Exceeding R GAWR?

[Flapper]

So I was explaining some of the information about weight and towing a fifth wheel that I had learned, when I was asked "What happens when you exceed the max for your rear axle?" I found that I didn't have a good answer. Overloading the tires is understandable. But what happens if you overload the rear axel (because that is the one most likely to be overloaded) by say 5% or so....?? All I can find are references that you never should do it. But no explanation as to what you will be endangering. And we're obviously not into a "test to failure" scenario, hence why I'm not asking about massive overweight conditions. Can anyone enlighten?

[Flapper]

Thanks for the responses! This really is hypothetical, so far... I'm running just barely below max tire and rear end with my rig. Have to be careful not to put too much stuff in the Fifth or truck on a trip. Currently shopping for a heavy bike rack to put on the fifth's trailer hitch, to help take a few pounds of tongue weight off! So it is informational at this point - tires are obviously the very critical part, but I was wondering "what else?" happens as you exceed the limits...and you all have helped educate me on that.

[azrving]

Nothing will happen if you overload it by 5 %. I explained the same thing that you are asking to my wife the other day after going to the cat scale. My pin weight is good and I'm under by 800 lbs on the axles. We have a lot of bedding and kitchen stuff already loaded and I wanted to know where we are as we load up. I shoot for staying under the numbers.

I told her that even if we were a hundred or 200 or 300 over, the axle or frame or spring isn't going to break instantly. If the tire says 2680 and we put 125 lbs more on it it's not going to blow out just sitting there and its probably not going too blow as soon as it rolls. Imagine the trailer just sitting there and start adding weight. As it got heavier you would see the tire squat more and the spring would compress until it was smashed to the frame. At the same time the axle may be starting to bend and some point in there the tire would blow.

So its like looking at a graph and as the weight goes up the risk of the tire blowing, spring breaking or axle bending goes up too. Then its a matter of all the variables that are involved. If you overloaded by say 10% now that tire has another 268 lb on it. Will it blow? Probably not right away but its more likely and the chances go up as the conditions that the tire is subjected to worsen. It would blow quicker if it was on 140 degree pavement vs 40 degree or 70 mph vs 45 mph or riding a very rough road edge on the curb side vs smoother on the drivers side.

I used to wrench at a landscaping yard and watched them load customers vehicles and trailers. People would come in with snowmobile trailers to get top soil and have no idea how little it could carry or how heavy dirt is. I watched them go out with the axles bent so far that the tires were almost rubbing the frame. The axles bent but the tires didn't blow. Watched one guy make it out the driveway and as he turned onto the hwy the side force popped the tires off the beads and both ends of the axles bent. It was priceless entertainment.

The owner/office lady said hey can you go help him, I said no, there is nothing I can do, back a pickup up to his trailer and tell him to unload it. The landscaper did snow removal and used an F350 with a heavy full width salt spreader on the back of a dump box. They figured that if you put higher side boards on you could carry all the salt they want. They didn't want to run back and forth for two jobs that were about 10 miles away so they would have salt running over they sides. They said the truck broke and sent me out to the job. He had turned off the hwy into the black top parking lot and blew most of the studs off both sides of the rear duals.

The tires didn't blow, springs didn't break and the frame didn't break. It was so heavy that our little 2 ton floor jack wouldn't start to lift it. I said _ _ _ _ this and drove over to a tool supply place where we had an account and bought the big long floor jack that was around 7 or 8 ton and used in truck shops. It lifted it but pushed the wheels into the blacktop and it was dead winter. They were ticked and made me return the jack as it cost too much. Idiots.
So.....what will break first? It's like watching those Jackass videos, you never know what the outcome is until it happens.

[bid_time]

Golden_HVAC wrote:
...Your insurance company can 'excuse itself' from covering the accident too, leaving you without insurance paying for the accident due to your buying and towing with the wrong vehicle...

Fred.

That's pure hogwash. You can be drunk and involved in an accident and your insurance company is still on the hook. They may cancel you, but they can't un-insure you after the fact. Only way they can refuse cover you is for gross negligence, and even drunk driving doesn't rise to that level.

[AH64ID]

Golden_HVAC wrote:
So if you intentionally tow something and are exceeding the GVWR, In California at least they might check the weight of your RV and truck, then charge you with causing the accident due to overloading the truck.

Your insurance company can 'excuse itself' from covering the accident too, leaving you without insurance paying for the accident due to your buying and towing with the wrong vehicle.

Overload the tires and you really "Expect" them to not have a blowout? You can overload a tire by about 50 or 75 pounds, but not really 200 or 400 pounds.

It is much better to buy a dually truck than to overload one. The dually Ford has a 5700 pound cargo rating, without overloading the tires or axle, or brakes, or transmission, or springs, or more importantly the radiator and transmission cooler.

The dually F-350 has a larger capacity cooling system than lessor trucks. Step up to the F-450 cab and chassis, and the radiator and transmission cooler, oil cooler, angd such get even larger, with more capacity to cool the engine and transmission while climbing the mountains while towing a 18,500 pound trailer!

So why pick a 2500 series truck to tow a fifth wheel? Pick the 3500 series, or better yet the F-350. Dually might not be required, yet pick that one if you need to carry 5,000+ pounds!

Fred.

Not sure where you get your info, but Ford would disagree with your comments on cooling capacity and oil coolers. Ford specs show the came cooling system F-250 thru F-550 for a given engine in the same model year.

Legal bearing... Maybe in California, but then again everything is illegal and causes cancer there and I am sure exceeding RAWR is no exception.

Old-Biscuit wrote:
Exceeding RAWR (or any weight rating)......means more stress which can result in increased wear/tear. Possible axle bearing failure, pinion/ring gear increased wear, stripped axle spines.

Are axle ratings downgraded by vehicle mfg.? YES.
Axle mfg. ratings are higher then vehicle mfg. ratings assigned to the axles because of suspension components (tires, springs). Vehicle mfg. rate the whole set up where as axle mfg. rates the individual component.

So......
How much can you exceed vehicle mfg. ratings without causing harm?
About as much as the rear tires can handle.

It comes down to the platform. When a 9,000lb GVWR 2500 uses the same frame, brake, steering, axles, cooling, drivetrain, and nearly the same suspension as it's 12,200lb GVWR DRW big brother then one can safely modify the suspension and run at the same weights, tires permitting and not be exceeding any published design spec for individual components or the assembled vehicle.

Many people see ratings as black and white, and ignore the marketing that gets put into them.

The only RAWR I know of that is at the axle mfgr limit is the F-150 with the HD package. It's 4800 RAWR is the axles limit in any applications. I am sure there are others, but I don't know about them. Any modern 3/4 or 1 ton pickup is nowhere near the axle limit, SRW or DRW.

[Old-Biscuit]

Exceeding RAWR (or any weight rating)......means more stress which can result in increased wear/tear. Possible axle bearing failure, pinion/ring gear increased wear, stripped axle spines.

Are axle ratings downgraded by vehicle mfg.? YES.
Axle mfg. ratings are higher then vehicle mfg. ratings assigned to the axles because of suspension components (tires, springs). Vehicle mfg. rate the whole set up where as axle mfg. rates the individual component.

So......
How much can you exceed vehicle mfg. ratings without causing harm?
About as much as the rear tires can handle.

[Golden_HVAC]

So if you intentionally tow something and are exceeding the GVWR, In California at least they might check the weight of your RV and truck, then charge you with causing the accident due to overloading the truck.

Your insurance company can 'excuse itself' from covering the accident too, leaving you without insurance paying for the accident due to your buying and towing with the wrong vehicle.

Overload the tires and you really "Expect" them to not have a blowout? You can overload a tire by about 50 or 75 pounds, but not really 200 or 400 pounds.

It is much better to buy a dually truck than to overload one. The dually Ford has a 5700 pound cargo rating, without overloading the tires or axle, or brakes, or transmission, or springs, or more importantly the radiator and transmission cooler.

The dually F-350 has a larger capacity cooling system than lessor trucks. Step up to the F-450 cab and chassis, and the radiator and transmission cooler, oil cooler, and such get even larger, with more capacity to cool the engine and transmission while climbing the mountains while towing a 18,500 pound trailer!

So why pick a 2500 series truck to tow a fifth wheel? Pick the 3500 series, or better yet the F-350. Dually might not be required, yet pick that one if you need to carry 5,000+ pounds!

Fred.

[MitchF150]

No idea, but I've never seen a non HD payload F150 with more than #4050 rear axle rating..

Even on #7200 rigs, they seem to have #4050 rear axles.

My #7700 Max Tow only has a #4050 rear axle.

When I weighed it last time with my loaded #5000+ TT in tow I was at #3400 on the front, #3640 on the rear and #4500 on the trailer axles.

I ran my 97 F150 over it's GVWR and rear GAWR for over 11 years towing the same TT. It had the same Sterling 9.75" rear axle as the 13 F150 and I was running LT rated 16" tires and overload springs on the 97.. Yes, I know either of those did not raise the weight limits, but I was okay with it.. Or just got lucky.. 😉

Dunno how you all are staying under your #4050 axle weights with the trailers you are towing with your Eco's, but as long as you are comfortable with it and it's working for you, I've been there too. 😉

Mitch

[AH64ID]

Flapper wrote:
So I was explaining some of the information about weight and towing a fifth wheel that I had learned, when I was asked "What happens when you exceed the max for your rear axle?" I found that I didn't have a good answer. Overloading the tires is understandable. But what happens if you overload the rear axel (because that is the one most likely to be overloaded) by say 5% or so....?? All I can find are references that you never should do it. But no explanation as to what you will be endangering. And we're obviously not into a "test to failure" scenario, hence why I'm not asking about massive overweight conditions. Can anyone enlighten?

Each setup will be slightly different but I would say your order of limits is tires, suspension, brakes, axle components (housing/bearings).

Case in point is the current F-150, it has an axle that can support up to 4800lbs structurally. Not many F-150's have that capability according to the door sticker, so on the trucks that have a lower rating what could happen?

It's not going down the road all hunky-dory that will be an issue, it's what happens when you have to slam on the brakes. Overloaded tires won't provide the stability under heavy deceleration while going straight, let alone if one has to swerve. Then there is the suspension to consider, can the suspension provide the stability needed when the payload effect increases under heavy deceleration and swerving? Or will it induce body roll that decreases steering and braking?

So, with some research and proper upgrades it is possible to safety exceed the door sticker RAWR and be fine. Personally I will take my truck to 145% of the sticker RAWR, thou I am likely to hit my personal limit for GVWR first.

I don't know, thou am curious, how many different spring rates the F-150 has. Does it uses different rear springs based on RAWR? Or are they all the same?

[rhagfo]

Number 1 not a good idea!

Number many are set by the stock tire rating, if lower than the tire rating likely spring rate is the limiting factor

[newman_fulltime]

on facebook there is a good example a ford f350 with a broke frame looks like a dumptruck.it has a lance truck camper and a big carhauler trailer