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Old 10-03-2010, 06:19 PM   #1
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tire pressure

I'm packing up the 99 Jayco Eagle 26 footer and was just second guessing myself concerning tire pressure. This is only my second trip and we will be travelling about 250 miles away to the coast. It is about a four hour drive. I consider myself a newby and am very thankful for all the wonderful knowledge on this site.

I know that a lot depends on type of tire, weight you are carrying etc., but I was wondering if there are any generalities. I have always thought that tire pressure was indicated by what the maximum is on the side of the tire. Then I have been told that you are supposed to go by the sticker on the doorframe of the vehicle. If that is true, my question has always been how does the car manufacturer know what type of tires I am going to use and how heavy my load will be.

A few weeks ago I took my TT to a local well respected tire shop to have them check and pack the wheel bearings. Everything was fine with the bearings and when the tech was putting the wheels back on I asked him about tire pressures. He said he always put what the maximum was on the side of the tire. In my case, he put 50 lbs in all four tires of the Jayco. I am running Goodyear Marathon Radials. Here is what is on the side of the tire. Load range C, For Trailer Service Only, Max Load 2150 lbs @ 50 psi. Anyone got any thoughts on this?
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Old 10-03-2010, 06:33 PM   #2
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5th wheels and travel trailers are different animals from motorhomes in that (1.) they generally come from the OEM with ST (trailer specific) tires as you note as being your case and (2.) the OEMs usually install the bare minimum tire size which results in the tires being loaded to 90% to 95% of their rated load. For that reason, running the tires at the sidewall rated load pressure of 50 PSIG isn't a bad idea.

I can run less than the sidewall rated load pressure with our 5th wheel, but I've upgraded the tires and wheels from the 3750 lbs @ 110 PSIG tires supplied by the OEM to 4805 lb @ 120 PSIG tires, so I'm only running at about 66% of rated load.

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Old 10-03-2010, 11:10 PM   #3
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All ST (special trailer) tire manufacturers state that sidewall maximum pressure must be used. Carlisle Tire even states in their warranty that if sidewall maximum pressure is not used their warranty is void .http://www.carlisletire.com/product_...are_safety.pdf
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Old 10-04-2010, 07:25 AM   #4
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Thanks everyone. I'll use the sidewall rating and feel a little bit better about it.
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Old 10-04-2010, 11:26 AM   #5
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Quote:
Originally Posted by ANiforos View Post
Then I have been told that you are supposed to go by the sticker on the doorframe of the vehicle. If that is true, my question has always been how does the car manufacturer know what type of tires I am going to use and how heavy my load will be.
I'm assuming since you posted this under the Fifth Wheel/Travel Trailer forum, your Jayco is one of those two, not a motorhome.

If that is, indeed, the case, then what's on the sticker on the door frame of your TV has absolutely NOTHING to do with the pressures for the tires on your fifth wheel/travel trailer.
Quote:
A few weeks ago I took my TT to a local well respected tire shop to have them check and pack the wheel bearings. Everything was fine with the bearings and when the tech was putting the wheels back on I asked him about tire pressures.
It has been my personal experience that just because someone works at a tire shop, doesn't mean that s/he knows anything about tires (much like RV sales people)! We've received INCORRECT information from people who work at tire shops, just as we've received incorrect (and, in some cases, downright dangerous) information from RV sales people.
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Old 10-07-2010, 03:07 PM   #6
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Exclamation Weigh it and do your engineering.

Door stickers onl are valid for the exact tire that the unit left the factory with.

Genericly it may be constant as long as the same type and tires are used as replacements.

But when things get close such as manufacturers using tires near their limit then you may have a manufacturer who uses a specific tire because it can carry more to reduce the wheel count.

The first step is always read the nomenclature plate, this is the MINIMUM air pressure to consider as long as it is less than the sidewall maximum.

To be best practice find a scale house, weigh each wheel and each axle, call ahead and ask for the slowest time so you can take your time.

Some scale operators may wish to know why, tell them and explain the need, they may learn from this and be more involved and happy to help, it is something different from weighing tomato trucks all day...

Knowing all of the weights you will know the tongue weight, load on each axple and on each wheel, (by wheel is option but helps to confirm balance in load).

Once you have this, next locate your manufacturer data sheets online for EVERY tire in your combined vehicle.

In these data sheets you will see the manufacturer inflation data, ALL tires on the same axle get equal pressure, minimum pressure is for the heaviest wheel, and the pressure NEVER to exceed the rating stamped on the wheel or tire when COLD.

Print them out, make copies of your weight report and circle the line that applies, place a copy of this in your "warranty file" incase one blows, and another in your operations book so you have easy listing of what the tires need to be before you hit the road.

You may find the rear tires on your tow vehicle are not suitable for the weight while towing or the wheels on the trailer are only suitable for 90 PSI or a weight too close to actual weight.

This stuff is way too simple but many tire folks do not have a clue, they just do not take the time to look up the data and do the required homework.

Finally CHECK THE DATES, old tires kill.

If it is 1999 and original tires they are due for change, regardless of what they look like they may be "expired".

Tires are cheap, people are not.
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Old 10-07-2010, 03:28 PM   #7
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Once you've been to the scales, HERE is Goodyear's load/inflation table for RV tires. You should find the ST-type Marathons in the first table shown which lists ST-prefix 14", 15" and 16" - match your tire size and load range. From the information you've given, it sounds like you have the ST225/75R-15 tires on row 6.

Note that the maximum speed rating on these ST tires is 65 MPH.

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Old 10-08-2010, 03:58 PM   #8
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Quote:
Originally Posted by RustyJC View Post
Once you've been to the scales, HERE is Goodyear's load/inflation table for RV tires. You should find the ST-type Marathons in the first table shown which lists ST-prefix 14", 15" and 16" - match your tire size and load range. From the information you've given, it sounds like you have the ST225/75R-15 tires on row 6.

Note that the maximum speed rating on these ST tires is 65 MPH.

Rusty
All of the inflation tables in your reference are invalid. You can send GY an email for verification.

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Old 10-09-2010, 01:25 PM   #9
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I agree with the max tire pressure based on the side wall rating but also Goodyear has on there web page about speeds over 65 mph to reduce the weight being carried and to add 10 lbs more air for high speeds sustained. look it up , its some place under the ST tire section on Goodyears web site. Also be carefull running tires that are more then 5 years old they like to blow out when they start to dry rot. check the DOT date codes on your tires!
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Old 10-09-2010, 09:43 PM   #10
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For the most part Goodyear tire inflation charts found on the internet ARE NOT valid. They are seldom up dated. Any that are dated prior to the DOT "final" rules changes of 2007 are suspect. If you’re looking for validation you can email their technical representatives and get valid, up to date answers to your questions.

The ST tire is too volatile to have its speed rating changed to anything above 65 MPH under any circumstances and I don’t think you’ll be able to find anyone at GY that will validate that procedure on anything other than commercial truck tires.

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Old 10-10-2010, 04:35 PM   #11
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All of the inflation tables in your reference are invalid. You can send GY an email for verification.

FastEagle
Ummm....that's the table that is linked to the CURRENT Goodyear RV tire website. Seems to me that, if Goodyear didn't intend for it to be used, they would sever the link.

Don't make me no nevermind - I no longer own any Goodyear tires.

Rusty
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Old 10-10-2010, 10:54 PM   #12
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I always inflated the load range "C" tires on my 2000 Jayco Eagle 266 FBS to 50 lbs. When I replaced them, I moved to load range "D" tires, the sidewall requests 60 lbs and that's what I inflated them to. My spare is still a load range "C" though, so it only gets 50 lbs.
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Old 10-12-2010, 06:03 AM   #13
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I always inflated the load range "C" tires on my 2000 Jayco Eagle 266 FBS to 50 lbs. When I replaced them, I moved to load range "D" tires, the sidewall requests 60 lbs and that's what I inflated them to. My spare is still a load range "C" though, so it only gets 50 lbs.
The 60 psi on the sidewall of your LRD tires indicates they are bias belted. Lots of people do not know that and air them to 65 psi.

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