MARATHONS/TPMS

[jcurryii]

The problems with GY Marathons may be an unrealistic pressure gain. Purchase a TPMS for Christmas for our Monty. On our spring trip to Gulf coast, left home tire pressure set at 80#, as we traveled(about 120 miles)air temp about 72, Tire temps were running 90+. Tire pressures went to 95+, setting off alarm on TPMS. TV tires gain average 6#. Lowered tire pressure continued on trip. After a couple days, checked tire pressures cold, 75# average. On return trip air temps in mid 80's, tire temps 90-95, pressure 85-90. G614's before fall trip. Highly recommend TPMS for all Monty owners, or for any rver out there.

[Irlpguy]

Don't be fooled into thinking you won't have temperature and pressure gains with the G614's as well.
I have them and over a 3000 mile trip with pressures set at 110 lbs and air temperatures ranging as high as low 90's and down to 65 or so the average pressure gain was 15 to 20 lbs. The ambient air temp did not make a real big difference except on our first leg when it was only 45 degrees and climbed to around 70 during the day.

At 80# your pressure gain was about 15 lbs or a bit more, the same gain was indicated when you set the tires at 75#. Every day the pressures on my G614's rose by at least 15# but rather than lower the pressure from the 110# I upped the alarm pressure 10 lbs.

I don't think the pressure gain was abnormal on your Marathons, I bought the TPMS after trading in my Marathons so can't compare on a personal level.

You won't go wrong with the G614's but they are pricey...

[1retired06]

Interesting, but I would bet the overriding issue with Marathons is lack of weight carrying capacity when used with heavier rigs.

[woodtic]

quote:Originally posted by 1retired06

Interesting, but I would bet the overriding issue with Marathons is lack of weight carrying capacity when used with heavier rigs.

Also could be poor construction and quality control.

[Tom S.]

By the nature of their construction, all trailer tires will generate more heat. One way to help combat this is to keep your speeds down to 60 or 65 at the max (especially since that's the max speed the tires are rated at). You may also notice a difference running on blacktop as opposed to concrete because the surface temps on the darker surface should be higher than the lighter colored surface. My tires run 90 to 94 psi, and I would expect higher temps if the ambient temps are higher, but even that is subjective. For example, if the ambient temp in the morning when starting out is 70 and later reaches 80, I would expect less change than if the temps reached 100. Remember, all tire manufacturers state cold tire pressure, but that is for wherever you happen to be at the time. If you left Minnesota at 10 degrees with 80 psi and drove to Texas where it was 110, you are going to have pressure issues! :D

[woodtic]

I also saw the same pressure gains when driving. I tried running 90 psi in each tire after reading the Goodyear service bulliten on the Marathons. They preformed fine and showed less temperature and pressure gains during operation. Still run 85 - 90 psi cold psi..

[WaltBennett]

"By the nature of their construction, all trailer tires will generate more heat."

I'm not all that certain about that. Trailer tires have much stiffer sidewalls than LT tires, and tire flexing is what generates heat. That doesn't take into count how much the tire flexes where it contacts the ground (low pressure w/high load will generate more heat than normal). Race cars swerve back and forth on warm-up & caution laps to flex the sidewalls & generate heat. I know that the Firestone LTs on our Montana flex considerably more than trailer tires would - I see it every time I've got to get it out and in our narrow driveway and our narrow street.

I totally agree that Marathons are not designed for the loads any good sized 5th wheel will put on them, but I had them on my old TT (10k gross) with no problems in five years. Got rid of them right away when we bought our Montana though.

[DQDick]

My 614's tend to gain about 16# once they are warmed up. That is normal and air should not be taken out when they do that. That's why tires are checked when cold, to get the lowest pressure it's going to be. The real problem with Marathons is that they have no reserve capacity and so any issue with the road or otherwise will affect them.

[richfaa]

Temperature and pressure gains are normal when running. Our gains are about the same as IRlguy.

[jcurtis934]

Like folks have said, the real killer is the tire construction and the weight of the larger montys affecting the marathon...And I would add how they heat up during travel. Monitor tire temps... I was seeing temps into the 140's with them. And I can say that my new tires run way cooler and the monty is much more "quiet in its movement" when towing than the old marathons. John

[Tom S.]

quote:Originally posted by WaltBennett

"By the nature of their construction, all trailer tires will generate more heat."

I'm not all that certain about that. Trailer tires have much stiffer sidewalls than LT tires, and tire flexing is what generates heat. That doesn't take into count how much the tire flexes where it contacts the ground (low pressure w/high load will generate more heat than normal). Race cars swerve back and forth on warm-up & caution laps to flex the sidewalls & generate heat. I know that the Firestone LTs on our Montana flex considerably more than trailer tires would - I see it every time I've got to get it out and in our narrow driveway and our narrow street.

I totally agree that Marathons are not designed for the loads any good sized 5th wheel will put on them, but I had them on my old TT (10k gross) with no problems in five years. Got rid of them right away when we bought our Montana though.


Compare the weight of comparable sizes, that is an "E" rated truck and an "E" rated trailer tire. The trailer tire is a lot heavier. That means more mass, which is flexing with each rotation of the tire. It's the flexing that increases the heat. If you look at various tire manufacturers, you will see I'm only repeating what they say.

[rohrmann]

If you look at the G614, it weighs even more than a Marathon, but with the additional 30psi, it doesn't flex near as much, so the pressure and strength of the carcass allows the tire to run much cooler.

[Irlpguy]

There is a huge difference between the Marathon and the G614. For one thing the Marathon has fabric sidewalls, the 614 has steel. The 614 is rated for 75 mph and the Marathon only 65 maximum. The Marathon weighs 34 lbs and the 614 weighs 58 lbs, that is a considerable difference.

Every tire changes shape as it rotates, it is this changing of shape or sidewall flexing that causes the heat buildup, the 614 will do the same thing. If the tire is close to or over it's carrying capacity particularly if not inflated to it's maximum pressure the tire will flex more and generate more heat and if you are near or exceeding the speed rating this will magnify the problem significantly.

You cannot compare trailer tires and truck tires, all passenger cars and light trucks load capacities are calculated using a 12% safety factor on the rating of the tires being used, that is not the case with trailers and in fact most have had the GAWR reduced on the 7k axles down to 6750 so they are within the spec's of the tires they are using ie: Marathons. If you compare a Michelin XPS rib in size LT235/85R16 you will see it weighs around 55 lbs, much heavier than the Marathon, but it will have all steel construction which the Marathon does not have. Unfortunately it is only rated for just over 3000 lbs carry capacity.

The Marathon tires will last a long time if used in applications that do not put them near capacity and when they are not driven at freeway speeds. We tend to point at the tire because it is manufactured offshore, however we should be blaming the RV manufacturer for not using a tire with a higher rating.

I had no problems with my Marathons in about 10,000 miles but I feel more at ease with the G614's knowing they are rated higher in capacity and speed rating.

Back to the pressure increase and heat increase, you will see this on all tires to varying degree's.

[DonandBonnie]

We have experienced pressure differences too. We maintain 110 in the G614's which can be verified by a hand gauge. While parked the monitor pressure will indicate 90 to 95 lbs. Once the Big Sky is in motion the pressure rapidly restores to match the hand gauge. This restoration usually occurs before we exit the campground property. We have no idea why this happens. Our only guess is that there must be some relationship between motion and the accuracy of the monitor.

[DmaxDually]

Here is a artical with some good info and explaining the difference between ST and LT tires.

http://rvingwithmarkpolk.com/2012/11/08/trailer-towing-st-tires-vs-lt-tires/

[psomers]

quote:Originally posted by DmaxDually

Here is a artical with some good info and explaining the difference between ST and LT tires.

http://rvingwithmarkpolk.com/2012/11/08/trailer-towing-st-tires-vs-lt-tires/

Good article. Very informative. I had Maxxis M8008 ST on previous rig with no problems. Even had wheel and tire come off sheering studs off. Drove with one tire on one side for about ten miles for service. Put flashers on and drove 10 MPH and hub clears road by about two inches.
Fellow camper has Michelin XPS rib and has been pleased but is unable to find any for replacement. Tirerack shows they have six but un-sure they really do. Seems they are in short supply.