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post #1 of (permalink) Old 08-18-2004, 07:58 PM Thread Starter
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OT - determining towing capacity

Does anyone know how the auto manufacturers determine towing capacity for their vehicles. For example, I have a Tahoe and Chevy says the towing capacity is 7500 pounds. My question is, how did they arrive at that number.

Just wondering
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post #2 of (permalink) Old 08-18-2004, 08:43 PM
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Re: OT - determining towing capacity

[img]images/graemlins/tongue.gif[/img] They have determined that 7500 is the most weight you can handle, taking into consideration the WEIGHT and the WHEELBASE of the tow rig. If you tow a heavier trailer there is always the possibility that the trailer might determine which way the tow rig should go, and that's always kind of scary. [img]images/graemlins/crazy.gif[/img]
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post #3 of (permalink) Old 08-18-2004, 08:47 PM
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Re: OT - determining towing capacity

A lot of things go in to the equations, and I don't even pretend to know them all but...

What it boils down to is the amount of weight the vehicle is able to "safely" control on the road. What most people don't realize is that being physically capable of getting the trailer moving (enough power) is one of the smallest considerations. Handling and especially braking are your two biggest items. If you ever looked at the suspension and brakes on a Class 5 or better truck, you would quickly understand.

Unfortunately, the rating is also somewhat subjective as far as I'm concerned. I suspect the mfrs put whatever rating on there they think they can get away with. There is no way on earth I would spend any decent amount of time on the road in a 1-ton pickup pulling a 5th wheel camper with triple slides. I don't care if it is rated to pull it or not, it would scare the crap out of me.

If you want the simple, stupid answer... it is the GCWR (Gross Combined Weight Rating) minus the GVWR (Gross Vehicle Weight Rating). In other words, the total amount of weight between the tow vehicle and trailer that the tow vehicle can handle minus the maximum loaded weight of the tow vehicle by itself.

But in my mind, that still doesn't tell me how they came up with thier number.

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post #4 of (permalink) Old 08-19-2004, 07:41 AM
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Re: OT - determining towing capacity

When the manufacturer comes up with that max. towing capacity, they figure towing down a flat, straight road with no cross winds. About 2/3 of that rating is what most people could tow comfortably without over taxing their drivetrain and getting white knuckles. If you are dealing with mountains, you better figure even less. Also consider what you are towing. Towing a long pull behind camper, is like pulling a long billboard down the road. Cross winds can really play havoc with them. It doesn't help that camper manufacturers keep building them lighter and higher off the ground. A fifth wheel is going to tow easier, because the tongue weight is centered over the vehicle. When a manufacturer claims you can tow in over drive, remember that is only under ideal conditions. Any time your tranny is shifting up and down, it's time to go to the next lower gear, that's if you want your trans to last. When towing up long grades in the mountains, shift down, take your time, and get in the slow lane with the semis. This may sometimes mean using second or even first gear.(Watch your RPMs).
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