Thor Forums

[gte534j]

Originally Posted by DavidEM

Vehicle GVWRs, GCWRs, and tow weight limits are made up of a lot of things: capability of the frame and suspension, tire weight carrying capacity, hitch strength, engine and transmission wear, brake capability, etc.

Is it an absolute drop dead limit? No of course not. 99.999% of the time going over even 100 lbs won't cause any harm. But you will be stressing the components a percent more than they were designed for.

Some components like the steel frame can be designed somewhat precisely and does have a safety factor built in, probably 100% to count for dynamic loads (bouncing and braking) and another 50% or so safety factor before the metal stretches permanently. Other things are somewhat subjective like brake wear and stopping performance. Engine wear is another very subjective criteria. How long does the manufacturer expect the engine to last running at full GCWR 100% of the time.

In regard to engine wear, it is interesting that the new E350 chassis has a 4.10:1 rear end ratio and the heavier F53 chassis has a 4.56:1 ratio. The numerically higher ratio lets the engine work at lower stresses or looked at another way, it lets the engine pull a heavier load while working the engine the same.

The one vehicle rating that I totally pay attention to is tow ratings. I have found when I pull something at 100% of the maximum rating, I am uncomfortable. I like to stay at 75%.

David

agree with you on the tow rating- both horizontal and vertial rating. Thats why i measure my tongue weight load when towing and check the trailer+vehicle weight.