Just thought that id post up a bit of a note on this, seeing as I was reminded of its' importance during our recent trip through the WA deserts and north Kimberleys.
Whilst on the Gibb River Road heading up towards Mitchell Plateau, we stopped to talk to the owner/driver of a MAN tour coach, broken down with a snapped front axle. At the time we agreed with him, that there must be something wrong with the axle cast (these axles are ridiculously strong, 6.5T rated), but having since been on the rough road up the plateau (where he came from), and having talked with the driver again, we have a substantailly different view.
The tyres he runs are 385/65R22.5, same as the old 15R22.5 truck super singles, which are incredibly hard tyres, with not much sidewall. apon encountering the rough track to the plateau, we dropped our pressures to 40psi, which made a massive difference in ride (both dad's MAN and my canter run offroad michelins with large, baggy sidewalls), and also the constant pounding to the trucks. as the road got worse, we lowered them further, to around 30psi, this made the road quite bearable and actually quite fun.
Anyways, we saw the driver again on the way south (he had the axle welded up in Broome, but only 130 highway km later it broke again). We told him of our experiences on the Mitchell Plateau, and our tyre pressures. At this he was most surprised (that we went down to 30 psi), indicating to us that he hadnt let his tyres out, probly at all. Through dads fairly extensive experience in the offroad truck scene, we are quite convinced that his tyre selection, combined with failure to drop pressures are what caused all his troubles.
Which brings up a point of debate- tyre selection. had he been running XZL's on 20" rims, he may well have gotten away with not changing pressures, as the tyres naturally have alot of give. But the with the rock-hard semi-trailer super singles on 22.5s, which IMHO is very much like running 19.5" rims on a fuso or NPS, there is no room for error, as every bump is transferred directly through to the axle.
Sorry for being so long-winded, but i felt i had to tell the whole story.
Andrew
Whilst on the Gibb River Road heading up towards Mitchell Plateau, we stopped to talk to the owner/driver of a MAN tour coach, broken down with a snapped front axle. At the time we agreed with him, that there must be something wrong with the axle cast (these axles are ridiculously strong, 6.5T rated), but having since been on the rough road up the plateau (where he came from), and having talked with the driver again, we have a substantailly different view.
The tyres he runs are 385/65R22.5, same as the old 15R22.5 truck super singles, which are incredibly hard tyres, with not much sidewall. apon encountering the rough track to the plateau, we dropped our pressures to 40psi, which made a massive difference in ride (both dad's MAN and my canter run offroad michelins with large, baggy sidewalls), and also the constant pounding to the trucks. as the road got worse, we lowered them further, to around 30psi, this made the road quite bearable and actually quite fun.
Anyways, we saw the driver again on the way south (he had the axle welded up in Broome, but only 130 highway km later it broke again). We told him of our experiences on the Mitchell Plateau, and our tyre pressures. At this he was most surprised (that we went down to 30 psi), indicating to us that he hadnt let his tyres out, probly at all. Through dads fairly extensive experience in the offroad truck scene, we are quite convinced that his tyre selection, combined with failure to drop pressures are what caused all his troubles.
Which brings up a point of debate- tyre selection. had he been running XZL's on 20" rims, he may well have gotten away with not changing pressures, as the tyres naturally have alot of give. But the with the rock-hard semi-trailer super singles on 22.5s, which IMHO is very much like running 19.5" rims on a fuso or NPS, there is no room for error, as every bump is transferred directly through to the axle.
Sorry for being so long-winded, but i felt i had to tell the whole story.
Andrew
