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Old 06-14-2013, 01:03 AM   #1
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I have a new 33BD TTand have a question about the tires. Some other forums claim that trailer tires are speed rated to about 60mph. I have looked at my tires and I do not see any limitation. I normally tow about 60-65 to help with MPG and sway, but occasionally get on a 70mph interstate. Are the tires speed rated? Is 70mph safe for the tires?
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Old 06-14-2013, 01:14 AM   #2
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If they are ST trailer tires I believe they are rated for no more than 65 mph. I switched to LT tires soI no longer worry about that. I still try and drive no more than 65 mph but have gone as high as 70 mph a few times.
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Old 06-14-2013, 05:53 AM   #3
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Me to I switched to lt's My st's road hard and did't make 16,000 miles before they were wore out.
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Old 06-14-2013, 11:46 AM   #4
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ST tires are speed rated at 65 mph. Somewhere on the sidewall it is listed in very small print.
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Old 06-14-2013, 02:20 PM   #5
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Thank you, I will check the sidewalls again. Is ST a speed rating for trailer tires?
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Old 06-14-2013, 07:51 PM   #6
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ST means "Special Trailer". All ST tires have a speed rating of 65 mph.
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Old 06-15-2013, 01:29 PM   #7
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I would add to the debate over the speed rating a caution to not run your ST tires underinflated. If you have a load range D, they should be inflated to 65 psi cold. If you have a load range E, they should be inflated to 80 psi cold. Speed and under inflation are a tires worst enemy.
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Old 06-15-2013, 11:32 PM   #8
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And if you have load range C, which I do, they should be inflated to 50 psi cold.
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Old 06-15-2013, 11:34 PM   #9
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Max air pressure inflation is intended for max load.



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Old 06-16-2013, 02:25 AM   #10
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Quote:
Originally Posted by Old Farmer
Max air pressure inflation is intended for max load.



I agree, I would only inflate to max psi IF I didn't have any idea how much weight each tire needed to actually carry. There is a reason that tire manufacturers publish load inflation tables. Consider the situation that exists with truck tires. My GM door sticker clearly states 80 psi for the rear tires and 50 psi for the front tires. So even though all 4 tires are load range E (80 psi), max psi is not needed since the front axle GAWR is much less than the tire capacity and the front tires would be over inflated at 80 psi. In fact, most owners don't run the rear tires at 80 psi when running solo in order to improve the truck's ride.

Actually, my Cruiser is an even better example. The factory installed ST tires had a capacity of just over 7000 lbs per axle, yet the GAWR is just 5200 lbs. So, running the tires at 80 psi means they are over inflated for any legal trailer weight. Tire flex is one of the components in handling road shock, so over inflated tires means more stress on axles, springs, hangers, eye bolts and the rest of the trailer.
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Old 06-16-2013, 02:38 AM   #11
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What pressure do you run yours at Larry?.....Thks...Al
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Old 06-16-2013, 05:59 AM   #12
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While tire pressure charts can be found for LT tires running at less than max load I've never seen one for ST tires. Maybe the thicker sidewall on LT tires allows this(lower pressure) and not on the ST tires, I don't know.

I do know I just replaced my trailer tires (Trail Express) because on one the tread was separating. They have always been run at 80 PSI cold and were wearing evenly. I'm with Dayle on one respect. I have 5200 lb axles and the tires are rated 3500 each for 14k of tire on 10,400 axles. Actual axle weight is 7800. I don't know what each tire has on it. Doesn't make sense to me but I'm not an injuneer.
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Old 06-16-2013, 07:48 AM   #13
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Here is an inflation chart from Maxxis for ST tires.

http://www.maxxis.com/Repository/Files/m8008load.pdf

Note, load range E tires have the same carrying capacity at lower psi as lower load range tires, not more and not less, but exactly the same. So, there seems to be no advantage in running higher load range tires than what the actual loaded trailer weight requires.

I switched to LT tires and run them around 71-72 psi. I don't feel that ST tires make sense anymore, at least for RVs, and it isn't just the 65 mph speed rating. ST tires are supposed to use different rubber compounds to fight ozone and increase tire life for tires that are not used on a daily basis. Well, today most ST tire manufacturers now advise tire replacement in as few as 3-5 years, so where is the extended tire life? Meanwhile most heavier (i.e. expensive) fivers come from the factory with LT tires as standard equipment, even though LT tires have a lower load capacity.

Edited by: Dayle1
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Old 06-16-2013, 08:12 AM   #14
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I have 235 80 16 E rated tires.My weight is 2400 lbs on each tire. According to this chart I could use 45 psi. Is this correct? Am I reading it right?...Thks
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Old 06-16-2013, 10:38 PM   #15
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This is a cut & paste from the Goodyear RV tire website:

" Unless trying to resolve poor ride quality problems with an RV trailer,
it is recommended that trailer tires be inflated to the
pressure indicated on the sidewall of the tire. Trailer tires
experience significant lateral (side-to-side) loads due to vehicle sway
from uneven roads or passing vehicles. Using the inflation pressure
engraved on the sidewall will provide optimum load carrying capacity
and minimize heat build-up."

I run mine just a couple of psi under max.
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Old 06-16-2013, 11:40 PM   #16
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Quote:
Originally Posted by jererp
This is a cut & paste from the Goodyear RV tire website:

" Unless trying to resolve poor ride quality problems with an RV trailer,
it is recommended that trailer tires be inflated to the
pressure indicated on the sidewall of the tire. Trailer tires
experience significant lateral (side-to-side) loads due to vehicle sway
from uneven roads or passing vehicles. Using the inflation pressure
engraved on the sidewall will provide optimum load carrying capacity
and minimize heat build-up."

I run mine just a couple of psi under max.
If you are running ST, D rated tires , I agree with that on your size rig. If you are running LT, E rated tires, I don't agree.

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Old 06-17-2013, 01:52 AM   #17
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I'm running ST E rated tires right now. when I'm ready to replace, I'll be looking at LT tires.

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Old 06-17-2013, 04:45 AM   #18
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Quote:
Originally Posted by albertr

I have 235 80 16 E rated tires.My weight is 2400 lbs on each tire. According to this chart I could use 45 psi. Is this correct? Am I reading it right?...Thks

You are reading it correctly, however do you really want the tire load capacity to be less than the axle capacity of 5200 lbs? Especially when you have a choice. I suspect that 50 or 55 psi would be a better bottom limit, but even that is hard to comprehend on an 80 psi max tire. So, a compromise might be 65 psi, I don't really know.

My '04 Cruiser came with D rated tires and I ran them at 61-62 psi w/o problems. When it was time for replacements I "upgraded" to E rated ST tires since there was almost no price difference. I ran them at 71-72 psi since the OEM rims were only rated for 75 psi. In hindsight, this was probably overinflated for the load and the tires failed at 3 yrs (they ballooned and started rubbing against the fender skirt and bottom of the trailer).
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Old 06-17-2013, 06:25 AM   #19
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Quote:
Originally Posted by jererp
This is a cut & paste from the Goodyear RV tire website:

" Unless trying to resolve poor ride quality problems with an RV trailer,
it is recommended that trailer tires be inflated to the
pressure indicated on the sidewall of the tire. Trailer tires
experience significant lateral (side-to-side) loads due to vehicle sway
from uneven roads or passing vehicles. Using the inflation pressure
engraved on the sidewall will provide optimum load carrying capacity
and minimize heat build-up."

I run mine just a couple of psi under max.

Makes you wonder why Goodyear bothers to publish a load inflation chart for RVs using their ST tires as the link below shows??

http://www.goodyearrvtires.com/pdfs/rv_inflation.pdf

And who rides in their trailer to know if it is riding poorly?

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Old 06-17-2013, 04:10 PM   #20
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Thanks for all of the great info. I won't be exceeding 65mph anymore until I replace my tires. My tires are filled with Nitrogen. Do all Crossroads tires use nitrogen? How do you maintain Nitrogen preasure or do you just use air?
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