Suspension spring or hard bar on dozer?

I have an old Fiat 70CI dozer. As built by Fiat, the rear of the body of the machine is attached to the tracks via a couple of bushes and the front of the body is supported by a leaf spring that rests on either track frame and is bolted to the sump.
The old bloke I bought the dozer from replaced this front spring with a solid bar. He's dead now so I can't ask him why, but presumably he had some reason for doing this, as he'd been working with dozers all his life. It could just have been...

Suspension spring or hard bar on dozer?

Suspension spring or hard bar on dozer?