What This Air Spring Is
This is a reversible-sleeve air spring, not a convoluted bellows. The rubber sleeve rolls down over a flat piston as the axle moves, which gives a longer stroke and a softer rate than a two- or three-convolution bag. Collapsed height is 8.7 in, extended height is 27.3 in, and maximum diameter is 10-5/8 in. Assembled weight is roughly 21.8 lb.
The top mount is a 5-stud plate on an 11-5/16 in bolt pattern. The bottom is a flat piston with a 1/4 in NPT air inlet. Air feeds through the bottom on this configuration, so if your current bag plumbs through the top plate you are looking at a different build and the studs will not line up with your hanger bracket.
Typical positions are Neway/Holland AR120, AR120L, AR125 and AR125L trailer suspensions, US-style underslung auxiliary-axle systems, and some Hendrickson trailer, Ridewell, Watson and Chalin air-ride arrangements. Measure your ride height at the bag before ordering — same bag family, different setup height, different result at the axle.
Why These Numbers Cross
Air springs get catalogued by physical build, not by who sold them. Bead plate stud count and bolt circle, piston diameter and air inlet size, collapsed and extended height, and sleeve diameter are what define the part. When two numbers describe the same geometry and the same rate curve, they are the same assembly with a different label on the box.
That is why W01-358-9158 lines up with ContiTech 11 10.5-21 A 318, Goodyear 1R14-030 and 1R14-031, Hendrickson B-12514-004 and S-2063, SAF-Holland 90557005, Ridewell 1003589158C, and Triangle 8318. Suspension builders buy the bag from an air spring maker and issue their own service number for it, so one physical part ends up with eight or nine identities across parts books.
These numbers are listed for identification only. PartStop is not affiliated with, endorsed by, or authorised by any of the manufacturers named. A cross-reference is a starting point — confirm fit against the number stamped or moulded into your old bag, or by VIN and suspension tag, before you order.
How These Fail
Most failures start at the rolling lobe. Road debris, curb strikes and a dragging or misadjusted height control valve let the sleeve contact the piston edge or the hanger, and the sleeve chafes through. Once air escapes the corner sits on the bump stop, ride height drops on that side, and the axle starts to walk under braking.
Check the piston surface before fitting a new bag. Rust scale, gravel packed against the piston, or a bent piston will cut a new sleeve in short order. Inspect the height control valve linkage and the bump stops at the same time — a bag that ran collapsed usually took the stop with it. Torque the 5 studs evenly and leak-check the 1/4 in NPT fitting at operating pressure.
W01-358-9158 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to W01-358-9158. Use them to identify the part — then confirm the exact fit by VIN or the number stamped on your old unit before you order. An interchange is a starting point, not a fitment guarantee.
| Brand / Line | Cross-Reference Numbers |
|---|---|
| ContiTech | 11 10.5-21 A 318 |
| Goodyear | 1R14-030, 1R14-031 |
| Hendrickson | B-12514-004, S-2063 |
| Ridewell | 1003589158C |
| SAF-Holland | 90557005 |
| Triangle | 8318 |
Frequently asked questions
How do I confirm this is the right bag for my trailer?
Read the number moulded into the old bag or stamped on the bead plate first. Then check the mounting: 5 studs on an 11-5/16 in plate up top, flat piston with a 1/4 in NPT inlet at the bottom. Confirm your suspension model and ride height as well. Cross-reference gets you close; the old part number or VIN confirms it.
Do I have to replace air springs in pairs?
Replacing both sides of an axle is common practice. A bag that has been in service for years has a different rate and set than a new one, and mismatched corners can affect ride height and load sharing. If one failed from age rather than impact damage, the other is usually not far behind.
Is this the same as the Hendrickson S-2063 bag?
S-2063 is listed as a cross-reference to W01-358-9158, along with B-12514-004 from the same brand. Those numbers are shown for identification only and do not imply any affiliation with Hendrickson. Verify against the number on your removed air spring and your suspension tag before ordering.
Not sure it fits? We check before you pay.
Run your VIN and we’ll match parts to your exact truck, or call the counter — a person who knows trucks verifies fitment by OEM number before the order ships. No wrong-box returns.
More cross-reference guides
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