In 4th gear, the gear ratio of 1:1 means that the engine and the transmission’s output rotate at the same speed. If our input gear (10 teeth) is rotating at 5 rpms and it is connected to our output gear (50 teeth), our output gear will rotate at 1 rpms, thus our large gear will be said to be rotating at 1/5th of the speed required. Aspect ratio is simply identified as a percentage of the section height divided by the section width. It is the gear ratio that tells us how fast one gear is rotating when compared to another. The two-digit number following the section width identifies the tire’s aspect ratio. Making a choice therefore depends on what you want to achieve. But it will also use more fuel in all situations because the engine’s rpm will be higher. Low gears give fast acceleration while high gears give better cruising.Ī smaller engine will need a lower rear end to give adequate acceleration and a truck with optional 3.73 gears will tow a heavier trailer than one with 3.55 or 3.21. A high numerical gear ratio is called a low gear or low rear end, and vice versa. Lower gears are required if the car is very heavy or if the engine makes its power at the upper end of the rpm scale. In the real world, typical street machines with aspirations for good drag-strip performance generally run quicker with 4.10:1 gears. Can I Increase The Aspect Ratio On My Tires Yes, you can increase the aspect ratio on your tires. For example, if your tire has a width of 205 mm and a sidewall height of 55 mm, its aspect ratio would be 55. Is it better to have a higher or lower gear ratio? Once you have these dimensions, you can calculate the aspect ratio by dividing the sidewall’s height by the tire’s width. When changing gears for taller tires, you are heading to a numerically higher gear ratio. The ideal cruising speed is usually around 1600-2000 RPM for diesels and 2000-2500 RPM for petrol engines.Ĭhanging tire size will ultimately affect the power and drivability of your vehicle. In general, a taller gear ratio means better fuel mileage and less noise, although you may need to shift down if you need to overtake.

The higher the number the better the car will accelerate but at the expense of high speed cruising. The lower the number, the faster the car will go with the same number of engine revolutions. If you are a daily driver, chances are you will want to keep your gear ratio at 3.23 or below for optimal performance and lower cruising RPMs.įor street and strip applications, a popular choice ranges between 3.42s and 3.90s, giving you that extra 00mph on the track while maintaining a tolerable cruising RPM on the street. Maintaining a good gearing ratio depends on your choice. You can also check out our tire size calculator, wheel offset calculator, tire height calculator and tire comparison calculator.Ģ35/35R19 Size: 235 Aspect Ratio: 35 Rim diameter: 19 What is a good gearing ratio? Just type in your tire size, aspect ratio, diameter, old gear ratio and it will calculate it for you. Use our gear ratio calculator to calculate your new gear ratio and rpm.

Tyre aspect ratio calculator