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trailer tires


lazysusan

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Walking Thunder, if you crawl under the rig, I will bet you both rigs have 7,000 lb axles. regardless of the tires. On our 2012 Montana, which came with the Marathons, the 7,000 lb Dexter axles were de-rated on the data tag to 6750 lbs, only because the tires were only capable of 6840 lbs, (3420 lbs per tire). The Goodyear G614's were offered as an option, and on those that came with the option, the axles were full rated at 7,000 lbs. Of course, this difference did not increase the GVWR of the trailer, but since we upgraded a couple years ago, I'm not constantly looking at the rear view mirror to see if tire debris is flying off the trailer.

Let’s look at this from the trailer builders point of view. Here are the manufacturer’s published specs for a 2012 Montana 3455SA.

 

GVWR: 15,560#

GAWR: 6750# (2 axles)

Hitch: 2060#

 

Keystone, like’s (I’m sure) to build their trailers to specifications where a lot of like items can be used on all models in a particular line-up - it keeps the costs down.

 

Axles are not manufactured in increments for all uses. Federal Motor Vehicle Safety Standards (FMVSS) allow the vehicle manufacturer to set GAWR values to the needs of the target GVWR. Both of those values must be certified and depicted on the trailer’s federal certification label.

 

One of the mandatory measurements required in FMVSS is the manufacturer’s established hitch pin weight added to total established GAWR. The sum must equal or exceed GVWR.

 

The addition of optional plus sized tires to a certified GAWR has no influence other than an added amount of available tire load capacity reserves. Industry standards does not require those reserves to be used. The only requirement is that the replacement tires must provide - via inflation - a load capacity equal to or greater than the original equipment tires.

 

The ST235/80R16E tires are unique in that they - depending on manufacturer - have three distinct maximum load capacities. 3420#, 3500# and 3520#, all @ 80 PSI. Without documentation from the vehicle manufacturer describing the load capacity of the OE tires and the brand names of suitable replacements for them the maximum load capacity for all of them default to the lowest value.

 

NHTSA has issued a number of recalls to RV trailer manufacturers for certification label/tire placard and owner manual errors for the use of improper OE tires on 7000# GAWR axles.

 

The wise builder using all ST235/80R16E tires on a series of trailer models will build to a GVWR and GAWR combination that will allow the use of all of those tires without NHTSA intervention.

 

Somewhere in my memory bank there is a little light flickering that says NHTSA no longer requires trailer manufacturers to weigh each unit before it is shipped. Supposedly the big RV trailer originations persuaded NHTSA that the manufacturer’s know the curb weight of their units because they have to account for materials used to build it. The curb/dry weight is determined at shipment time when the cargo label is applied. The dealer is required to change the cargo label if they install options with weight values in excess of minimum values allowed by FMVSS.

 

When I run across the bulletin about weight I’ll provide a reference.

 

Dealers are not allowed to change tires before first sale unless they are approved as optional equipment by the vehicle manufacturer. However, they can change brands as long as the size is identical to the OE size from the manufacturer as depicted on the certification label.

 

Once you own it all those responsibilities are in your ball park. Industry standards are then your guide. Using them will be the best thing to do safety wise.

38' fiver - Dodge Dually

AKA: FastEagle

USN Retired - DOD Retired - SSA Retired

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While we are on the topic of tires and wheels, not wanting to hijack the thread, but what seems to be a reasonable interval between full blown greasing the bearings and checking the brakes. It was 3 yrs since last re-pack and 2 since one was pulled, deemed Ok and nothing more done since. Maybe 10-14k miles since repack..

 

Thanks

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While we are on the topic of tires and wheels, not wanting to hijack the thread, but what seems to be a reasonable interval between full blown greasing the bearings and checking the brakes. It was 3 yrs since last re-pack and 2 since one was pulled, deemed Ok and nothing more done since. Maybe 10-14k miles since repack..

 

Thanks

 

Some do it yearly, some every 2 yrs, some more. I did my initial after a 12K+ trip. I'll do it again after this season, then decide if I can go every 2 yrs.

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OP... I have a trailer that's just a little lighter than yours, not much. It had 6k# axles and LRE tires on it from the factory. While "technically" within spec, I was never comfortable with it. Even good tires squatted more than I liked.

 

About 5 years ago, I decided that it was time to do something about it. I installed 7k# axles, went to 17.5" rims and a good set of H rated truck steer tires. I've never regretted that decision. Tows very smoothly. Tires do not squat. Granted, I do not put on the miles like some do but at about 10k miles, I can't see ANY wear of any kind, they still look almost brand new. It's gonna hurt my feelings to have to discard them due to age in the near future.

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I've decided to do a check brakes and repack of bearings when I get back to FL in 3 weeks. Not going to push the envelope on this...too much at stake. Rear end and pinion seal and perhaps ac will be dealt with when I'm away for 2 weeks. Truck will be ready when I return. Then another 2 months with Habitat b4 winding back up to Victoria.

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OK Guys I thought this when I first saw the topic, but it could also be a common problem - bent axles. . Read this article containing descriptions along with pictures: http://www.vehicleservicepros.com/article/10329093/can-you-read-tire-tread-damage

 

Here are some images of axle geometry damage: http://www.bing.com/images/search?q=axle+damage+and+trailer+tire+wear&qpvt=axle+damage+and+trailer+tire+wear&qpvt=axle+damage+and+trailer+tire+wear&FORM=IGRE

 

More:

https://www.etrailer.com/question-75480.html

 

Here is a video of a bad tire from a bent axle: https://www.youtube.com/watch?v=XymZYF5xU9A

 

From what y'all are describing it sounds like bent axles to me. A good shop can check. If your electric brakes are in good shape as well as the hubs and your axles are bent after an alignment check, a good shop can get just the axles and reuse your hubs etc for somewhere between 200-500 for parts and then labor. I had to replace my entire axle assembly in 1999 on a tandem axle 34.5 foot HitchHiker 5th wheel and the axles cost back then $150.00 and the hubs another $150.00 with brakes and shoes on both sides back then. They are a bit more today but getting twice the life from your tires or more gives ROI pretty quick.

 

The primary reason we have difficulty with axles is because many manufacturers use the cheapest and lowest weight rating that is needed. Minimums. There are lots of options if your trailer axles are bent or damaged beyond repair. I'd go one step up in weight ratings at least, and replace both axles at the same time. You could also go with some of the upscale new designs.

 

Check your axles with a good qualified shop.

RV/Derek
http://www.rvroadie.com Email on the bottom of my website page.
Retired AF 1971-1998


When you see a worthy man, endeavor to emulate him. When you see an unworthy man, look inside yourself. - Confucius

 

“Those who can make you believe absurdities, can make you commit atrocities.” ... Voltaire

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