How tyres can affect your fuel consumption

Thursday December 6 2018

Maintaining the right tyre pressure and

Maintaining the right tyre pressure and changing a car tyre are simple things that should not require any driver to wait for a mechanic. File photo 

By Roland D. Nasasira

There is no doubt that every motorist wishes to cover a much longer distance on the lowest amount of fuel possible. Much as the size of your car engine greatly determines how much fuel you use, it is important to note is that your tyres too have an effect as far as fuel consumption is concerned.
While motorists such as Ivan Kalyango think that big tyres provide his Mitsubishi Pajero with more stability on the road, Sula Kilimani, a mechanic at Kisekka market in Kampala says a number of features or aspects on your car tyres, beyond just their size, determine fuel consumption. These features include tyre treads, pressure, type and condition of the tyres. “Every time I am buying tyres, I choose the big ones because when I am driving on slippery roads, the car is more stable. I do not easily slide off the road,” Kalyango says.

Tyre size
Kilimani says when it comes to fuel consumption, bigger tyres, which in most cases are accompanied by big rims, add an extra weight to the car and therefore, the tyre rolling resistance becomes hectic. Technically, rolling resistance refers or means a force that opposes movement of car tyres against the surface on which they are moving.
“When you are driving on big tyres and you get to a point where you have to step harder on the accelerator, especially on murram roads, it means the engine is burning on more fuel to move the tyres and the entire car body as well. This means that your level of fuel economy will be low,” Kilimani explains.

Tyre pressure
It is common scenario to see a car on the road when one or two of its tyres are low on pressure. This happens not because the motorist or owner wants, but at times they are actually not aware that they are low on pressure, until they are alerted by a pump attendant while refuelling, or when they remember to check the tyres themselves.
“If one of or more of your car tyres is low on pressure, your engine will have to burn more fuel to move the tyres that are low on pressure to match their functionality with those that have the right tyre pressure,” Kilimani explains.
To understand the recommended or right pressure that goes in your tyres, it is advisable to check on your external tyres writings that are always on the tyre sides. The markings do not only guide you on the right pressure but also alert you of the expiry date of your tyres, among other factors. Any decline in tyre pressure means you will burn more fuel.

Type of tyres
Most motorists prefer using certain types of tyres over others. As such, it makes it hard to recommend a given motorist to use, say Pirelli tyres yet they have been driving on Dunlop or Kumho tyres. They would find no reason to roam from one tyre type to another, unless they find a genuine reason to move on.
Hamza Massadda, a mechanic at Wamuco Motors in Industrial Area, Kampala, says the type of tyres you use on your car is in most cases determined by the type and quality of the rims.
“Some cars have alloy rims which are compatible with most types of tyres that are tubeless while the market also has steel rims that are only compatible with tube tyres. It is all about understanding the type of rims you drive on and the type of suitable tyres you can drive along those rims,” Massadda advises.

Condition of the tyres
If your tyres are old and are left with less treads, it means their rolling resistance will be low. This means there will be no opposing force or friction between the tyres and the surface on which they move. This also means that your fuel economy will be high.
However, Massadda cautions that it does not mean that you look out for old tyres. They come along with challenges such as being slippery not only when you are driving on murram roads but also when it rains on tarmacked roads as a result of compromised driving traction.

Note
The bulge at the bottom of the tyres is important. It is called the foot or contact patch . The name implies its purpose. Afterall, you cannot walk without your feet or feet that have a problem and are not balancing.
Overinfalted tyres have the same effect. Vehicles with over inflated tyres are unstable and difficult to control. Therefore, do not go by appearance when inflating your tyres. Inflate them to the proper pressure recommended by the manufacturer or go to a good tyre fitting centre to have the professionals do it.
It is also recommended that every car owner has a tyre pressure gauge, which is used to measure tyre pressure.

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