At the grocery store the other day, my cart suddenly broke into what I can only describe as the grocery store version of a motorcycle death wobble—wheels shaking, screeching, veering like a lemming in sight of a cliff. It caused, and this might be a slight exaggeration, a huge scene. At one point, I abandoned the cart entirely and carried all 57 items to checkout in my arms like a deranged contestant on “Supermarket Sweep.” As I walked away (dignity in shreds), I kicked one of the offending wheels (do not recommend, I was wearing sandals) and spotted a small U-shaped bar around it.
If that little bar was supposed to help the cart steer straight, it was doing a terrible job.
“That’s called chattering when the wheels do that, and it really can be alarming,” says Brett Nelson, CEO of The Peggs Company, a U.S. company that does all things shopping carts. (Who knew that actually had a name?!) “And no, that bar on the back wheel had nothing to do with your steering issues. It has a different purpose entirely.”
So what is that mysterious bar on the wheel of your shopping cart? You’ll usually find it near the base of a rear wheel—angled, curved or slanted—and it’s not just a random piece of cart bling. It’s a real, functional feature that’s been quietly showing up on more and more carts across the country. And what is it for? I knew exactly who to ask.
Turns out Nelson isn’t just a cart expert—he’s a third-generation shopping cart guy who quite literally grew up in the business. He started working in the family factory at age 4, picking up stray nuts and bolts off the floor (which is kind of a genius way to tire out a preschooler). From there, he graduated to building carts, repairing them at stores, working in sales and eventually leading the company. So if it rolls and holds groceries, Nelson knows exactly how and why it works—and probably has a strong opinion about the wheel material too. Read on for the truth behind the shopping cart bar, straight from the person who makes them. Let’s roll.
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What is the purpose of those little bars on shopping cart wheels?
In short: They are there to stop the cart from going where it shouldn’t.
Not every bar serves exactly the same purpose, but many of them are part of an anti-theft or anti-tilt system. According to Nelson, “There are two main types of anti-theft systems: a perimeter system and a push-out theft prevention system.” These devices are increasingly mandated by city ordinances in high-theft or urban areas to keep carts from being stolen or abandoned on sidewalks, under bridges or in someone’s backyard repurposed as a mobile greenhouse. (Yes, that happens.)
To keep the carts at the store
“The rigid bars on the back wheel are called ‘anti-tilt bars,'” Nelson says. “They are designed to stop people from popping a wheelie to override the anti-theft lock.” (More on those high-tech systems in a minute.) This tech keeps people from accidentally or intentionally taking the carts off the property.
To prevent cart surfing
Tilting the cart back is how you start “cart surfing”—that thing where you push the cart full speed and then leap onto the bottom rack like you’re starring in The Fast and the Furious: Grocery Drift—and the anti-tilt part stops that trick. The bar is basically a buzzkill on wheels.
To stop the cart from rolling into cars
There’s also a friction wheel mechanism, designed to add resistance when the cart is rolling downhill so it doesn’t go rogue and ding someone’s car. “A runaway shopping cart is a major cause of vehicle damage in parking lots,” Nelson says.
Downside? Those friction wheels make the cart feel like it’s dragging an invisible toddler. Upside? No car gets totaled by your Costco mega tub of vanilla yogurt.
Are they high-tech devices?
The anti-tilt bar itself isn’t high-tech, but the anti-theft systems used to deter shopping cart crimes can be. The high-tech models typically involve a sensor embedded in the front wheel, and they’re smart enough to know if you’re trying to sneak off the premises.
“Perimeter systems use radio frequencies to create an invisible boundary around the store,” Nelson explains. “The front left wheel is a ‘smart’ wheel containing a sensor that causes the wheel to lock if it crosses the perimeter. The anti-tilt bar then prevents you from tilting the cart to lift the locked wheel off the ground and over the perimeter.”
In newer push-out theft-prevention systems, carts can actually detect whether you’ve gone through a checkout lane. If you haven’t, and you try to leave the store, the wheels will lock with the fury of a nightclub bouncer in a college town. These are primarily used to prevent people from shoplifting by simply running out with a cart full of items, Nelson says.
How long have they been around?
Shopping carts have been around since 1937, but the anti-tilt bar was not patented until 2005. Nelson says the earliest forms of theft prevention on carts go back decades, but specific designs really started gaining popularity in the late 1990s and early 2000s, as theft rates increased, especially in dense urban areas.
“The systems can be really expensive,” says Nelson. “They add $60 to $100 per cart, not counting the cost of the system itself or maintenance.” That’s a significant investment for grocery stores that already operate on razor-thin profit margins. But they are more than worth it for many stores.
Where will you mostly see these?
If your go-to store is a Whole Foods in a busy downtown, you’ve probably encountered a bar or two. If you’re shopping at a Kohl’s in rural Iowa? Probably not.
“These systems are most common in busy cities, areas with high theft or homelessness, high levels of organized crime or at high-end retailers, like Erewhon [the famously overpriced organic grocery store in Los Angeles],” Nelson says. The idea is to stop both casual cart bandits and organized retail theft rings (yes, that’s a real thing) from wheeling away with hundreds of dollars in merchandise—or the cart itself.
And yes, cart theft is a big deal. Approximately 2 million shopping carts are stolen or go missing from retailers each year. This translates to about $175 million lost annually in the U.S. alone, according to the Food Industry Network. And those losses can translate into increased prices for you at the checkout. So that little bar is protecting the store and you, the customer.
Why do shopping cart wheels wobble?
Anyone who has ever had a grocery cart experience like mine—and that’s 100% of shoppers, right?—knows the feeling of being sabotaged by obstinate cart wheels. And it’s natural to wonder if that back bar is adding to the wheel dysfunction. But the truth is that if your cart’s pulling to one side or making that unmistakable “chattering,” you shouldn’t blame the bar or the wheel hardware. “Far more often than not, it usually means the frame is damaged,” Nelson clarifies.
Interestingly, the material of the wheels matters too, he says. Most are made from polyurethane, but some are rubber, which performs better in high-traffic or heavy-load environments (like Costco). Plastic wheels are cheaper but can generate static electricity, which is how you end up shocking yourself in the cereal aisle. “Those carts have to be grounded,” Nelson says. Who knew shopping required electrical engineering?
And all this can be more high-stakes than you think. Not only are the carts expensive for the store, but they’re also walking advertisements. “A bad cart can ruin the shopping experience and make customers not want to return to your store,” Nelson says. “Stores put a lot of effort into buying, maintaining and keeping their shopping carts.”
So the next time you find yourself swearing at a cart that locks up in the parking lot, just remember—it’s not personal. It’s part public policy, part safety and part not wanting you to drag your frozen chicken nuggets home like a medieval peasant with a chattering wheelbarrow.
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At Reader’s Digest, we’re committed to producing high-quality content by writers with expertise and experience in their field in consultation with relevant, qualified experts. We rely on reputable primary sources, including government and professional organizations and academic institutions as well as our writers’ personal experiences where appropriate. For this piece on grocery store cart design and theft prevention, Charlotte Hilton Andersen tapped her experience as a longtime journalist who specializes in common curiosities, etiquette and communication for Reader’s Digest. We verify all facts and data, back them with credible sourcing and revisit them over time to ensure they remain accurate and up to date. Read more about our team, our contributors and our editorial policies.
Sources:
- Brett Nelson, CEO of The Peggs Company; phone interview, Aug. 19, 2025
- Food Industry Network: “Grocers taking steps to combat shopping cart theft”
- US Patent US7225903B2: “Shopping cart tilt and tip prevention device”
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