Does the size of your rims affect fuel consumption?
It's a question that's probably on the minds of many after the recent hike in fuel prices, but if it is true is it significant enough to cause you to put off purchasing those brand new 19-inchers?
Ten to fifteen years ago, changing the aesthetics of one’s car wasn’t exactly at the top of the to do list after purchasing one. Today however, the import market has made car modification a serious business. Aftermarket bodykits, suspensions and rims are must buy items for those into the tuning and racing scene.
These types of mods are usually meant to provide a car with a more aggressive stance. But the question is, though they benefit the car visually, is real world performance affected as well? With the recent hike in fuel prices, many are going to be looking for ways to reduce their fuel expense.
So, today we are here to find out if the size of a car’s rims really does affect fuel consumption. Normally, a bigger size rim would mean added weight. As the size of the rim is increased, it would weigh more, which would mean more energy is needed to overcome the mass to get the car going. If this is done continuously over a certain duration of time, you will see an increase in fuel consumption when compared to using smaller sized rims.
This does not mean that moving from 16 to 17-inch rims will ruin your fc figures. Moving up or down an inch will only provide change of around 0.1km/L. As the difference in size becomes larger, the effect becomes more apparent. However, this is only true if your driving behaviour stays the same, traffic patterns are identical and you take the same route each time.
That being said, moving to a bigger size rim isn’t all bad news as though it’s detrimental to fuel consumption in stop and go traffic, it does offer a significant improvement when cruising on highways. As inertia causes a negative effect when getting bigger sized rim to rotate from a standstill, it has a positive effect while on the move. As a result of inertia, it will take less energy to keep a heavy rim moving than it is to keep a lighter one rotating at the same given speed. This statement is only true if the overall diameter (rim+tyre) is kept constant throughout.
Bigger sized rims are beneficial in other ways as well such as higher top speed and better maneuverability. Unless the overall diameter (rim + tyre) is kept constant, torque and accuracy of the speedometer will be affected as well.
Car and Driver, a motoring magazine in the US conducted a test to figure out how much of a hit would fuel consumption take if the size of a car’s rims were increased or decreased. To make sure the rim size was the only variable, the tyre make was kept the same, tyre pressure was kept as recommended and tyre compounds were nearly identical. All tests were conducted using a standard Volkswagen Golf and all but the 15 inch rims, were aftermarket alloys.
The results of this test was as expected:
Rim Size (inches)/Overall weight (rim + tyre)/Fuel Consumption
19/24.5kg/(9km/L)
18/23kg/(9.3km/L)
17/22kg/(9.7km/L)
16/21kg/(9.74km/L)
15/18kg/(9.9km/L)
After carefully looking at the results you can confidently say that bigger rims ruin fuel consumption. At this point a few may say, but wait…. aftermarket sports rims especially the lightweight variety are usually lighter than the regular smaller sized rims and will negate the weight effect. Though that maybe true to a certain extent, but the weight of the tyre needs to be taken into consideration as well. As overall diameter is kept constant, the width of the tyre wall would have to be reduced. In order to strengthen the tyre, the walls have to be reinforced and this adds weight.
Apart from that, the lightweight rims especially those from Japanese manufacturers such as SSR cost nearly RM 5,000 for 16 inch ones. Bigger sized rims would cost even more but those opting for rims such as these are usually from the tuning fraternity and its very rare that they would care about fuel consumption figures.
For us commoners, smaller sized rims are a better bet in reducing the number of visits to the petrol station and in turn save us more money in the long run. But if you do decide to go an inch up for posing purposes, your fc won't be affected too much. However, always follow manufacturer specifications as failing to do so will not only affect warranty but cause excessive wear on the engine and gearbox of your vehicle.
