Auto Club Speedway was the last track on the NASCAR Sprint Cup schedule to be added to iRacing. It is a 2.5 mile D-shaped oval that drives like a champ kart on a block of ice (it’s bumpy and slick.) You can’t take the fixed setup and expect to make some small changes here. This time, get a sink and anything else you can find and wind-up.
The best place to start building a base for these D-shaped ovals is the caster. Some of you may be unfamiliar with caster and how it affects the car. It is the forward and negative lean of the front suspension. What it does is it changes the “sluggishness” of the steering. Less caster means that your steering will be less twitchy. Start with a 4.0 on both sides and adjust as necessary.
The sway bar settings are fine. Just make sure you adjust pre-load before you change anything dramatically. At a track like this however, you need the splitter to be as sealed as possible. Instead of changing the sway bar I decided to take out bumpstop this time. 0 will be fine as long as you run the tire pressures correctly. When you run that low of a bumpstop you need to make sure you aren’t dragging. Start at 55.0 PSI on the right and 45.0 PSI on the left. That is enough to set the splitter where it needs to be while still giving the car enough handling.
From there I would add rear spring and take out front, if possible. I like 350 left springs and 325 rights. However at Auto Club, there is a gigantic pot hole that will send you up 4 lanes if you hit it wrong in Turn 3. If you feel like it won’t let you turn you can take out some left spring to 325. I would not venture to 300 or below.
The track bar setting depends on the handling. A good starting point is 15.000 on the right and about 8.000 on the left. Also, run bottom truck arm mounts. These are some reliable starting points for these settings.
So now that we have the splitter and the caster where we want it you can find your line and tweak from there. I recommend putting your lefts on the lowest seam and letting it roll. Before you deviate from this baseline I highly recommend trying a different line. The best way to pass is putting a door on someone or pinching extremely hard.
You can also expect the draft to play into effect a little. If you mess up your nose or suspension you are really going to hurt your car. Also, the car will want to tighten up a lot as the run goes on. If you need to, start a little bit on the loose side. (As I am publishing this Wednesday night’s sim-race went as predicted. Start loose if you decide to run these settings.)
That’s going to be about it for this week. As a final note I would run 40 tape. If you are a little snappy on entry I would add brake bias (or caster) before changing cross weight. This should be a reliable starting point (this is actually a little more than a starting point) for your set-up. Just try to run the correct line and this baseline should treat you well.