A four-post lift is the easiest lift to live with — drive on, lock, and you're up. But there's one thing a four-post can't do on its own: get the wheels off the runways. And plenty of the jobs you actually want a lift for — brakes, tires, rotors, suspension — need the wheels hanging free. That's exactly the gap a rolling jack fills. This guide explains how they work, how to size one correctly, and what to look for before you buy.
What is a rolling jack?
A rolling jack — also called a rolling bridge jack, sliding jack, or jacking beam — is a hydraulic or air/hydraulic jack that rides across the two runways of a four-post lift. It rolls along the length of the lift, positions under the vehicle's frame or lift points, and raises the vehicle off the runways so the wheels drop free.
Think of it as the accessory that converts a drive-on parking-and-storage lift into a genuine service lift. Without one, a four-post is great for oil changes, inspections, and storage. With one, it does most of what a two-post does — while keeping the drive-on convenience and stability that made you want a four-post in the first place. (New to the four-post vs. two-post question? Start with our guide on 2-post vs. 4-post car lifts.)
How wheels-free service works
The sequence is simple, which is the appeal:
- Drive the vehicle onto the four-post runways and set the lift's safety locks.
- Roll the jack along the runways until its lift pads line up with the vehicle's frame or manufacturer lift points.
- Raise the jack. The vehicle lifts off the runways and the wheels hang free.
- Do your work — rotate tires, pull wheels, service brakes and suspension.
Most rolling jacks have their own safety locks independent of the lift, so the vehicle is supported on two locked systems at once. On many setups the jack runs off shop air to power the hydraulics (an air/hydraulic design), so factor a compressor into your plan; other models are purely hydraulic.
Matching capacity — the number that matters most
This is the part people get wrong, so read it twice. A rolling jack has its own weight rating, separate from the lift's rating, and you have to size it to the load it will lift — not to the lift's total capacity.
- A rolling jack typically only needs to lift one end of the vehicle at a time (front or rear), so its rating is sized to a portion of the vehicle weight — but you should still size up, not down, and confirm the jack covers the heaviest vehicles you'll service.
- The jack's rating must never exceed the runway/lift's capacity, and its width has to match your lift's runway spacing. Rolling jacks are not universal — a jack has to fit the specific runway width of your lift.
If you're unsure how vehicle weight maps to equipment ratings, our car lift capacity guide explains how to size to your vehicles rather than guessing.
Single vs. dual rolling jacks
- A single rolling jack lifts one axle at a time. It's the most common choice for home garages and lighter shop use — affordable, flexible, and enough for tire rotations and brake jobs.
- A pair of rolling jacks lets you lift the front and rear independently, or get all four wheels free by raising both ends. Busy shops that want true full-service capability on a four-post often run two.
Start with one if you're a home user; plan for two if throughput matters.
What to look for before you buy
- Runway-width compatibility. Confirm the jack is rated to fit your lift's runway spacing. This is the #1 fit issue — check it first.
- Capacity headroom. Size the rating above the heaviest vehicle end you'll lift. Don't buy right at the limit.
- Independent safety locks. Look for a jack with its own mechanical locking positions, not just hydraulic hold.
- Air vs. pure hydraulic. Decide whether you want air/hydraulic (needs shop air, faster) or manual hydraulic (no air required).
- Reach and pad options. Adjustable saddles and frame adapters help you reach factory lift points on a range of vehicles.
- Build quality and support. A rolling jack takes abuse. Buy from a supplier who publishes real specs and stands behind the equipment.
Once it's in service, treat the jack like the rest of your lift — regular inspection and lock testing. Our guide to car lift safety and maintenance applies to jacks too.
Frequently asked questions
Do I need a rolling jack for my 4-post lift? If you only do oil changes, inspections, or vehicle storage, no. If you want to rotate tires, pull wheels, or service brakes and suspension — anything that needs the wheels off the deck — then yes, a rolling jack is what makes that possible on a four-post.
Will any rolling jack fit my lift? No. Rolling jacks are sized to a lift's runway spacing and capacity. Always confirm the jack is compatible with your specific lift's runway width before buying.
How much weight does a rolling jack need to lift? It generally lifts one end of the vehicle at a time, so it's rated to a portion of total vehicle weight — but always size the rating above the heaviest vehicle you'll service, and never above your lift's capacity.
Can I get all four wheels off the ground? Yes — either by lifting one end, repositioning, and lifting the other, or by running two rolling jacks to raise front and rear together.
Turn your 4-post into a full-service lift
Browse our Rolling Jacks and pair one with a 4-Post Car Lift for the best of both worlds: drive-on convenience and true wheels-free service. Not sure which jack fits your lift's runway width? Call us at 331-272-5655 or email support@projectfoundry.co and we'll match it for you.
