What limits tow ratings for unibody vehicles?

[Bob77064]

There are some unibody vehicles that are very strong.

 

[David_Kb7uns]

Have a 2006 Jeep Commander, 5.7 Hemi with 4 speed auto(545RFE??) and Quadra Drive II, it has a 7000Lb tow rating with weight distributing hitch but the frontal area of the trailer must be under a certain square foot area. the Commander has unibody construction, but it is very stout in construction with 2-3 layers of steel in some places. While this is not every vehicle, there are unibodies out their that have respectable tow capacities. The new Dodge Durango shares a similar platform and no longer has a frame either with similar tow capacities of the Jeep.

David Kb7uns

 

[jeffsw6]

Have a 2006 Jeep Commander, 5.7 Hemi with 4 speed auto(545RFE??) and Quadra Drive II, it has a 7000Lb tow rating with weight distributing hitch but the frontal area of the trailer must be under a certain square foot area.

That is true of my 05 Suburban, a ladder-frame vehicle, as well. I imagine many light trucks have something in the manual these days about the front area of whatever you are towing so the manufacturer has their butt covered if some owner tears up his transmission pulling a huge TT or work trailer (like I do.)

 

[JDgreen227]

That is true of my 05 Suburban, a ladder-frame vehicle, as well. I imagine many light trucks have something in the manual these days about the front area of whatever you are towing so the manufacturer has their butt covered if some owner tears up his transmission pulling a huge TT or work trailer (like I do.)[/QUOT

I had a towing guide published by Ford for the 1990 year and it noted frontal area limitations for all vehcles towing trailers. My F-150 was limited to something like 60 square feet which was the frontal area of a large travel trailer.

 

[Diamondpilot]

Big thing I usually see is the rear axle rating. Its pretty east to exceed it with just passengers and bags not to mention a trailer.

Chris

 

[triptester]

Newer vehicles are designed for increased fuel economy. Axle ratios used to be 3.50-3.75 to 1. Now to improve gas mileage the ratios are running at 2.50 to 1 or less in overdrive.

 

[radioman]

Big thing I usually see is the rear axle rating. Its pretty east to exceed it with just passengers and bags not to mention a trailer.

Chris

Good point.

On unibody construction the 1/4" or thicker hitch material attaches to and is supported by only 14 guage sheet metal.

Another good point.

I guess that what OP is saying -- nothing is like in past, and we TBN'rs are one of safest drivers I would say towing stuff since we are aware of weights/ limitation/etc.
If weight limitation is exceeded, then what? who to blame and who picks up the tab of cost from so called damage?

Can anybody provide real documented facts on unibody towing and effects on the said vehicle?

 

[ultrarunner]

BMW does not permit BMW North America to sell factory hitches for passenger cars.

BMW in Europe sells a full line of factory hitches.

So the same BMW wagon in Europe is seen going down the Autobahn towing travel trailers and small horse trailers can't tow anything per BMW North America.

Some of the guys buy the hitches in Europe and they just bolt on...

This is one concrete example...

There was a time when you would see Buicks, Cadillacs and Station Wagons towing horse trailers... not uncommon at all in the 1960's...

 

[JDgreen227]

I purchased a 1985 LTD Crown Victoria with the factory towing package and drove it until 1996 and stored it away in my barn. It had the 302 (5 liter) V8 and was rated to tow 5,000 pounds with the proper WD hitch, although it weighed only about 3,800 pounds with a driver and full tank of fuel. My '04 Lesabre weighs about the same, develops greater horsepower, yet has a measly 1,000 pound tow rating. The ultimate American tow car in recent years would be the body-on-frame 1994-1996 Cadillac Fleetwood, with the Corvette-derived 260 hp. LT-1 engine and the available factory towing package it was rated for a full 7,000 pound trailering capacity.

 

[Diamondpilot]

Cars used to tow those weights all the time but they also did not travel at the speeds we do now days and were sitting on a full frame. New cars are about the same weight but use many weight saving techniques to allow for all the goodies to be put in like power seats, gps, ac, power windows, ect. Look at a new car and they hold less coolant, tranny fluid, oil, ect. This lessens the heat dissipation.

Chris