For most car owners, slapping on a set of aftermarket bigger, fancier wheels are the first thing to do when trying to personalise or improve our cars.
After all, who doesn't want just a little bit more of that elusive “street-cred” when cruising down the road, or when parked at your favourite mamak.
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But, as with anything in automotive engineering, there's always an optimal point in the middle and trade-offs at either end of the spectrum. In short, there are probably a thousand reasons why that particular wheel (you plan to change) was fitted to your particular car.
Manufacturers calculate hundreds of parameters before choosing a particular wheel and tyre package for any car model – the most important aspects of those being dry and wet road grip, dry and wet braking, high-speed stability, comfort and refinement levels, steering geometry, and cost. Also, all of these come before the actual aesthetics of the wheel and tyre package.
So it is unwise to think that simply fitting on bigger wheels and tyres are going to improve on all parameters, all at once.
While there are benefits to fitting bigger wheels, there are drawbacks that you will need to take into consideration before heading to the tyre store.
In addition, there are other factors also at play when moving to aftermarket wheels, which include the overall weight, width, and wheel offset (which make the wheels stick further in/ out of the sides of the car, and the effects they have on the overall steering geometry – so to be concise we are going to assume that weight and offset are constant and only address the additional diameter and width of the aftermarket wheels.
Dry and Wet Handling and Braking
Dry and wet handling is probably the biggest changes you will feel when upsizing your wheels. It's important to note that manufacturers normally choose tyres with larger sidewalls for better comfort and impact absorption, but they also tend to deform more when in a corner and under braking. Hence, going to a larger wheel size (1-2-inches), and hence smaller tyre aspect ratios should sharpen up the handling and offer better feedback to the driver.
However, this also makes the car more “darty” and responsive to the road which will undoubtedly require more inputs and steering effort. On the upside, you will see improved sportiness and braking in dry conditions.
In the wet however, it can be the opposite – tyres with fatter sidewalls actually deform more and hence bite the road surface better in the wet, it is much the same with wet braking too. Therefore, while handling and braking in the dry may improve, you might be still better off in the wet with a smaller rim and tyre package.
Of course, one also needs to take into account the overall performance characteristics of the tyre when it comes to dry/ wet handling. Some tyres – such as the Michelin Pilot Sport 4 or Goodyear Eagle F1 Asymmetric 3 – can really offer improvements across the board, but they don't come cheap.
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Overall refinement and comfort levels
This is perhaps the most important parameter when going to a larger wheel size. Thinner sidewalls as you might surmise offers less impact absorption hence you are going to feel more of the bumps, hardness, and ruts of the road. Though certain tyre and wheel packages can still offer a good balance despite the bigger wheel size so there are safe ways to upgrade your rim size without all the drawbacks, as we will get into.
Another factor to consider is tyre roar and the effect it has on the overall refinement of a vehicle. Going a size or two up, might also require wider rims and tyres, so this usually attributes to more road noise and tyre roar. Again, tyres do play a big part here, but what you need to know is that almost all of the time, a larger wheel and tyre package is going to cause more roads noise. Now you might not think it will make much of a difference – but sometimes even going from an interior with 68dB to 69dB of road-noise, can have a large effect on how comfortable your daily commutes are going to be.
Other Considerations
Upsizing your wheel and tyre package can also result in a different rolling circumference – basically, how far the wheel travels with every rotation – so this can cause small errors in your speedometer readings, there are great websites like willtheyfit.com that help you calculate most of these parameters before deciding on aftermarket wheels and tyres.
It's also important to note that bigger wheels normally are heavier, so this can also affect the acceleration, braking and steering setup, which in turn may contribute or detract from the overall performance of your car.
Of course, there are many lightweight wheels that can be larger but lighter than your stock ones but again, these do not come cheap and will need to be part of your consideration.
So how do you play it safe…
There are ways of playing it safe when upgrading the wheel and tyre package of your car.
Generally, moving a size up – like say from 16- to 17-inch rims – is safe. You'd obtain the looks without too much of the relative drawbacks, but do research many options and tyre packages before settling on a particular set.
Going up two sizes, let's say from a 16-inch to an 18-inch is less recommended. Unless you take into account the entire package and have also taken into account the overall suspension setup, it's a challenge to negate the aforementioned negative effects the bigger wheel size will have on the performance of your car.
In some cases, you can upgrade the rim size more than an inch if it's still within the confines of the manufacturer's design. Take for instance a Volkswagen Golf 1.4 TSI, which is supplied as standard with 16-inch wheels, but Volkswagen also offer optional wheel packages of up to 18 inches depending on the market. Perhaps in cases like these, one can afford to go with 18-inch wheels since the suspension setup may have been designed to accept larger wheel and tyre packages within the catalogue.
The same could be true for other premium and sports car models.
With that said, don't go fitting 20-inch wheels to your Honda Civic (FC) to mimic the (FK8) Type R because this won't go as well. The FK8 Type R received a plethora of chassis and aerodynamic work to accommodate those wheels.
In short, do your research well, get input from owners who have upsized their wheels before planning your own modifications.
Image credit: redbull.com
And most of all, please do not be fooled into thinking “stancing” your car out is going to make it faster or drive better… that's just not going to happen!
Keyword: Are bigger wheels and tyres really better?