Make sure to bulletproof your tires to get the full effect. Keep in mind that this does not bulletproof your windows. However, a 100% armor increase does not make your vehicle invulnerable, it only doubles its durability, by adding 100% of the original durability. This makes your vehicle extremely durable. Once unlocked, there are five armor options available from 20% to a full 100% armor upgrade. The window you break while stealing a vehicle counts as 'damage', and must be repaired before customization is available.
