MFL
Midwest
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ScottG wrote:Bob2952 wrote:
Because the tires are ST are they safe to use with 80psi and an average speed of 60mph?
Thank you
Yes.
Agree, yes, but to last part of OPs question, many have run E-rated ST tires with good success, and some, not so good. Reason...all ST tires are not created equal, and by design, some more dependable than others. What brand tires are they? If just 2 yo, could be a quality, newer, improved ST tire, with higher speed rating.
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way2roll
Wilmington NC
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The first thing I would do on any TT or FW is inspect the tires. If they are a cheap brand ST type tire I would replace them with a brand name LT tire. We had 2 blowouts on cheap OEM tires when we had our FW. The blowouts were within 5 miles of each other and did significant damage to the FW. They put the cheapest tires they can on TT's and FW's and they are a disaster waiting to happen. The term tire bomb comes up quite a bit on various RV forums. Now if the previous owner replaced the tires then that could mitigate the issue.
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NamMedevac 70
Reno
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For many years of travel in high summer heat in the western USA that began in Texas I have had excellent results with new ST Maxxis and Goodyear trailer tires on my 28 foot 5000lb TT with no flats or blow outs and only one slow valve stem leak. My TT was always heavily loaded and drove at speeds between 55 and 70MPH.
I always use LT Goodyear tires on my Dodge Ram trucks that were 1500 and 2500 V10 series. Very great experiences.
Cheers to the big wizard.
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Ponderosa
Western US
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ST tires used to be rated for only 65 mph continuous use. Today, they come in various speed ratings given by a letter code on the side wall like regular tires. L is 75. M is 81 and N 87. You don't see a lot of N's.
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theoldwizard1
SE MI
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Bob2952 wrote:
The tires say maximum cold tire pressure is 80 psi.
Because the tires are ST are they safe to use with 80psi and an average speed of 60mph?
ST tires (and LT tires when used on a trailer) are design and safe to run at their maximum pressure. There are speed rating for all tires, (not sure if it is on the sidewall), but I do know that unless the tire is specifically stamped "not safe for highway use", it can be run at legal highway speeds all day long !
Ply rating and letter ratings on tires are "old school". All tires sold in the US MUST have their load ratings, stated in pounds, embossed on the sidewall.
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Bob2952
Texas
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Not sure how I put this in Class A motor homes? My first post.
Appreciate all the info. To modify my question (my travel trailer is 6000lbs dry. With added cargo 2000lbs it has max weight 8000lbs) my tires are ST225/75R15 load range E speed rating 75mph. Load 2830lbs single/2470lbs dual.
If I put 70-80 psi in my tires and average 60mph am I good to go 1000 miles?
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CapriRacer
Somewhere in the US
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Bob2952 wrote:Not sure how I put this in Class A motor homes? My first post.
Appreciate all the info. To modify my question (my travel trailer is 6000lbs dry. With added cargo 2000lbs it has max weight 8000lbs) my tires are ST225/75R15 load range E speed rating 75mph. Load 2830lbs single/2470lbs dual.
If I put 70-80 psi in my tires and average 60mph am I good to go 1000 miles?
OK, doing the math:
If 4 tires are 8000#, then 1 tire is 2000#, but if we account for front to rear and side to side variation (12%) we get 2240#. An ST225/75R15 Load Range E has a load carrying capacity of 2830# at 80 psi and at 70 psi, 2620#, so at 70 psi, the reserve capacity is 17%.
That sounds good to me. But here's a way to check it. It's called Pressure Buildup.
Measure the pressure and the ambient temperature right before you start out.
An hour later check the pressures and temp again!
You don't want any more than a 10% buildup excluding ambient temperature effects (2% for every 10°F)
********************************************************************
CapriRacer
Visit my web site: www.BarrysTireTech.com
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JRscooby
Indepmo
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Bob2952 wrote:Not sure how I put this in Class A motor homes? My first post.
Appreciate all the info. To modify my question (my travel trailer is 6000lbs dry. With added cargo 2000lbs it has max weight 8000lbs) my tires are ST225/75R15 load range E speed rating 75mph. Load 2830lbs single/2470lbs dual.
If I put 70-80 psi in my tires and average 60mph am I good to go 1000 miles?
Why would you want to run less than the Max pressure on a trailer tire? Do you want more sidewall flex creating heat? That heat is what causes most tires to blow.
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Grit dog
Black Diamond, WA
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^Great explanation.
And I’ll add, you actually have about another 200-250lbs reserve or less load per tire than the above explanation, since reasonably, about 800- 1000lbs of the trailer weight is on the tongue and not the axles.
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Ponderosa
Western US
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Don't run an ST at anything less than the rated load pressure (80 psi in the case of and E tire). There is not a load based adjustment for ST tires.
So yes, pump em up to 80, cold, meaning before you take off, and roll. There's a couple variables like how old they are and is the rubber in good shape (no hairline cracks in the tread grooves, weather checking on the sidewalls. But otherwise...
* This post was
edited 09/01/23 11:35am by Ponderosa *
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