Two terms decide whether a truck tire can be sold or run in many US markets: SmartWay and CARB. Hankook’s e3 MAX family, particularly the AL21 and DL21, is built to meet both, and the data book also attaches a long-life casing promise to it. This guide explains what compliance means for a fleet, how the AL21 and DL21 fit into a tractor-trailer spec, how to read their load and pressure rows, and how to avoid the mistakes that make a compliant tire cost more than a non-compliant one.
Why compliance matters to fleets
California’s greenhouse gas regulation for heavy tractors and 53-foot trailers requires low-rolling-resistance tires on affected equipment. The federal SmartWay program lists tires that meet a defined rolling resistance level. Fleets that haul into California, or that work with shippers that track SmartWay equipment, need tires that appear on the relevant lists. A fleet that ignores this can face fines, delivery restrictions or lost freight contracts. The details change over time, so verify the current rules and lists for your lanes rather than relying on a data book.
For the physics behind the requirement, see our explanation of low rolling resistance truck tires, and for total cost framing see truck tire total cost of ownership.
The e3 MAX AL21 and DL21 in the data book
Hankook’s data book lists the AL21 and DL21 as e3 MAX products with SmartWay and CARB references. In Hankook’s naming, AL denotes an all-position pattern and DL a drive pattern, so a fleet can run AL21 on steer and trailer positions and DL21 on drive axles. Confirm the position suitability of each size on the specification sheet before ordering.
The data book also gives these tires its strongest casing statement: AL21, AL11, DL11 and DL21 are listed as unlimited retreads within seven years. That is a casing-policy statement, and it deserves a careful reading, which we cover in what unlimited retreads actually means.
Reading the load and pressure rows
The data book rows show load by load range and pressure. These examples are typical:
| Size | Ply rating | Cold pressure | Max load single | Max load dual |
|---|---|---|---|---|
| 11R22.5 | 14PR | 105 psi | 6,175 lb | 5,840 lb |
| 11R22.5 | 16PR | 120 psi | 6,610 lb | 6,005 lb |
| 295/75R22.5 | 14PR | 110 psi | 6,175 lb | 5,675 lb |
Three lessons come from these rows.
- A higher ply rating raises capacity, but it needs higher pressure.** The 16PR 11R22.5 carries 435 lb more per tire on a single fitment than the 14PR, but only at 120 psi instead of 105 psi.
- Dual capacity is lower than single capacity. The difference exists because duals share the load unevenly. This is explained in [[8625|dual tire pressure matching and diameter differences.
- Pressure should follow your axle load.** Running 120 psi on a lightly loaded axle makes the tire stiff and can cause uneven wear. Use the method in [[6429|our pressure chart guide.
For more on how Hankook presents these tables, see Hankook TBR load and inflation table explained and our overview of the Hankook truck tire pressure chart.
What a compliant tire does not do
Compliance is a minimum, not a guarantee of savings. Four limits are worth knowing.
- It does not fix pressure problems.** A SmartWay tire at 20 psi below target is a high-resistance tire. See [[8622|underinflation damage in truck tires.
- It does not fix alignment.** Misalignment drags tires sideways and erases any benefit.
- It does not guarantee mileage. Low rolling resistance compounds may wear faster in scrubby applications. Compare actual wear.
- It does not make every size verified. Verification applies to specific models and sizes.
Matching positions
A practical specification for a long-haul tractor-trailer looks like this:
- Steer: an all-position or steer-specific e3 MAX model in the correct size and load range.
- Drive: the drive pattern in the same technology family.
- Trailer: a low rolling resistance trailer or all-position tire.
Keeping the whole vehicle in a verified family makes compliance reporting simpler and avoids a mixed-resistance combination where one axle drags the others. It also lets you stock fewer sizes.
Checking cost, not just compliance
Run the numbers on cost per kilometer. Take purchase price, expected mileage, the number of retreads the casing will accept and the resale or credit value of the casing. A tire that is slightly more expensive but takes more retreads can win on total cost. Our guide to [[6480|hot retreading for truck fleets describes the process, and the data book’s casing program is covered in Hankook warranty and claim basics.
An illustrative calculation: if a new tire costs 100 units and a retread costs 40, a casing that takes two retreads gives three lives for 180 units, which is 60 per life. A casing that takes none gives one life for 100. The saving depends entirely on casing quality, which depends on pressure discipline.
Pressure routine for compliant tires
- Check cold pressure weekly with a calibrated gauge. Follow the weekly tire pressure routine.
- Record pressure by position, not just by truck.
- Replace valve caps and cores that leak.
- Check duals for equal pressure and similar diameter.
- Investigate any tire that loses more than a few psi in a month.
A compliance workflow for the fleet office
Compliance fails most often at the administrative level, not on the road. A simple workflow keeps it under control:
- Keep a register of every tractor and trailer, with the tire model and size fitted on each axle.
- Mark which units operate in regulated areas, because only those need the strictest control.
- Check the official list each quarter and flag any model that has been removed or revised.
- Brief the workshop and the purchasing team so that replacement tires are chosen from the approved list, not from whatever is in stock.
- Keep purchase invoices and tire markings, since an inspector or customer may ask for proof.
When a driver has a flat on the road, the replacement is often whatever the roadside service has. Agree a policy: a non-compliant emergency tire is replaced with an approved one at the next workshop visit, and the exception is recorded.
Trial design for AL21 and DL21
If you are moving from another brand, avoid a fleet-wide switch. Fit the AL21 and DL21 on a group of trucks on one lane and keep a control group. Record starting tread depth, cold pressure every week and fuel use per 100 km. After three to six months, compare wear rate per 10,000 km, removal reasons and fuel use. If you can, also ask your retreader to inspect the first casings that come off, since casing acceptance is where the long-life promise is proven.
Costs people forget
- The time spent checking lists and keeping registers.
- Stock duplication when a fleet holds both compliant and non-compliant sizes.
- Casings rejected because of low-pressure running, which turn a retread cycle into a scrap cost.
- Downtime caused by mixed pairs that were removed early.
Count these in your total cost comparison, not just the purchase price.
Frequently asked questions
Is the Hankook AL21 SmartWay and CARB compliant?
The data book lists the e3 MAX AL21 with SmartWay and CARB references. Always confirm the exact size on the current official list before specifying it.
What does unlimited retreads within seven years mean?
It is a casing program statement for specific models. Read the terms, since conditions apply to maintenance, damage and age. See our dedicated article on the subject.
Which pressure should I run on 11R22.5 14PR?
105 psi is the cold pressure for maximum load in the data book. If your axle load is lower, use a lower pressure from the load table.
Can I use AL21 on drive axles?
The AL pattern is designed as all-position, but the DL21 is the drive-specific pattern. Choose based on traction needs and the data book’s position guidance.
Do compliant tires wear faster?
Not necessarily, but low rolling resistance compounds can behave differently in severe service. Measure wear in a trial.
Conclusion
Compliance with SmartWay and CARB is a requirement for many fleets, and Hankook’s e3 MAX AL21 and DL21 give a documented way to meet it. Treat the data book as a starting point, verify the exact sizes on the official lists, set pressure by axle load and track cost per kilometer. Then compliance becomes a saving rather than only a cost.
