[Bill]

On our way from Yellowstone to Maine last week, we had a tire failure on I-90, just south of Pierre, South Dakota. This is third failure of a Goodyear Marathon that we have had in about 25,000 miles of TM'ing, and I admit I'm getting really tired of it.

In this case, it was the curbside tire that failed. The tread simply peeled off and disintegrated. On the way out, it beat up the underside of the TM, put big black marks on both the inner and outer walls of the shells, destroyed the white plastic wheel-opening cover, bent one of the main hold-down latches, tore up a bag seal, and jammed chunks of disintegrated tread between the shells, and between the shells and the body. The wheel well liner stayed intact, so there was no damage inside except some big black marks on the wall in the area of the wardrobe. But if the roadside tire had failed, I'm sure it would have taken out the plumbing, as Wayne described in another thread.

The failure happened at about noon (killing the rest of the day, of course). The wheel/tire had been balanced before installation, I had checked the tire pressure that morning, and I had checked the temperature (with my hand) about an hour before the incident. Because of the previous failures, I have been extra-careful about weight and speed - in this case, I was driving 65 mph on a good road, and the TM weight was well within specs, as measured on a scale. So I'm mystified.

We drove into Pierre to the Goodyear store for a replacement. The clerk made an interesting comment - I will check it out with the Goodyear factory, and report back to the group. He said "What they don't tell you is that if you run the tires at the rated speed (65 mph), then you have to derate the load capacity by 10%." Has anybody else heard this? The pair of tires is listed at 3750 pounds, so deducting 375 pounds leaves a "real" rating of 3375 pounds. Since this is just a squidge more than the weight of my loaded TM, there is no margin.

So anyway, after three failures, I am going to lobby the TM factory for two things.
1. There should be a "skid plate" of some kind under the TM on the curbside behind the wheel, and a protective barrier in front of the plumbing on the roadside.
2. TM really needs to move to a 15" load range D tire. There is simply not enough margin in the 14" load range C tires. In my lifetime, I've driven at least half a million miles in various cars, and never had a catastrophic tire failure. Three failures in 25,000 miles would have been expected in 1935, but is simply not acceptable today.

On a related note, changing the tire was easy. I carry a 4-ton bottle jack, so I simply jacked up the TM as far as the jack would take it, lowered the stabilizers to support it, then lowered the jack, put blocks under it, and jacked it up some more until I reached the required height. My TM has the 2" lift kit, which made it possible to remove and replace the tire without opening the shells.

And finally, I am pleased to report (again) that the TM handled perfectly with a blowout. There was a lot of noise, but no tendency to sway or to drag the tow vehicle sideways. I attribute this to the same design considerations that make the TM so sway-resistant under normal conditions. Nice job, TM!

Bill