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Old 02-01-2012, 07:29 PM   #1
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Tire Pressure

We have just purchased a brand new 5'er Crusader by Forest River. When checking the inflation pressure on the coach, the data plate says to inflate tires to 65 psi. The sidewall on the tires say 80 psi max pressure cold. Who is right, the unit weighs 7760 dry, so figure another 1000 for junk...Need to find out...HELP?
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Old 02-01-2012, 07:39 PM   #2
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Some tire manufacturers require you to run the max pressure for the tire/wheel to keep the warranty in effect, others you go by the weight of the rig. You'll need to find out what your tires take.
Also, you need to remember that the tires have a maximum pressure as do the wheels. The lowest rating takes precedence!
For truck type tires the pressure on the sidewall is the MINIMUM cold pressure required to support the maximum weight the tire can ever support. On car tires it is the maximum cold pressure the tire should ever have
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Old 02-01-2012, 07:56 PM   #3
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As long as you have the coach manufacturers recommended tire size installed on your rig, their data plate info should be good, regardless of what the tire says (Mr_D did a great job of explaining why )
Have fun with your new toy!
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Old 02-01-2012, 09:19 PM   #4
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to be safe, i would pump them up to 80 # until I get the rig weighed. load it up and go to a truck stop to weigh it. then you can do the math and figure out just what pressure you need to run.
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Old 02-01-2012, 09:53 PM   #5
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Are the 80 psi tires a upgrade option from 65 psi OEM tires ?? Those tires are severally underinflated for trailer operation.
Trailer tires need max sidewall pressure for several reasons. One is a tire on a trailer slides sideways while going around cornors. The tire with max pressure holds its shape and internal belts in place much while sliding sideways. Also rolling over a curb with only 65 psi in a 80 psi rated tire can result in the rim cutting the sidewall. And of couse we all know about max pressures = a cooler running/longer lasting tire.

Now if the owner has done something silly like using a E tire in place a C tire then 80 psi will be too much pressure.
Goodyear Tire and Rubber says this;

Goodyear max tire pressures
Special Considerations
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.
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Old 02-02-2012, 01:26 AM   #6
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Quote:
Originally Posted by LKicklight View Post
We have just purchased a brand new 5'er Crusader by Forest River. When checking the inflation pressure on the coach, the data plate says to inflate tires to 65 psi. The sidewall on the tires say 80 psi max pressure cold. Who is right, the unit weighs 7760 dry, so figure another 1000 for junk...Need to find out...HELP?
LKicklight@aol.com
Dallas, GA.
After looking at some of the specs for your trailer and studying your post I think your vehicle manufacturer has given you more than adequate tires. The 65 psi found on the tire placard will remain the minimum tire pressure requirement within that tire design. Once you find out what youíre actually carrying on your axles you can adjust that pressure up to, and including the 80 psi. Itís important for you to find out if your trailer has ST or LT tires and if they are ST who made them.

Prime Time Manufacturing, Manufacturers of travel trailers and fifth wheels

http://www.trucktires.com/bridgestone/us_eng/press/zip/WeighForm.pdf

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Old 02-02-2012, 08:43 AM   #7
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Tires

These are brand new tires on 16" Rims on our Brand New Forest River Crusader 5'er. The coach weighs 7780 dry....We are the first owners of the rig. Will check with the service department at three way campers here in Marietta, GA.
Thanks


Quote:
Originally Posted by JIMNLIN View Post
Are the 80 psi tires a upgrade option from 65 psi OEM tires ?? Those tires are severally underinflated for trailer operation.
Trailer tires need max sidewall pressure for several reasons. One is a tire on a trailer slides sideways while going around cornors. The tire with max pressure holds its shape and internal belts in place much while sliding sideways. Also rolling over a curb with only 65 psi in a 80 psi rated tire can result in the rim cutting the sidewall. And of couse we all know about max pressures = a cooler running/longer lasting tire.

Now if the owner has done something silly like using a E tire in place a C tire then 80 psi will be too much pressure.
Goodyear Tire and Rubber says this;

Goodyear max tire pressures
Special Considerations
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.
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Old 02-02-2012, 11:08 AM   #8
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About tire pressure I inflated the tires on my truck it's
a silverado 2500 HD has air pressure gage built in
50lb front 80lb back aired back to 80lb cool next day
when I drove the truck they started at 79lb and as
I drove they went up to 82lb now my question is
the tag on the trailer has 80lb on it if I inflate the
trailer tires to 80lb cold are they going to
increase in pressure like the truck
should I just put 78lb in them?
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Old 02-02-2012, 02:43 PM   #9
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Quote:
Originally Posted by 1stCougar View Post
About tire pressure I inflated the tires on my truck it's
a silverado 2500 HD has air pressure gage built in
50lb front 80lb back aired back to 80lb cool next day
when I drove the truck they started at 79lb and as
I drove they went up to 82lb now my question is
the tag on the trailer has 80lb on it if I inflate the
trailer tires to 80lb cold are they going to
increase in pressure like the truck
should I just put 78lb in them?

Tire pressure info.

http://www.safercar.gov/Vehicle+Shop...nd+Load+Limits

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Old 02-02-2012, 02:52 PM   #10
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Quote:
Originally Posted by LKicklight View Post
These are brand new tires on 16" Rims on our Brand New Forest River Crusader 5'er. The coach weighs 7780 dry....We are the first owners of the rig. Will check with the service department at three way campers here in Marietta, GA.
Thanks
Sorry, in my previous post I referenced Prime Time Manufacturing....They are a division of Forest River and that's where the Crusader fivers are made.

Are the tires ST or LT?

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Old 02-07-2012, 07:17 AM   #11
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Quote:
Originally Posted by LKicklight View Post
We have just purchased a brand new 5'er Crusader by Forest River. When checking the inflation pressure on the coach, the data plate says to inflate tires to 65 psi. The sidewall on the tires say 80 psi max pressure cold. Who is right, the unit weighs 7760 dry, so figure another 1000 for junk....
In your case, the data plate on the trailer is right. And the tire manufacturer agrees that provided you don't overload the trailer over the GVWR of the trailer, then 65 PSI is more than enough for those tires on that trailer.

With other info you posted, your trailer has a GVWR of about 10,500, and the tires are ST225/75R15E.

Assuming the minimum 10% hitch weight, that leaves 9,450 pounds on the trailer tires when wet and loaded for the road. That's 2,363 pounds per tire.

Your trailer tires can support 2,830 pounds each @ 80 PSI, so you can get by with a lot less PSI and still support your max load of 2,363 per tire. Pumping the tires up to 80 PSI will result in a harsher ride, banging around the dishes and glasses and other contents of the trailer. Plus overinflated tires will wear out the center of the tread.

Most trailers come with tires that have barely enough weight capacity for the weight of the wet and loaded trailer. So for most trailers you'd want to pump the tires up to the max PSI on the sidewall. But your trailer is different. Your trailer tires have enough weight capacity that you need to find a load/inflation table to determine the PSI you should run in your tires.

Finding a load/inflation table for your ST (special trailer) tires can be a challenge, but Maxxis put it on their website. It confirms that the trailer manufacturer's use of 65 PSI in those tires is more than enough if you don't overload the trailer. Here is the high end of that table:

ST225/75R15E
------------------------
PSI . Max weight on the tire
--- . ----------------
60 . 2,380 pounds
65 . 2,540
70 . 2,620
75 . 2,720
80 . 2,830

Conclusion: Go by the load/inflation table published by the Tire and Rim Assn. (TRA) and reprinted by some tire manufacturers. The TRA is a bunch of engineers who know their stuff, so ignore any contrary info you might find in forums on the internet.

If you use 65 PSI in those tires, you'll have plenty of air in the tires to support your wet and loaded trailer at speeds up to 65 MPH. (Most ST tires are rated for a max speed of 65 MPH.)

Trailer Load/Inflation Chart
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