On a dually, reach the inner wheel’s valve stem through the hand hole in the outer wheel using a long-reach chuck or an extension, then fill the tire to the cold pressure on your vehicle’s Tire and Loading Information placard, usually on the driver’s door jamb.
Step-by-Step Inflation Process
- Identify the access hole in the wheel where the inward facing tire stem is visible.
- Remove the valve cap: Reach through the outer wheel’s hole to unscrew the inner valve stem cap. If your fingers do not fit, use needle-nose pliers.
- Attach the air chuck: Push or pull the correct angled end of your dual-head air chuck straight onto the inner valve stem until it latches securely.
- Inflate the tire: Connect the air compressor hose, fill the inner tire to the recommended PSI level, and check the reading with your gauge.
- Replace the cap: Remove the chuck carefully and screw the valve cap back on tightly to prevent slow leaks.
Why is the inner dually valve stem so hard to reach?
The inner valve stem sits behind the outer wheel, so you can only get to it through a hand hole. A dually, or dual rear wheel (DRW) vehicle, has two wheels on each side of the rear axle. The inner dual is the one closer to the vehicle. A hand hole is an opening in the outer wheel that gives access to the inner valve stem.
On many setups the inner stem sits deep and at an angle, so a straight chuck on a short inflator hose often can’t reach it or press on squarely.
What tools reach an inner dually valve stem?
You have three practical options: a longer chuck, an extension between the chuck and the stem, or an extender fitted permanently to the stem.
| Option | What it is | Trade-off |
|---|---|---|
| Dual-foot or long-reach chuck | A chuck with an angled head, or two heads facing opposite ways, on a long body | Many are built for shop air, so check the flow type before using one with a portable inflator |
| Swiveling extension | A short extension that fits between your chuck and the stem and angles through the hand hole | One more connection to seat; lets you keep your existing inflator |
| Valve-stem extender | A hose or rigid extension installed on the inner stem that brings the valve out to the hand hole | Adds a sealed joint that can leak; have a tire shop install or inspect it |
If you use a portable inflator, match the flow type. An open-flow chuck is the one portable inflators generally work with, as explained in our open-flow vs closed-flow guide.
How do you air up an inner dually tire, step by step?
Work cold, reach through the hand hole, and add air in short bursts:
- Check before driving, while the tires are cold. Placard pressure is a cold-tire spec.
- Find the rear pressure on the Tire and Loading Information placard, usually on the driver’s door jamb. For an RV, also check the chassis and tire manufacturer’s guidance and load tables for your actual weight.
- If the inner stem isn’t lined up with a hand hole, move the vehicle a short distance until it is.
- Remove the valve cap carefully so it doesn’t drop between the duals.
- Seat the chuck or extension squarely on the stem. A steady hiss means it isn’t fully on.
- Measure with a gauge, add air in short bursts, and measure again.
- Replace the cap, then repeat on the outer tire.
Should inner and outer dually tires have the same pressure?
In most cases, yes: the placard normally lists one rear pressure for both tires in the pair. Follow the placard, or the tire manufacturer’s load and inflation tables if you run different tires or carry heavy loads. Don’t carry over passenger-car rules of thumb to a DRW truck or motorhome.
The same goes for duallys and RVs. Those vehicles depend on load tables, and passenger-car rules of thumb don’t carry over. Our dually guide covers inner-tire access.
Can a portable inflator handle dually tires?
It can if its maximum output is higher than your placard pressure and its hose reaches, or reaches with an extension. Duallys and RVs often run higher pressures than passenger cars, so compare your inflator’s published maximum with the number on your placard before you rely on it.
For our part, SKOG makes the Reach360, a 7-inch extension for Chuck Mates® that the SKOG FAQ recommends for “blind” valve stems on duallies, and the Flex360, a 7-inch flexible open-flow extension for tight spaces. Both are on the Platinum Series page.