At the Sep 28 close, Shanghai front-month natural rubber (NR) settled at RMB 19,025/t, down 2.21% on the day, while butadiene rubber (BR) closed at RMB 15,390/t, off 0.87%. The NR-BR spread widened back to RMB 3,635/t as NR sold off harder than BR.

In tire compounds NR and BR substitute for each other within limits. When NR is expensive, mix designers shift weight to BR, and vice versa. With NR retracing and BR holding steadier, the cost of truck-tire tread compounds eases, and the formulation window tilts toward more BR and less NR. But BR is capped by butadiene feedstock, so the spread cannot widen without bound.

On the warehouse side, NR carries a high import dependency, and title certificates for Qingdao bonded stocks are hard currency for both entrepot trade and pledge financing. After NR's pullback, pledge haircuts usually tighten first, squeezing the working capital tied up in transit until the board stabilizes.