More success with 15-inch Goodyear Marathon tires

[Bill]

Another update for the tire upgrade experiment that we started a while ago. My wife and I just completed our yearly dash from Scottsdale, AZ to Wells, ME. About 2900 miles in 6 days, all but about 200 miles of it of it on Interstate highways, cruising for hours at 65-70 mph. Once again the 15-inch Goodyear Marathons on our 2720SL performed flawlessly. I do a back-of-the-hand check of tire temperature at every stop, and these tires at 60 psi were stone-cold - cooler than the 18-inch tires on my Explorer, which run slightly warm at 40 psi under those conditions.

Those who have been following the saga will recall that I had tremendous trouble over several years with the OEM 14-inch Marathons. Other board members had problems that seemed to echo my own. As events developed, there is no way to be sure if the trouble was the tires themselves or faulty Chinese valve stems. Bottom line, though, is that the 14-inchers were running pretty close to their rated load, and they always ran warm.

This was, I think, our 4th cross-country dash on the new tires. I have been entirely satisfied with the move to 15-inch Marathons on 15-inch rims. Thanks, Bobby, for making this possible.

Bill

Glad to hear your story Bill. We recently changed to the 15" Marathons, but don't have nearly the mileage on them that you do. So far, our experience is completely positive. And I sleep better at night without having potential tire problems in the back of my mind...

For those of you with a 2720 that have gone to the 15 inch wheels...

How much taller is the TM, when backing it into a garage?

I have 1/4 inch of vertical clearance. It isn't the diameter of the wheel tha is the problem, it's the diameter of the tire.

I suppose I could let some air out when backing it in and out of the garage for each trip, but that would be rather annoying.

The one time I weighed it, I was 3380 on the TM axle, which is 120 pounds below the limit, so I am running a little heavy.

Between the weight I carry in the TM, 4 year old Marathons, highway speeds and 100 degree temperature, I suppose it was not a complete surprise to have the blow out last July about an hour after DW hit a small pothole.

[Bill]

Wayne -

Unfortunately, I didn't do before-and-after measurements of the height, and now in Maine, I can't do an absolute height measurement with any accuracy. But according to the Goodyear web site, the difference in diameter of the two tires is 1.6 inches, so I would expect the larger tire to raise the trailer something on the order of 3/4 of an inch.

Just to be clear, your garage height is limited by the height of the door frame, right? Not the door itself - the height of the door can be adjusted.

Bill

When we bought the TM in 2005, I replaced the one piece flip up door with a roll up door. I have a 10 foot ceiling in the garage, but the top of the door frame is an inch shy of 7 foot. The bottom of the door is several inches higher than the top of the frame.

Not to step on anyone who has upgraded to the 15 inch Marathons....But isn't that a little overkill? I see that the Marathons in load range D are 2540 pounds of capacity. Now I just put on 14 inch Kumhos and they have a capacity of 2270. I wonder if it is REALLY necessary to get the extra 270 pounds of capacity. As the original Marathons had a capacity of 1870 it would seem to me that the Kumhos 400 extra pounds of capacity per wheel would be more than adequate. Plus you don't need to buy new wheels and they are only 3/10's of an inch taller than the original equipment tires...

Mike Anderson

[Bill]

Mike -

I think you are right. Either the Kumhos at 2270 pounds, or the Marathons at 2540 pounds, would be a great upgrade. The point of the investigation project was to note that the 14-inch Marathons were kind of marginal, and to gather some experiences - high-mileage or multi-year experiences - on upgrades to Load Range D tires. There are many possible Load Range D tires, and thanks to WMTire, we are able to gather actual user experiences with several of them. Since the goal is multi-year or multi-thousand-mile experience with various tires, the experiment is still in progress. I'm glad the Kumhos worked out well for you, as are other tires for other participants.

Bill

I am also glad you have success with the Kumhos. They have an excellent reputation. I would have considered them had they actually been available when I did my upgrade. As I recall from reports on this forum, their availability for awhile was a little sketchy... and I couldn't find them anywhere locally. As far as a "little overkill", I wouldn't consider ANY tire upgrade on a TM to be overkill! :-)

A couple of weeks ago I bought 3 new Marathons and had some metal valve stems installed. I had to get the valve stems from O'Reilly Automotive but this weekend when I was was about to hook up I noticed all 3 had gone flat. I had dropped the corner stablizers when I installed them, so they were still standing nice and tall. After wheeling the aircompressor out I discovered the air was leaking at the valve stem seals. I took them off and had rubber valve stems installed but I am wondering if anyone else has had a problem like this. I went back to O'Reilly but they said they only had two sizes. The other size being for old Volkswagens and it appeared much to large for the wheels. The ones I bought appears to have rubber o-rings much too tiny to ever make a good seal.

[Bill]

Tom -

There are at least a couple different standard sizes for valve stem holes. Perhaps you got a grommet intended for a 0.453" hole and installed it in a 0.625" hole. I know that some valve stems come with two grommets of different sizes, and you use the proper one for the hole size you have.

I'll defer to wmtire here, but it certainly sounds like you got the wrong size valve stem, or the wrong size grommet - or the grommet was installed outside the wheel, not inside.

Bill