This mini-howto was inspired by the thread 7.3IDI towing limit? and covers how you can accurately estimate how fast your truck can pull a given weight, on the level or up any % grade. I have broken the material down into 4 smaller sections. Many will not have a need for this, but it may be interesting to a few perhaps. Anyone can do these calculations with basic math (Algebra/Pre-Algebra) so nothing too difficult. To calculate this for your truck you will need:
People often wonder how much weight their truck will pull, and what speed they might be able to maintain running up a grade. The good news is, these calculations are available to anyone with some dyno data, truck weight, and a little spare time. Having this information will give you a much better picture of how your truck will tow on the Interstate or even local roads, allowing you to have a much better idea of what speed and gears you will be able to pull on certain hills, for example.
There are three primary factors we need to consider when figuring out how much power a given road speed will require:
The next installment will cover wind resistance in detail. Keep in mind, these calculations will tell you how much power you will have for a given load, but does not address suspension, tires, brakes or any other limitations that you will need to address separately.
- Your dyno graph (or one from a similarly equipped truck) must be true rear wheel horsepower
- Your truck weight and/or combined truck and trailer weight
- For trailers, the width and height, to make a rough guess of frontal area
- Gear ratios for your transmission and rear end
- Road surface types you plan to encounter (concrete, asphalt, etc)
People often wonder how much weight their truck will pull, and what speed they might be able to maintain running up a grade. The good news is, these calculations are available to anyone with some dyno data, truck weight, and a little spare time. Having this information will give you a much better picture of how your truck will tow on the Interstate or even local roads, allowing you to have a much better idea of what speed and gears you will be able to pull on certain hills, for example.
There are three primary factors we need to consider when figuring out how much power a given road speed will require:
- Wind Resistance (Drag)
- Rolling Resistance (Friction)
- Grade Resistance (Inclines, hills)
The next installment will cover wind resistance in detail. Keep in mind, these calculations will tell you how much power you will have for a given load, but does not address suspension, tires, brakes or any other limitations that you will need to address separately.