Can some of you guys that live, eat, and breathe cars for longer than I have please explain to me what the hell the numbers mean when talking about Gear Ratios. What I do know:

Pretty much nothing.

Do better gear ratios translate into more WHP?

Are larger or smaller numbers better in a gear ratio?

Thanks for your help peeps.

 

higher number = hiher speed at a given rpm

lower number - quicker acceloration, but you run out of breathe fast.


It's just:

Whele RPM = engine RPM * gear ratio * final drive ratio

 

Have you ever riden a 10 speed bicycle? Is it easier to start in 1st gear or 10th? Easy to answer, right? Rear (Final Drive) end ratios act the same way. A street car uses a gear ratio that will give good MPG (2.53:1 to 3.91:1). A drag racer wants to get to the end quick and dosesn't care about MPG (4.10:1 to 5.14:1). It simply makes it easier (as in mechanical leverage) on the engine to accelerate. Overdrive transmissions have made it better in that you can have a "Low gear" (higher numerically) and still get better MPG. For example, I've driven cars with 2.53:1 ratio gears and it felt like I was towing a boat behind me off a light. Just changing the gears to 3.23:1 made the car quick off the line.

If you have two identical cars except that one has a 3.00:1 ratio and the other has a 3.90:1 the 3.90:1 equipped car will be quicker under acceleration. A VERY BIG misconception is that the 3.00:1 car will have a higher top end than the 3.90:1 car. This is not true in all cases -- top end speed is determined by horsepower NOT engine RPM. If an engine has a flat horsepower curve IE., 200 HP from 5500 to 6300 RPM then the gear ratio will not matter. The car with the 3.00:1 will run top speed at 5500 RPM and the 3.90:1 car will run the same top speed but will be turning 6300 RPM.

Not so easy to understand but it is a fact...been there, done that!