A Sioux City RV Shop’s First Year With a Hydraulic Lift: Automotive Slab, Rebar, and Alignment Realities

The hardest part of a hydraulic lift automotive install for an RV and trailer shop is almost never the lift — it’s the four inches of concrete underneath it. We spent most of a spring working with a trailer and RV service business northwest of Sioux City that wanted to add alignment capability, and the first eight weeks of that project had nothing to do with steel or hydraulics. It was core samples, rebar location, and a hard conversation about what their 1990s slab could actually hold. A year later they’re aligning motorhome chassis and dual-axle trailers every week, so it worked out. But the path there is worth walking through, because we have this same conversation with shops all over western Iowa.

Why an RV Shop Wanted Alignment in the First Place

This shop had built a good business on brakes, bearings, axles, and suspension for travel trailers and Class A motorhomes. What they kept sending away was alignment. A customer would come in complaining that a 34-foot coach wandered on I-29, they’d replace worn front-end components, and then the coach had to go somewhere else to get toe and caster set. That’s revenue walking out the door, and it’s also a warranty exposure — you don’t want to hand back a chassis you know isn’t aligned.

Alignment work drives specific equipment choices. You need the suspension loaded, which means a drive-on platform rather than frame-engaging arms, and you need turnplates at the front and slip plates at the rear. You need the runways long enough and rated heavy enough for a tandem-axle chassis, and you need them dead level under load, not just level when empty. That last requirement is what makes alignment the most demanding job you can ask of a runway lift, and it’s what put us back on the concrete question. A four-post spreads its weight across four columns, which is gentler on a slab than a two-post — but an alignment rack has to hold geometry, and geometry lives or dies on whether the columns settle. We told them straight: we can install the lift on your existing floor, but we can’t guarantee alignment accuracy until we know what’s down there.

Coring the Slab: What We Found

We pulled three cores in the target bay. Two came back at right around four inches, which is the bare minimum most manufacturers specify, and the third came back at three and a quarter — the slab thinned out toward an old drain trench that had been filled and topped years earlier. Concrete strength tested acceptable, in the 3,000 PSI neighborhood, but thickness is the variable that decides whether an anchor holds. A wedge anchor develops its capacity by expanding against sound concrete along its embedment depth. If you only have three inches to work with and the anchor needs three and a quarter, you’ve got nothing.

We also mapped rebar with a scanner before drilling anything. Older Iowa shop slabs are a mixed bag — some have a proper mat of #4 bar on 18-inch centers, some have welded wire mesh that’s been pushed to the bottom of the pour and does nothing, and plenty have nothing at all beyond fiber. This shop had mesh, poorly placed. The scan mattered for a second reason: you do not want to drill through a bar with a rotary hammer while setting anchors. It stalls the bit, wallows the hole, and leaves you with an anchor that never seats properly. We shift the layout an inch or two to miss steel when we can, and when we can’t, the layout is telling us the floor needs work. Cutting and repouring a proper pad is not the expensive part of a hydraulic lift automotive project — it’s the cheap insurance that makes everything above it trustworthy.

What We Poured and Why

We cut out two footing pads under the column locations, each roughly four feet by four feet, and took them down to six inches of new 4,000 PSI concrete with a tied mat of #4 rebar and doweled connections into the existing slab. That’s more than the manufacturer minimum, and we did it on purpose. For an alignment rack carrying a motorhome chassis, we want zero settlement over the life of the equipment, and the incremental cost of going from four inches to six is small compared to re-shimming a rack every year.

Cure time is the part nobody budgets for. Anchor manufacturers want full cure before you load anchors, and that means 28 days on paper. In practice we won’t set anchors on a fresh pour under about three weeks, and we won’t load-test until the full 28. The shop lost most of a month of that bay, which stung during their busy spring, but they’d have lost far more than a month if the columns had walked. If you’re planning a new build instead of a retrofit, this is your one chance to do it easy: tell your concrete contractor where the lift is going before the pour, spec six inches with rebar in that footprint, and keep control joints away from the anchor field. We’ve had to relocate more than one lift because a control joint ran right through where a column wanted to sit, and an anchor set next to a joint is an anchor that will eventually crack out.

Picking the Lift: Capacity, Runway Length, and Turnplates

For their mix of dual-axle trailers and Class A chassis, we specced a heavy four-post alignment-ready model with extended runways. Capacity math on RV work is not intuitive. A 30,000 lb GVWR coach doesn’t put 30,000 lb evenly on four wheels, and it also doesn’t fit a standard 168-inch runway. Wheelbase drove the runway length more than weight did. We also had to check overall height with the coach on the runways against their door header — an RV shop with 16-foot doors has more room than most, but full lift height plus a 12-foot-tall body eats it fast.

Alignment-specific hardware matters as much as the base lift. Front turnplates need to be sized and rated for the axle loads you’ll see, and we always add rear slip plates for a long-wheelbase chassis so the rear axle can find its natural position instead of binding the springs. Runway-level accuracy came from a rolling jack setup plus a laser check after install. On the brand side, we stick with Rotary and Challenger for commercial work like this because the parts pipeline is real — when a cylinder or a power unit fails, we can get components fast. That’s not a small thing in Sioux City, where the alternative is waiting on a container from overseas. Our overview of choosing a four-post lift walks through the capacity and length math in more detail.

Install Week and the First Load Test

Install itself was two days. Day one was layout, drilling and setting anchors in the new footings, standing columns, and setting runways. Day two was hydraulics, cable routing, sheave alignment, bleeding air out of the system, and cycling the lift twenty-odd times empty while adjusting the slack cable and locking positions. Bleeding is where impatience shows up. Air trapped in a cylinder makes the lift rise in stutters and settle unevenly, and it feels exactly like a failing cylinder to someone who hasn’t seen it before. Cycle it, purge it, top the reservoir, cycle again.

The first real load test was a customer’s tandem trailer, then a coach the following day. We check runway level under load, verify all four locks engage simultaneously, and confirm that the lift holds height for a full shift with a load on it. If it creeps down overnight, you have either a bypassing lower valve or an internally leaking cylinder — those are the two most common failures we see on any hydraulic lift automotive system, and a creep test is how you catch them on day one instead of month six. We also walked their techs through the daily checks: look at the reservoir, look at the cable sheaves, listen to the motor, and never lift with a load off-center on the runways. We hand every install customer a laminated card with that list, because training turnover is real and the guy who was there on install day may not be there next year.

The First Service Call, Nine Months In

Nine months after install we got the call we expected — not a failure, but a question. The lift had started rising more slowly than it used to, and the motor sounded like it was working harder. Their assumption was pump failure. It almost always is. The actual cause was fluid level: the reservoir had dropped from a weeping hose fitting nobody had noticed, and a hydraulic pump pulling partly on air labors, heats up, and moves fluid slowly. We tightened the fitting, topped the reservoir with the correct fluid, bled the system, and the lift went back to full speed in under an hour.

The reason we tell this story is that most “my lift is dying” calls are cheap fixes if you catch them early. We’ve talked shop owners through getting a stuck vehicle down over the phone. We’ve rebuilt rams for four-post owners who already had the seal kit in hand and just needed someone who knew the sequence. We’ve replaced cables that snapped a week after being installed, because the worn sheave that killed the first cable was still in place. The pattern is always the same: a small ignored symptom becomes an expensive one. Slow rise, a whine from the power unit, a wet spot under a column, a frayed strand at a sheave — those are all early warnings. Call at the warning stage and it’s a service visit. Call after the failure and it’s a rebuild plus lost bay time. See also our piece on rebuilding versus replacing a lift cylinder.

What Year Two Looks Like — and How to Start Your Own Project

The shop northwest of Sioux City is now doing alignment in-house on chassis they used to send away, and the bay pays for itself. They’ve added a second, lighter drive-on for trailer brake and bearing work so the alignment rack isn’t tied up on routine jobs. Their annual maintenance is a fluid change, a full cable and sheave inspection, anchor torque check, and a lock function test — we do it on a scheduled visit and it takes a couple of hours.

If you’re an RV, trailer, truck, or general repair shop in western Iowa thinking about adding lift capacity, start with the floor. Before you shop for equipment, find out how thick your slab is and where the rebar sits. That single piece of information changes the budget, the timeline, and sometimes the lift you should buy. We’re based in Ames and we cover the whole state and beyond — we’ll come out, core the slab, scan for steel, measure your ceiling and door heights, and give you a written spec that includes any concrete work needed. Then you know the real number instead of the equipment-only number. Whether you end up with a four-post alignment rack, a heavy two-post, or a mobile column set for the big stuff, the goal is the same: equipment that holds its geometry and doesn’t strand a customer’s coach in the air. Call us at 800-674-9302 or email [email protected] and we’ll get a site visit on the calendar.