sessions and want to more with that soon also.
You can get the Texas setup on the Nascar B setups page