Often we come across cars and SUVs with modified tyres and rims. The bulky, wide tyres do look impressive and do make us think about upsizing tyres and wheels. But have you thought about the impact of larger tyres on your vehicle's mileage? Maybe not, because most people are unaware of the benefits of having the right sized tyres on their car or SUV. So, in this post, we are covering this matter in its entirety.

The science behind car tyres

Since cars are all about movement, laws of physics dictate their performance. So, let's dive into the scientific reasons that govern car mileage and movement.

The most obvious reason is quite simple, heavier objects need more energy to move. So, when you replace stock tyres with larger tyres, you are increasing your car's kerb weight. Which in turn impacts its mileage. Because now the car requires more energy from the engine to move about.

The second reason is friction, also known as rolling resistance in car tyre jargon. Larger tyres have larger contact area with the road. This means there is higher friction and thus, increased resistance to movement. So, the larger the tyre, the higher its rolling resistance.

Now, when you consider the two facts together, you have:

• A vehicle that requires more energy to move
• Tyres that are more resistant to movement

Combined, these facts increase your car's fuel consumption.

Getting the right tyres for your car

So, it's clear that when you upsize simply for the looks, you are impacting the mileage. But, upsizing car tyres is not a bad practice, if done with expert guidance. Here are the things to consider when upsizing car tyres.

Tyre size and width

Every vehicle manufacturer has guidelines for the right tyre size for  their products. Your car manual will list the smallest and the largest tyres you can use. So, the first thing when considering upsizing car tyres is to consult the vehicle manual. You can upsize (or downsize) within those values without worrying about impacting performance.

Tyre weight

While a larger tyre will weigh more for obvious reasons, tyre weight also depends on its material. There are some rubber compounds and tyre constructions which use heavier material. Hence, increasing the tyre weight. So, even if you are upsizing within the limits specified by the automaker, keep a check on tyre weight as well.

Type of wheels

Upsizing tyres generally includes buying new wheels. In general, the fancy wheels we see on modified cars are known as "alloy wheels". That's because these wheels are not pure steel but alloys of aluminium or magnesium. Considering only the science, alloy wheels will be lighter than steel wheels of the same size. But when upsizing to larger tyres, you need larger wheels as well. Which cancels any mileage benefits you might have achieved. So, here too, you should consult the OEM specifications for wheels on your vehicle.

Looks also matter

Once you have considered the above factors, there is also the matter of looks. It may be, that following the OEM requirements is not giving your car the best look. Here, you can consult the tyre dealer for guidance. Because there is always some margin for upsizing outside the OEM specs. You only need to be judicious and well-informed for that. Here, tyre makers who supply stock tyres to car makers are better equipped to help you choose the right tyre.

How much impact do large tyres have on fuel efficiency?

Independent studies show that the difference in fuel efficiency can be as low as 10% to as high as 25%. Because there are several driving factors that also have an effect on mileage, such as

• Driving speed - Higher speeds mean higher fuel consumption
• Air conditioning - A known factor that lowers fuel efficiency
• Driving conditions - For you get better fuel efficiency on highways than in city traffic
• Vehicle systems - The more complex the vehicle, the higher its weight and fuel consumption

But when using the right sized tyre and wheel combo, you can definitely expect gains in mileage. Experts recommend upsizing tyres within 3% of the manufacturer guidelines.

How to read tyre size information?

While you can figure out the right tyre size from your car's manual, buying new tyres is another story. Tyre makers often use standard labels which can be difficult to understand. Here is how to read the tyre size information.

Reading from left to right

• The first letter specifies the type of vehicle. For example, for passenger car tyres the letter will be a 'P'. For light trucks it will be 'LT', and so on.
• A three digit number will follow the first alphabet, e.g., 205. That's the tyre width in millimetres.
• After that, there will be a slash followed by two digit numerals, e.g., 65. This is the tyre's aspect ratio - width to its height off the rim. The number is delivered in percentage. So, 65 means the tyre height off the rim is 65% if its width.
• After that, there is another alphabet, an 'R' or 'D', which depict the tyre construction. R for radial and D for diagonal or bias-ply.
• Finally, you have another two digit numeral that represents the rim diameter. For example, a tyre size indicator that reads 205/65/R16 will fit a rim with a 16-inch diameter.

Benefits of upsizing your car tyres

As mentioned earlier, upsizing car tyres is not always a bad thing. Apart from giving your car a cosmetic upgrade, upsizing can also help in:

• Better traction - As wider tyres offer greater contact with the road
• Superior handling - Especially for base model cars that come with thinner tyres
• Greater stability - As larger tyres keep the vehicle planted at higher speeds
• Better braking - Wider tyres offer better braking due to their traction
• Driving comfort - Larger tyres are better at absorbing bumps and road noise

Our recommendation for upsizing car tyres

Buying new car tyres is always tricky. If you are looking to upsize from stock tyres to larger tyres, at Apollo Tyres, we offer expert assistance at our authorized tyre dealerships and via helpline for customers buying tyres from the Apollo online tyres shop. A few of our recommendations include the Apollo Alnac 4G tyres for premium hatchbacks and mid-segment sedans and the Apterra series for upsizing SUV tyres.

Frequently Asked Questions:

Can I put bigger size tyres on my car?

You can switch to larger car tyres but experts recommend upgrading within 3% of the original diameter of your car tyres. Switching to unnecessarily large tyres will not only affect your car’s mileage but may also impact handling and ride quality. Sometimes, large tyres can also lead to suspension breakdown and braking failures.

What happens if we increase tyre size?

When you switch to larger tyres without expert guidance, it may impact your car’s performance and reduce its mileage. Additionally, larger tyres also reduce the speed of your car as the engine needs to pull more weight and overcome the higher rolling resistance. Larger tyres also make the steering heavier and cumbersome, especially when driving in city traffic.

Do large tyres affect mileage?

Yes, larger tyres are more likely to reduce mileage because they are heavy and require more effort to move from a stationary position.

Which tyres give the most mileage?

It depends on the ideal combination of tyres, wheels and the engine. If you upsize your car tyres within the limits specified by the car maker, you can expect the best mileage. Of course, mileage also depends on road conditions and your style of driving.