California tandem axle weight limits let two consecutive sets of tandem axles carry up to 34,000 pounds each, for a combined 68,000 pounds, as long as the distance between the first axle of the front set and the last axle of the rear set is at least 36 feet. That allowance sits inside a stricter framework: no combination may exceed 80,000 pounds gross, no single axle may exceed 20,000 pounds, and the trailer must also satisfy kingpin-to-rear-axle rules. Miss any one of those layers and the tandem allowance won’t save you.
The 34,000-Pound Tandem Rule
CVC 35551 sets weight limits for any group of two or more consecutive axles using a distance-based table. The closer the axles sit to each other, the less weight the group is allowed to carry. Buried inside that section is the provision that most five-axle tractor-trailers are built around: two consecutive sets of tandem axles may each carry 34,000 pounds, for a combined 68,000 pounds, when the overall distance from the first axle of the front tandem to the last axle of the rear tandem is at least 36 feet.1Caltrans. Weight Limitation
Fall below that 36-foot spacing and you drop into the general distance table in CVC 35551(a), where the allowable weight for the group shrinks as the axles close in on each other. Slide your trailer tandems forward to gain maneuverability and you can quietly walk yourself out of the 68,000-pound allowance.
How the Spacing Is Measured
Distances between axles are measured to the nearest whole foot, and any fraction of exactly six inches rounds up to the next foot.2California Legislative Information. California Code VEH 35551 – Axle Limits Sometimes that rounding works for you; sometimes it works against you. Either way, guessing at your spacing is a bad idea when a foot in either direction can decide whether you’re legal.
Single-Axle and Gross Weight Ceilings
Tandem limits never operate alone. California weight enforcement stacks three layers, and the most restrictive layer controls.
The single-axle ceiling under CVC 35550 is 20,000 pounds, with no wheel end (one side of an axle) allowed to carry more than 10,500 pounds.1Caltrans. Weight Limitation A tandem is not a single axle for this purpose; it’s a group, and each axle inside the group is still measured individually against the 20,000-pound rule.
Combinations that include a trailer or semi-trailer face a tighter alternative under CVC 35551.5: 18,000 pounds per axle, 9,500 pounds per wheel end, and a front steering axle capped at 12,500 pounds. Several vehicle types are exempt from that front-axle limit, including dump trucks, transit-mix concrete trucks, and trucks equipped with a fifth wheel when towing a semi-trailer.
Above every axle and group rule sits the gross weight cap. The ceiling for any combination of vehicles is 80,000 pounds. Even if each tandem carries exactly 34,000 pounds and the steer axle is well under its limit, the combination still cannot cross 80,000 pounds gross.1Caltrans. Weight Limitation California’s weight tables track closely with the federal bridge formula concept, which balances total weight against the number of axles and the spacing between them to protect bridge decks and pavement.
KPRA Rules That Shape Where Tandems Sit
Weight isn’t the only reason your trailer tandems sit where they do. California also limits kingpin-to-rear-axle distance, which is measured from the trailer’s pivot point at the fifth wheel to the center of the rearmost axle. For a semi-trailer with two or more rear axles, the KPRA cannot exceed 40 feet. For a semi-trailer with a single axle, the cap is 38 feet.3California Legislative Information. California Code Vehicle Code 35400 – Length The same limits appear in CVC 35401.5 for trucks running on the STAA network.4California Legislative Information. California Code VEH 35401.5
The KPRA rule is the reason a 53-foot semi-trailer can operate in California at all: the kingpin sits well forward of the trailer’s front wall, and the rear tandem sits well forward of the tail, keeping the pivot-to-axle distance inside 40 feet. The rule exists to control offtracking, which is how far the trailer’s rear wheels cut inside the tractor’s path through a turn.
On advisory routes with tight geometry, Caltrans posts reduced KPRA limits, sometimes as short as 30 feet.5Caltrans. CA Truck Network Sliding your tandems back for weight distribution can push you past a posted KPRA limit even when the axle load is fine.
What Happens If You’re Over
Enforcement runs through California Highway Patrol commercial vehicle inspection stations. Under CVC 2813, every commercial driver must stop when signed to do so at a weigh station where the CHP is conducting inspections. Bypassing an open station is a misdemeanor on its own, before anyone weighs the truck.6Caltrans. Weigh-Stations (Enforcement Facilities)
Overweight fines are calculated by the pound above the limit, using the Uniform Bail and Penalty Schedule published by the Judicial Council. The amounts escalate quickly as the excess grows. Because California can cite you separately for each overweight axle or axle group and again for gross weight, a truck that’s over on two tandems and over on gross can face three stacked fines from a single stop. Overweight vehicles are typically required to offload before continuing.
When Legal Tandems Aren’t Enough: Permits
If the load itself pushes past 80,000 pounds gross or 34,000 pounds per tandem, and the load cannot be broken down into smaller legal pieces, you’ll need a special transportation permit from Caltrans.7Caltrans. Transportation Permits (Oversize/Overweight Vehicles) The controlling word is “non-divisible,” which Caltrans reads to mean that separating the load would either destroy its value or make it unable to serve its intended purpose.8Caltrans. Frequently Asked Questions A load that could be split into two legal loads doesn’t qualify just because splitting it costs more.
A permit also does not become a blanket immunity. Under CVC 35784, violating any term of a permit, including route, hours, or weight beyond what the permit authorized, can bring a fine up to $500, up to six months in county jail, or both, with additional weight-based penalties layered on when the truck exceeds even the permitted weight.9California Legislative Information. California Code Vehicle Code 35784 If you deviate from the permitted route or overload beyond what the permit covers, you’re back to being treated as an unpermitted overweight truck.
Quick Reference
- Single axle: 20,000 pounds maximum (18,000 for combinations under CVC 35551.5)
- Wheel end: 10,500 pounds maximum (9,500 for combinations)
- Steering axle in combinations: 12,500 pounds, with listed exemptions
- Two tandems, 34,000 pounds each: allowed when spacing between the outer axles of the pair is at least 36 feet
- Gross combination weight: 80,000 pounds
- KPRA: 40 feet with two or more trailer axles, 38 feet with a single trailer axle, less on posted advisory routes
- Axle spacing measurement: to the nearest foot, six inches rounds up