Tire pressure question

Going from the specifications 8500 lbs GVWR.
4 tires on the road 2 axles 4 tires.
And your ST tire specifications so for max speed of 65 m/h.

Filled in my spreadsheet gives 54 psi .

But if you would give the tire a deflection that belongs to a speed of 99m/h and even some reserve for unequall load R/L so yust no bumping , the spreadsheet gives 65 psi.

So my advice is to fill to 65 psi cold pressure, and then no bumping and still acceptable grip.
But if in use it drops to 54 psi real pressure , with a bit of luck you did not damage the tires .

And this luck is that your pressure measurement is 100% accurate ( wich it never is), and you did not have more then a combined overload and unequal load R/L of 850 lbs, and you did not drive for even a minute over the 65m/h.

BubbaChris wrote:
For all the Max indicated versus Less discussion, I'm not sure I saw anyone suggest running the TT's tires at what the TT manufacturer suggests. OP has a brand new TT and I'm willing to bet there is a sticker that specifies the tire details (size and recommended pressure).

In my case since my TV is an SUV, I run those tires at what the mfg recommends when not towing (for better comfort and performance, however you want to measure). But I run the rears up near the sidewall rated max for towing since they're not LT's.

The stickers are not reccommended pressure and loads they are maximum pressure and maximum loads, just like sidewall information.

My owners manual states to run max pressure until a scale can be found, and then to reduce the pressure to the amount required for the load.

AH64ID wrote:

nomad297 wrote:

AH64ID wrote:
Goodyear even lets you run up to 10 over the sidewall pressure on the Marathon for speeds of 66-75.

You're trying to tell us that Goodyear actually recommends that we drive over the maximum speed rating of their tires -- as long as we over-inflate them? This sure doesn't sound likely to me.

Bruce

If you don't believe me do the research yourself.

http://www.tirerack.com/images/tires/goodyear/Marathon_Special_Trailer_Applications.pdf

rbpru wrote:
Paw Paw amd Gram,

Who would tell you to run your TT tires under inflated?

That has to be the number one NO NO for tires.

Exactly. Overinflated is better than underinflated, and underinflated is probably the #1 killer of tires; however, proper pressure is best.

Wow! Thanks.

Bruce

Dupe post deleted

For all the Max indicated versus Less discussion, I'm not sure I saw anyone suggest running the TT's tires at what the TT manufacturer suggests. OP has a brand new TT and I'm willing to bet there is a sticker that specifies the tire details (size and recommended pressure).

In my case since my TV is an SUV, I run those tires at what the mfg recommends when not towing (for better comfort and performance, however you want to measure). But I run the rears up near the sidewall rated max for towing since they're not LT's.

In searching teh Google for a copy of the "TRA 2013 Year Book" (Which I found costs $119.00 for the paper version or $275.00 for single user Flash Drive version) I stumbled on this site. I cannot in any way vouch for the veracity of the information contained therein, but it did make for some interesting reading per tires and the speed rating process.

Clicky

Upon further search I found this on ST tires. Toward the bottom are dimension tables from the TRA 2005 Year Book

ST Tires

"Turn me over, I'm well done.!" -- St. Lawrence of Rome 258AD

jwoods61us wrote:
"• Goodyear Marathon Special Trailer tires, with the “ST” size designation, are speed rated
at 65 MPH (105 km/h) under normal inflation and load conditions.
• This speed rating is based on Tire and Rim Association loads and inflation pressures for ST
trailer tires without a service description for speeds up through 65 mph. (ref: TRA 2013
Year Book)"

So if I read this correctly,(and I'm sure someone will point out that I did, in fact, not) Goodyear tires are speed rated not on their engineered capacity, but according to the Tire and Rim Association recommendations contained in a document known as the TRA 2013 Year Book. So all the tire experts on here that recite the 65mph speed rating for ST tires as some sort of from on high gospel might be incorrect? Can that be possible?

:? If it is on the internet, it must be true! Right? ;)
;) :S

You are reading it correctly, and yes ST tires only carry a 65 limit by the fact that they are ST. STupid as it is... The problem is that the only ST tire I know of that addresses the difference between engineering design and ST designation is the Marathon. The published critera is all we can use for 99.9% of the ST tires out there.

My 0.02 is that the ST designation should be dropped and all tires receive a speed raiting and a load index number. Tires can be trailer service only and not ST. Just my 0.02.

I currently use LT tires, but for different reasons.

samhain7 wrote:

wrgrs50s wrote:
Seriously, watch the towmax tires for tread seperation before and after every trip.

And the sign of pending tread separation is...........?

A sign of tread seperation is a bubble on the inside or outside of the tire, or swelling of the tread itself. Early on you can look at the tread and see that the lines or grooves in the tire will look wavy instead of straight.

I was checking mine regularly, due to being warned by another towmax owner, and found the tread swelling, so I contacted treadit tire which sent me to a local dealer that verified the tire was coming apart inside and credited me $90 toward a new set of Maxxis

"• Goodyear Marathon Special Trailer tires, with the “ST” size designation, are speed rated
at 65 MPH (105 km/h) under normal inflation and load conditions.
• This speed rating is based on Tire and Rim Association loads and inflation pressures for ST
trailer tires without a service description for speeds up through 65 mph. (ref: TRA 2013
Year Book)"

So if I read this correctly,(and I'm sure someone will point out that I did, in fact, not) Goodyear tires are speed rated not on their engineered capacity, but according to the Tire and Rim Association recommendations contained in a document known as the TRA 2013 Year Book. So all the tire experts on here that recite the 65mph speed rating for ST tires as some sort of from on high gospel might be incorrect? Can that be possible?

:? If it is on the internet, it must be true! Right? ;)
;) :S

op wrote:
I have Towmaxx STR tires (yes, I know junk, garbage get rid of them as soon as I can). On the sidewall and tires it reads:

ST225/75R 15D 65 PSI

They may well be junk as Towmax issued a recall on their ST225/75-15 D tires in 11/'14 ;

http://www.towmaxtires.com/content/towmax/docs/Recall%20Notice%20Effective%20December%2015%202014_2.pdf
check it out to your satisfaction