New sidewall tire pressure different than old tires

BoomJammer

Jason
May 17, 2012
217
I had bearings packed and new tires put on at a local tire store that had been referred to me by the local RV store. The old tires had a sidewall pressure rating of 65 psi. The new tires have a pressure rating of 50 psi. When I got home and saw this difference, I got concerned.

The "Tire and Loading Information" sticker on the camper says the tires should be ST185/80D13D, inflated to 65 PSI. The GVWR is 3450. The GAWR is 3300.

The old tires said "8 ply" and were bias ply tires. I believe that means they were D rated tires, as they should be per the ST185/80D13D designation, right?

The new tires are
  • Power King Towmax STR Radial Tires
  • ST185/80R13
  • LR C
  • 6 PR
  • Tread 3 plies: 1 polyester + 2 steel
  • Sidewall 1 ply polyester
  • DOT ADB7 GPB 3514
  • MAX Load single 670 KG (1480 lbs) at 850 KPa (50 psi)
That means they are load rating C and would only support an axle load of 2960 lbs, right?

Did they give me the wrong tires for my trailer? It's ok to use radial tires, isn't it? But shouldn't even the radial tires use the same load rating (D) as the original bias tires?

I went to the Towmax website. It appears that they don't have a D rated tire in the 13" size that I need.

I went to the etrailer website. They don't have ST185/80 13" radial D rated tires. Only bias ply tires. The only 13" D-rated radial tires that they have are ST175/80R13.

Should I return these tires and insist on Load Rated D tires? ...and be satisfied if the only option is bias ply? From my limited knowledge of tires, that seems like my best option, but I am open to suggestions.
 

friartuck

Super Active Member
Nov 1, 2007
2,978
Perry, MI
Were it me, yes I would return the tires for what was on the camper originally. The correct tires size and range should be on the sticker with the VIN and weights.
 

Snow

Super Active Member
Jul 19, 2007
11,983
Ontario
So the old tires could handle 1650 lbs each and the new tires can handle 1480 lbs each.. So you are 170 lbs per tire under what your should have..

Simple... return the new tires and is you can't find radials in your size (I think Goodyear Marathons are available) then go back to bias ply tires with the proper load rating..

Edit: 90% of tire shops have no clue when it comes to RV's and tires... 60% of the RV dealers also have no idea when it comes to tires for the products they sell...

Also do your best to read up on reviews of what ever tires you decide to get, many are substandard Chinese produced bombs..
 

BoomJammer

Jason
May 17, 2012
217
Snow said:
Also do your best to read up on reviews of what ever tires you decide to get, many are substandard Chinese produced bombs..

Really? Ugh. Is that why they need to be replaced every 3 to 5 years?
 

Snow

Super Active Member
Jul 19, 2007
11,983
Ontario
BoomJammer said:
Really? Ugh. Is that why they need to be replaced every 3 to 5 years?

Nope the 3-5 year recommendation comes from the Sun and the uv rays that deteriorate the rubber compounds and the weather..

It has been noted on here and many of the other camping/RV forums that some of the lower grade, lower cost tires from China and other "Third World" Countries ( term used to clump them all together) are not quite built to the same standards as they should be... Probably the leader in the field of poor tire construction and very poor reviews has to be anything manufactured by Green Ball tires and marketed under various names..
 

BoomJammer

Jason
May 17, 2012
217
Snow said:
Simple... return the new tires and is you can't find radials in your size (I think Goodyear Marathons are available) then go back to bias ply tires with the proper load rating..

The only D-rated Goodyear Marathon Radials are for 15 and 16 inch size wheels. I can't find any evidence on the Goodyear website that they even make bias ply tires.

Etrailer ($87) and trailertiresandwheels.com ($66) both carry the Kenda Loadstar K550 ST185/80D13 Load Range D 8 Ply Bias Trailer Tire with 1,725 lbs max load rating at 65.

trailertiresandwheels.com Also carries the ST 185/80R13 Load Range D 8 Ply Rated West Lake Super ST Radial Trailer Tire for $71 (1,710 LBS @ 65 PSI).

Both of those options are a big difference from 1480 lbs.

Your comment about 90% and 60% is discouraging.
 

Old_Geezer

Super Active Member
Sep 29, 2009
2,760
Southwest PA
Get the Kenda bias ply with the 1725lb rating. You will not find a D rated ST radial tire in a 13".

As far as where they are made and such, I wouldn't put much faith in online reviews or posts in RV and camping forums when it comes to tires for a whole host of reasons.

No one towing a camper that posts in the RV fourm ever does anything wrong, and never would make a mistake. When someone has a wear issue or blowout it is never because they ran the tire on half pressure, grossly overloaded the trailer, hit a curb, knocked the trailer out of alignment, etc etc etc. Its always because the manufacturer of the RV used junk "Chinese made" tires. As far as that go's the highly "forum" rated Goodyear Marathon ST tires are also made in....you guessed it......China. Click on the spec GOODYEAR tab and look at the country of origin column, the CN does not stand for Canada even though a few specific sizes I understand are now being made in Canada. The simple fact is where they are made can and does change so the tires you bought 3 years ago that were made in Rangoon may now be made in Peru, and the tire supplier will not go out of his way to mention it because he does not give a crap.

For every negative review or post of any specific brand of tire, I can find you a positive post. Snow mentions Green Ball tires. A lot of the negative posts with them can be traced back to some issues with the brand "Tow Master" in 08/09. I had Tow Master tires on a 2011 Hybrid (Which was built in 2010 so very well could of had tires made in the period mentioned) and had no issues at all in the 2 years I had the trailer. They had quite a few miles on them.

If you search for complaints and recalls at NHTSA you'll find that Goodyear Marathons have more complaints than Green Balls Tow Master tires. Take that for what it is. I am not sure if it means much however the Tow Master brand of Chinese made bomb tires have 8 complaints filed by consumers and no official recalls. Since these tires are or have been installed by both Forest River and Thor Industries, meaning there are literally thousands upon thousands of them on trailers currently on the road, I would say that's somewhat of an indicator they are not total garbage? Maybe not?
 

Novarich

Active Member
Dec 8, 2014
387
If you have the room you might have to switch to a 14" C rated radial to get the load rating you need. Your tire supplier should have checked that.
 

vinmaker

Super Active Member
Aug 22, 2014
862
I too am surprised that the OEM tires were D rated on a 13" rim. That is very unusual now. maybe it was more common back then. I think the C rated tires would be fine. I had them on my 2006 HW256 and it too had a high GVWR that exceeded to sum of the two tire loads. It is because the hitch takes some weight.

You need to feel comfortable with the tires you have on the unit. So if you have negative thoughts, then you should go back to the tire guy and have them changed. I am not sure what your option would be if the guy says he cannot get them. As was mentioned, try to upgrade to 14" wheels if you can.

Good luck.

Vin.
 

BoomJammer

Jason
May 17, 2012
217
Thanks for all the replies and insight.

I called the tire shop today. When I explained the situation, they confirmed that the tires they installed were not appropriate and apologized for the error. They also confirmed that they had no access to Load Rated D radial tires in the 185/80R13 size. They are ordering Specialty Tire Corporation ST185/80D13 Load Rated D, 8 ply, bias ply tires with single load rating of 1710 lbs and will install them while I wait tomorrow.

I feel better about this than leaving the C Rated tires on.
 

Snow

Super Active Member
Jul 19, 2007
11,983
Ontario
BoomJammer said:
They are ordering Specialty Tire Corporation ST185/80D13 Load Rated D, 8 ply, bias ply tires with single load rating of 1710 lbs and will install them while I wait tomorrow.

Is that the manufacture ?
 

BoomJammer

Jason
May 17, 2012
217
I thought that's what he said. But when I search for it, the closest I get is Specialty Tires of America. And I don't see any ST tires at their website. Now I'm confused...
 

BoomJammer

Jason
May 17, 2012
217
4campers+g-kids said:
This place has 13" Load Range D radial tires-

Thanks, but that is a little smaller tire (ST175) than what my camper calls for (ST185). The maximum load for the ST175 Radial is only 1610 which would still be lower than my axle rating of 3300 (but not by much). I suppose that it would do in a pinch, but I think I'm going to move forward with the 1710 lbs (3420 lbs) bias ply ST185/80D13 tires.
 

Old_Geezer

Super Active Member
Sep 29, 2009
2,760
Southwest PA
4campers+g-kids said:
This place has 13" Load Range D radial tires-

Load range letter simply refers to number of ply's in the construction. A=2, B=4,C=6 etc. They have load range D which is 8 ply, however not with the weight carrying capacity he is looking for of 1700+ lbs. The Kendas 13" D's at Etrailer are rated at 1660 lbs.

Typically the more ply's the more weight capacity but its not a 100% relative to actual load capacity.
 

BoomJammer

Jason
May 17, 2012
217
Old_Geezer said:
The Kendas 13" D's at Etrailer are rated at 1660 lbs.

I think that was the rating for the wheels. the tires themselves are rated at 1610 lbs. Regardless, your point is still valid.

I think that the only way I could get radial tires, would be to upgrade to 14" wheels. I'm not sure that I have room to upgrade. I'll ask the tire shop when I'm there. If I understand the tire numbers, ST205/75R14 tires would be 8.07" wide and 26.11" tall. That's about .8" wider and 1.5" taller than my current ST185/80D13 tires (7.28" wide and 24.65" tall). ...I think.
 

BoomJammer

Jason
May 17, 2012
217
I found the date code on the original spare: 4607. That's 7 years 4.5 months old. ...a little too old for comfort if I need to rely on the spare for several hundred miles to get me home. So I called the tire shop and asked them to order a third Load Range D bias ply tire so I can have fresh tires all around.

I just got back from the tire shop. They noted that the curb side wheel bearings (that they had cleaned, inspected, packed, and reinstalled last week) were loose. The wheel had some play when the camper was jacked up. So they pulled the assembly apart reinspected and reinstalled everything. I never got a clear understanding of what had failed. One tech said that the cotter pin must have broken and the nut backed off. I didn't know I had cotter pins, let alone that they could fail and result in loose bearings within a 20 mile round trip. Anyway, they say it's all fixed. I'll keep an eye on it.

They installed the new Load Range D tires in about 20 minutes while I waited. At checkout, the manager said there was no additional charge for the third tire; their way of apologizing for the trouble of having to bring the camper back in and for the issue with the bearings. So that was nice.

The new tires are Hi-Run ST185/80D13, LR D, 8 PR, Max Load single 1710 @ 65 psi cold.

The street side tire is the only one with the date code exposed: DOT R2FK 2414. Not as new as I was hoping (already has 9.5 months of life used up). I'll have to look at the backside of the other tires later to get their date codes.

Ended up paying $183.90 for the two Towmax radial Load Range C tires (including disposal fees, metal tubeless valves, and taxes) that were returned, and got three (presumably) not-quite-fresh Hi-Run bias ply Load Range D tires. It wasn't the happiest of experiences, but it wasn't too bad considering I essentially got the third tire free.

Plus I paid $45 for the bearing repacking. That was a significant savings over the RV dealership price ($~140).

Lastly, they said moving up to 14" wheels would be tight, even with the smallest size 205/75R14 radials. They suggested it might be more feasible if the trailer were lifted an inch or two. As estimated by eye, the rear beam in the wheel well appears to be slightly inside the extra 0.75 inches required by the 205/75 tires. The beam is currently higher than the center waterline of the axle/wheel. But the unknown question is: how much vertical travel does the suspension allow and how much lift would be required to avoid interference between the larger 205/75 tires and the rear wheel well beam at the maximum vertical travel position?

My lessons learned during this process are
[list type=decimal]
[*]I need to learn to inspect and repack my own bearings.
[*]I need to give serious consideration to on-line tire suppliers like etrailer or TrailerTiresAndWheels.com. Presumably the tires would be fresher than what I got. And at least I would know what brand/size/load range I was getting at the beginning of the transaction.
[*]I need to begin researching potential lift solutions.
[/list]

The good news is that I should have about 4 years before I need to go through the tire process again.

Thanks for everyone's helpful comments and suggestions! I love this community!
 

BoomJammer

Jason
May 17, 2012
217
Snow, I'm not sure. The service adviser said he ordered them through Specialty Tire Corporation. I don't know if that is a distributor/wholesaler/manufacturer or what. I don't see any other identifying information on the tires themselves. They have some cryptic marks as follows:

Replaces C78-13
H-187-02

This reference lists Hi-Run as being from Sutong China Tire Resources Co. Inc.
http://www.tirebusiness.com/assets/PDF/TB88774521.PDF
 




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