Cross Country Trip - Axle/Suspension Failure

[sourdough]

Originally Posted by markcee

I understand that you are providing help and not riding me about this and I really appreciate the help.

I will hit the scales again when I get home, but I am skeptical that can be an issue. I have 1700 and change of available cargo capacity based on my trailer’s sticker and there is no way I have personally loaded that much on board....even with partially full tanks. Perhaps I am not understanding things properly. For example, where are you coming up with that 9180 figure? I don’t see it on the sheet I posted. I’m pretty sure the 8160 figure I listed was raw weight of trailer as scaled, so even if the WDH transfers 200-300 lbs back, that’s still well under 9180.

Finally, I am really confused why my trailer is rated at 9500 GVWR but my axles can’t carry it?? (8800 lbs total). This to me is not like the bs tow ratings on a truck....this is the GVWR of a particular vehicle, shouldn’t the rest of the trailer be built to support the weight they say it can be?

Looking forward to more info! Thanks for the replies.

I am headed to bed and would further address your questions but the above is easy; your axles are rated at 8800lbs. Your gvwr is 9500. Those numbers subtract the anticipated tongue weight from that number leaving you, IMO, overloaded if not careful. There is no way in this world that your trailer is always towing "level" and weight is not being shifted back to the trailer....but that is another "weight" issue and yet another reason you don't want to come close to any weight limit on a sticker.

[CWtheMan]

Originally Posted by markcee

Finally, I am really confused why my trailer is rated at 9500 GVWR but my axles can’t carry it?? (8800 lbs total). This to me is not like the bs tow ratings on a truck....this is the GVWR of a particular vehicle, shouldn’t the rest of the trailer be built to support the weight they say it can be?

When the vehicle manufacturer certifies GVWR and GAWR weights, they add the trailers carrying capacity to the GVW and subtract their recommended tongue weight. In your case they have subtracted 700# from the GVWR and set the vehicle certified axles at 4400#.

The RV trailer industry does not want to invite consumers to overload their trailers because they provided axle load capacity reserves.

[LewisB]

Originally Posted by markcee

...Finally, I am really confused why my trailer is rated at 9500 GVWR but my axles can’t carry it?? (8800 lbs total). This to me is not like the bs tow ratings on a truck....this is the GVWR of a particular vehicle, shouldn’t the rest of the trailer be built to support the weight they say it can be?

Looking forward to more info! Thanks for the replies.

The Gross Vehicle Weight of the trailer will be the combined weight resting on the axles PLUS the weight resting on the hitch. (Yes, the WD hitch will move some of that weight around, but it doesn't make it disappear; so for this part of the discussion, you can ignore the fact you will use a WD hitch. The total (gross) weight of the trailer will be axles plus hitch; from your prior worksheet (8160+1020=9180) or 97% of GVWR.

A couple of things to remember: the "factory dry weight" only applies as the trailer leaves the factory. So, propane, batteries, water heater, tank contents, options added by the dealer, the trailer portion of your hitch setup, etc. all are considered "cargo." If your GVWR=9500 and your factory dry weight=7600, then your cargo weight max would be 1900#. In your prior weight, your cargo weight was (total weight of trailer axles & hitch = 9180 less dry wt of 7600 = 1580, which leaves you 320# of space.

The axles will never be rated to carry the entire weight of the trailer (GVWR). If you look at the specs for your trailer, the manufacturer assumes that the weight will be carried by the axles (2 X 4400 =8800) and (say) 700# on the hitch = 9500 GVWR. By the way, verify that the tires on your trailer are rated to carry at least 2200# each.

The WD hitch, while helping maintain reasonable hitch weight and keep the rig essentially level, can actually make axle overloading even worse. The 700# of (factory assumed) hitch weight will be impacted by how you load the trailer, height of the hitch, etc. The purpose of the WD hitch is to help distribute some of the hitch weight through the frame forward into the TV axles and rearward into the trailer axles. That weight hasn't disappeared - it has just been moved. You need to account for it when loaded. So let's assume you load the front of the trailer REALLY heavy...instead of 700# of hitch weight you end up with 1200#. Now your TV bumper is really low, so you crank up the WD hitch to level out the rig. What you have actually done is to add about (say) 250# to the TV and 250# to the trailer axles to get the rig level again. If your trailer axles were already close to their load limit, now they are even worse. And as already pointed out by Danny, as your rig moves around on the road, going over driveways, dips, pot holes, etc. the WD hitch is adding stress through the frame on you trailer axles throughout the entire trip.

Please don't quote me on the numbers above - they are provided as examples. This is a complex issue and I'm attempting to simplify it to be easier to understand. The engineers in the crowd are probably cringing at my simplistic answers.

The bottom line for the OP: your move to an F350 from an F150 was an EXCELLENT choice. I suspect you may be very close on your trailer loading. Set it up for your next trip. Be honest with yourself - if you travel with water, load it that way. If you don't dump your waste tanks until you get home, then fill them with fresh water just as you would be while you are travelling. It's a little extra work - but the last thing you want is to have to replace another set of axles! And the second time around, it's likely to be on your own dime.

if you post your weight stickers to the forum, I'm sure you will get volunteers who will help you with the numbers.

Best of luck!

[markcee]

Thanks all! I will post back as soon as I make it to the scales.

I appreciate all your input.

[JRTJH]

Brad's post helps explain how manufacturers "cut corners" in trailer/axle selection. As he said, there are very few trailers manufactured with axles that can carry the entire GVW of the trailer. About the only exception I can think of is the extremely light, dual axle trailers with a GVW of, as an example, 4000 pounds. The "lightest axles with brakes" that are available to the manufacturer are 2500 pound axles with 10" hubs/brakes, so they would be forced to use those axles, since brakes are required in many states on trailers with a GVW greater than 3000 or 3500 pounds.

That would "force" the manufacturer to have axles under the trailer rated to carry 5000 pounds, more than the GVW of the trailer. Some manufacturers would "derate" those axles to, say, 1500 pounds and put cheap 13" tires on it (to save money) while other manufacturers might leave the axle rating at 2500 and put 14" tires in load range C, which is 1820 pounds, for an "axle total of 3640, providing a significant tire surplus rating as well as a significant axle rating, actually greater than the trailer GVW. I'd guess most manufacturers would opt to build that trailer as a single axle model, so that would make the point moot, but there are a few on the market.

Most (actually all) Keystone RV's that I know of, use the trailer tongue weight to offset a part of the GVW when the engineers select the size axles to install on the trailer model.

On another subject, you stated that you were unsure about the wheelwell clearance above the tires. As I recall, it was about 1.5". You commented that you didn't know if the springs were also going to be replaced and that you would report the "tire/wheelwell clearance". Did you check the wheelwell clearance ? And, were the old springs reused or did the new axles come with spring packs installed? What is the "top of tire to DARCO distance with the new axles?

[skids]

LewisB said “ The axles will never be rated to carry the entire weight of the trailer (GVWR).”

Lewis, never is a long time. . My 2019 Bullet RKS has two 3500 lb Dexter axles and the GVWR is 6500 lbs. I admire your explanation however. What worries me a bit is when weight is shifted as a tire is being changed. I have a ramp to drive up onto to raise the other tire off the ground. Maybe a jack is a better choice.

[JRTJH]

Originally Posted by skids

LewisB said “ The axles will never be rated to carry the entire weight of the trailer (GVWR).”

Lewis, never is a long time. . My 2019 Bullet RKS has two 3500 lb Dexter axles and the GVWR is 6500 lbs. I admire your explanation however. What worries me a bit is when weight is shifted as a tire is being changed. I have a ramp to drive up onto to raise the other tire off the ground. Maybe a jack is a better choice.

I'd suppose that tire engineers "build in considerations" for momentary maintenance actions...

Tire ratings are designed for "dynamic, in use road stresses" not "static load weight for a maintenance action".. What I mean by that is the tires are built to withstand the bumps, ruts, undulations and stress of travelling at the rated speed (for most ST tires that's 81MPH) at the rated "maximum load". Subjecting that tire to a greater load for 5 or 10 minutes, in a static, non-mobile condition, would not be the same "weight or conditions" the tire is rated to carry at 81MPH on a bumpy road...

I don't think you have anything to "worry about" when changing a tire on the side of the road using a ramp to elevate the tire being changed. Maybe one of the "resident tire experts" will add their opinion....

I'd suppose it's "sort of like" a generator rated at 1600 watts continuous/2000 watts surge. You can run it at 1600 watts all day, but only "momentarily" run it at 1800 watts. Same with a 14" LRC tire. You can load it at 1820 pounds and run it all day, but only "momentarily, in a static condition" load it at 2200 pounds to change the other tire.

Tireman/CW: What's your take???

[flybouy]

Originally Posted by skids

LewisB said “ The axles will never be rated to carry the entire weight of the trailer (GVWR).”

Lewis, never is a long time. . My 2019 Bullet RKS has two 3500 lb Dexter axles and the GVWR is 6500 lbs. I admire your explanation however. What worries me a bit is when weight is shifted as a tire is being changed. I have a ramp to drive up onto to raise the other tire off the ground. Maybe a jack is a better choice.

What's the difference? You are shifting the weight of one wheel to the other 3 (and a little to the tongue) using either method. For just changing a tire I like the ramp as it drops the axle that you're changing the tire on. That makes it easier, at least on my unit, to remove the tire from under the fender.

The Trailer Aid+ that I use has a "cradle" the tire sets in so the trailer isn't going to move. Doing anything other that tire changing calls for a jack and some other supports such as jack stands or cribbing.

[skids]

Originally Posted by flybouy

[/B]

What's the difference? You are shifting the weight of one wheel to the other 3 (and a little to the tongue) using either method. For just changing a tire I like the ramp as it drops the axle that you're changing the tire on. That makes it easier, at least on my unit, to remove the tire from under the fender.

The Trailer Aid+ that I use has a "cradle" the tire sets in so the trailer isn't going to move. Doing anything other that tire changing calls for a jack and some other supports such as jack stands or cribbing.

I think the difference is that when the wheel is hanging, the weight of the wheel, and part of the axle are added to the other three. I know there is supposed to be a surplus capacity for the axles to handle impact loads from rough roads, but with all of the talk about bent axles it still makes me wonder...

[MarkEHansen]

The amount of extra weight placed on the other wheels while jacking one wheel up is far less than the extra weight placed on the other wheels when, for example, you pull the trailer around a bend in the highway or around a corner.

[flybouy]

Originally Posted by skids

I think the difference is that when the wheel is hanging, the weight of the wheel, and part of the axle are added to the other three. I know there is supposed to be a surplus capacity for the axles to handle impact loads from rough roads, but with all of the talk about bent axles it still makes me wonder...

Never heard of it causing an issue. I have seen/heard of bent axle issues from incorrectly jacking up an axle. It's your choice but long before the "ramp" type products folks would drive one wheel up on wooden blocks to change a tire.

[JRTJH]

Originally Posted by skids

I think the difference is that when the wheel is hanging, the weight of the wheel, and part of the axle are added to the other three. I know there is supposed to be a surplus capacity for the axles to handle impact loads from rough roads, but with all of the talk about bent axles it still makes me wonder...

Now you're combining two entirely different issues. Tire capacity has absolutely NOTHING to do with bent axles or spindle strength. Jacking an axle would likely have a greater potential to damage or "misalign" an axle than backing the other axle onto a ramp so one is "hanging by its suspension....

I think you're waaaaay overthinking possibilities for things that aren't even related to each other.

[skids]

Originally Posted by JRTJH

Now you're combining two entirely different issues. Tire capacity has absolutely NOTHING to do with bent axles or spindle strength. Jacking an axle would likely have a greater potential to damage or "misalign" an axle than backing the other axle onto a ramp so one is "hanging by its suspension....

I think you're waaaaay overthinking possibilities for things that aren't even related to each other.

Don’t misundertake me John! . I said nothing about tire capacity.

[markcee]

Originally Posted by JRTJH

On another subject, you stated that you were unsure about the wheelwell clearance above the tires. As I recall, it was about 1.5". You commented that you didn't know if the springs were also going to be replaced and that you would report the "tire/wheelwell clearance". Did you check the wheelwell clearance ? And, were the old springs reused or did the new axles come with spring packs installed? What is the "top of tire to DARCO distance with the new axles?

The clearance is much improved now....I can fit my entire hand in sideways, so it's about 3.5". And yes, they did replace all the springs and mounting hardware as well. They noted the cause of the failure as 'defective'. I've just arrived in Memphis, AR - another 380 miles and all is well. No fresh rub marks on the new material.

[flybouy]

Thanks for the follow-up . It's nice to hear when the dealer and manufacturer step up and do the right thing. Safe travels!

[JRTJH]

Originally Posted by skids

Don’t misundertake me John! . I said nothing about tire capacity.

First, I'm not in the funeral business, so I wouldn't be "undertaking you" much less "misundertaking you".... That said, your initial question was, "What worries me a bit is when weight is shifted as a tire is being changed. I have a ramp to drive up onto to raise the other tire off the ground. Maybe a jack is a better choice." If that doesn't address "overloading a tire capacity" then please explain what your post "intended to ask or say" .....

On second thought, never mind, it's suppertime and I've got a plate of baked spaghetti sitting on the table with an impatient DW... Cheers.....

[skids]

Originally Posted by JRTJH

First, I'm not in the funeral business, so I wouldn't be "undertaking you" much less "misundertaking you".... That said, your initial question was, "What worries me a bit is when weight is shifted as a tire is being changed. I have a ramp to drive up onto to raise the other tire off the ground. Maybe a jack is a better choice." If that doesn't address "overloading a tire capacity" then please explain what your post "intended to ask or say" .....

On second thought, never mind, it's suppertime and I've got a plate of baked spaghetti sitting on the table with an impatient DW... Cheers.....

Axles. We were talking about bent axle/spindles. Lets say the trailer imparts 7000 lbs equally on the axles at 3500 lbs each. Lets say it has 2 Dexter axles rated at 3500 lbs each. Now, you drive one wheel up the ramp to where an wheel is suspended. 7000 lbs trailer load is now shared between three wheels/spindles. To add to the situation, the suspended wheel/axle/spindle has to be supported by the other three. Normally, it sits on the ground, no?

Now if you use a jack, the weight that was carried by the wheel/axle/spindle is not transferred to the other three, instead it is carried by the jack and in fact some load may be reduced from the neighboring wheel.

Keep your sense of humor. I was kidding about “misundertakeing” me. It comes from a comedy routine and I don’t remember which...

[CWtheMan]

It would behoove all RV owners to read and become familiar with FMVSS (standards).

FMVSS tells vehicle manufacturers what the minimum standards are for everything related to vehicle safety. The vehicle manufacturer cannot do less and expect to certify a vehicle with less than required in FMVSS.

For RV trailers there is no requirement to do more with the axles, wheels or tires than what is required in FMVSS. However, there is a stipulation (caveat) in the tire fitment standard which directs the vehicle manufacturer to set cold tire inflation pressures to a value that is appropriate for that fitment.

The vehicle manufacturer designs and builds to a target GVWR for each vehicle. That target will include some cargo capacity which is thoroughly explained in FMVSS.

Unlike the auto industry vehicles, RV trailers do not have to provide any load capacity reserves with their axle and tire fitments. The tires MUST support the maximum weight of the vehicle certified GAWR (s). The vehicle certified GAWR (s) MUST support the GVWR. The GVWR MUST not be exceeded.

This is a verbatim quote from FMVSS; “On RV trailers, the sum of the GAWRs of all axles on the vehicle plus the vehicle manufacturer's recommended tongue weight must not be less than the GVWR. If tongue weight is specified as a range, the minimum value must be used.”

[larryflew]

Example of the axle weights vs GVW. My Alpine has 7000 pound axles x 2 = 14,000 on a trailer with 16,500 GVW.

[CWtheMan]

Originally Posted by larryflew

Example of the axle weights vs GVW. My Alpine has 7000 pound axles x 2 = 14,000 on a trailer with 16,500 GVW.

GVW is the trailer's gross weight, it can change from one trip to another. GVWR is the maximum weight allotment for that trailer.

You can have axle manufacturer certified 7000# axles. However, the vehicle manufacturer is free to lower those axles certifications to satisfy other requirements. The real usable axle weights are what is depicted on the vehicle certification label as GAWR.

“On RV trailers, the sum of the GAWRs of all axles on the vehicle plus the vehicle manufacturer's recommended tongue weight must not be less than the GVWR. If tongue weight is specified as a range, the minimum value must be used.”