# What causes the clicking of a grocery cart wheel? **URL:** \ **Category:** Factual Questions\ **Created:** [April 12, 2014, 9:54pm UTC](https://boards.straightdope.com/t/what-causes-the-clicking-of-a-grocery-cart-wheel/685965 "2014-04-12T21:54:04Z")\ **Posts on this page:** 19\ **Page:** 1
**Author:** ![wei\_ji](https://avatars.discourse-cdn.com/v4/letter/w/e9a140/32.png) [@wei\_ji](https://boards.straightdope.com/u/wei_ji)\ **Post date:** [April 12, 2014, 9:54pm UTC](https://boards.straightdope.com/t/what-causes-the-clicking-of-a-grocery-cart-wheel/685965/1 "2014-04-12T21:54:04Z")
Just curious: What causes a cart at the grocery store to rhythmically click or thump as you push the cart around? It’s something on one of the wheels, but I can’t see what it is when I’ve made a quick examination out of curiosity. Exactly what causes it? What can the store do to correct it? ---
**Author:** ![Superhal](https://avatars.discourse-cdn.com/v4/letter/s/b4bc9f/32.png) [@Superhal](https://boards.straightdope.com/u/Superhal)\ **Post date:** [April 12, 2014, 9:54pm UTC](https://boards.straightdope.com/t/what-causes-the-clicking-of-a-grocery-cart-wheel/685965/2 "2014-04-12T21:54:29Z")
Floor tiles. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [April 12, 2014, 10:02pm UTC](https://boards.straightdope.com/t/what-causes-the-clicking-of-a-grocery-cart-wheel/685965/3 "2014-04-12T22:02:28Z")
Bad ball-bearing. Something stuck to the outside of the wheel or other flaw on the wheel tread. ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [April 12, 2014, 10:17pm UTC](https://boards.straightdope.com/t/what-causes-the-clicking-of-a-grocery-cart-wheel/685965/4 "2014-04-12T22:17:24Z")
Or a bend in the – um – whatever it’s called. The vertical post that goes between the wheel bearing frame and the frame of the shopping cart. Somebody ran it too hard against a concrete parking lot curb and gave it a small permanent bend. The wheels themselves can also get chipped. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [April 12, 2014, 11:55pm UTC](https://boards.straightdope.com/t/what-causes-the-clicking-of-a-grocery-cart-wheel/685965/5 "2014-04-12T23:55:49Z")
None of the above. When carts are stacked for transport back to the store, the stack is swiveled and wheels are ground into flat spots, since they are being scraped sideways on the asphalt and are not turning. This happens in our new Wal-Mart store, where the carts are almost new, all bearings work, and there are no tiles. All the carts have flat spots on their wheels. ---
**Author:** ![california\_jobcase](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@california\_jobcase](https://boards.straightdope.com/u/california_jobcase)\ **Post date:** [April 13, 2014, 1:05am UTC](https://boards.straightdope.com/t/what-causes-the-clicking-of-a-grocery-cart-wheel/685965/6 "2014-04-13T01:05:09Z")
Musicat has it right. A buddy of mine traveled around a lot because he was in the army. He said at one place he lived all the stores had four wheel casters on the carts (the rear wheels were like the fronts). Anyone know where a place like that is in the U.S. ? It would seem to solve the problem of all those flat rear wheels. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [April 13, 2014, 9:47am UTC](https://boards.straightdope.com/t/what-causes-the-clicking-of-a-grocery-cart-wheel/685965/7 "2014-04-13T09:47:23Z")
> [@california\_jobcase](#): > > Musicat has it right. A buddy of mine traveled around a lot because he was in the army. He said at one place he lived all the stores had four wheel casters on the carts (the rear wheels were like the fronts). Anyone know where a place like that is in the U.S. ? It would seem to solve the problem of all those flat rear wheels. It solves that problem at the expense of another - getting the thing to go where you want. A slightly worn (i.e. used and abused) trolley with four castors is a control nightmare, compared to a two castor implementation with the same level of abuse and wear. (Imperfection of wheel circularity is only one way in which these things go wrong). ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [April 13, 2014, 12:05pm UTC](https://boards.straightdope.com/t/what-causes-the-clicking-of-a-grocery-cart-wheel/685965/8 "2014-04-13T12:05:13Z")
> [@Musicat](#): > > None of the above. When carts are stacked for transport back to the store, the stack is swiveled and wheels are ground into flat spots, since they are being scraped sideways on the asphalt and are not turning. This happens in our new Wal-Mart store, where the carts are almost new, all bearings work, and there are no tiles. All the carts have flat spots on their wheels. This doesn’t count as a flaw on the tread? ---
**Author:** ![Red\_Stilettos](https://avatars.discourse-cdn.com/v4/letter/r/fbc32d/32.png) [@Red\_Stilettos](https://boards.straightdope.com/u/Red_Stilettos)\ **Post date:** [April 13, 2014, 12:18pm UTC](https://boards.straightdope.com/t/what-causes-the-clicking-of-a-grocery-cart-wheel/685965/9 "2014-04-13T12:18:43Z")
> [@california\_jobcase](#): > > Musicat has it right. A buddy of mine traveled around a lot because he was in the army. He said at one place he lived all the stores had four wheel casters on the carts (the rear wheels were like the fronts). Anyone know where a place like that is in the U.S. ? It would seem to solve the problem of all those flat rear wheels. I don’t know of any grocery stores like that, but all of the carts at IKEA have four caster wheels. It’s great and doesn’t seem to result in the utter chaos some are predicting. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [April 13, 2014, 1:07pm UTC](https://boards.straightdope.com/t/what-causes-the-clicking-of-a-grocery-cart-wheel/685965/10 "2014-04-13T13:07:38Z")
> [@ftg](#): > > This doesn’t count as a flaw on the tread? Carts have treads now? Like tanks? ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [April 13, 2014, 4:12pm UTC](https://boards.straightdope.com/t/what-causes-the-clicking-of-a-grocery-cart-wheel/685965/11 "2014-04-13T16:12:07Z")
> [@Musicat](#): > > Carts have treads now? Like tanks? Automobiles too, if you think tire treads means tank treads. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [April 13, 2014, 4:33pm UTC](https://boards.straightdope.com/t/what-causes-the-clicking-of-a-grocery-cart-wheel/685965/12 "2014-04-13T16:33:43Z")
> [@ftg](#): > > Automobiles too, if you think tire treads means tank treads. I’m not an expert on how grocery carts are put together, but aren’t wheels usually solid, not a disc-body-plus-tread construction? Or are you using “tread” to mean the rolling surface only? I’m not sure why any of this is important. The wheel has been ground flat and doesn’t roll smoothly anymore, which is the source of the noise in most cases. ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [April 13, 2014, 4:42pm UTC](https://boards.straightdope.com/t/what-causes-the-clicking-of-a-grocery-cart-wheel/685965/13 "2014-04-13T16:42:26Z")
> [@Red\_Stilettos](#): > > > [@california\_jobcase](#): > > > > Musicat has it right. A buddy of mine traveled around a lot because he was in the army. He said at one place he lived all the stores had four wheel casters on the carts (the rear wheels were like the fronts). Anyone know where a place like that is in the U.S. ? It would seem to solve the problem of all those flat rear wheels. > > I don’t know of any grocery stores like that, but all of the carts at IKEA have four caster wheels. It’s great and doesn’t seem to result in the utter chaos some are predicting. _All_ shopping carts I’ve _ever_ seen have four caster wheels. Now, generally, in the US they only have _swivel_ caster wheels in the front, but in my limited experience, European shopping carts have four swivel wheels. And given that IKEA is a European chain, that may be the reason they have four swivel wheels even in the US stores. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [April 13, 2014, 5:35pm UTC](https://boards.straightdope.com/t/what-causes-the-clicking-of-a-grocery-cart-wheel/685965/14 "2014-04-13T17:35:54Z")
See thread: [Why do shopping carts always pull to the left?](http://boards.straightdope.com/sdmb/showthread.php?t=675518) In particular, Post #18: > [@Why do shopping carts always pull to the left?](https://boards.straightdope.com/t/why-do-shopping-carts-always-pull-to-the-left/644009/18): > > I worked at Safeway for 12 years, and repaired quite a few carts in my time (“baskarts” in supermarket lingo). In my experience the problem breaks down like this: > > - Baskarts pull to one side because of a failure in one or more of the moving parts. > > - The moving parts of a baskart are 2 fixed wheels in the rear, 2 swiveling wheels in front, and each wheel on an axle. That’s 10 total potential points of failure. > > - The main cause of failure is debris jamming the movement of one of these points. > > - Typically the items I found jamming up the moving parts of baskarts were pieces or strips of plastic bags, rubber bands, and small pieces of paper (like balled-up receipts or candy wrappers). > > - Debris at a supermarket is most commonly encountered in the parking lot and in the produce department, but can be anywhere in or around the store. > > - The produce department, and most all of the aisle shelves, are either recessed at the bottom or raised up off the floor an inch or two. > > - The produce department is practically impossible to keep clean because customers do things like shuck corn right at the display and throw the debris directly onto the floor. Also, it’s impossible to keep up with the constant dropping of errant onion skins, grapes, and loose greens onto the floor. > > - Additionally, baskarts are typically composed of wire, welded together or plastic, in either case they are very “open,” and any small items tend to fall out. > > - Debris tends to collect at the base of displays and shelves, or in the middle of the aisle/floor. > > - People tend to keep their baskarts to the right, so debris from middle of the aisle/floor tends to get jammed into the left-side wheels, causing them to pull to the left. > > Obviously this will not be the case in all instances, but in my experience that is what is happening. > > Also, the rough treatment by customers and employees alike as mentioned above will of course be a factor. :: I can’t believe I remembered this. Ignorance once fought… :: ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [April 13, 2014, 7:10pm UTC](https://boards.straightdope.com/t/what-causes-the-clicking-of-a-grocery-cart-wheel/685965/15 "2014-04-13T19:10:10Z")
> [@Leo\_Bloom](#): > > See thread: > > [Why do shopping carts always pull to the left?](http://boards.straightdope.com/sdmb/showthread.php?t=675518) Assumes what is yet to be proven. The shopping carts at my 3 local supermarkets do **not** consistently pull to the left, and most of the claims in that thread do not apply to any of my local markets what-so-ev-er. This is not to say that some of those reasons might apply elsewhere, but they are not universal. Yet we have almost-new carts with flat spots on the wheels locally, and I have observed employees wrestling lines of 30 carts around a curved path, grinding the wheels flat several times a day. Debris caught in all 50x4 wheels? Puleeze. :dubious: ---
**Author:** ![Amateur\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)\ **Post date:** [April 13, 2014, 8:20pm UTC](https://boards.straightdope.com/t/what-causes-the-clicking-of-a-grocery-cart-wheel/685965/16 "2014-04-13T20:20:10Z")
Thumbtacks, sometimes, but only if someone takes a fiendish moment to put one in a rear wheel, or the rear wheels of a whole row of them, and I’ve never done anything like that. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [April 13, 2014, 9:10pm UTC](https://boards.straightdope.com/t/what-causes-the-clicking-of-a-grocery-cart-wheel/685965/17 "2014-04-13T21:10:54Z")
> [@Musicat](#): > > Debris caught in all 50x4 wheels? Puleeze. :dubious: I’ve seen it. The wheels are typically hard rigid plastic or metal with a resilient hard rubber or plastic tyre - sharp pieces of gravel or small screws can get embedded in this. Flat spots are often the problem, but not always. ---
**Author:** ![Washoe](https://avatars.discourse-cdn.com/v4/letter/w/ecae2f/32.png) [@Washoe](https://boards.straightdope.com/u/Washoe)\ **Post date:** [April 13, 2014, 9:46pm UTC](https://boards.straightdope.com/t/what-causes-the-clicking-of-a-grocery-cart-wheel/685965/18 "2014-04-13T21:46:59Z")
Perfect thread for inserting one of my favorite jokes: Q. How do you spot four tweakers in a supermarket? A. They’ve got the cart upside-down and they’re trying to fix the wheel. ---
**Author:** ![wei\_ji](https://avatars.discourse-cdn.com/v4/letter/w/e9a140/32.png) [@wei\_ji](https://boards.straightdope.com/u/wei_ji)\ **Post date:** [April 14, 2014, 9:47pm UTC](https://boards.straightdope.com/t/what-causes-the-clicking-of-a-grocery-cart-wheel/685965/19 "2014-04-14T21:47:44Z")
> [@Washoe](#): > > Perfect thread for inserting one of my favorite jokes: > > Q. How do you spot four tweakers in a supermarket? > > A. They’ve got the cart upside-down and they’re trying to fix the wheel. Actually, my neighbor was a “tweaker” (user of crystal methamphetamine), and she would smoke her little glass pipe in her car while listening to techno-funk turned up all the way, then scream curses at her cats for not coming when she called them.