The main parts of a truck are the base plate (the part connected to the board
The axle (the part that your wheels with bearings slide on to), the Hanger and the King Pin
Each truck company has a different measurement for odd reason. Here at Active 8 Sports, we measure the trucks by their axle width and provide you with a sizing chart to help you choose the best one for you. Some companies also offer Hi & Low Trucks, this is the height of the axle from the bottom of the board. If you are using larger wheels or if you are a heavier person and want to increase the gap between your wheel and deck, then you can go in for a HI model, if you are a very technical skater and want to reduce the gap between the deck and wheels you can go for a LO model.
You will want your truck width to match the width of the board. You don’t want them too under or over extend the board.
For more help on choosing the right truck, click here to view the axle width to deck chart.