New Mexico Truck Weight Limits

How much a truck can weigh in New Mexico

New Mexico's legal max is 86,400 pounds, and that number holds on its Interstates by grandfather, not the usual 80,000 (NMSA 66-7-410; 23 CFR 658 App. C). Single axles can carry 21,600 pounds under state law, above the federal 20,000. Overweight penalties are flat assessments from $50 at 1,000-3,000 over up to $1,000 past 10,000 over (NMSA 66-7-411, 66-8-116.1).

Axles, off-Interstate, and permits

• Off the Interstate: 86,400 lb
• Single axle: 21,600 lb (state law; 20,000 lb federal applies on the Interstate)
• Tandem axle: 34,320 lb (state, two-axle group with 4 ft spacing per 66-7-410; 34,000 lb federal on the Interstate)
• With a permit: 86,400 lb is the legal ceiling; heavier loads only by single-trip non-divisible/oversize-overweight permit case-by-case
• New Mexico is the divergent case in this group: its own 86,400-lb gross and 21,600-lb single-axle limits are higher than the federal baseline and are grandfathered onto the Interstate (23 CFR 658 App. C). Off the Interstate the state axle numbers govern; on the Interstate the federal 20,000/34,000 axle limits apply alongside the 86,400 gross.

Posted bridge and road limits

NMDOT and local authorities post bridges with MUTCD 'WEIGHT LIMIT X TONS' signs; tons are 2,000-pound short tons, so 10 TONS is 20,000 pounds. A posted limit overrides the legal max. A truck legal at 86,400 still cannot cross a bridge posted below that and must detour. Crossing an under-posted bridge is a separate violation and can bring repair liability.

What running heavy costs

Flat penalty assessments by excess weight (NMSA 66-7-411, assessed under 66-8-116.1). 1,000-3,000 over $50; 3,001-4,000 $80; 4,001-5,000 $150; 5,001-6,000 $250; 6,001-7,000 $400; 7,001-8,000 $550; 8,001-9,000 $700; 9,001-10,000 $850; more than 10,000 over $1,000. Operating without a required size/weight permit carries its own assessments (about $250 second offense, $500 third).

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