I had a lot of trouble heaving my 4/5 around on a mossy lawn when I test pitched it the weekend after I bought it. The moss was deep enough that the jockey wheel sank in nearly half way and the regular wheels also sank in a couple of inches.
Given that the jockey wheel on it has seen better days, I thought about a larger pneumatic wheel as a replacement. Getting the old clamp off proved difficult and I put the project on hold. The bolt on the clamp handle end was OK. Just get a socket (3/4) inside the C section beam with a short bar to stop it moving and another on the bolt on the front. The one where the clamp hinges was a right pain in the proverbial. You cannot get a socket on it, just an open spanner, and even then you cannot turn it as it fouls in the clamp. The best option was to get a socket on the nut on the inside of the C section beam. There is just enough clearance to get a ratchet onto the socket, then use the open spanner at the front to stop the bolt rotating. Access is awkward under the hitch and I was defeated by rust and too short a lever even after liberal WD40 squirts. Yesterday I was able to borrow some tools and this gave me access to a 20" bar to turn the socket. With the extra leverage it was going to move....either undo or sheer, but move it would. Fortunately it did not sheer and the bracket came off.
See the picture below for measurements.[You must be registered and logged in to see this image.]
The clamp is still attached as a reinforcing strip had been welded across underneath.
This is what I was looking at purchasing assuming the holes in the clamp match those I already have in the beam. I will have to confirm with the seller as they don't give this measurement.....Once I have the details I will post on the forum.[You must be registered and logged in to see this link.]
I will be using it later this year on the NT Langdale site and I will have to heave it a good 100 yards over grass, as cars are not allowed on the camping field. I suspect I will be glad of the bigger jockey wheel if my friends have all gone off to the ODG before I arrive.
It will also be useful on the steep bumpy slope up to my garage......I can just get the 4/5 up on my own, but an extra shove from the back really helps. I used a 1 tonne hoist with a 5m pull to get the Destiny up the same slope.