Tire Specs

[Shayne]

Anyone running tires that can handle over 5,000 pounds each? Also, did you swap your rims? Looking to see if there is a 16" tire available.

Assuming a GVWR of just a squeak over 20,000, that's a load per tire of 5000 lbs.

Thoughts appreciated. Seeking tires and brands.

Details:

42', two axle, four wheel total FR Cardinal. Looking to upgrade to tires capable of a shared load of 20,812 lbs - that's Load Index 138 which is 5203 lbs each multiplied by 4.

Balance: In the front of the 5th wheel, is a diesel generator with 32 Gal diesel tank and at the rear is a Swivel wheel platform hauling an electric golf cart. The weight difference between front weight and rear tongue is fairly neutral with a difference of just 200lbs but collectively with tongue weight from the platform and the generator + fuel the weight goes up. Each end of the rig has been strengthened: the front with heavy steel box section L rails bolted across the I beams and box section inside, and the rear hitch assembly bolted between the I beams.

Thoughts appreciated.

Thanks

[Happy Vibe]

What Cardinal do you have? All the ones on the web site max at just over 16000 lbs.

[btritschler1437]

Try Continental HTL2ECO 235/75R17.5 6,000 lbs @ 125 psi. or Michelin, Goodyear G114, Sailun's 215/75R/17.5 @ 4,805 @ 125 psi. I don't think you will find a 16" tire in the 5,000 lb range. Talk at Scott at trailertiresandwheels.com.

[Shayne]

I have a 3875FB, GVWR 16314 lbs. Have had each end of the chassis strengthened.


Let me explain the weight distribution though, as I've been re-doing my weight distribution calcs.


The first post did not factor where the pin weight goes. MFG says pin weight loaded is 2634 fully loaded. I calculate about 5,175 pin weight taking steer and drive axle and deducting known weights including cargo, truck etc. This seems high though, but I did add a big generator and 30 Gals of fuel up front total 840 lbs inc chassis steel.


Yesterday I weighed on a 3 section truck scale at 29,960 with truck and rig and tow behind swivel wheel trailer with golf cart loaded.


The truck steer axle was 5700 lb, the drive axle was 8100 lb so assuming that the truck+pin weight = 13,800 lbs. The "Trailer Axle" (includes tow behing swivel wheel) recorded 16,160 lbs, so I deducted 2000 lbs for the swivel wheel, golf cart and bikes, leaving a net weight on both axles of 14160 lbs or 7080 per axle. I know that the present trailer is probably 65/35 weight distribution giving tongue weight of an extra 700 lbs which reduce to 100lbs when I add a balanced Idaho tote trailer, so I'm not counting it.


The axles are rated at 7,000 lbs and I'm assuming have a little bit of wiggle room.


I conclude that if I get tires rated at 4,000 lb each that should be plenty and the final load distribution will be:


Truck inc. pin weight with extra 40 gal tank and other acces = 13,939
New tow behind platform & cargo = 3,000
5th Wheel combined axle weight (assumed) 14,500 (existing 14160 + extra 340 from tow behind tongue weight and any extra cargo)


Total towing weight (not axle weight) inc. truck = 31,300
Axle weight 14,500 - or approx. 3625 per wheel.


Maybe add 10% wiggle room and spec 4,000 lbs tires?



Thoughts?

[ependydad]

Originally Posted by btritschler1437

Try Continental HTL2ECO 235/75R17.5 6,000 lbs @ 125 psi. or Michelin, Goodyear G114, Sailun's 215/75R/17.5 @ 4,805 @ 125 psi. I don't think you will find a 16" tire in the 5,000 lb range. Talk at Scott at trailertiresandwheels.com.

I think the Continentals are 4,900 lbs. at that size and pressure. It's what I just installed.

[Shayne]

thanks for this. Looks.like.I would.need 17.5" rims. Continental Corporation*-Low Platform, High Load Capacity Trailer Tire from Continental

tomorrow's task is a re-weigh to establish the exact pin weight, and weight on each axle to validate the calcs I have.

after all the known calcs, I'll make a.tire decision and probably pull the trigger Monday.

regards

shayne

[Airdale]

Originally Posted by Shayne

I have a 3875FB, GVWR 16314 lbs. Have had each end of the chassis strengthened.

Was that work certified by Forest River or a certified vehicle modifier or is it a gray area modification?

It's very risky to go over any of the limitations found on the trailer's certification label (except those that are variable, such as tires, which provide reserve load capacity for themselves when increased).

[Shayne]

the rear hitch was installed by a certified welder familiar with RV's. Chose to custom build the hitch for max strength with a large plate area each side and bolt it on in case we changed anything. That turned out to be a good idea because we are about to swap to an even more capable Idaho Tote trailer (worth a search to see this technology). The platform has hydraulic steering wheels so it will move with the RV, as well as electric brakes. This combination when balanced won't add much load and is a nice counter balance for the generator up front.

The front was strengthened as part of the generator install at the front by a very experienced RV dealer who is also a Cummins generator dealer. I called for strengthening to more than 3G's of force per the Cummins install spec.

For those considering a genset in the Cardinal at the front, it has only a thin plate across the base and even using the specified 5KW Cummins genset (I have a 7.5KW diesel), I would recommend considering strengthening it anyway.

The weigh in yesterday on CAT scales at Pilot was very helpful. FYI, cat can weight both axles as well as a "split axle" weight by positioning each axle on two of the 3 scales. We spent a couple of hours weighing everything. We weighed the truck attached with rig, and without rig to derive the pin weight, as well as the combined axle, split axle, and even our golf cart. We also.did tue split axle weight of the golf cart to establish how much weight differential exists on the GC axles. This is because the GC will be loaded sideways on the towing platform, over the axle and we can counter balance the lighter side with cargo, for an even smooth ride.

I am now satisfied the axle weights are good and each piece of our package has a known weight.

In summary, for the many RV'ers who have not considered their weight dynamics, a trip to a weigh scale at a truck stop may be very valuable, and avoid unpleasant surprises down the road.

[ependydad]

Originally Posted by ependydad

I think the Continentals are 4,900 lbs. at that size and pressure. It's what I just installed.

I happened to think about this, this morning. 4,805 per the tire.



Yes, you have to upgrade to 17.5" rims for these tires. There are 2 outfits that I found who do it:
http://www.ricksontruckwheels.com/
http://www.trailertiresandwheels.com/

I liked the woman that I spoke with at Rickson a lot. Very friendly, knowledgeable, and super helpful in answering my newbie questions. BUT- their turn around time was just too long for me, I didn't like the rims, and TT&W ended up being about $400 cheaper.

With going to a 17.5" rim + tire, you end up with the same basic outer diameter of the tire because you have a shorter sidewall. I actually decreased my outer diameter size by about 1/2". Many people only upgrade their 4 wheels and keep their 16" spare as the size is so close. It's what I did, just to save some money for now. I'll get a cheap steel wheel and tire for a spare at some point.

The closest 16" ST tire is going to have a capacity of 3,900 lbs. in the Goodyear G614. Otherwise, ST and LT tires aren't going to have the carrying capacity in a 16" wheel. I was space constrained and ultimately wanted out of a ST tire, so I opted for this.

I only have 300-400 miles on these wheels + tires, so I can't speak to longevity. But, for now- I'm happy with my decision.

[Tireman9]

Originally Posted by Shayne

thanks for this. Looks.like.I would.need 17.5" rims. Continental Corporation*-Low Platform, High Load Capacity Trailer Tire from Continental

tomorrow's task is a re-weigh to establish the exact pin weight, and weight on each axle to validate the calcs I have.

after all the known calcs, I'll make a.tire decision and probably pull the trigger Monday.

regards

shayne

Be sure you understand the MAX operating speed for Low Platform Trailer tires. Many say 62 mph. This is MAX not average speed. Think of it as you would engine red line .

[ependydad]

Originally Posted by Tireman9

Be sure you understand the MAX operating speed for Low Platform Trailer tires. Many say 62 mph. This is MAX not average speed. Think of it as you would engine red line .

Their documentation says 75mph:
http://www.continental-truck.com/www...ss_htl2_ep.pdf

Or am I misunderstanding it?

[Tireman9]

Nope in this case you appear to be OK for speed.

Too many folks don't really do the homework and forget that tires in RV application can have a different speed rating than in their "normal" application.

[Iwannacamp]

Dang...you guys are heavy.

How long before someone puts tandoms on their trailer? It really seems like a viable option


Sent from my iPhone using Forest River Forums

[ependydad]

Originally Posted by Tireman9

Nope in this case you appear to be OK for speed.

Too many folks don't really do the homework and forget that tires in RV application can have a different speed rating than in their "normal" application.

Thanks for clarifying. I thought I had looked into the speed rating, but - as you say, I wasn't sure if it was different in our case.

Not that it matters for me, I generally do no more than 62 or so.

[Tireman9]

Originally Posted by Iwannacamp

Dang...you guys are heavy.

How long before someone puts tandoms on their trailer? It really seems like a viable option


Sent from my iPhone using Forest River Forums

Slight confusion of terms.

"Tandem" axles is when there are two axles and "Triple" would be three axle.

"Dual" is when there are two tires next to each other on the same end of an axle as seen on the rear of most Class-A and Class C motorhomes.

The trailer in this thread should have had triple axles to achieve more reasonable tire loading but that would have cost money.

[Airdale]

Overloaded Recreational Vehicle (RV).

"The FMVSS have requirements for the manufacturer to use proper tires and rims for the gross axle weight rating (GAWR) and the gross vehicle weight rating (GVWR). The manufacturer may determine the GVWR by adding cargo capacity (if any) to the curb weight of the vehicle as manufactured. The wise consumer, before purchase, will determine if the vehicle has sufficient cargo capacity to carry the weight of water, additional equipment (such as televisions, and microwave ovens), and luggage. The manufacturer’s certification label must show the GVWR. The GVWR must not be exceeded by overloading the vehicle. There is little the government can do to assist a consumer who has purchased a vehicle that has insufficient cargo capacity for its intended use."

That's a direct quote from a NHTSA Q&A link about RVs. It sort of fits what the OP is doing to his trailer.

[B and B]

Doug, are you changing tires again?

[ependydad]

Originally Posted by Airdale

The FMVSS have requirements for the manufacturer to use proper tires and rims for the gross axle weight rating (GAWR) ...

Interestingly enough, my camper's tires came up short for the axle ratings from the factory: 7,000 lbs. axles but only 6,480 lbs. between the 2 tires. And, without thinking about it- I did the same thing when I put Maxxis tires on it 2 years ago. But, then again- some folks here have asked if my "problems" weren't self-inflicted. Maybe, maybe not- but I took a big step in increasing my tire capacity.

Originally Posted by B and B

Doug, are you changing tires again?

I did a couple of weeks back. I found that the Maxxis tires that I put in '13 were maxxed out and overloaded with our current "long trip" weights where we're a bit over the camper's GVWR. I might not be maxxed out on any tire if I was at the GVWR, but I'd still be at their absolute max.

So, I went nutty and opted for a whole new rim + tire. Jumped up to a 17.5" rim and commercial truck tire.

[Airdale]

Does your trailer's certification label depict the axles GAWR as 7000# or something less such as 6750#.

You have described a perfect example of why the GAWR needs to be around 6750#.

The ST235/80R16E tires are manufactured in three distinct load capacities, 3520#, 3500# & 3420# all @ 80 psi.

It is a violation of federal regulations (FMVSS) for your trailer manufacturer to install 7000# axles and not make a notation about the Original Equipment tires having to be able to support at the very least 7000# axles. The trailer manufacturer commonly reduces the axles 7000# capability to something that will allow all three of those ST tires to be fitted in accordance with the regulations. The Maxxis tires are one of the brands that provide 3420# of load capacity @ 80 psi.

If in fact you do have a certification label that depicts 7000# GAWR for each axle without the accompanying documentation for the OE tires you can force the trailer manufacturer into a recall situation.

INFO: There is another tire regulation that states - in part - that any tire of the same size and load range manufactured with different load capacities must be defaulted to the lowest manufactured load capacity when used on a higher rated axle without documentation to allow it's fitment.

[ependydad]

Here's the sticker:
https://flic.kr/p/e87CyK

I don't recall seeing anything about a lesser GAWR.