Arm Restraint Myths on a 2 Post Car Lift: What EV Shops Get Wrong

An EV specialty shop in Dubuque called us this spring about their 2 post car lift arm restraints because they’d heard three different things from three different sales reps and wanted a straight answer. They were doing a lot of alignment work on EVs — heavier curb weights, low ground clearance, battery packs that make pad placement a real puzzle — and every time an arm rotated a quarter turn under load, someone re-lined the alignment rack. Half the myths they’d been told about arm restraints were wrong. Here’s what we told them, because the same myths circulate at almost every shop we visit, EV or otherwise.

Myth One: Arm Restraints Are There to Hold Weight

The most common myth we hear about a 2 post car lift arm restraint is that it holds the weight of the vehicle. It doesn’t. The vehicle’s weight is held by the arm’s mechanical connection at the column, and by the safety pawl engaged in a locking ladder. The arm restraint holds the arm’s rotational position, so it can’t swing horizontally under the vehicle while it’s lifted. Those are two completely different jobs.

Once you understand that, a lot of downstream shop practices start to make sense. Alignment technicians who complain about arms drifting mid-lift are looking at a restraint problem, not a capacity problem. Techs who assume the restraint failing means the car falls have it backwards — the restraint failing means the pad moves sideways, which unloads the pad point on the vehicle’s pinch weld and can eventually let the vehicle slide off the pad if the tech isn’t paying attention. Nasty, but not a free-fall scenario. Different failure mode, different mitigation.

Myth Two: Gear-Type Restraints Are Better Than Pin-Type

Sales reps love to sell gear-type arm restraints on a 2 post car lift by calling them the premium option. Gear-type restraints use a set of teeth on the arm base and a spring-loaded pawl that drops into the teeth when the arm is loaded. Pin-type restraints use a bolt or a pin that drops into a hole. Both are ANSI-compliant when properly designed, and both hold in real-world load conditions. The pin type is arguably more positive because the engagement is either fully seated or clearly not — there’s no partial engagement.

What matters more than gear versus pin is the wear condition of whichever mechanism you have. A gear-type restraint with worn teeth is worse than a fresh pin-type. A pin-type with a bent pin is worse than a fresh gear. The Dubuque EV shop had gear-type restraints that had been chewed down by three years of hard cycling, and no one had inspected the teeth in the daily walkaround. That was the actual problem, not the mechanism type. We replaced the arm-restraint assemblies with the same gear-type from the same manufacturer, and the drift stopped.

Myth Three: The Safety Cam Engages Automatically When You Lower

The safety cam — the mechanical pawl that catches the lift at every locking position — is separate from the arm restraint, and no, it does not always engage automatically as you lower a 2 post car lift. On most machines the cam is spring-biased to engage, meaning it drops into position whenever a lock ladder tooth passes by. But if the ladder is worn, if the spring is fatigued, or if debris is caught in the mechanism, the cam can skate past a tooth without engaging. That’s a myth that’s cost shops real injuries.

The right practice is: raise, lower onto locks with an audible engagement, and visually verify both columns are seated before anyone goes under. Don’t assume. Any 2 post car lift older than five years should have its safety cam mechanism inspected annually, and the springs replaced at the manufacturer’s interval. For EV work where the vehicles are heavier and the lift cycles more often, we tell shops to check the cam engagement every single lift — takes three seconds and prevents a lot of downstream problems.

Myth Four: EV Weight Makes Restraint Failure More Likely

The Dubuque shop’s crew thought EV curb weights were causing their restraint problems. Actually, no. A 5,200 lb EV sedan puts about the same load per arm as a 5,000 lb SUV, and both are well inside the 10,000 lb rating of a properly-specced machine. The arm restraint isn’t seeing more load in an EV scenario; the vehicle is on it longer during alignment work, and each rotational disturbance during a wheel-off task compounds if the restraint is already worn.

The mitigation isn’t a beefier lift — it’s a shorter service interval and cleaner pad placement. We showed the Dubuque techs the manufacturer’s recommended weekly restraint inspection and got them into a shop routine of checking pin or tooth wear at the start of every shift. That’s not a marketing recommendation — that’s the actual ALI-referenced maintenance schedule. Most shops skip it because nobody hands it to them. If you want us to send you the checklist for your specific machine, we can pull it from the manual and email it.

Myth Five: Aftermarket Restraint Pins Are Interchangeable

They usually aren’t. Aftermarket pins for a 2 post car lift are dimensioned to the same rough spec but the heat-treat and the exact diameter tolerance vary. A pin that’s a few thousandths undersize on the wear surface will start rocking in the socket within weeks. A pin that’s a few thousandths oversize won’t seat all the way, giving you the false impression of engagement while actually leaving the arm partially free.

We tell shops to buy restraint pins from the original manufacturer’s parts channel, or from the ALI-sanctioned parts distributors that hold the OE specs. That’s more expensive per pin than the generic aftermarket, but it’s the only way to be sure the geometry is right. We stock the mainstream brand pins on our shelf and can source anything else within a week — no ocean-freight import waits. That was actually one of the Dubuque shop’s original complaints, that they’d been ordering generic pins because their previous dealer didn’t stock OE. Solved with one supplier change.

What a Correct Daily Restraint Check Looks Like

The daily restraint check on a 2 post car lift takes under a minute and it’s the single highest-return maintenance action you can do. Start with the arm at rest, rotate it through its full sweep, and confirm the restraint engages positively at every stop. Listen for the audible click on a gear type, watch the pin drop cleanly on a pin type. If either sounds mushy, spongy, or delayed, stop using the arm until it’s inspected.

Then load-test by putting a vehicle on the pads at low lift height and giving each arm a firm attempt at rotation. It should not budge. If it moves at all, the restraint is compromised. Neither test costs money, both take under a minute, and either one would have caught the Dubuque shop’s problem eighteen months before it started chewing up alignments. Post the checklist in the bay if you have to. The habit is worth more than the checklist itself, because habits stick and clipboards don’t.

What the Dubuque EV Shop Ended Up Doing

The Dubuque EV shop replaced both arm-restraint assemblies on their 2 post car lift, moved to OE-sourced pins for their pin-type auxiliary restraints on a second machine, and adopted the pre-shift check we walked them through. Alignment drift on lifted vehicles dropped to essentially zero within a week. Total parts cost was well under a full new lift’s price. Total downtime was one Saturday.

If you’re running an EV shop or any high-volume alignment operation and you’ve been chasing arm drift or restraint noise, we can walk your bay and diagnose the actual failure mode instead of guessing. Call 800-674-9302 or email founder@autoliftserv.com. We stock the OE restraint parts for every major brand and we’re an installer, not a reseller — the diagnosis and the fix come from the same team.