California wants your next set of replacement tires to be more efficient

Automakers spend significant engineering effort tuning the original equipment (OE) tires that ship on a new vehicle for low rolling resistance, since that efficiency directly counts toward the vehicle's fuel economy or EV range rating. Once those tires wear out, most drivers replace them with whatever tire fits their budget and preferences, and the CEC's testing found that the aftermarket options are, on average, less efficient than the tires the car shipped with.

Because rolling resistance is just friction between the tire and the road, it costs energy regardless of what powers the vehicle. A gasoline or diesel engine burns more fuel to overcome it, and an EV drains its battery faster, which is why the CEC frames this as a program that affects "all vehicle types" rather than one aimed only at combustion engines.

The legal basis for the program is not new: Assembly Bill 844, passed in 2003, already directs the CEC to regulate replacement tire efficiency under Public Resources Code Sections 25770 through 25773. This proposal is the agency's current step toward actually implementing that authority.

CEC staff determined the proposed regulations are technically feasible and cost-effective, and that they will not compromise safety, reduce tire life, or increase tire waste. That last point tends to be the biggest objection to efficiency-focused tire rules, since low-rolling-resistance tire designs can sometimes trade off against tread life or wet-weather grip. The agency's analysis found the proposal avoids that tradeoff.

The CEC's published materials do not list a specific implementation deadline or public comment deadline as of this writing, so the program remains a proposal rather than an enforceable requirement. Drivers currently shopping for replacement tires will not see a mandated efficiency label yet, but that is the direction the rule is headed.