Use the Traction Torque formula in the "Useful Formulae" sidebar to calculate traction torque at your axle weight at both the existing tire radius and the radius you project. Subtract the lesser from the larger and the difference is the added torque load your axle will see when wearing the bigger tire. Remember, radius is half diameter. Here are some common tire swaps pre-calculated for you.
| Tire Diameter (in.) | Percent Increase inAxle Torque |
| 28-31 | 10.6 |
| 28-33 | 17.8 |
| 28-35 | 25.0 |
| 28-37 | 32.1 |
| 31-33 | 6.5 |
| 31-35 | 12.9 |
| 31-37 | 19.4 |
| 31-38 | 22.6 |
| 35-38 | 8.5 |
| 35-40 | 14.3 |
| 35-44 | 25.7 |
Axle Torque- Aka output torque. The amount of torque delivered to the axleshaft; engine torque multiplied by the transmission gear ratio, transfer-case gear ratio and ring-and-pinion ratio.
Driveline Torque- The amount of torque delivered to the axle at the pinion, which is engine torque multiplied by the transmission gear ratio and transfer-case ratio.
Grip- Weight on the tire plus the coefficient of friction of the ground surface and the added effects of the tread design equals grip. The ground surface is infinitely variable. Weight is variable according to how much stuff you load for a particular trip and according to weight transfer from acceleration or uneven terrain.
Spline Diameter- The axle diameter over the splines. The commonly touted axle-size number, but the least accurate in terms of strength.
Tensile Strength- The point just before metal breaks.
Torque Multiplication- Gearing multiplies torque (but not horsepower). If the engine makes 250 lb-ft, then a 4:1 tranny First gear multiplies it four times to 1,000 lb-ft. That 1,000 lb-ft enters the transfer case and when in low range, it's multiplied by the low-range ratio, and again by the axle ratio.
Traction- Engine torque turned into vehicle motion. Essentially, it's tire grip plus torque.
Yield Strength- The point at which the material permanently deforms. This is the most important steel property, because when it reaches this point, it's lost most of its strength, even if it hasn't broken yet.
(Typical specs shown, actual may vary)
| SAE Classification | Yield Strength (psi) | Tensile Strength (psi) | Note |
| 1040 | 106,000 | 120,000 | 1 |
| 1050 | 146,000 | 162,000 | 2 |
| 1541H | 164,000 | 181,000 | 3 |
| 4340 | 210,000 | 228,000 | 4 |
| 300M | - | 270,000 | 5 |
Notes
1. Induction-hardened carbon steel, the industry standard for most of the OEM.2. A higher grade of carbon steel sometimes used by the OEM and the better manufacturers of aftermarket OEM replacements. About 38 percent stronger than most 1040 grades.
3. A high silicon, manganese steel alloy. Approximately 55 percent stronger than 1040.
4. Chrome-moly steel alloy. Excellent strength and resistance to fatigue. Almost 100 percent stronger than 1040
5. Sometimes known as 4340M, it's an aircraft grade of 4340. It has outstanding fatigue resistance. At least 150 percent stronger than 1040, but very expensive and hard to get.