I tried to do the chalk test once but I failed at it.
Take a stick of sidewalk chalk (Children's toy section of Walmart), or regular chalk, scrape the side of the stick across the pavement to rough it up, then rub it across the tire tread back and forth many times. It make take a dozen stokes to get enough chalk on the tread. But once you get the hang of it, it's easy. And worth it to determine your proper tire pressure.
2008 2-dr Rubicon, auto,
RK 2.5" Max Travel, Rancho 9000XL shocks, 37" Nittos, 5.38's, RR skids, Warn VR8000-S.
RIPP Gen 2 Stg 2 Supercharger.
Political Correctness offends me.