Between Your Boots and Wheels...Plates, Kingpins, and Trucks.

Photo of Shocker Khan by John Nyman

Let’s see, we've gone over wheels, bearings, cushions, and toe stops…so I guess it’s time to talk about plates, more specifically plates, trucks, and kingpins (which is usually how they come when you purchase them).  There are many plates on the market now-a-days, which is good and bad.  Good that we have so many choices and can find something that will work for our personal skating style, but bad when you are new to skating and get overwhelmed with all the choices!  It also doesn't help that there aren't industry standards for things like screw hole locations.  At least there are only two sizes of axles you are likely to encounter, so let’s start there.

Trucks
Trucks are what we call the piece that comprises the axle and pivot pin. Our wheels and bearings go on the axle, and the pivot pin (or just pivot) is what is inserted into the pivot cup in the plate.  There is also a ring coming out of the axle that I like to call the "axhole", but it's actually called the "boss".

There are two trucks per skate, so four trucks for a complete pair of skates.  There are single action and double action trucks.  Single action have one cushion that sits between the boss and then plate, and double action trucks have one cushion above the boss and another one under.  Most plates found in roller derby today are double action.

There is a hole in the boss that the kingpin goes through.  There are also some cushions like the Crazy Skates cushions where the cushions touch each other through the boss.  This helps to make the best of both worlds of the single and double action trucks by allowing the speed and stability that a single action truck gives a skater, as well as the agility and mobility that the double action truck provides.  Not every boss is big enough for these cushions so make sure you have the proper trucks before purchasing these cushions.

There are two sizes of axles, 7mm and 8mm.  Sometimes you have a choice as to which size you get with your plates, but some manufacturers only make their axles in one size.  The most common size for roller derby skates is 8mm.  It is important to know what size you have so you know what size bearings and tools to get.

Nerdy technical info: Most 7mm and 8mm axles are actually threaded for 9/32", 32-tpi and 5/16", 24-tpi (fine), nuts respectively, but they are still called 7mm and 8mm because that is the measurement of the actual smooth part of the axle. If you go out and buy metric nuts from a hardware store, they won't fit. There are a few older and less common plates that have true metric or 5/16", 18-tpi (coarse) threads, but these are not commonly used for derby.

Kingpins

Kingpins hold the trucks in place and run from the plate through the cushion cup (or retainer), top cushion, boss, bottom cushion, cushion cup, then the kingpin nut holds the whole shebang together.  The angle that the kingpin comes out of the plate is very important and can run anywhere from 10 degrees to 45 degrees.

Double Action Truck with
Kingpin and Cushions

Most entry-level plates come with a 10 degree kingpin, which is nice and stable for new skaters.  Other plates come with 15 to 45 degree kingpins; the more severe the angle, the easier it will be to make sharper turns; however, this can make a skater feel unstable and it can be difficult to control because your weight is over the pivot pin instead of the kingpin.  Some skaters stick with the 10 degree kingpins, while others choose to go for a larger angle.  The best thing to do is just try out different angles and see what fits your skating style and ability.

Some kingpins come with a micro-adjustable lock nut and washer which allows for more precise adjustments.  Usually plates with this type of kingpin come with a hefty price tag, but the new Luigino Eagle plates come with the micro-adjustable lock nut and washer for only $100.

Nerdy technical info: Most kingpins are 3/8" in diameter, however not all kingpins are the same. Some have a hex head (like a standard bolt), some thread into the plate (technically called a "stud"), some are made of steel, some are made of aluminum. When replacing a nut or broken kingpin, it is important that you replace it with the correct kingpin for your plate. Even kingpins that look the same at first glance are often threaded differently. Some are threaded 3/8", 16 tpi (coarse), others are threaded 3/8", 24tpi (fine). Still others (most notably Sure Grip) are threaded 3/8", 20 tpi, which is a funky thread called British Standard Fine (BSF). It all can be quite confusing, but it's worth paying attention to, because screwing up the threads is a quick and easy way to ruin your kingpin or plate.

Pivot Pins

The pivot pin is what connects the truck to the plate via the pivot cup.  It is designed to give the skater support and I like to think of it as the third leg of a tripod, with the axles/wheels as the other two legs.  The pivot cup, which is usually either metal or rubber, usually needs to be replaced about once a year and you should check it every once in a while to make sure there aren't any holes or lots of wear in them.  If you are able to wiggle your truck back and forth and see the pivot pin moving, it is time to either get new pivot cups or adjust the kingpin.

The pivot pin needs to be seated properly into the pivot cup.  If it is not seated correctly, too much stress is placed on the kingpin when landing a jump and you can break a kingpin, which is no fun. Pivot pins should fit securely into the bottom of the pivot cup without having to have any weight on the skate.  Some trucks come with adjustable pivot pins, while others are non-adjustable so if the pivot pin is not seated into the pivot cup you will need to adjust it by adjusting the kingpin. Incorrectly adjusted pivot pins or worn out pivot cups are a common cause of broken kingpins or trucks, so it is important to keep an eye on them for wear and adjustment.

Plates

Roller skate plates are usually made from either nylon or aluminum.  Nylon plates are nice and light, but break more easily than aluminum plates.  Some plates are made from aircraft aluminum and are therefore super light and strong, but they can be pricey.  If you are looking at replacing your current plates, know that there is no standardization of screw hole patterns so if you are changing brands or upgrading, you may need to have more holes drilled into your boot.  Some manufacturers have lines of plates that have the same hole patterns, which makes it a lot easier to upgrade.

PowerDyne Reactor Plate with
Micro Adjustable Kingpins

Plate sizing can be a little tricky.  If you are a beginner skater, you will probably want to go with a plate that is almost as long as your boot.  Make sure you look at the sizing charts for whatever plates you want to purchase because sizes are not standardized.  You may need a size 8 in one plate and a 4 in another one.  Also, there are some plates that are meant to be "short forward" mounted, which means that the plate doesn't cover most of the heel of the boot.  This is done on purpose to reduce weight while keeping your body positioned correctly.  You can order plates that are smaller than what would normally be mounted on the boot to be more agile, but I wouldn't do this until you have skated quite a few miles.

Some plates have offset toe stop design which makes the pair have left and right plates.  This seats the toe stop off-center so it sits inside toward your big toes more than plates that don't have this design.  Some skaters prefer their plates to have the toe stops right down the middle, while others like the off-set design because of how they use their toe stops.  As with pretty much any skate option, you will need to try out the different styles to see what feels best.

Bionic Super Stoppers

Lastly, there are a couple different ways that toe stops are connected to the plate. The first is with a nut and lock washer that goes around the toe stop stem, the second is with a screw that goes into the side of the plate and squeezes the plate around the toe stop to keep it in place. If you have the toe stop nut, Gumball toe stops work really well because you don't have to have them a certain way when you screw them in, at least until you flatten them a bit). If you have the type of plate with the screw on the side, I highly recommend Bionic Super Stoppers. When you have the toe stop where you want it, you just have to tighten the screw instead of having to hold the toe stop in place while you use a wrench to tighten the toe stop nut.

Well, I think that is enough for now.  If you have questions I haven't answered yet, don't hesitate to post it in the comments or send me an e-mail.  I don't have all the answers, but I'll help you out if I can! 

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Until we skate again,
Shocker