42X13.50R17LT Tire Size

All You Need to Know About 42X13.50R17LT Tires

A 42X13.50R17LT tire is an extreme Light Truck radial flotation size combining a nominal 42-inch diameter, a 13.5-inch section width, radial construction, a 17-inch wheel diameter, and the LT designation - signaling a casing built for load support and structural strength beyond standard flotation construction. This is the largest size in the 13.5-inch-wide flotation family and one of the most demanding 17-inch tire fitments available in the consumer market.

42X13.50R17LT Size Quick Specs

The specifications below are based on the Mickey Thompson Baja Boss M/T 42X13.50R17LT - the primary and most prominent tire available in this size as of its launch. 42X13.50R17LT size has very limited production, and the Mickey Thompson figures represent the most reliable published data available.

Critical note on 42X13.50R17LT actual dimensions: The Mickey Thompson Baja Boss 42X13.50R17LT measures 41.9" in actual inflated diameter, not 42". Actual width also runs wider than stated: approximately 14.2" versus the nominal 13.50". Always use manufacturer-published inflated dimensions for speedometer calibration, clearance planning, and gear ratio calculations.

What 42X13.50R17LT Means - Notation Explained

• 42 = nominal tire height in inches
• 13.50 = nominal tire width in inches
• R = radial construction
• 17 = wheel diameter in inches
• LT = Light Truck service category - heavier casing, higher load capacity than standard flotation

42X13.50R17LT vs 40X13.50R17LT - Size Comparison

Both 42X13.50R17LT and 40X13.50R17LT are LT-rated radial flotation tires on 17-inch wheels in the 13.5-inch section width family. The table below shows the dimensional relationship.

The 42X13.50R17LT adds approximately 2 inches of nominal diameter over the 40X13.50R17LT - translating to roughly 1 inch of additional axle clearance. The step from 40 to 42 inches is not trivial: the 42-inch tire's circumference (~132 inches) versus the 40-inch (~125 inches) requires a proportionally greater gear ratio correction, imposes more load on steering and braking components, and demands additional suspension and body clearance modifications beyond those already required for the 40-inch size.

42X13.50R17LT vs 42x13.50-17 - Construction

Both 42X13.50R17LT and 42x13.50-17 tires share the nominal 42-inch diameter, 13.5-inch section width, and 17-inch wheel fitment. Construction and service categories differ entirely.

For the bias-ply version, see 42x13.50-17. 

Market Availability for 42X13.50R17LT

42X13.50R17LT is a limited but growing size. The Mickey Thompson Baja Boss M/T is the most prominent offering and was specifically engineered for the 17x9-inch wheel - the common aftermarket fitment for Jeep Wranglers, Jeep Gladiators, and similar off-road platforms.

The 42X13.50R17LT size was designed to deliver enhanced under-axle clearance while keeping the 13.50-inch section width narrower than wider-diameter tire alternatives, which helps manage track width on tight trail terrain. Buyers should confirm current availability across brands before committing to this size, as the selection remains narrower than 37- or 40-inch equivalents.

42X13.50R17LT Fitment Check

Running 42X13.50R17LT tires demands the following on most vehicle platforms:

• Large suspension lift - 6"+ on most platforms; many Jeep and truck applications require more for adequate full-travel clearance
• Body clearance modifications, including fender cutting - the 41.9" actual diameter and 14.2" actual width require more clearance than the nominal size suggests
• Axle regearing to 4.88 or lower for Jeep JK/JL and comparable truck platforms - the 42-inch rolling circumference significantly alters the effective gear ratio
• Strengthened steering components - the 42-inch diameter increases the mechanical moment arm at tie rod ends and drag links beyond what most factory steering components are rated for
• Full braking and drivetrain assessment - rotating mass increases substantially from the 40-inch size; brake rotors, calipers, and axle shafts should be evaluated
• Wheel offset planning - 42X13.50R17LT size is specifically engineered for 17x9" fitment; mismatched offset or backspacing can cause inboard sidewall contact.