The leaf springs in my 2023 Isuzu D-Max are flattening

There’s a bit to unpack here. The first is that the D-Max is rated to safely tow 3.5 tonnes, so it’s not as if you constantly have the vehicle overloaded in terms of what it’s towing.

But if you also have the tray full of gear as well as 2.3 tonnes of caravan on the hitch, you might find that you’ve been inadvertently running overloaded for most of the time. It happens more than you think. At which point, the Pedders specialist is right; you need a suspension upgrade.

Even then, however, you still need to stay within the manufacturer’s maximum GCM (Gross Combination Mass) and the GVM (Gross Vehicle Mass) to stay legal. You can sometimes officially upgrade the GVM with a suspension upgrade that’s been properly engineered, tested and approved (which Pedders is a specialist in) but the GCM is generally not able to be upgraded according to the law in each state and territory.

But none of this explains why a vehicle designed to two 3.5 tonnes is wearing out its rear springs with 2.3 tonnes hitched up. Is the tow-ball down-weight within the legal limit (usually 10 per cent of the weight of the towed load)? Incorrect loading in this manner could affect the springs. Perhaps a fully-loaded visit to an accredited weighbridge might net more answers.

However, if it’s a simple case of the springs wearing out prematurely, then it’s possibly Isuzu’s problem to fix under warranty. Perhaps there was a bad batch of springs fitted at the factory that is affecting your vehicle and others built at the same time. Stranger things have happened.