Does Tire Size Affect Gear Ratio?

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There is an alarming number of car owners who lost the performance of their cars following the installation of a different tire size.

This number is growing because not everyone understands what the tire size cause and how crucial it is to cross-check whether the tire size is right for your car or not. why gear ratio and how does tire size connect to gear ratio?

So, does tire size affect gear ratio? Yes, it does.  This question got me thinking about tire size beyond just big or small.

When tire size is mentioned, don’t think much about it aside from bigger tires having an aesthetic advantage over the small size tires. It is high time we begin thinking beyond this scope and ask relevant questions concerning which aspect of the car’s performance would the tire change impact negatively.

It is questions such as this that will reveal what necessary measures to take when going for a large or smaller size tire to ensure that no aspect of the car’s performance is compromised.

While it may not be a crime to go beyond the factory tires or carry out other car modifications to create a customized look that sets your car on a different pedestal from others, it could be liable to legal action when such is done without following the right procedure or taking the necessary precautions as some modifications can increase the risk of road traffic accidents.

I do not expect you to be a car expert, however, if you are a quick learner like myself or a car enthusiast or someone who prefers to have things done with their own hands, then be ready to learn how to determine your tire diameter,  how to calculate the gear ratio and other parameters.

Buckle up and get ready for some learning. Yes, there are a few calculations and formulas mentioned here, particularly on how to determine the tire diameter amongst other parameters. You must not force yourself to understand this formula or learn how to apply them. For some tires, it is unnecessary, as the diameters are well stated.

Aside from the calculation or formula method, a gear ratio calculator equally exists. If however, you wish to feel powerful coming up with a value from the mathematical equation that is the same or close to the values provided by the calculator, then you are welcome to give the formula method a shot.

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What is the effect of bigger tire size on the gear ratio?

when speaking of gear ratio, this aspect of the car performance cannot be glossed over without apportioning any form of significance. This is because the gear ratio has bearing on how well or poorly the car accelerates and also dictates other aspects of the car’s performance.

Therefore, if looking to change the size of the tire from the factory size to a customized size, and hoping to maintain the optimal performance of your car, you must ensure the size is not such that compromises the gear ratio.

Technical terms such as gear ratio are not easily understood by those who are unfamiliar with automobile terminologies or those who did not major in this field. It is, therefore, necessary for my experience to always state what these terms mean to offer a better and more in-depth understanding of the topic of discussion.

So, what do you understand by gear ratio in the first place? Every car has an output and input shaft, these two are compared to arrive at what is being referred to as gear ratio. Simply put, the gear is the ratio of the number of turns or rotations made by the output shaft to the single turn made by the input shaft.

Do not be taken away by the thought of how good a tall tire will look on the car. that desired final finish is as important as another aspect of the car can good be affected adversely. Therefore, before attempting to have a new set of tires installed, the size of your current tire, the current gear ratio, the size of the incoming tires, and the gear ratio this will produce should all be figured out.

Without undertaking the necessary calculations, you could inadvertently compromise the car’s acceleration and overall performance at the expense of beauty. If the larger size tires were desired given improve the performance of the car, then this will be equally defeated when the right thing is not done.

Yes, I understand you are not a mathematical and probably do not like to do any form of mathematical calculations, simple or complex. But if you are asking these questions, there is a chance you are familiar with simple calculations associated with the automobile field, if not, you can turn to your tire dealer to explain this to you and do the calculation on your behalf.

However, if you are ready to form some simple mathematical calculations, here is how to determine on your own what your tire diameter is;

Tire diameter = 2 x section width x aspect ratio + rim diameter

Note however that some tire types do not require you to undergo this calculation. The large tires, off-road tires, street style tires, and similar categories of tires come with the tire diameter specified of the sidewall and therefore do not need to be calculated. This is because this size of tires is more likely to need you to account for the gear ratio than the regular size tires.

However, for tires such as passenger and light truck tires, this calculation becomes necessary.  What you are mostly concerned about is the drive ratio, therefore, after figuring out what the diameter of the current tires about to be replaced is, and the diameter of the tires you wish to install, these two diameters can be multiplied by each other and the total multiplied by the gear ratio. This will give you the value for the drive ratio.

From these calculations, it will be evident that the large-size tires affect the drive ratio in that it reduces the drive ratio.

Should gear ratio be considered when going a big or small tire size?

Without undergoing any calculation, anyone who in the past has upgraded the tire size from a smaller size to a larger size must have noted the change in the performance of the car, particularly in terms of acceleration. 

Although this can be proven mathematically as demonstrated in the section above, the manifestation is a much appreciable sign. Simply going ahead to have the tires changed to a bigger size tire without considering what this could do to another aspect of the car is not advisable.

This is why all car owners who intend to upgrade the tire size must ensure to consult the experts such as auto repair shops or tire experts for a professional consultation.

Without a matching size gear ratio, there is no way a larger size tire will not mess up the acceleration of the car or other aspects of the car’s performance.

Questions such as this are usually asked by those who have never had to install off-road tires on their vehicle. This set of drivers or car owners may find it difficult to understand the need to have the gear ratio changed as the tire size changes.

Note that lower gears have a higher numerical representation when expressed in a ratio. What is required of you when you upgrade to a larger tire size is to downsize the gear, that is a lower gear should go with a larger tire size. Note however that numerically, this will have a higher gear ratio.

Is the gear ratio affected by small tire size?

Gear ratio should not be only worried about by those attempting to upgrade to a larger size tire. Although what is common is drivers changing from small size tires to larger size tires, however, there are reasons why you may want to go the other way, that is, change from a large size tire to a small size tire. In this situation, the gear ratio is equally affected and should therefore be factored in before undergoing such change.

The benefits of ensuring the appropriate gear size are what you have on your car by your tire size is that the fuel economy, acceleration, speedometer, and other aspects of the car are properly maintained.

One of the key aspects of the car performance affected by the size of the tire you have on is the fuel mileage. Without the necessary adjustment and modifications, a non-matching tire size could cause you to spend double or more of the amount spent on gas.

The speedometer which is sensitive to the revolution of the tire is equally altered and produces a false reading following a change in the tire. 

Does increasing your tire size adversely affect the gear ratio?

There are no excuses for installing a new tire of different sizes from the factory size without considering the gear ratio. There are multiple ways of knowing what gear ratio fits your desired tire size.

The easiest method would be to simply give the car dealer a call and ask about this thing before proceeding to install the tire. Right from the retail shop where the tires are bought, the tire expert can take a look at the specification of the car and calculate what is appropriate for it.

Today, there is also the gear ratio chart where you can easily find what is recommended for your tire height and diameter. Aside from these two methods, a third option is the gear ratio calculator, which will only require you to input the specification of the old and new tire to come up with the appropriate gear ratio for the tire size.

Does Tire Size Affect Gear Ratio – Conclusion 

It is a big deal to change tire size, several factors must be considered as this change comes with numerous consequences ranging from car performance to fuel economy. One such consideration is the gear ratio, a numerically higher ratio is required for a large size tire. 

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