Tyre Pressures

How to check my car tyre pressures?

image: How to check my car tyre pressures

Low tyre pressure increase fuel consumption, CO2 emissions and contribute to tyre safety. Tyres under inflated by 15psi, have increased rolling resistance leading to around 6% greater fuel consumption.

A car normally averages 40mpg, would only get 37.6mpg with tyres under inflated.

A correctly inflated tyre improves the safety of your vehicle, is more economical to use and is better for the environment. Find out the correct tyre pressures by looking in your hand book, fuel cap cover or front door panel, remembering to check the size of the tyre for comparison on the chart. Also a lot of vehicles have different tyre pressures from front to rear, so check carefully. It is recommended that you check your tyre pressures once a week, but, you should definitely check them once a month. Also before a long journey or towing.

Even if tyres are inflated with nitrogen, the pressures and overall tyre condition must still be checked frequently.

Find out more about nitrogen


How to check Tyre Pressures

Cold Pressures

Always check your tyre pressures when the tyres are cold, which have not yet been used in the last two hours or have covered less than two miles at low speed. If tyres are hot when they are checked add 4-5 psi to the pressure recommended by the vehicle manufacturer, Re-Check the pressures when the tyres are cold.

Wear

Tyres under-inflated ( not enough) will wear much quicker on the outer edges, whereas over-inflated (too much) will wear in the centre. Both will speed up the wear on your tyres and not giving you the most mileage out of your tyres.
Endurance

Driving on under inflated tyres reduce the endurance capability, leading to deteriation which could even result in rapid deflation. 7psi or more under inflated is classified as dangerously underinflated.

Road holding

With under inflated tyres, the vehicles steering is less precise, if a bend can be taken at 50mph at a pressure of 30psi, this speed drops to 44mph at pressure of 15psi or about 6mph less. Your tyres safety will take care of you.

Lower pressure = worse road holding.

Aquaplaning

If tyre pressures are 30% below the recommended pressure there is a sharp increase in the risk of a aquaplaning.

Lower pressure = higher risk of aquaplaning.

Braking

In addition, test show that braking distance from 56mph to 44mph are 40 meters at 30psi, 45 meters at 15psi. That is 5 meters longer (find out what is five meters?)

Under inflation = longer braking distances.

Fuel Consumption

Low tyre pressure increase both fuel consumption and CO2 emissions. Tyres underinflated by 15psi, have increased rolling resistance leading to around 6% greater fuel consumption.

A car normally averages 40mpg, would only get 37.6mpg with tyres under inflated.

Low tyre pressures cause excessive tyre wear, increases fuel consumption and gives back poor road handling. So why wouldn’t you check your tyre pressures and condition on a weekly basis. If you really do struggle with checking your pressures then you need TPMS

What is TPMS: Tyre Pressure Monitoring System?

20% of cars fuel consumption is due to the tyre, to reduce fuel consumption, the forces opposing the vehicles movement needs to be decreased. Therefore a decrease in tyre rolling resistance leads to a reduction in fuel consumption.

The tyre plays an important role with regards to the environment by enabling a reduction in fuel consumption; the tyre also reduces vehicle CO2 emissions. (CO2 emissions are one of the main green house gases).

How to check my car tyre pressures

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Tyre pressures PSI and BAR


psi

bar

bar

psi

1

0.07

0.1

1.5

2

0.14

0.5

7.3

5

0.34

1.5

21.8

10

0.69

2.0

29.0

15

1.03

2.2

31.9

20

1.38

2.4

34.8

30

2.07

2.6

37.7

35

2.41

2.8

40.6

40

2.76

3.0

43.5

45

3.10

3.2

46.4

50

3.45

3.4

49.3

tyre symbolTyre pressure conversions.


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