Wheel size and car performance – an intimate relationship

If you’re considering changing the wheel size of your car there are a few things to think about first.

Changing the wheel size of a car can have a huge impact if it isn’t done correctly, and it isn’t as simple as buying a set of aftermarket wheels and bolting them on.

Below we’ll explain some of the things you need to take into account if you want to upgrade your car’s wheels.


The need for speed

If you’re thinking about your car’s speed, then a consideration will obviously be how does wheel size affect speed? Well, the answer is, it depends on what you expect from the car. Larger wheels will produce better grip but decrease acceleration. Smaller wheels will improve ride quality.

Unsurprisingly, the speedometer is finely calibrated to give the correct reading. This calibration includes measurements from the gears, differential and the tyres. Increasing the size of the wheels throws out this calibration and means the speedometer can under read the speed the car is travelling – which is illegal. It’s best to refer to your user manual for advice on changing the wheel size to ensure you don’t negatively impact anything.


Fuel economy

There are some who believe a larger tyre will increase a car’s fuel economy. Unfortunately, this simply isn’t the case. Many things affect a car’s mpg, but the larger tyres usually will not help due to the weight. Larger wheels usually mean more weight and higher rolling resistance, making the engine work harder to turn the wheels, increasing the fuel consumption and decreasing efficiency.

However, the decrease in efficiency usually isn’t one that will have too much impact. It wholly depends on your driving style, the tyres you have fitted, and the type of driving you do most often. If you’re regularly driving on motorways above 60mph then larger wheels could actually increase fuel efficiency – as long as you have tyres with a low rolling resistance fitted.



Along with how your car looks, this is probably the thing you’ll notice most if you’re thinking of changing the size of your car’s wheels. If you’re increasing the size of the alloys, you’ll need to decrease the size of the tyres, as the car is calibrated to the diameter of the tyre and wheel together. This means the tyre sidewall has to be stronger which leads to a rougher ride overall.>

Larger wheels can improve the handling, making it sharper, however, the noise levels and vibration will also increase. Smaller wheels with larger tyres make for a smoother, quieter ride. Smaller wheels are preferable if you do a lot of city driving, with smaller rims and larger tyres you’re much less likely to be affected by potholes and poor road surfaces.



Wheels: large vs small

Ultimately, the size of wheels you choose needs to work for how you want to use the car. Smaller wheels will be the most suitable if comfort and fuel economy are what’s important to you. If you want to improve your car’s handling and performance, then opt for larger wheels. Of course, before you spend money on expensive new wheels you should think about if simply changing the tyres could achieve your desired result.

And, finally, perhaps the most important thing to consider when making any modifications to your car – tell your insurance company. Making excess modifications can affect the handling, speed and overall safety of the vehicle. If you do this and fail to let your insurance company know you could void your policy.


6th December 2018

Author: wheelsforwomen

Ireland's first and only motoring website for women. Car reviews, News & Advice written by women for women. We make it all female friendly

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