Best way to get the diameter is by a vernier caliper. To get the length, unscrew one, hook the bent end over a ruler and see wher the threaded tip ends up.
It depends if you have a 3 piece crank, spokes, brakes.
Tyres/tires are the rubber things that makes contact with the ground, they don't come with spokes. Rims are the (usually) metal hoops that the tyres/tires sit on, and they too usually don't come with spokes. Wheels consist of hub, spokes, and rim when you buy them. To make them rideable you need to add tyres/tires and tubes.
To measure BMX handlebars accurately, use a measuring tape to determine the width of the handlebars from end to end. Additionally, measure the rise of the handlebars from the center of the stem to the top of the bars. These measurements will help ensure a proper fit for your BMX bike.
Spokes are the thin metal rods that run from the hub(the center of the wheel) to the rim( the hoop where the tire sits). Inches usually refers to the approximate size of the wheel, 20" for BMX, 26" for MTB, and 28" for road bikes.
To measure bike spokes accurately for replacement or customization, use a spoke ruler or a measuring tape to determine the length from the inside of the elbow to the end of the spoke. Make sure to measure in millimeters for precision.
To accurately measure spokes for your bicycle wheel, use a spoke ruler or a measuring tape to determine the length from the inside of the bend at one end to the tip of the thread at the other end. Make sure to measure in millimeters for precision. Additionally, count the number of spokes needed for your wheel to ensure you have the correct quantity.
To measure bicycle spokes accurately for replacement or customization, use a spoke ruler or a measuring tape to determine the length from the inside of the bend at one end to the tip of the threaded section at the other end. Be sure to measure in millimeters for precision.
Kinda-sorta. If the new rim has the exact same diameter where the spoke nipples are, then you can reuse the old spokes and hub. Easiest way to do this is to tape the new rim alongside the old one. As long as you get the alignment right(valve hole, and left/right staggered spoke holes...) you just move one spoke at the time over and you're done. Keep in mind that it'll take e it apart, but be sure to check the hub to make sure that it won't be seized or the flange is broken and the spokes aren't broken too on the old wheel.
You measure it. A ruler and a caliper are useful.
The angle is pi/4 radian. If you are at an early stage in studying mathematics, that is 45 degrees.
working from back to front: tyre, innertube, rim, spokes, nipples, hubs, frame, cranks, pedals, sprocket, seat clamp, seat post, seat, bars, grips, bar ends, stem, headset, top cap, forks, hubs, spokes, nipples, rim, innertube, tyre :)
A wheel with 64 spokes will have 64 spaces between the spokes.