AITB for making a buddy pay for damaging my utility trailer after he lied about the weight of his cargo?

I own a standard heavy-duty utility trailer with a dual-axle setup that I use for hauling lumber and parts for my home projects. A guy from my local car club asked if he could borrow it for a few hours to haul some "light metal framing and spare parts" from a warehouse to his garage. I told him he could use it, but specifically reminded him that the payload limit on the axles is 3,500 pounds and to make sure he secured everything properly.

He picked it up on Saturday morning. About four hours later, I got a text from him saying he had a flat tire on the highway and needed me to bring a jack and a spare. When I pulled up to the shoulder, I instantly realized why the tire blew out. The trailer frame was visibly bowing in the middle, and the leaf springs were fully flattened against the stops.

Turns out he wasn't hauling light framing at all. He had packed the trailer wall-to-wall with solid cast iron machine bases, industrial lathe parts, and scrap steel. When I weighed the rig at a commercial scale after getting the tire swapped, the total cargo weight was almost 6,800 pounds, nearly double the maximum capacity.

Because of the massive overload, both structural leaf springs were permanently bent, the main axle spindle was scorched from the friction, and the tires were wrecked. The repair bill from the local trailer shop came out to just under 1,400 dollars.

I sent him the repair estimate and told him he needed to cover the entire cost since he deliberately lied about the cargo and destroyed my equipment. He paid for the replacement tire on the spot, but he is refusing to pay for the axles or leaf springs. He claims the trailer was "already old and worn out" and that I am taking advantage of an unfortunate highway accident to rebuild my trailer on his dime.

A few members of our car club are calling me unreasonable for demanding over a grand for a trailer I bought secondhand, but I feel like he completely destroyed my property through negligence and deceit.

AITB for holding my ground on this?