While making a buying decision, we today have multiple choices and automobiles are no different. Though factors like price and performance play an important role but look and aesthetics impact decision making to a large extent especially for automobile enthusiasts. The majority of the auto-enthusiasts are always yearning to have sporty and unique vehicle charisma. This eagerness at a time leads to customization and modifications, and ‘tyre upsizing’ is no exception.
Although tyre upsizing gives a vehicle a bold stance but along with the joy of resolute appearance it also does offer performance drawbacks. Therefore, vehicle owners may like to consider a number of factors before upsizing their tyres.
Technically, tyre upsizing can be performed in two ways:
#1: Mounting wider tyres while retaining the original wheels
#2: Upgrading to larger wheels and installing wider tyres
Advantages of Tyre Upsizing
Besides a cosmetic uplift in car’s profile, tyre upsizing brings the following benefits for owners.
Personalization: For many car owners, tyre upsizing is one of the quickest ways to personalise their vehicle and add oomph to its side profile. In other words, wider tyres make your vehicle look cool and boost its style quotient.
Greater Stance: Technically, wider tyres offer a larger contact patch generating more grip on the road. This helps the driver maintain greater control and stability, especially when the vehicle is cruising at a relatively higher speed.
Safe Breaking: Larger tyres significantly reduce the breaking distances offering better control while breaking. This also means little or no skid and therefore, more safety.
Easy Cornering: Suspension plays a key role in corning your car. Wider tyres tend to have slimmer sidewall flex which enables the driver to corner better even when the vehicle is moving at high speed.
Overall Control: Tyre upsizing enhances the overall performance of a vehicle with regards to its balance, stability and traction. This can prove to be an asset for vehicles that have understeering or oversteering nature since wider tyres help the driver balance the vehicle properly thus making the driving safe and secure.
Disadvantages of Tyre Upsizing
Despite the aforementioned benefits, tyre upsizing also has a few significant drawbacks that discourage many car owners.
Higher Cost: Tyre upsizing can be an expensive proposition for some, depending on factors such as the type of vehicle and tyres used. However, in general, larger wheels and tyres mean more expenses for the car owner.
Reduced Acceleration: While large wheels and wider tyres mean a great grip on the road, they can cost vehicle’s performance in terms of affecting its acceleration. Wider tyres add to the overall body weight of the vehicle thereby increasing the burden on the engine capacity and slowing down its acceleration.
Weighted Steering: With a larger contact patch, wider tyres and large wheels improve stability. However, at the same time, they mean a heavy steering, which requires more effort from the driver to manoeuvre and control the steering. This can cause a significant disadvantage to drivers who prefer to drive vehicles with a light steering, and in a slow traffic scenario.
Low Fuel Efficiency: Tyre upsizing can also affect the fuel efficiency of a vehicle. With wider tyres and larger wheels, the car has a better grip on the road, which affects the rolling resistance negatively. As a result, the car will need more revs to move efficiently, consuming more fuel in the process.
Wrong Speedometer Reading: Done incorrectly, tyre upsizing can affect the reading in your vehicle’s speedometer. Car owners must exercise care in choosing the right tyre for upsizing. Tyre experts recommend upsizing tyres proportionately; meaning the increase in width of tyres should be equally proportionate to the decrease in tyre’s sidewalls. If the diameter of upsized tyres goes higher than that of the original tyres, it may affect the reading of the speedometer and hamper the performance many other modern systems such as ABS, ETC, ESP and TPMS.
Little Driving Comfort: Tyre upsizing can adversely affect the riding quality. With larger wheels and wider tyres, the length of the sidewalls goes drastically down, leaving little or no sidewall flex for the wheels to absorb shock on bumpy roads. Hence, this makes riding less comfortable for the driver and passengers alike.
So, should one upsize or not?
While tyre upsizing is a compelling proposition from the standpoint of a vehicle’s aesthetic appeal, vehicle owners must factor in a number of aspects related to their regular driving requirements. Moreover, it is highly recommended that vehicle owners consult professional tyre experts in order to determine if tyre upsizing is a wide move for them.
How to Calculate Tyre Upsizing?
Tyre size calculator is the key to achieve optimal performance for your vehicle. With the help of tyre upsizing calculations, the best compatible plus size wheels for your vehicle can be chosen. There are two ways to do upsizing calculations:
1) Retaining Original Wheels/Alloys:
When you talk of upsizing your car tyres and retaining the original set of wheels, it means that no modification will be done to the metal portion i.e. the alloy or the rim of the tyre, however, the tyre will be changed as per the fitment requirement and possibility.
For safe tyre upsizing, you must ensure the OD (overall diameter) of the new tyres remains within the permissible tolerance, which is only up to 3% of the OD of stock tyre.
For example, if the OD of the stock tyre is 24.47 inches, then the OD of the new tyre should not go beyond 25.20 inches.
Here’s how to achieve the permissible tolerance.
Let’s assume the original tyre size is 185/65 R15 with an OD of 24.47 inches.
So, the width of our stock tyre is 185mm.
For safe upsize, let’s add 20mm to the width of your stock tyre.
So, the width of your new tire should be 205mm.
The sidewall height of our stock tyre is 65% of the thread width.
As per the thumb rule, for every 10mm increase in width of tyre, the sidewall height (or aspect ratio) should be reduced by 5 percent.
In our example, the sidewall height should be reduced by 10 percent since there was a 20mm increase in the width of our tyre.
So, the sidewall height of the new tyre should be 55% of the thread width.
The Rim size or diameter should remain the same. In this example, it is 15 inches.
Therefore, the max upsize for a stock tyre size (185/65 R15) should be 205/55 R15.
2) Upgrading to Larger to Wheels/Alloys:
When you talk of upsizing your car tyres thereby upgrading to a larger set of wheels or alloys, it means that you are modifying the company fitted wheels in order to increase its diameter and make it look more appealing. The tyres of these increased diameter alloys are called low-profile tyres and are fitted as per the possibility of the gap between the wheels and the vehicle wheel arcs. The above example image shows how a company fitted alloy wheel is upgraded to a larger wheel that has low-profile tyres.
If we want to upgrade to a bigger alloy, we still need to stick to the permissible tolerance mentioned in the previous example.
If we want to upgrade to a 16-inch alloy wheel, then the size of the new tyre should be 205/55 R16, keeping the OD within 3% permissible tolerance, i.e., 24.47 – 25.20 inches.