Two numbers on a tyre sidewall decide whether your truck is legal, safe and profitable: the load index and the ply rating. Fleet buyers who shop on price alone usually pay for it in casings that will not retread and steer tyres that scallop before half-life.
Reading the sidewall
Take a common drive tyre marking: 11R22.5 148/145M 16PR. 11R22.5 is the size; 148/145 is the load index for single/dual fitment (148 = 3,150 kg per tyre single); M is the speed symbol; 16PR is the ply rating — a strength convention inherited from bias construction that still signals casing robustness.
Load index is per tyre, per axle position
The classic overload mistake: rating the truck, not the axle. A tandem-drive tipper grossing at T&T's limits can still overload its steer axle when the body is loaded nose-heavy. Check the axle weights on the worst real load, divide by tyres on that axle, and buy index above that number — heat from chronic 5–10% overload is what delaminates casings long before the tread wears out.
Position matters more than brand
Steer, drive and trailer tyres are engineered differently: five-rib steer patterns for even wear and wet grip, lugged drive patterns for traction, stiff free-rolling trailer casings that resist scrub. Running a drive pattern on a steer axle is legal-ish and terrible — expect rapid irregular wear and a vague front end.
Retreadability is the hidden economics
A quality casing retreads two, sometimes three times at a fraction of new-tyre cost. That only works if the casing was never chronically overloaded, never run flat, and repaired properly the first time it picked up a bolt. This is why the cheap-casing "bargain" usually loses over a 4-year fleet cycle.
What we stock
GML distributes Royal Black commercial tyres in Trinidad & Tobago — steer, drive, trailer, mixed-service and OTR patterns in the common 22.5 sizes, warehoused locally with volume pricing for fleets. Send us your axle weights and current wear pattern; we will spec the fitment rather than just sell you rubber.