What should tyre pressure be in my car

Appx1 It works well for most low-pressure gases. First, we take the Ideal Gas Law equation and apply it to our circumstance:. Given the n and R are both constants, and the gas volume in the tire is also a constant, we can take those constants out of the equation, and suddenly we get this straightforward one:.

Put all that into the equation,. Both overinflation and underinflation affect your tire performance a lot, and serious problems might occur. So how will a bad tire pressure affect driving safety? We will explain in detail below. The grip is mostly associated with the size of the contact patch between the tire and the road. An over-inflated tire radically decreases the contact patch while an under-inflated tire does the opposite. A larger contact patch gives you more grip, and this is the exact reason why lots of racers will intentionally decrease their tire pressures to create a larger contact patch on a dry race track.

However, despite the fact that an under-inflated tire will cause more fuel consumption and improper tear and wear of the tires, for most daily commuters, it might cause an even scarier problem, which is hydroplaning. Hydroplaning is a hazardous event when a layer of water builds between the wheels and the road surface, leading to a loss of traction that prevents the vehicle from responding to control inputs.

Hydroplaning occurs when the pressure of the tire pushing on the ground is equal to the water pushing back up on that tire. The size of the contact patch, given the force or the weight of the tire, is the same, directly affects the average pressure the tire's putting down on the road. The larger the contact patch by deflating the tires , the less pressure it puts on that same area.

So there's a causal relationship between your tire pressure and the possibility of a hydroplaning event. Here's a more visual explanation of what is happening between a properly-inflated tire and an underinflated tire when driving on a wet road.

Also, check your tires' treads, which make the water flow around the tires more efficiently, and of course, driving slow is always a big plus. The contact patch directly decides the pattern of the tire's wear and tear. You don't want your tires to wear out prematurely just because you have an over or under-inflated tire. But with so many different types of vehicles and tyre options you should always refer to your vehicle handbook for the required tyre pressure. A tyre pressure under 20 PSI is considered a flat tyre and puts you at risk of a blowout.

Using a tyre gauge is one of the quickest and easiest ways to check if your tyres are inflated correctly. Many fuel stations also offer an air pump service, with some services free.

A tyre typically loses around 1 psi 0. If your tyres are warm, the pressure inside them increases so any change in pressure will probably be too low.

But how do tyre pressure sensors work? Driving with low tyre pressure for a long period of time will cause excessive wear on the inside and outside edges of the tread because of the uneven contact between tyre and road.

Underinflated tyres also increase rolling resistance, which means the fuel efficiency of your car is reduced as it uses more power to make up for the resistance. If your tyres need a little more air, use a suitable pump, adding small amounts of air at a time. Overinflated tyres can really impact the handling of your car. Due to the increased friction caused by under-inflation, more fuel is needed to push the vehicle forward. This leads to high fuel consumption and greater CO2 emissions.

Equally, if tyre pressures are too high, these can cause the tyres to bounce as you drive and cause mass uneven wear across your tyres. Run flat tyres can be used even if they deflate. Even with reduced air pressure, run flat tyres are capable of 50 miles at 29mph or slower, before needing to be replaced.

Tyre pressure monitoring systems TPMS are required when using run flat tyres because tyre pressure levels cannot be confirmed. Not only does low tyre pressure wear your tyres out more quickly but you may also experience increased rolling resistance with the road - which means reduced fuel efficiency and increased CO2 emissions.

On the other hand, putting too much air in your tyres can be just as damaging and costly. Over inflated tyres will have a smaller contact patch the part of the tyre that makes contact with the road which can in turn lead to a loss of traction and poorer braking distances.

Overly high tyre pressure will also cause heavy and uneven wear across the central part of the tyre leading to shorter tyre lifespans than if it was correctly inflated. It's not always apparent that air is being lost from your tyres, but it generally escapes at the rate of up to two PSI of air every month. More air is usually lost during warm weather, so more regular checks are needed when temperatures rise.

You can find the recommended tyre pressure for your vehicle in your vehicle handbook or printed either in the sill of the driver's door or on the inside of the fuel tank flap. Your vehicle manufacturer may suggest different tyre pressures for your front and rear tyres so make sure you're aware of these guidelines.

Alternatively use our tyre pressure finder. Always check the tyre pressure with a tyre pressure gauge when your tyres are cold. Finally, if you are using your vehicle to carry additional load or weight, always consult your vehicle handbook for the correct loaded tyre pressure. Find Your Tyre Pressure. Bar and psi are both units of pressure used by car manufacturers to specify the correct tyre pressure for a particular vehicle.

You can convert bar to psi and psi to bar using the chart below:. Back To Tyres. Unsure where to find your tyre size? Click here for more information. We are committed to offering customers our most competitive tyre prices. Read about our exclusive online tyre pricing. Kwik Fit has over centres across the UK including Northern Ireland, many of which are open 7 days a week for your convenience.

We endeavour to ensure we are displaying the correct tyres for your vehicle. However, we recommend all customers check the tyre size printed on the side wall of their tyres before proceeding with a tyre purchase as occasionally discrepancies do occur. By selecting the tyre sizes above and clicking 'Continue', you are indicating that you have checked your tyre sizes.