Goodyear Marathons - overinflate/overspeed

[Bill]

We have talked a lot about Goodyear's overinflate/overspeed statement in the past, and no one was quite sure how to interpret the rather ambiguous wording on their web site. I spotted the following this morning on RV Tire Safety http://www.rvtiresafety.com/2013/10/...ype-tires.html. "TRA" is the Tire and Rim Association. I have no idea who they are.

I'll be interested in any comment from wmtire.

Bill

For Goodyear Marathon tires only:
There is a Goodyear Tech bulletin PSB#2011-13 that uses information from TRA.
The tech bulletin says that the normal max speed for Marathon ST type tires is 65 mph. This speed can be increased up to 75mph only if the inflation pressure is increased by 10 psi. This new inflation can be 10 psi higher than the pressure molded on the sidewall of the tire that is associated with the tire max load.
The load does not increase beyond the load molded on the tire sidewall.
Goodyear does not support or condone operation above 75 at any time.
The trailer owner is responsible to confirm the rim is rated for the new inflation level.
While TRA indicates a further increase in speed might be achieved Goodyear has decided not to adopt this option.

The person I talked with at Tire Rack said they had already changed their web site to indicate this applied to Goodyear tires only and that they were attempting to learn if any other ST tire manufacturers were willing to make a similar change. As of Saturday Oct 19, 2013 they had not identified any other tire manufacturer willing to make an increase in max speed above 65.

++++++++++++++++++++++++++++
Info added 10/26/13 10:51 AM EDT
Example:
If you have a Goodyear Marathon ST225/75R15 LR-D it is rated for 2540# @ 65psi and a max speed of 65 mph. If you increase the cold inflation to 75psi the tire would now be rated for 2540# @ 75psi and a max speed of 75 mph.
The example currently only is OK for Goodyear Marathon ST tires as I have not seen a published document from any other tire manufacturer.

The pressure increase must not exceed the max pressure capability of the wheel. You need to find a max pressure rating stamped on the wheel or get something in writing from the wheel MANUFACTURER.

[Redtail Cruiser]

There are a few roads in this country where it's legal to drive 75 MPH towing a trailer. Recently we took a trip that took us thru Nevada, Arizona and Utah. I was taken by surprise when the 18 wheelers were blowing past me doing 70 to 75 MPH. I found myself tempted to try it; however I decided not to, because the outside temperature was in the 90's and a blowout would have spoiled my whole day. California has a 55 MPH max towing speed and we normally put the cruise control on 60, so setting it at 65 in Nevada and Arizona seemed plenty fast enough. The faster your traveling the longer it takes to stop in the event of an emergency.

[TM Pilot]

So the practical application I'm getting from Tech bulletin PSB#2011-13 is to increase the pressure of the Goodyear Marathon tires to 60psi yet still drive on the highway at 65mph max. The increased pressure gives an additional +10mph buffer (75mph red line) for things like going downhill; passing traffic; not paying attention to speed; etc.

[Bill]

That is how I read it as well. However, there is no hint given as to whether the extra pressure will result in an over-inflation wear pattern, in which the center of the tread wears out rapidly. I suspect that it might, but since I moved to 15-inch tires and run them at 60 psi, I don't have to experiment to find out.

FWIW, if I increase the pressure in the Michelin tires on my Explorer to 40 psi (sidewall max is 44 psi), I definitely experience rather rapid over-inflation wear. This tells me that sidewall pressure on my Explorer tires (and presumably on my TM tires) is related to tire safety, not tread wear.

Bill

[TM Pilot]

Good point about the safety vs tread wear relation to tire pressure.

Since it is recommended that the Goodyear Marathons ST tires should be changed out every 3-5 years, excessive center tread wear due to over inflation by 10psi should not be a very big issue during that time frame for the average yearly mileage put on TM's. I agree that Goodyear is siding with the safety and not tread wear issue with this bulletin but the big assumption/expectation is that the TM owners are changing out the tires every 3-5 years and not putting extremely high mileage on the TM tires every year.

Each TM owner has to evaluate their own circumstances to see if the 10psi over inflation works for them. It should for most.

Of course having Goodyear redesign this 14" tire to carry a bigger load would be ideal even if it costs consumers a bit more.

[davlin]

Vedddy interesting.

Many of us folks who are running Load Range E tires (80 psi) are complaining about the extra "trailer bounce" with tires that hard. The fine china is getting a bit more jumbled. In fact, some are lowering the psi (while staying within the necessary load capacity) to get a bit softer ride.

I expect there may be some of the same experiences if you take the Marathon Load Range D tires up to 70-75 psi.

Dave