No person shall operate or move on a paved highway any motor vehicle, trailer, or semitrailer having any metal tire or metal track in contact with the roadway.
1. Every solid rubber tire on a vehicle shall have rubber on its entire traction surface at least one inch thick above the edge of the flange of the entire periphery. Any pneumatic tire on a vehicle shall be considered unsafe if it has:
- Any part of the ply or cord exposed.
- Any bump, bulge or separation.
- A tread design depth of less than one-sixteenth of an inch measured in any two or more adjacent tread grooves, exclusive of tie bars or, for those tires with tread wear indicators, worn to the level of the tread wear indicators in any two tread grooves.
- A marking “not for highway use”, “for racing purposes only”, “unsafe for highway use”.
- Tread or sidewall cracks, cuts or snags deep enough to expose the body cord.
- Such other conditions as may be reasonably demonstrated to render it unsafe.
- Been regrooved or recut below the original tread design depth, excepting special tires which have extra under tread rubber and are identified as such, or if a pneumatic tire was originally designed without grooves or tread.
2. A vehicle, except an implement of husbandry, equipped with either solid rubber or pneumatic tires shall not be operated where the weight per inch of tire width is greater than five hundred seventy-five pounds per inch of tire width based on the tire width rating, except on a steering axle, in which case six hundred pounds per inch of tire width is permitted based on the tire width rating.
No tire on a vehicle moved on a highway shall have on its periphery any block, stud, flange, cleat, or spike or any other protuberances of any material other than rubber which projects beyond the tread of the traction surface of the tire except that it shall be permissible to use:
- Farm machinery with tires having protuberances which will not injure the highway.
- Tire chains of reasonable proportions upon any vehicle when required for safety because of snow, ice, or other conditions tending to cause a vehicle to skid.
- Pneumatic tires with inserted ice grips or tire studs projecting not more than 1/16 (one-sixteenth) inch beyond the tread of the traction surface of the tire upon any vehicle from November 1 of each year to April 1 of the following year, except that a school bus and fire department emergency apparatus may use such tires at any time.
Tables to §393.108 [Working load limits (WLL), chains and synthetic webbing] The following Chart has been supplied as a courtesy. For a full listing of approved devices and application of working load limits please refer to 49CFR 393.106 through 393.108
WLL IN POUNDS
| SIZE IN INCHES | GRADE 30 Proof Coil | Grade 43 high test | Grade 70 transport | Grade 80 alloy | Grade 100 alloy |
| 1/4 | 1,300 | 2,600 | 3,150 | 3,500 | 4,300 |
| 5/16 | 1,900 | 3,900 | 4,700 | 4,500 | 5,700 |
| 3/8 | 2,650 | 5,400 | 6,600 | 7,100 | 8,800 |
| 7/16 | 3,700 | 7,200 | 8,750 | ||
| 1/2 | 4,500 | 9,200 | 11,300 | 12,000 | 15,00 |
| 5/8 | 6,900 | 13,000 | 15,80 | 18,100 | 22,600 |
| CHAIN MARK EXAMPLES | Chains that have no markings or markings no longer discernible will be considered Grade 30 proof coil |
| Example 1 | 3 | 4 | 7 | 8 | 10 |
| Example 2 | 30 | 41 | 70 | 80 | 100 |
| Example 3 | 300 | 430 | 700 | 800 | 1000 |
Synthetic Webbing
| Width in inches | WLL in pounds |
| 1 3/4 | 1,1750 |
| 2 | 2000 |
| 3 | 3000 |
| 4 | 4000 |
Source: https://www.iowadot.gov/mvd/motorcarriers/truckguide.pdf
