Firstly, let's talk about the type of race you're participating in. If you're racing in a straight-line drag race, then you'll need different gears than if you're racing on a track with tight corners. For drag racing, you would want a lower gear ratio to give you faster acceleration off the line. However, for a track that has many turns, you'll need a higher gear ratio to help you maintain your momentum through the corners.
Another thing you need to consider is the type of car you're driving. A car with a smaller engine will need a lower gear ratio as opposed to a car with a larger engine. This is because smaller engines produce less power, and a lower gear ratio will help them reach their peak power range faster. On the other hand, a car with a larger engine can handle a higher gear ratio as it has more power and can handle higher speeds.
Now let's talk about the keywords mentioned in the prompt, and how they relate to gears. Custom Gear Manufacturers are companies that specialize in creating gears that are specific to a customer's needs. This means that they can create gears with unique ratios, materials, and specifications that can be tailored to the customers' needs. So, if you're looking for a gear that is not readily available, then custom gear manufacturers are the way to go.
Overall, deciding what gear to run depends on many factors. From the type of race to your car's engine size, everything plays a role in determining the right gear ratio. If you're looking for something specific that is not readily available, then custom gear manufacturers are the way to go. In any case, always remember to do your research and test out different gears to see which one gives you the best performance.