* Specific Z71 trim level: Different Z71s might have slightly different factory wheel and suspension setups.
* Wheelbackspacing: This is crucial. Larger tires often require wheels with different backspacing to avoid rubbing against the suspension, body, or fenders. Stock wheels are unlikely to accommodate significantly larger tires.
* Lift kit: Stock suspension has limited clearance. To fit much larger tires, you'll almost certainly need a lift kit. The height of the lift dictates how much bigger a tire you can fit.
* Tire brand and construction: Even within the same size, different tire brands have varying dimensions. Some might be slightly taller or wider than others.
Without modifications (lift kit and potentially new wheels), you'll likely be limited to only slightly larger tires than what came stock, maybe one size up. Attempting to force significantly larger tires onto a stock Z71 will lead to rubbing and potential damage.
To find the answer specific to YOUR truck:
1. Check your current tire size: It should be listed on the sidewall of your tire and possibly on a sticker inside the driver's side doorjamb.
2. Research tire size charts: Many websites and forums dedicated to trucks and off-roading offer tire size guides for the 1999 Chevy Z71. These charts often indicate the maximum size achievable without modifications.
3. Consult a 4x4 shop: A local shop specializing in truck modifications can assess your truck and give you accurate advice on the largest tire size that will fit without causing problems.
In short, there's no single "biggest" size. It's highly dependent on the specifics of your individual truck and the modifications you're willing to make.
