Remove Wheels & Old Tyres Off Rim
Fit New Tyres To Rims
Balance New Tyre & Rim Assembly
Check All Tyre Pressures
Refit Wheels Back On Car
When you're looking for new tyres, the number of different brands and sizes can be a little overwhelming. This is where knowing how to calculate tyre size and what differences it can make will help you out. In looking at a tyre website you’ll see a huge array of brands, prices, and sizes. But what does all this mean and is it important to know?
At Lube Mobile, we know that most people are more interested in having a fast service to replace tyres when they need them. But other people enjoy knowing exactly what they’re buying and if getting different tyres to those currently on the vehicle is going to give them increased performance. Before choosing to install a different size of tyre on your rims, you need to know what changes it will make to how your car operates and then decide if it is worthwhile.
If you calculate tyre size and decide to get larger tyres (rarely will people get a smaller tyre) you need to know how it will affect the readings on your speedometer and your ride comfort. In most cases, a larger tyre than what was on the car previously will make the speedometer reading incorrect. This is because it reads speed based on internal workings from the driveshaft and not the actual tyres.
Essentially no speedometer is a hundred per cent accurate in its readings, and most are designed to fall within a certain error range of around 1-5 per cent. This can mean that at 100 km/h the car can actually be travelling at either 95 km/h, or 105 km/h. If you install different tyres on your vehicle it will change this and your speedometer may need to be recalibrated to ensure your readings are accurate. This is simply because larger tyres will cover more ground in a single revolution.
If you calculate the tyre size you can determine the exact amount of change in your speedometer, and adjust your driving accordingly, but this math can get complicated. An easy way to see how much larger tyres have affected your speed is to use the GPS on your phone and download a GPS speed tracker app. Place your phone in a cradle near the dash and find a smooth and straight road (the more unused the better) and run through a few different speeds. Measure the speed reading in your speedometer against the app and note the difference. You can repeat this for the different posted speed signs (40, 50, 60, etc.). If you’re happy doing some math you can do it once for 100 km/h and then use the percentage difference to work out the reading for the others. For example, if you drive at 100 km/h but the app is showing 108 km/h you know there is about an 8% difference, so to drive at 60 km/h your speedometer needs to read 55 km/h (60 / 100 x 8 = 4.8).
At Lube Mobile, we’re your mobile mechanic specialist and we can install tyres that are suitable for your car. If you’re interested in having a smoother ride than you’ll often get from having larger tyres we can supply those for you. We are operating all over Australia, and as we come to you, you can consider us as the tyres shops ‘near me’. With our vans working in large cities including Sydney, Melbourne, Brisbane, Adelaide, Perth, Canberra, and many other towns and small cities, we’ll always be there when you require a car service or car repairs. You can book in through our website, or by calling our customer service team on 13 30 32. If you're not sure how to calculate tyre size we can help you find out that information.
In most cases, you can find out the exact size of your tyre from reading the numbers in the sidewall. However, knowing what these numbers mean will help you to calculate tyre size and that can save you time in searching for a tyre that is the same size as those currently on your vehicle.
If you look on the side of the tyre you can find numbers in this format xxx/xx Rxx, as an example it may read 245/45 R18. These numbers relate to a certain aspect of your tyre, using our example, here is what they mean:
245 - is the normal section width, measured in millimetres
45 - is the aspect ratio or a comparison of the tyre height, measured as a percentage
R - indicates a radial construction
18 - is the diameter of the wheel rim, measured in inches
If you can’t find the numbers on your tyre sidewalls you can take all these measurements and calculate the tyre size you require. However, for the best results, you can call tyres shops in your area and they’ll help you find the correct tyre size.
At Lube Mobile, we can supply and fit all sizes of tyres. On our website, you can find the correct tyre size for your vehicle by entering in a few details, such as make, model, and year of manufacture. This makes finding out what tyres you need very easy, and you won’t need to go looking for those elusive tyre numbers. If you can’t find your car using the form, you can call our customer service team and they’ll be able to search up your car and give you a price for the tyres that will fit.