Frequently Asked Questions (FAQs)
Since the debut of RV Tow Check, we have been monitoring what others have been saying and replying to several emailed questions. Here are some answers and explanations to typical questions.
The best way to answer this question is to use a real example from a client.
Q: "The RV Tow Check states that my 2015 Silverado 2500 with Duramax, CC, LB, 2WD, can only tow 11,250 lbs @20% pin weight with a 5th wheel. The dealer told me I could tow 17,300 pounds. Is the dealer wrong?" The weights are: GCWR: 24,500, GVWR: 10,000, GVW: 7,750 (includes two people, cargo and hitch). The scaled axle weights without the trailer attached are—front: 4,750 and rear: 3,000.
A: The RV Tow Check (RVTC) calculator computes tow capacity based on available payload—a part of the gross vehicle weight rating (GVWR), the gross vehicle weight (GVW) of the vehicle to avoid exceeding the gross combination weight rating (GCWR), and the trailer weight rating (TWR). All vehicle manufacturers use words like "never" or "must not" in reference to exceeding these ratings: GCWR, GVWR, GAWR, and TWR. As revealed below, you will learn that GVW plays a very significant factor in real towing capacity.
The following shows you how RV Tow Check calculates for fifth wheel towing only.
Method 1—Available payload formula: GVWR-GVW-(unscaled equipment, cargo, driver and passenger weight)=Available payload.
Your truck's available payload is 2,250 pounds. RV Tow Check uses the available payload and applies the SAE J2807 methodology to calculate the realistic vehicle towing capacity. Per SAE J2807 specifications, vehicle manufacturers use 15% to calculate the vehicle TWR. RV Tow Check allows you to view the towing capacity for a full range of recommended percentages. (10%-15% for conventional trailers and 15%-25% for fifth wheel and gooseneck trailers.)
Method 2—The standard GCWR formula: GCWR-GVW-(unscaled equipment, cargo, driver, and passenger weight)=Towing Capacity
With this standard formula, your truck's tow capacity is 16,750 pounds.
Method 3—Trailer weight ratings (TWR): Some manufacturers derate the towing capacity below methods 1 and 2 described above to ensure the rear GAWR will not be exceeded or for other reasons, such as OEM hitch ratings. Therefore, this rating is critical to consider as it should not be exceeded. For your truck, the 5th wheel TWR is 17,300 pounds.
Decision time—RV Tow Check throws out the highest towing capacities from the three calculation formulas. In this case, method 2 is discarded because it would cause the GVWR to be exceeded and Method 3 is higher than method 1. Method 2 will be used only when the tow capacity is limited by the GCWR, or the available payload is very high. The high available payload is common with some one-ton dually trucks, yet method 2 may exceed the TWR.
Percentage selections—After the initial max towing capacity appears, you may instantly view different towing capacities by selecting any of the available kingpin or tongue weight percentage buttons for the two trailer classifications. It is your decision when selecting the pin weight percentage that you feel is safe for your towing situation. The safest selection will always be the highest percentage.
Typical GCWR formula—When towing capacity is calculated with the standard GCWR formula that has been used for years; the results will reveal that your truck could tow 17,300 pounds as you stated (GCWR-curb weight=Towing Capacity). Notice that this GCWR formula does not include optional equipment, passengers, a fifth wheel hitch or any other cargo you may carry in your truck. The potential PW @20% for a fifth wheel weighing 17,300 pounds would be 3,460 pounds. Add the potential PW to the scaled rear axle weight (3,000), then your rear gross axle weight (GAW) adds up to 6,460 pounds.
Here is the problem with the typical formula—When adding the potential rear axle weight (6,460) to the scaled front axle weight (4,750), the GVW is 11,210 pounds. That exceeds the GVWR by 1,210 pounds. Additionally, the rear gross axle weight rating (6,200) is exceeded by 260 pounds.
The typical formula is one small reason towing guides and the standard dealer's formula gets buyers into mismatched RV combinations that exceed the tow vehicle's certification ratings. Towing without exceeding the weight ratings is primarily about SAFETY and vehicle longevity. Moreover, for most manufacturers, exceeding the weight ratings may invalidate the vehicle warranty.
No. That is one reason RVTC has multiple PW/TW selections. The results you see are the actual capacity weight limits for each selection. It is up to you if you wish to provide a safety margin, which may be accomplished by selecting a higher PW/TW percentage when you do not know the trailer's real PW/TW percentage.
The certification label weight rating already includes a small percentage of safety margin for emergency type situations. I do not know of any reason that a vehicle or driving condition would be unsafe if it were towing up to the certification label limits. However, if one chooses to exceed the weight safety ratings or ignore required safety practices if involved in a severe accident, that could lead to a liability lawsuit and or criminal charges.
Thanks for asking an excellent question. The RV Tow Check (RVTC) calculator computes three capacity formulas based on available payload, gross vehicle weight (GVW) of the vehicle to avoid exceeding the gross combination weight rating (GCWR), the gross vehicle weight rating (GVWR) and trailer weight rating (TWR).
When you see changes occur as you select different percentages, these results are based on not exceeding the GVWR. At the point where the capacity stops changing and remains the same for the other percentage selections, the towing capacity is based on the GCWR or the TWR. In some cases, no change may occur because the vehicle has a high available payload. When there is a high available payload, towing capacity is limited by GCWR or the TWR.
The results are part of the checks and balances approach provided by RV Tow Check and the multiple formulas built into the calculator.
Q4: "Your tow calculator doesn't ask for vehicle info like engine or axle ratio which makes a big difference per the owner's manual chart. I put my info into your [calculator] and got max tow of 4,384, but owner's manual for my specific truck shows max trailer weight of 8,100 lbs. That's a huge difference. What am I not understanding about your calculator vs. my owner's manual?" [sic]
That is a very good question. Let's define gross combination weight rating (GCWR) and gross vehicle weight rating (GVWR) a little more to answer your question.
The GCWR is assigned by manufacturers and includes the powertrain's capabilities. All the components that you mentioned are built into this rating. You may note that two identical vehicles with the only mechanical difference being the gear ratio will have different GCWRs and maximum towing capacities. See the Ram examples on this page: How Much Can A One Ton Truck Tow Without Exceeding Ratings?
The GVWR, as required by NHTSA, primarily considers the frames, axles, springs, braking, rims, and tires. Based on the lowest component rating within the braking and load bearing systems, manufacturers assign the GVWR. Part of the safety requirement for GVWR is that the vehicle is expected to stop within a required distance when it is fully loaded to the max GVWR. This appears to be a primary safety concern of NHTSA when tow vehicles are overloaded by too much pin or tongue weight coming from the trailer. Some owner's manuals may state: "The towing vehicle's brake system is rated for operation at the GVWR—NOT GCWR. Separate functional brake systems should be used for safe control of towed vehicles and for trailers weighing more than 1,500 lbs. when loaded."With these two ratings and knowing the gross vehicle weight (GVW), which plays a very significant factor in real towing capacity, RV Tow Check calculates three formulas and selects the lowest result for the towing capacity. The result is based either on payload availability (part of GVWR) or GCWR or the TWR. Although you did not mention your truck's GVW, it is most likely the reason for such a low tow capacity as revealed by RV Tow Check.
Great question. The results for conventional tow are the maximum recommended weight based on real tongue weight regardless of a WD system or the TWR. In reality, and it took us a while to grasp it, WD systems don't really remove tongue weight from the hitch ball, but redistribute the felt weight across the axles. Therefore, the result you see is the maximum towing weight regardless of a WD system. For a very informative discussion on WD systems, visit this forum thread at RV.net. Additionally, SAE recommends a TW of 10% for best towing performance.
The short answer is, no. Here is a direct quote from Firestone/Ride-Rite: "Please remember that air springs do not increase the load carrying capacity of your vehicle. *DO NOT EXCEED THE VEHICLE'S RECOMMENDED GROSS VEHICLE WEIGHT RATING (GVWR)"
All manufacturers calculations are primarily gross combination weight rating (GCWR) minus GVW or curb weight equals towing capacity. (Ram's calculator does have a slider scale that includes payload adjustments.) Manufacturer's GVW is the curb weight. By the time anyone drives a vehicle off the lot it will most likely exceed the published curb weight. Moreover, by the time anyone has his or her vehicle ready for towing, it will be much heavier. All this additional vehicle weight may reduce towing capacity. What's additionally important is that no tow vehicle's gross vehicle weight rating (GVWR) and gross axle weight rating (GAWR) should be exceeded because of safety and vehicle longevity. All manufacturers state that in print and most never read it. None of the manufacturers take into account the GVWR when calculating tow rating.
(If one would use a calculator and crunch Ram's sliding scale calculator results, they'll discover it doesn't add up correctly.) Note: Apparently, Ram reacted to my, and maybe others, concerns on this and they have removed the slider scale starting with the 2016 models.
Thank you for asking that question. RVTC's primary purpose is to assist the buyer with their potential new vehicle purchase. A new vehicle purchase can be difficult, and many buyers are not sure if the vehicle they are considering has enough towing capacity to tow their trailer, or in other cases, the prospective trailer they are considering buying.
You, on the other hand, like many others, have discovered from using RVTC that you may be towing with an overloaded truck. The only way to know if your tow vehicle is exceeding or not exceeding the weight safety ratings is to weigh your rig. Weighing your rig is not difficult. There is a simplified four-step weighing program available for free at Fifth Wheel Street. Start with Step 1 by downloading and printing the appropriate worksheet for the type of scale you plan to weigh on. The worksheet is detailed and explains the process step-by-step. Once you've completed the worksheet after the two weigh-ins, go to Step 3 at the Fifth Wheel Street website and enter the weight data to obtain the only industry-leading 13-point RV weight safety report available on the Internet.
Hopefully, your rig is not overweight. Even if you discover that some of your vehicle's weight safety ratings are exceeded, you are better off knowing than driving unknowingly down the road while exceeding the ratings. It is our hope that you would at least be conscious of an overload condition and change your driving habits accordingly. Depending on how excessive the overweight may be, you may need to consider measures to eliminate the overweight condition. Most importantly, we hope you will drive and tow safely.
Additionally, you may be interested in reading the following article: My Truck Pulls it Just Fine!
It is not uncommon to find a hitch assembly installed that is rated more or less than the manufacturer's published TWR. Considering that the hitch assembly is made up of the three primary components you mentioned, it is possible that each one could be rated differently. When considering the hitch assembly components and the published TWR, the one with the lowest rating will be maximum tow rating.
i.e. If the ball is rated at 16,000 pounds and it's the lowest among these components and the published TWR, 16,000 pounds will be the maximum tow rating. However, if your truck towing capacity results in RV Tow Check (RVTC) is less than the hitch assembly components and published TWR, it is recommended you not tow more than the capacity as indicated by RVTC.
Yes, we recommend it. The most common weight safety issue for motor coaches is exceeding the vehicle's gross combination weight rating (GCWR). As for the tongue weight (TW) measurements, there is a little more flexibility in this area depending on the towing method. If you're towing a car with all four wheels on the ground (flat tow), expect minimal TW. Even when towing a car on a dolly, the TW will remain fairly low, but, ensure you're not exceeding the rear gross axle weight rating (GAWR) by weighing your motorcoach with the dolly and car attached.
Now, if you're towing a conventional trailer, read the max conventional towing capacity the same as any other conventional towing combination.
Finally, we strongly encourage you to weigh your fully loaded motorcoach with any TOAD to ensure you're not exceeding any of the weight safety ratings. Weighing is easy by following the simplified four-step plan at Fifth Wheel Street.
No. Rarely will the published dry pin weight percentage be an acceptable representation of a loaded trailer’s pin weight percentage. In many cases, the pin weight of identical trailers will be different between two separate families. It all depends on how the trailer is loaded.
Example: The published dry pin weight percentage for my 2009 Heartland Cyclone is about 22%. My loaded trailer actual pin weight percentage has ranged between 17% to 20%. I have a record of one trailer, and the dry pin weight is 19%, but the loaded pin weight was 26%.
I recommend buyers who do not know the loaded pin weight of a trailer, to select the maximum pin weight percentage on the scale when selecting a new tow vehicle.
Absolutely! Short wheelbase vehicles such as some SUVs, vans, half-ton and three-quarter ton pickup trucks have limitations when it comes to towing safety and stability.
Some time ago, there used to be a rule of thumb for tow vehicle wheelbase length versus trailer length. That rule no longer exists, and there is currently no verified replacement.
We recommend you read the tow vehicle owner’s manual. Many owner’s manuals provide a maximum frontal trailer limitation. Measuring and knowing the trailer’s frontal area alone may prevent towing many trailers from being towed by short wheelbase vehicles.
Several accidents occur annually due to trailers being too long for the tow vehicle. Read one such true story here.
Note: We have interpreted glossary terms from the UK and Australia the best we know how. If you are from one of these countries and find a mistake or can provide an improved interpretation or web link, please contact us.