Time for a bit of an update. The truck has been going grreat, and we had no problems at all until this Sunday, when one of the sidewalls on our rear tyre cracked on the Karunjie Track. There was no evidence of any damage for rocks or anything, just a neat split. We tried to plug the hole as we were only 1 km from the Gibb River Road. We got about 100m before the sidewall split completely. We put the spare on, and continued back to the main road.
Since we could not get any tyres anywhere local. We are running Continental MPT81, and to our surprise, there are none in Australia at all. We contacted a lot of tyre dealers with the same story - no tyres available. Our only choice was Michelin XZLs. Contacting all the tyre dealers in Port Hedland, Kununarra and Broome. The closest town - Kununarra said they did not exist. Port Hedland and Broome said they could get them in 3-4 days. So we decided to drive the 1000km to Broome, by which time should be able to a new tyre from Perth would arrive.
We got about 400km before the other rear tyre blew - same problem, small crack in the sidewall with no sign of any damage. This time I took the tyre off the rim and did a proper internal patch hoping to be able limp back to the nearest town being Halls Creek. When I put the weight back on the tyre, I watched the split open up slightly. A helpful truck driver stopped and suggested we flag down a drop deck truck, and ask him to take us to Broome, for a bit of cash of course. I tried the local tyre shop, to get a tube, or for them to come out and get the tyre, put in a tube and get it back to us. They were not interested, said they would get a tow truck out of Kununarra for us. Then another local stopped and gave us the phone number of the local mechanic who was much more helpful. He said he had a tube that would work, and dropped it off to us the next day on the way to another job. I took the tyre off again, fitted the tube and we limped back to Halls Creek.
Lots of phone calls and after speaking to the Michelin State Manager, we managed to arrange 3 tyres to be sent to Kununarra. We then swapped the damaged tyre to the front, and drove back to Kununarra through the night at 50-60kph to keep the tyre cool.
We will get three XZLs fitted in Kununarra, then head up the Gibb River Road with the Continental on the front, and two spare tubes, and when the two extra XZL arrive in Port Hedland in three weeks time, we will get the fitted.
Looking at the date of manufacture, the tyres are 8 1/2 years old, and according to the tyre people, basically past their used by date. The tyres were already more than 2 years old when we bought them and it took us 6 years to build the truck.
So, if you are building a a truck, buy your tyres last, and try we something that is a bit more common than a 365/80R20.
We are going to look into getting some 22.5" wheel made, as that is a pretty common size now.