Tyre Upsizing – Rules & Guidelines for proper Upgradation of Tyres

Tyre Upsizing

Your vehicle came fitted with the most suitable tyres providing the best performance. These have the manufacturer’s name, the name of the tyre and reading (215/60R15). In other words, the tyres’ width: 215 mm, profile: 60, R: radial construction, diameter: 15 inches. Generally, this is the common size of tyres that are fit in most vehicles.

Now, on purchasing your fancy vehicle, you might decide to improve its look. The first thing that would come to your mind is to upgrade the tyres. This upgrading process is known as “Tyre upsizing”. It sounds cool and easy but, it is not always practical. There are points to ponder before changing tyres.

In the first place, automobile engineers fitted them for a purpose. Moreover, automobile engineers have to abide by specific rules as follows:

  • No contact with vehicle’s body:

Engineers at automobile industry design vehicles requiring the ready-made, specified sizes. Keeping this in mind, you should approach the wheel manufacturing Company. Ensure the new tyre does not touch your vehicle’s body in any way. The new ones should not touch your vehicle’s fenders. This would cause friction due to rubbing and damage the new tyres. Ensure that they have free movement when the vehicle is fully loaded.

  • Load Bearing Capacity:

Vehicles have specific threshold value beyond which they cannot bear its load. This threshold value is referred to as load-bearing capacity. Fitted tyres of your vehicle require certain load-bearing capacity. When overloaded, tyres burst, causing sudden accidents, so during upgrading, ensure they have a similar or higher load-bearing capacity.

  • Sidewall and width proportionality:

The profile or sidewall is indirectly proportional to the vehicle’s tyre width. Hence, selecting one with a higher width should have a lower profile. Selecting higher profile results in the narrower set of your vehicle’s tyres. However, choosing bigger wheels means you need wider tyres.

  • Speedometer Reading:

The aspect ratio/profile/sidewall of your vehicle’s tyre is indirectly proportional to speed. Vehicles that move at a very high speed have lower profiles. The profile range is usually between 30% and 50%.  The lower profile helps you to control the vehicle around sharp corners. While buying upgraded ones, ensure they provide similar or higher speed reading.

  • Recalibrate speedometer:

Automobile manufacturers set speedometer and electronic functions based on fitted tyres. Tyre upsizing often means a change in its circumference size. As a result, the speedometer has to be recalibrated. Always purchase new ones of similar size. Otherwise, consult a speedometer and electronics professional after buying tyres.

What are the pros and cons of Tyre upsizing?

The rules stated above should help you decide on upgrading tyres. There are two broad methods of upgrading them. You may mount wider ones while keeping the original wheels. Otherwise, you can upgrade to larger wheels while installing wider tyres.

There are both pros and cons you should consider before upsizing.

Pros:

  • Design of Vehicle – Upgrading enhances elegance to overall vehicle’s design. Simply changing to bigger ones, you can boost your ego. Your friends and relatives would notice the change in your personality.
  • Improved bearing – Wider tyres have improved contact and grip on the road. At a relatively high speed, you get better control over your vehicle.
  • Safe Braking – The faster the grip the lesser the braking distances. Even while driving at high speed, you can rapidly brake to stop. Moreover, your vehicle would not skid while you use the brakes.
  • Improved Cornering – Wider and larger tyres have narrower sidewall flex. This helps in controlling your vehicle while moving around corners. You will not have to slow down to achieve this.
  • Overall Control – Wider tyres improve your vehicle’s overall performance, including stability, balance, and traction. Under-steering/over-steering vehicle owners should opt for upsizing for improving vehicle’s performance. Hence, your vehicle would become safe and secure after balanced driving.

Cons:

  • Higher Cost – Purchasing most suitable wider or larger ones for your vehicle is expensive. Also, you should consult a professional to calibrate your speedometer. You have to approach the Company manufacturing ideal ones for your vehicle.
  • Lowers performance – Wider tyres add bulk to vehicle’s overall body weight. These are a burden on your vehicle’s engine whose performance reduces. Of course, these wider and larger ones grip better on the road. As a result, your vehicle does not perform to its fullest.
  • Weighted Steering – Large and wider tyres enhance stable steering that turns heavier than usual.  You require more effort to drive while controlling the steering. You may prefer light steering in less crowded areas. Then, it is better you do not upgrade them.
  • High Fuel Consumption – With better grip better on the road comes more resistance, while the wheels keep rolling on the road. While driving your vehicle, you have to rev or accelerate more. This would cause your vehicle’s fuel consumption.
  • Incorrect speedometer reading – Selecting wrong sized tyre causes incorrect speedometer reading. You should buy new ones having a larger width, but lower profile/sidewalls. You may end up with larger diameters compared to vehicle’s original ones. If you find incorrect speedometer reading, then consult a speedometer professional.
  • Reduced Driving Comfort – Changing your vehicle’s tyres to larger/wider ones can change your riding quality. These offer lower sidewalls flex or profiles resulting in bumpy rides. You and everyone else present with you in your vehicle are uncomfortable.

Should you go for your vehicle’s tyre upgrading?

You wish to upgrade tyre for aesthetic looks of your vehicle. You have already been exposed to the pros and cons of upsizing. Hence, you are now in two minds. Before making your final decision, consult a professional automobile and tyre manufacturers. They would be able to provide the best guidance in this matter. The make, model, and brand of your vehicle have to be considered.

Guidance to Tyre upgrading

Calculation: There are two methods for calculating the best performance for your vehicle.

  • Retaining Original Wheels/Alloys:

Overall diameter (OD) of new tyres should be within permissible tolerance. The figure can be up to 3% of the OD of your vehicle’s tyre. Say, original tyre size of 185/65 R15 has an OD of 24.47 inches. The width of the original tyre is 185mm. Add 20mm resulting in 205 mm should be the width of the new tyre.

In the said example, a profile/sidewall height is 65% of tread width. 10 mm Increase in original width should have 5% profile reduction. Width increased 20mm and sidewall height is 55% of tread width. In this case, rim size or diameter remains same as the original tyre. Thus, after calculations, the new tyre is 205/55 R15 where original is 185/65 R15.

  • Upgrading to Larger to Wheels/Alloys:

In case of upgrading to bigger alloy, you should use permitted factors. You wish to change to 16-inch alloy wheel. The size of the new tyre should be 205/55 R16. Thus, OD of 24.87 inches should be within 3% permissible tolerance.

Conclusion:

Here in this article, we have discussed tyre upsizing in general along with the pros, cons, benefits, and disadvantages of upgrading them. You would notice there are several reputed companies, some of which enable you to provide the vehicle’s make and model. They supply the required tyre size. Before taking any expensive decision you should consult professionals to guide you.

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