Old School Racing

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iRacing Big Block Modified Setup Guide

iRacing Big Block Modified Setup Baseline Settings

Use these settings as a good starting point for your iRacing Big Block or 358 Modifieds setup.

Tires

  • 10 PSI on front tires
  • 8 PSI on rear tires
  • 1 inch front stagger
  • 0 rear stagger

Thrustmaster T300RS GT Steering Wheel & Pedal Set

The T300 is a proven mid-range wheel with smooth belt-driven force feedback and a responsive brushless motor for clear track feel. An 11-inch leather wheel, solid three-pedal GT set, and PS5, PS4, and PC compatibility give racers the precision to brake later, hold tighter lines, and improve lap after lap.

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Suspension

  • LF Spring – 250
  • RF Spring – 150
  • LR Spring – 250
  • RR Spring – 150
  • Shock settings for a tacky track: 9 bump, 2 rebound on left, 2 bump, 9 rebound on right.
  • Shock settings for a slick track: 6 bump, 9 rebound on RF, all others 9 and 9.
  • LR Trailing Arm – 30
  • RR Trailing Arm – 18
  • Droop Chain – 19.500

Axle Lead – +4/16 (lower if too tight)

iRacing Big Block Modified Setup Speed Tips

Use this guide to get more speed out of your iRacing Big Block or 358 Modified setup.

Ride Heights

Logitech G923 Racing Wheel & Pedals

One of the most popular entry-to-mid level sim racing wheels available today. The G923 delivers strong TRUEFORCE feedback up to 1000 Hz that lets you feel the road with refreshing clarity, a responsive brake pedal with progressive spring, and a solid set of pedals built for consistent control. It includes a programmable dual-clutch launch system for cleaner starts, a genuine leather-wrapped wheel, and straightforward compatibility with PC, Xbox Series X|S, and Xbox One.

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  • Keep your rear ride heights about one inch higher than your front ride heights. (Right rear one inch higher than right front, left rear one inch higher than left front.)
  • Keep your left side ride heights even with or higher than your right side ride heights.

Other

  • Keep left rear bite/cross weight as high as possible.
  • Keep deck height as high as possible.

Bumpy Track Adjustments

For a rough, bumpy track, try these adjustments.

  • Stiffer springs, especially right front and left rear.
  • Set both ends of your J-Bar at 12 inches.

Notes

  • If you adjust spring rates, use the spring perch offsets to reset the ride heights to their original values.
  • After making any adjustments, make sure your ride heights and left rear bite/cross weight are where you want them to be. Remember, wheel spacing adjustments can have a drastic effect on those values.
  • To increase left rear bite/cross weight, increase left front and right rear spring perch offsets, and decrease right front and left rear spring perch offsets. If you do it evenly (same number of clicks on all four), your ride heights will stay about the same. Do the opposite to decrease left rear bite/cross weight.