Strategies For Saving - Cut Car Tyre (And Other) Costs

In these dark times, we must all tighten our belts, as well as having them tightened for us by the powers-that-be in Whitehall. It therefore makes sense to do what we can to save on our motoring costs, from saving fuel to making our car tyres last as long as possible. Here are a few hints to deter the wolf from ringing your doorbell too frequently.

Turning fuel into forward motion is a conversion of energy, from potential to kinetic. Maintaining as much of the former while benefitting from the latter involves applying efficient practices. Maximizing mpg starts with starting the car. Cold car tyres are softer than hot ones and cold engines are distinctly fuel-inefficient. So, if it’s a short trip, don’t use the car. Equally, you can save by being gentle on the gas when the car is cold.

Once the engine (and the tyres) are hot, keep to the highest possible gear. This doesn’t mean accelerating hard until you can use top gear. Instead, keep the rev counter needle low on the scale and change up sooner to keep it there. At the top end of the speed scale, observe the speed limit. We all know that speed camera or police radar gun fines aren’t cheap and they increase insurance premiums. It’s also the case that pressing on costs; the difference between 60 and 70 mph cruising can be up to 5 mpg in some cars.

There are several ways in which life can be a drag or rather, drag can be a costly luxury. Underinflated car tyres give greater rolling resistance and increase fuel consumption. Got a roof rack? If you have and it’s empty, dismount it. The air drag of even an empty roof rack is quite startling and you can do without it, and the weight of the rack itself. Similarly, air conditioning is lovely, especially on a muggy day, but it costs. Specifically, it can cost you to the tune of an 11 percent reduction in mpg. This is about balance. Open car windows create aerodynamic drag too. In general, open the windows to cool down around town but at over 40 mph, use the air con.

Underinflated car tyres aren’t the only things that weigh down fuel consumption figures. Some people carry the essentials but if your car is full of junk, every kilogram is costing you fuel. Figure out how likely you are to need golf clubs, dog blankets, Thermos flasks and half a dozen old newspapers on the way to the supermarket. This is a question that answers itself!

Some savings are more obvious than others. The number of miles of tarmac that pass under your car tyres is probably a given. That said, are you using the most fuel-efficient route? Try to avoid traffic if you can and keep up to date with en route road works. Motorways and dual carriageways, without all that thirsty stopping and starting, save fuel, as does the shortest route. Remember that a motorway detour, though a little longer, could be less costly overall.

Lastly, hidden costs. This is all about shopping around. Many things, such as new car tyres, may be what’s called a distress purchase. However, the firms selling the tyres, car insurance, spare parts and even fuel are in distress too. It’s worth looking out for the best deal.

Merityre are a leading UK independent supplier of car tyres. Why not visit their website at www.merityre.co.uk and see where you can buy your next set of tyres.

Car Tyre Calculations: CRF

Looking at the above title, you could be forgiven for wondering, ‘What on Earth is a CRF?’ .As it happens, a CRF is one of those Michael Caine things: not a lot of people know what one is. To put you out of your misery, a CRF is a car tyre science value. It stands for the Coefficient of Rolling Friction. Still mystified? Don’t be - all will become clear!

A CRF is a figure that relates to how much force it takes for a car tyre to be driven along the road. The CRF is used to calculate the amount of drag, otherwise known as rolling resistance, that the tyre has in use. If you need a still simpler example of what rolling resistance is all about, imagine that you’re trying to ride a bicycle with flat tyres. Is it easy? No it isn’t, because the tyres have a high CRF.

We can use our new knowledge practically, to calculate how much force a typical car uses to push its tyres along a road. The force is needed to overcome friction and we can calculate it simply: if we know the tyre’s CRF and the weight it is carrying, we can calculate the force used.

In this example, our car weighs 4,000 pounds and the tyres have a CRF of 0.015. If we now multiply one figure by the other, we can find out the force in pounds. So, 4,000 x 0.015 equals 60 pounds. Does this car tyre science figure mean anything yet? Not really, because we’ve one more sum to do.

The next calculation uses an equation that can tell us how much power the car uses to push its tyres along. The equation is simple enough and we can use it with some figures that are, again, typical. So, Power equals Force multiplied by Speed. Adding figures into this equation shows that the power used is dependent on the speed at which the car is travelling.

Our theoretical car tyres, therefore, use up more power as the car’s speed increases. At 55 miles per hour, they use 8.8 horsepower. At 75 miles per hour, they consume 12 horsepower. Moreover, like with our flat-tyred bicycle, the lower the air pressure in the tyres, the higher the CRF.

Apart from using more power and therefore burning more fuel, what does this friction do? As you can neither create nor destroy energy, it changes its form. In fact, it turns into heat energy. Should the road surface be soft, more heat is transmitted to the ground and less builds up in the tyres.

This car tyre theory is interesting but asking the question, ‘what is it for’ brings an equally interesting answer. Tyre manufacturers sometimes publish CRF figures for their various kinds of tyre. The lower the CRF the less the rolling resistance or, to put it simply, drag. The less the drag, the better the economy. This also shows what is costly about running your car tyres at too low a pressure. However, remember that wasted fuel isn’t the only cost of under inflation.

Lastly, here are the CRF figures for some typical wheel and tyre (and just wheel) configurations.

A low rolling resistance car tyre’s CRF is 0.006 to 0.01

A conventional car tyre’s CRF is 0.015

A lorry tyre’s CRF is 0.006 to 0.01

A train wheel has a CRF of 0.001

Meaningless figures? Look at the one for the all-iron train wheel and imagine how much engine power is used to keep it rolling. As the Americans say, go figure!

Merityre are a leading UK independent supplier of car tyres. Why not visit their website at www.merityre.co.uk and see where you can buy your next set of tyres.