Rim max PSI

myredracer wrote:
Maybe GY has been the only ST tire maker that explicitly stated that you can go above 65 mph (when normally running at max psi rating) if you increase psi by 10 ?

They don't explicitly state you can go 10 psi above the max sidewall pressure (I think that's what you were trying to say). Here's a link. It's ambiguous, because it references the placard load/pressure data. Personally if the existing tires needed max psi to handle the load, I'd first bump up a load range so the psi stays within the sidewall max.

mike-s wrote:

myredracer wrote:
Interestingly, the old Marathons according to GY could be run up to 75 mph if you added another 10 psi to the psi rating of the tire

Any ST tire can be run faster than the minimum speed rating of 65. Add 10 psi (without going over max pressure) and you can go to 75 mph. If you go further and reduce the load rating by 10%, they're good to 85 mph. That info is part of the TRA standard load/pressure tables.

Maybe GY has been the only ST tire maker that explicitly stated that you can go above 65 mph (when normally running at max psi rating) if you increase psi by 10 ? I've never heard of ST tire owners deciding they want to run faster than the max speed rating then go and check their load capacity rating vs their actual load and then intentionally raising psi so they can do it. I doubt the vast majority even look at their tire's load capacity ratings and know their actual TT's weight or even know they have a speed rating.

myredracer wrote:
Interestingly, the old Marathons according to GY could be run up to 75 mph if you added another 10 psi to the psi rating of the tire

Any ST tire can be run faster than the minimum speed rating of 65. Add 10 psi (without going over max pressure) and you can go to 75 mph. If you go further and reduce the load rating by 10%, they're good to 85 mph. That info is part of the TRA standard load/pressure tables.

Well, you *could* simply run the Endurance tires at 50 psi and get the same load capacity rating as on your old tires and get the benefits of higher speed rating and a quality tire. But you really want to be able to use 65 psi to get more reserve load capacity (helps reduce risk of a blowout) and improve handling/sway. It's normally recommended to run ST type tires at the max. sidewall rating.

Upgrading to Endurance tires has caused a lot of confusion out there because the tires have a higher psi rating in the equivalent size. The RVtiresafety.net blog has some great info. on the Endurance tires and pressure. You could always send Roger Marble a message too. Interestingly, the old Marathons according to GY could be run up to 75 mph if you added another 10 psi to the psi rating of the tire and I don't recall reading anywhere about GY stating you should check the max psi rating of the rims first. Aluminum TT rims allegedly may have a psi rating stamped on the rear/inside of them if you pull one off. I too have never heard of an aluminum rim being damaged from too high a pressure. If rims could be damaged from too high a pressure, you'd expect to hear of a lot of rim failures because tire pressure can go waay up in hot weather and/or when towing at speed on highways.

Our TT was available with optional LRD tires in place of standard LRC (15") and we got the optional Marathons in LRD. This also gave us much higher reserve load capacity of around 30% which is way above what most TT owners have. End of this season they're due for replacement and will be going with the Endurance tires which will have a higher psi rating of 80 (up from the original standard LRC 50 psi). If I can't find a rating on the rims I might just run them at 65 psi and still get the already much higher load capacity rating. FWIW, I always check psi (cold) on each leg of a trip on long road trips. Large swings in elevation and/or temp. can change tire pressure quite a bit besides the possibility of a slow leak.

I too have always worried about going over 65 mph. It's so easy to slip over 65 when cresting a hill, on long downhill sections or having a tail wind come up even with C/C on. I use our GPS as a speedometer and my copilot and I both keep our eyes on the speed. It would be sooo nice not having to worry about slipping over 65 now and then. I don't like going over 65 regardless tho. Never a tire issue in 4 seasons on Marathons, touch wood...

Many high end aluminum wheels like Alcoa (others) are built for higher load and pressure numbers for that size wheel. They tell us the valve stem dictates pressures. Don't assume all aluminum trailer wheels are the same....their not.

Other aluminum off shore brand trailer wheels can have different load and psi ratings.

Many Older steel wheels carried different load and psi ratings vs todays newer gen steel wheels may carry the max load/psi rating for common tire in that size and load range.

be safe out there...ask the mfg/wheel dealer first

my aluminum rims on my trailer do carry a max load AND max PSI rating. as do the steel rims on my cargo trailer. And the rims for my truck.

On steel wheels the max PSI is often stamped on the inside of the rim. On my aluminum rims, I went to the mfg web site, found my rims, and it gave the Max PSI rating.

the steel rims were rated for "D" load range, the aluminum rims rated for 80psi cold.

In general, the load and PSI ratings are consistent, at least on mine, given the acceptable max tire size for the rim width. The max Load corresponded to the max recomended tire size LR typically available. However, I'm sure there are exceptions so if in doubt check it out.

Thanks mike-s, that was exactly the sort of stuff I was looking for. And, I didn't even know there was such a thing as a Tire and Rim Association. Learn something new every day.

Marv

Looks like wheel psi ratings are for cold inflation, just like tires:

Tire and Rim Association Year Book wrote:
Rim dimensions are standardized ... to assure proper mounting and fit of the tire and rim. The load and cold inflation pressure imposed on the rim or wheel must not exceed the rim or wheel manufacturer's recommendations even though the tire may be approved for a higher load or inflation. Rims and wheels may be identified (stamped) with a maximum load and maximum cold inflation rating. For rims or wheels not so identified or for service conditions exceeding the rated capacities, consult the rim and wheel manufacturer to determine the rim and wheel capacities for the intended service.

marpel wrote:

I haven't checked my rims (not near trailer right now), but I am comfortable running the GY's on them with a difference of only 15 psi.

It seems necessary to repeat an important point:
The pressure you put in a tire has more to do with the weight load than with the upper limit of the tire's capability.

YOU DO NOT HAVE TO RUN THE NEW TIRES AT MAX. PRESSURE and that probably isn't even a good thing to do......since you stated that you are not even exceeding the rating on the old tires.

Just because you CAN run higher pressure in the new tires does NOT mean that you should.

So, my question: Does anyone know of any bonafide documentation that states whether the max psi of a rim is for cold pressure or is the max pressure, period?

Thanks,

Marv

Interesting question. We just assume wheels and tires are ok with pressure increases above max because of load and speed.
If I was worried about pressure increasing at highway speed above max pressure in my wheels, I would contact a USA made wheel mfg which may be your best bet on answering that question.

When you ask the mfg a question be sure and mention the wheel is used in a load carrying application...not a lightweight race vehicle.