Truck axles and tire ratings as they relate to TV capability - RV-Dreams Community Forum

BiggarView · RV-Dreams Family Member

Truck axles and tire ratings as they relate to TV capability

MarkS · RV-Dreams Family Member

Listen to your head.

But remember, mfr ratings are for continuous duty in all situations.

-- Edited by MarkS on Saturday 21st of February 2015 12:00:50 PM

Alie and Jims Carrilite · RV-Dreams Family Member

Here is a "For Instance" of using the tire rating before axle rating.
On a 2006 Dodge 2500 the rear axle is capable of carrying a total weight of 11,000lbs. The axle was used on both SRW and DRW. The dual have a shorter distance hub to hub, but the same weight rating.
On the SRW trucks most came with Michelin tires that were rated at 3195lbs per tire. So if you had a total load of 6400lbs on the rear axle you would be well under the axle rating but over the tire ratings.
6400lbs seems like plenty of weight capacity, but if the rear of the truck weighs 3340 (my truck with full fuel, hitch, dog and myself) that left 3000lbs for pin weight or other stuff to be carried in the truck like my wife, cooler, water for the dog, everything that wasn't in the truck when weighed.

So it's easy to exceed the tire weight ratings without going over the axle ratings o a SRW truck

Now on a dually, if you are carrying a heavy pin weight- 4-6000lbs and have extra fuel, tool box, and other stuff, you might exceed the axle before tire ratings but not likely.

BiggarView · RV-Dreams Family Member

Jim, in our case, we won't be considering SRW options, only DRW. The range of 5ers we have under consideration have GVWs ranging from 16500 to 18500 with a couple at a tad over 19K. I'm a bit cautious on the heavier units as the larger tow vehicles (MDT or HDT) that seem preferable are pretty much a "no go" for Cindi.

Anyway back to my question, so you're saying the TV's will have more tire load rating than axle rating so the MFR rating will be based on the axle not the tires, because it is lower?

Glenn West · RV-Dreams Family Member

Likely referring to my post. Axles and bearings on my truck are rated at 7k each. This gives me 14k capacity on axle. I researched the axles and bearings myself. Why then do GM stated -10k axle weight? Hot shoters do this on a regular basic with no problems. Air bags only for the added pin weight. But I am not telling you to over load your stated truck axle weight. I research components and discovered they are rated much higher. I "over load" according to GM, but not axle and bearing manufacturers. I have 11kish on rear axle. Do your own research and don't take my info for yours.

BiggarView · RV-Dreams Family Member

Glenn West wrote:
... I researched the axles and bearings myself. Why then do GM stated -10k axle weight? Hot shoters do this on a regular basic with no problems. Air bags only for the added pin weight. But I am not telling you to over load your stated truck axle weight. I research components and discovered they are rated much higher. I "over load" according to GM, but not axle and bearing manufacturers. I have 11kish on rear axle. Do your own research and don't take my info for yours.

Not sure I care what "Hot Shoters" are doing with no problems... The very name suggests a certain overconfidence I'm not comfortable with.

If GM is using 10K why would I want to go over that with stock axles and tires etc. Sorry, but without understanding why or how you "overload" according to GM but not the axle and bearing MFRs I'd be nervous... I hate nervous. I don't share your confidence in your research without a better explanation.

I'm still not sure what airbags do or why I might want them for my proposed trailer ideas, let alone whether they provide protection for the existing suspension components and how they do that. When I understand, I'll be able to decide if I should get them.

..and yes it was your post but I felt it deserved its own thread

Brian

-- Edited by biggaRView on Saturday 21st of February 2015 05:04:32 PM

Alie and Jims Carrilite · RV-Dreams Family Member

You really need to stay within the manufacturer's gross vehicle weight ratings. They have taken into consideration the stopping ability of the braking system, and the strength of all the components of the vehicle combined.
There are people though, myself included, that already owned vehicles that were almost capable of towing the RV we bought. In our case, the truck was a perfect match for our first 5th wheel. Not so much with our current one. What I did was add a bunch of aftermarket bandaids to increase stopping power- exhaust brake, bigger rotors and brake calipers, increased the transmission cooling ability- Dodge 48RE is not a performance transmission, increased the horsepower and torque of the engine so it would make it thru the mountains better, and had rear air bags to keep the truck level with 4500lbs of pin weight on it. Most of the modifications were actually done before we bought our first RV, because most of the other items I towed were big and heavy as well.
If you're looking to buy new or slightly used, I would research the tow ratings of various models from the big 3 brands to find what would be most suitable to tow the RV you chose.
But I would chose the RV first, then buy enough truck to tow it.
When you find your truck, make sure you're not using it at its max capacity, leave yourself 20% or so.

Glenn West · RV-Dreams Family Member

I am not over GM gross carring capacity just axle rating. So brakes don't apply. I have a heavy pin, 5800, and a hauler bed. This is why I did the research on rating of axles and bearings. I can actually stop my Teton without brakes working on Teton so truck not overloaded. Just over GM pin rating. But again I'm not advising anyone to do this but if you do, research your own trucks bearings and axles. Teton is 20k.

Terry and Jo · RV-Dreams Family Member

Glenn,

That is all duly noted and there is truth to what you are saying. However, just carrying the weight isn't enough. There are too many people that don't know trucks (or who Hot-Shotters are) and can buy a truck that is overpowered by their trailer. Sadly, there are too many salesmen, both RV and truck, that will tell a customer that they won't have any problem with towing with a truck the buyer is interested in, thus selling one that isn't really capable.

Brian,

Besides the axle ratings, one also needs to find the GCVW (Gross Combined Vehicular Weight) rating for the truck that has one's interest. One shouldn't exceed either the axle ratings or the GCVW. GCVW is the total weight the truck can "handle," which includes the gross weight of the trailer and the gross "practical" weight of the truck. Practical weight is the weight of the truck fully loaded with fuel, all passengers likely to be in the truck and any cargo that might be in the bed or back seat.

Incidentally, Hot-Shotters are those that drive smaller trucks than HDT's and are hauling products that need to be delivered quickly. Most of what I have seen of Hot-Shotters has been in the oilfield business, and those are hauling products, including drill stem pipe, to the rigs or other oilfield locations.

Terry

BiggarView · RV-Dreams Family Member

Jim, so far, the DRV 38RSSA and 39DBRS3 are the two heaviest rigs we have under consideration currently but there is plenty of time for that to change as we are not in a position to pull the trigger... yet. Though we don't see going much heavier or longer than the 39DBRS3. As to TVs, we like the current DRW offerings from GMC/Chev 3500HD or Dodge RAM 3500HD. Loaded out the way we envision, we should be under GVWR of the truck and the trailer and the combined rating by a sufficient safety margin but, again we have plenty of time to confirm this before actually going out picking out the final configuration.

The question of hauler bed or stock p/u bed may be an issue for the truck RAWR as near as I can see with GM products getting an edge here with the hauler bed owing to the fact the dodge is a heavier truck in stock configuration and adding the weight of the hauler bed will be a limitation for the available trailer pin weight and CGVWR for the 3.73 gears. Going up to 4.11 gears will help CGVWR but not RAWR if I understand that correctly. If we opt for a hauler bed, we may have to consider lighter 5ers with the stock 3.73 gears.

If I put on airbags on the truck to "level" the truck, isn't that effectively increasing the truck's load carrying capacity or is it still limited to what the MFR has published? Do the airbags smooth out the ride while towing by enhancing the other suspension components abilty to cope with the inputs from the road conditions?

By way of example, I have had a few PM conversations with Bill and Linda about such matters but the wrinkle that Glenn put in with the tire and axle ratings cause me to reconsider all of my assumptions. As you know Bill has a GM 3500HD with the hauler bed and tows a NH rig though I have no idea what weight he is towing but his conclusions and data tells me he is comfortable with his set-up. If we find a rig that is under his numbers I feel safe that our own rig/combo will be good to go also. We have a rig/tow vehicle weight calculator and that is how we are deriving our decisons on a "go/no go" basis for each rig under consideration.

Brian

Neil and Connie · RV-Dreams Family Member

Our New Horizons is 21,500 loaded and we are about 500 over on rear axle load on our F450 dually. All other ratings including tires we are well within. We have the hydraulic disk and ABS option on the rig and have no issues towing uphill or down, or braking. However, if we were doing it again I would get a Chevy 5500 HD and a hauler bed with rear air suspension. We are not unhappy enough to switch trucks though and I disagree that you should ignore the specs, do your own research, and run whatever weight you feel like. Your insurance commonly could deny a claim if they figured out you were overweight and deliberately ignored the spec. Of course, they could deny if you were accidentally over as well but I'm not going to court and testifying I had no idea about it.

I'm comfortable exceeding the source a little but at some point good engineering sense takes over, especially as we have zero idea as to how Ford or Chevy calculated their rated load. 5%, I'm good with that but 20 is another thing.

The Junkman · RV-Dreams Family Member

i'm 23,000 lbs and the 13' Ram pulls and stops it just fine.. all within spec..

Terry and Jo · RV-Dreams Family Member

Brian,

If I recall correctly from what others have said about the air bags, they do nothing to increase weight capacities. All they may do is smooth out the ride and perhaps level the truck and trailer a bit more. If you were to get an air ride fifth wheel hitch or an air ride pin box, either would smooth out the ride. If you don't go with the hauler bed, pay close attention to the bed height from the ground and the height of the bed rails on a regular pickup bed.

Terry

FastEagle · RV-Dreams Family Member

biggaRView wrote:
Jim, in our case, we won't be considering SRW options, only DRW. The range of 5ers we have under consideration have GVWs ranging from 16500 to 18500 with a couple at a tad over 19K. I'm a bit cautious on the heavier units as the larger tow vehicles (MDT or HDT) that seem preferable are pretty much a "no go" for Cindi.
Anyway back to my question, so you're saying the TV's will have more tire load rating than axle rating so the MFR rating will be based on the axle not the tires, because it is lower?

Vehicle manufacturers establish GVWR and then they set GAWR and fit the GAWR with tires having the load capacity to support the GAWR with the recommended inflation pressures. You will not be able to exceed your tires load capacity on a DRW truck without first exceeding the vehicle's GVWR.

Jot down the tire sizes from the tire placard, find the load inflation chart for them and do some math. In most cases with a DRW truck you wont even have to use more inflation pressure than recommended by the vehicle manufacturer.

Truck Manufacturers will normally set the combined GAWR at 20% - 22% above GVWR. All most all "hot shorters" exceed their truck's GVWR (their call).

FastEagle

-- Edited by FastEagle on Monday 23rd of February 2015 01:11:37 AM

Glenn West · RV-Dreams Family Member

The Junkman wrote:
i'm 23,000 lbs and the 13' Ram pulls and stops it just fine.. all within spec..

It is the rear axle weight in question. Curious, did you ever weigh your setup?

BiggarView · RV-Dreams Family Member

Glenn West wrote:
The Junkman wrote:
i'm 23,000 lbs and the 13' Ram pulls and stops it just fine.. all within spec..
It is the rear axle weight in question. Curious, did you ever weigh your setup?

Glenn, don't forget Steve has that big extra room at the back of his rig to stow a lot of weight thus taking pin weight down. In any event I'd be curious about his actual weights also, if for no other reason to see how it works and what changes the rest of us who might be considering such a set-up might have to do differently. Still, 23K is lot of weight no matter what way you slice and dice it for a 3500 DRW P/U.

Brian

BiggarView · RV-Dreams Family Member

The Junkman wrote:
i'm 23,000 lbs and the 13' Ram pulls and stops it just fine.. all within spec..

We won't be doing 23K... my numbers say 20.5K, give or take, is the practical limit for the TVs we have in mind (which by the way include the Dodge with the 3.73s), but nothing we have looked at comes even close to that. Besides DRV, the LifestyleLuxury 38RS, properly optioned with the 8k MorRyde IS, H tires will get us upto about 19.5K GVWR(according to the Lifestyle rep I spoke to) including plenty of CCC. This rig will still leave plenty of spare capacity on the TV rear axle and combined weight. Hopefully my calculation is right.

Brian

Glenn West · RV-Dreams Family Member

Teton's tend to be pin heavy. Before the hauler bed and air ride hitch I was within rear axle GM rating, but not a lot of margin. My hitch was maxed out and we had problems with it before. Bolts sheared. Couldn't level Teton either with stock bed. Unit is already high and raising it enough was out of the equation. Had considered HDT but would have put me in Smart for commute to work and back. Prefer my current set up. I mentioned "hot shoters" simply because they constantly push their trucks beyond specs and no problems until they get really crazy with it. Not one I know have had an axle failure. My work exposes me to them. In your setup, if you want an hauler bed, I'd put it on. You won't be a lot over if any.

BiggarView · RV-Dreams Family Member

For what we are considering, a hauler bed will work and not violate any spec. If we find a heavier rig... over the 20.5K, then all bets are off and we'll have to rethink our towing vehicle strategy. Again, I think 20.5K will be our theoretical trailer weight limit, and I prefer to have the safety margin of a lower trailer weight to TV weight ratio. If only, I could convince Cindi about an HDT as a viable option... So far my only usable argument has been "you like the Winnebago 42E Journey if we decide to get a MH... that's even bigger than a HDT", but that has fallen on deaf ears... biggrin . We both need to get behind the wheel of an HDT to see if we are upto the challenge. Wandering off topic a bit here.

At 20.5K trailer, there is no available axle capacity left according my calulations using a hauler bed, aux fuel tanks, tools, people and gear and 22% pin. Looking at 19500 gives me some wiggle room on truck weight, loaded out. I would also like to stay well under trailer GVWR also... to me it's peace of mind and not overworking my equipment or spending extra time and money in the shop. So we are kind of arbitrarily looking to about 750 lbs under trailer GVWR and 375 under the TV RAWR. If we meet those, we should be okay on CGWVR.

I hope our strategy is a sound one.

Brian

The Junkman · RV-Dreams Family Member

I have the scale and the dummy plates to weigh.. just have not done it. Been sitting in one spot a while now. we move to orlando april 1st. Will try then. Just not real important anymore. I have the factory weigh sheet, and have a idea of what is in it.. I don't think I'm over 23k.. if so, not much over..lol

I'm lightening up alot since sept.. I now have 4 20ft storage units full of freightliner stuff, and am looking for a warehouse to winter in / at..lol.. After all.. I'm not retired.. just semi retired. I need to make money.

Glenn West · RV-Dreams Family Member

Knowing your rear axle weight would help here. You state 23k and you are heavier than my Teton. My rear axle with stock bed was near max rating and our trucks rear axle rating is 9750. The OP is contemplating pin weight and has a question you could help with. I chose to ignore GM ratings since axles/bearings much more. Springs aren't and bags fix that. Tires is lowest so is weak point. I am good on tires.

The Junkman · RV-Dreams Family Member

Glenn West wrote:
Knowing your rear axle weight would help here. You state 23k and you are heavier than my Teton. My rear axle with stock bed was near max rating and our trucks rear axle rating is 9750. The OP is contemplating pin weight and has a question you could help with. I chose to ignore GM ratings since axles/bearings much more. Springs aren't and bags fix that. Tires is lowest so is weak point. I am good on tires.

As biggerview pointed out.. I have added weight hanging past the rear axle of the trailer.. getting leverage to lift some pressure off the pin..

I have also recently added a cargo carrier off the rear hitch, for lawn stuff..

I don't think there is your kinda weight on my pin.

I drove a Big Penske, with air brakes, to and from SC to FL.. couple weeks ago..I think my set up stops as good as that truck did when it was loaded with about 12k, ( I guess )

Biggerview.. Get a 13' and up Dually Ram 3500 with the aisen tranny... Add either the factory bag set up.. or just a aftermarket one.. and don't look back..No worries on whatever your going to throw at it. I don't think a air hitch would make much difference in mine.It rides great.. the bags help on the bridges hard hits, thats all.. and I'm always concerned with adding another point of failure ( blown bag ), and I feel when heavy.. you need the bags in the trucks suspension. Adding another one else where , in addition, makes no sense to me.Good luck.

BiggarView · RV-Dreams Family Member

The Junkman wrote:
...I have added weight hanging past the rear axle of the trailer.. getting leverage to lift some pressure off the pin..
I have also recently added a cargo carrier off the rear hitch, for lawn stuff..
I don't think there is your kinda weight on my pin....

Steve, it's true you may have 'unloaded' your pin, but my concern, if it was me, would be the loading on the real axle of the trailer. It occurs to me that is where you have the highest likelyhood of a catastrophic failure. Just sayin'

FWIW, Brian

Glenn West · RV-Dreams Family Member

It would be very interesting to get scale weights on Steve's unit. He is doing some "unusual" things. Axles are set to the rear and loading rear will increase rear axle weight. Do not believe it will unload front pin significantly. Rvs are not a fulcrum.

BiggarView · RV-Dreams Family Member

Glenn, it's simple mechanical advantage. If you put a ton on the rear the same distance the pin is from CofG you will "unload" a ton from the pin weight. Now the question, in Steve's case, is where was the C of G in his empty trailer.

Glenn West · RV-Dreams Family Member

But he has 3 axles. It would take a lot of weight to unload that pin. Add to the fact that those axles are rearward mounted also.

BiggarView · RV-Dreams Family Member

Glenn, I was speaking in strickly a physics sense. In actuality, yes, if he put 500 lbs in the very back he might take 250 lbs off the pin, maybe more but probably less, it all has to do with the CofG. True, the tires are most likely behind the CofG... but the theory is still valid... put the weight of a bulldozer on the rear end and the pin weight will definitely go negative. NOT good. I don't think Steve is any danger of destablizing his truck with too low a pin weight, he could most definitely overload the rear trailer axle, less so on the middle axle if he piles too much weight into the rear of his rig. I doubt he will put enough weight in there for that to occur... He could go over his CGVWR before the pin weight becomes an issue. In our possible setup, so far this does not appear that it will be an issue given the weight that we are looking at.

Steve, If we decide on the Dodge, it will have the Aisin trans, with the 3.73 gears. If Dodge has an airbag option we'll consider it. I have spoken to many mechanics and they rank the big three in terms of ease of repair, cost of repair, and frequency of repair like this this, GM overall best, Dodge second and Ford third. However the margin is very close for all three so it's really down to personal preference. For all intent and purposes they are equally capable for what we need. I have "history" with GM so they are in the lead. My main concern with the Dodge is the total truck weight and available rear axle capacity with the possible hauler bed should we desire to go that way. We are not considering anything other than a one ton dually (GM 3500HD, Ram 3500HD or F350SD) at this time. Other options will be considered as time goes by and if they will better suit our needs.

Brian

-- Edited by biggaRView on Wednesday 25th of February 2015 09:28:07 PM

The Junkman · RV-Dreams Family Member

There isn't a "ton" loaded in the rear.. just some guns and ammo and some art in my "bunk house" shelfs.

Been off loading some of the stuff to storage and auction lately. I estimate 1000 lb loaded in the rear now. Less by the time I leave 4/1. Will weigh everything then, as the "load" should be consistent from then on.

Biggar view.. RAM does offer a factory air bag system in the 2015 and up.
Seems to me if Ram can't handle the rear axle capacity with a hauler bed.. No one can.

Alie and Jims Carrilite · RV-Dreams Family Member

Steve-There isn't a "ton" loaded in the rear.. just some guns and ammo and some art in my "bunk house" shelfs.
You might be surprised how much a few 50 count boxes of ammo weighs. I weighed all mine and was surprised doh

53 Merc · RV-Dreams Family Member

All to often we get caught up on the "sticker/door plate weight limit/capacity" on these forums devoted to towing RVs. Then the self appointed weight police come in and rail about how unsafe it is and "I heard about thus and so from my cousin's hairdressers neighbors uncle being cited for being overweight."

Can anyone show that towing in excess of GVWR with a non-commercial light duty truck is illegal and the penalty for said violation? State or federal statutes required for proof.

Show statistics that show that dually trucks are safer than SRW? (not personal feelings)

Show proof of denial of insurance claim for an accident of a non-commercial vehicle towing in excess of its posted manufacturer weight rating? And how did they prove it?

Show that vehicle weight ratings are based on product testing, not the marketing department? Don't you find it odd the GVWR is always a round number?

Glenn West · RV-Dreams Family Member

Again we are not discussing being over weight on towing rating. We are discussing rear axle weight. Even a 22k unit is within specs on newer trucks. One can get beyond rated rear axle specs though. If they are like the Chevy dually though the axles/bearings far exceeds this rating. I have not researched Ford and Dodge. Knowing this I would not fret loading one to tire limits, which is beyond manufacture rear rating.

FastEagle · RV-Dreams Family Member

auto.howstuffworks.com/auto-parts/towing/towing-capacity/vehicle/gawr.htm

FE

The Junkman · RV-Dreams Family Member

Alie and Jims Carrilite wrote:
Steve-There isn't a "ton" loaded in the rear.. just some guns and ammo and some art in my "bunk house" shelfs.
You might be surprised how much a few 50 count boxes of ammo weighs. I weighed all mine and was surprised

Tell me about it.. I've moved the ammo cans a few times already..And they are the big ones.

Been selling off some of the stuff.. may put some in storage for a while.. before leaving FL. No reason to bring many of them.. and each ammo for them..

Cummins12V98 · RV-Dreams Family Member

My new RAM sitting in my driveway since yesterday has the Aisin/4:10 combo with rear air. The rear axle rating is 9,750# I weighed the truck with my wife and myself with full fuel. I did not have tool box in or hitch. The rear axle weighed 3,634# that leaves me with 6,116# of payload for my rear axle. My combined truck/RV capacity is 37,500# minus my truck scale weight of 9,004# I can tow 28,494# including hitch and tool box. Subtract about 600# for those and my truck can tow within spec 27,900#.

The Junkman · RV-Dreams Family Member

Cummins12V98 wrote:
My new RAM sitting in my driveway since yesterday has the Aisin/4:10 combo with rear air. The rear axle rating is 9,750# I weighed the truck with my wife and myself with full fuel. I did not have tool box in or hitch. The rear axle weighed 3,634# that leaves me with 6,116# of payload for my rear axle. My combined truck/RV capacity is 37,500# minus my truck scale weight of 9,004# I can tow 28,494# including hitch and tool box. Subtract about 600# for those and my truck can tow within spec 27,900#.

Congrads..

Awesome truck.. Pics would be great ! Cause not only to these things work the best.. they look the best too.. and yep, That includes "trucks"..lol

MarkS · RV-Dreams Family Member

After reading this thread I wanted to chime in on air bags and fulcrums at least as it relates to big trucks. I think most would also apply to RVs as well.

Air Bags are used on heavy trucks to maintain the geometry of the driveline. They do this by maintaining ride height at various loads. If the air bags aren't working, the u-joints will let you know. On the trailer, air bags are for smoothing the ride. I would imagine that you would want to maintain ride height on a pickup when under load. You are working the u-joints harder pulling your trailer increasing the wear significantly if the geometry is different than empty.

Fulcrums. Anytime you have a pivot point, it acts as a fulcrum. The slide axles and sliding fifth wheel on a semi are used only to shift weight from one axle group to another. The holes on a trailer axle are about 8" apart. Moving the axle forward will reduce pin weight 250 pounds per hole and visa versa. Moving the fifth wheel has the same effect but shifts weight between the steers and the drives. We have maximum weight allowed on each axle group, 12500 on steers, 34000 on the drives and tandems. We adjust weight to avoid tickets but it affects handling and ride too. I like mine to be about 11500 on the steers and equal weight on the drives and tandems.

On my RV its a little different because I am running at minimums on the truck. I want maximum weight on the pin to improve braking, especially on wet roads. My steers are about 11000 and I would give the Kings ransome to have 11000 on my drives. So, if I have an extra case of green beans guess where they go. That's right, under the bed or in the front closet. Because of the front axle weight, caused by that huge block of iron between your front tires, you have to be aware on slick surfaces because the truck will swap ends on you in one note if you brake too hard. In my 18 wheeler, When the roads are wet and my trailer is empty I increase my following distance by about three miles.

I tease about HDTs but, no wiser words were ever spoken than, "HDTs aren't for everybody". Personally, I think the choice to run a HDT is directly related to testosterone compensation and the little boy quotient. Of course, there is the convenience of having a dog house to go to when I don't get my chores done.

Glenn West · RV-Dreams Family Member

If not for my job an HDT would be my choice also. Duallys look very small towing these upscale 40' up 5thers.