Collars are designed to keep the plates from sliding off of the barbell sleeves. That's all they are for. If the plates are not sliding off, you don't need collars.

That said, let's take the opportunity to examine why plates slide off the barbell. When you put a plate on a bar, the hole in the middle of the plate interacts with the sleeve of the bar, and friction holds the plate in place – specifically, the friction between the upper surfaces of the plate hole and the barbell sleeve, since the plate “hangs” from the barbell and the lower surfaces are not in contact with each other. The nature of this frictional interaction determines the behavior of the loaded barbell. There are two factors to consider: the surfaces of the bar sleeve and the plate hole, and the diameters of the sleeve and the hole.

The Surfaces

Plates are cast iron, either gray iron or ductile iron, usually gray iron due to the extra expense of ductile iron. The casting is designed with a slight bevel at the edge of the hole on either side of the plate for ease of loading on the bar, and the inside diameter (ID) of the hole itself is finished smooth, with uniform parallel sides. Cast iron is very hard, and will not polish much against the softer steel of the bar sleeve.

The sleeve is usually made from 10xx series steel, usually 1018 or 1026, something easy to machine. The sleeve itself is not under a tensile or bending load – it's job is simply to hold the plates. Being softer than the bar material, a sleeve will polish over time, becoming smoother (very old bars may have a noticeable drop in sleeve diameter just outside the sleeve collar). Two very smooth surfaces interact in a predictable fashion, even if the iron is much harder than the steel, and the potential for these surfaces to slide against each other is what collars are designed to control.

Some bar sleeves are manufactured with a residual artifact of the machining process still present – a series of very fine ridges on the sleeve surface, perpendicular to the long axis of the sleeve, and therefore parallel to the diameter of the plate as it is loaded. These are a function of the tool used to turn down the outside diameter (OD) of the sleeve passing over the surface. A slower pass rate results in a smoother surface. These ridges might seem like a good idea, but remember that the cast iron of the plate is harder than the steel of the sleeve, and these ridges cannot “bite” into the ID of a cast iron plate. In fact, the ridges on the sleeve actually reduce the amount of surface area in contact between sleeve and plate (Fig.1), the spaces in the valleys of the grooves being perfect places for the accumulation of machine oil, chalk, and human hand goo, producing a a surface that may actually be lubricated, therefore reducing the friction that normally holds the plate in place.

One important factor that can increase the friction/decrease the slide between plate and sleeve is rust. Even in a climate-controlled building, plates are noticeably less “zippy” on the bar if the weather has been wet for some time. Tiny rust particles form on the sleeves and plate IDs in higher humidity, increasing the friction between the surfaces even in the absence of visible rust. This polishes off quickly, but the effect is quite profound. Some manufacturers actually chrome-plate their barbell sleeves to prevent rust – in doing so, they make collars absolutely necessary for these beautiful shiny expensive-looking showpiece bars, since the plates will always happily skate off the sleeve.

The Diameters

Cheap barbell plates are manufactured with larger IDs so that they will always fit on even cheap bars manufactured with larger sleeve IDs. This way the manufacturer doesn't have to accept returns, since his cheap plates will fit on any bar. Most barbell sleeves are 1.95 inches, so a cheap plate with a 2.05-inch ID will have quite a bit of slop between sleeve OD and plate ID. Better plates have a tighter ID – Uesaka plates are hideously expensive with a 1.97-inch ID, and won't fit on some bars. Most bumper plates are made with a tighter ID. Classic York cast iron plates have a 2.01-inch ID, while my old Sonata plates are sloppy as hell at 2.05. If you load a sloppy plate on a bar and set it on the floor, the slack between ID and OD will produce a significant “tilt” between the plate and the bar. Unless collared to keep them tight together against the sleeve collar, the plates will walk down the sleeve with every rep. Sloppy plates are a pain in the ass when pulling from the floor. Uncollared plates that are loose on the bar will shake during a squat, press, or bench press, and this can be distracting at heavy weights.

Another feature of sloppy plates is the mismatch between the curvature of the plate ID and the sleeve OD (Fig. 2). The smaller circumference of the sleeve OD reduces the area on top of the sleeve that is actually in contact with the ID of the plate. Friction is dependent on contact, and the more surface area in contact between the two surfaces, the more friction and the lower the tendency to slide down the sleeve.

When to Use Collars?

The factors we have discussed explain the situation: if the plates are sliding, use collars. If your equipment is cheap, or if you're training in a health club instead of a barbell gym, you're probably going to need collars. If your bar is not level across your back, or if you lock out pressing exercises unevenly, you'll need collars. If you walk out your squats with a pronounced side-to-side sway, the plates will slide and you'll need collars. If you're pulling sloppy plates off the floor, you need collars set tightly. If the gym has shitty collars, get your own and take them with you, just like your fractional plate set, your chalk, your belt, and your pulling straps.

But if the plates are not sliding, you don't need collars. If you're warming up your squats and the plates are behaving themselves, you don't need to collar the bar. You can if you want to, but you don't really need to. If the plates are stuck pretty well to the sleeve today, presses don't need the warmups collared. It's a good idea to collar your work sets for all exercises, since an uneven extension can develop quickly if you get off-balance or tweak something, and the result would be a catastrophic unloading of the low side immediately followed by the other side 2 seconds later, with the bar itself being thrown across the room. This is unnecessary damage to the equipment, and if you're in that bad a situation you probably don't want to compound it by destroying your surroundings.

A word about bench presses: we used to advise that the bar should never be collared if you were benching by yourself, so that if you got stuck you could tilt the bar and catastrophically unload one side at a time. But this is such an incredibly stupid thing to have to do that I'd rather advise you not to bench by yourself if you don't have access to a power rack or other protection from a crush injury. If the bar falls out of your hands and hits you in the chest (and this can happen at below-1RM weights), the presence or absence of collars won't matter. If you have protection and the plates aren't sliding, again, you don't need collars on the warmups, but go ahead and collar the work sets.

Since bumper plates are tighter on the sleeve, and since you're probably doing lower-rep sets for snatches and cleans, you may decide not to collar the bar. Really, collaring the bar with bumper plates dropped from overhead tends to tear up the plates faster – when the plates can move a little down the sleeve during the bounce on the platform, some of the energy is dissipated in the slide, and the plate hubs don't have to take all of the shock. It's not that much trouble to snug up the plates between reps anyway.

As far as the collars themselves, clever people have invented things we did not have 40 years ago. Competition collars weighing 2.5 kg are basically the same as they've always been, but training collars made of plastic or alloy are now available for not much money, and they work so much better than those old spring-clip pieces of shit that you'll never have to look at them again.

The important thing is that collaring the barbell – like almost every other thing in human experience – is not a black-and-white all-or-none set-in-stone situation. If your plates are sliding, collar the bar. If they are not, make yourself happy.

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