Derailleur Jockey Wheel or Pulley Wheel Selection or change for Racing or MTB bike

When you want to change or upgrade the jockey or pulley wheels in your Derailleur like a Shimano Dura-Ace / 105 / Ultegra / GRX / Tiagra, or a SRAM Eagle / GX / NX / X model derailleur for a MTB, racing, street, gravel, or e-bike, you will have different options to choose from. This video explains the 4 major types of options, from (1) a simple cheap plastic bushing wheel without bearings (2) one with open bearings, (3) one with closed steel bearings, and (4) one with closed ceramic bearings. It tells you what you need to measure (= number of teeth and width) before you can select the right one. Wheels can have anywhere from 9 to 14 teeth (T9 - T14) depending of the gear type and system on the bike and the width you need. Also, some bikes have a smaller upper wheel and larger lower wheel (for instance SRAM Eagle has 12T/14T). In terms of width, most wheels are 10 mm, a few are slimmer. The way to change a pulley wheel is very very simple if you have an Allen wrench and some blue thread-locker. To see a video about how to actually change the jockey wheel, please choose another video on YouTube. This video deals exclusively with explaining and showing the major types and how to determine what jockey wheel you need.