In a world that's sometimes a little unpredictable, it's always reassuring to be able to fall back on the insurance industry. If anyone has devoted real time and money to calculating the probability of different events occurring, it's the actuaries. They sit with their computers crunching numbers all day, shouting with delight every time a new insight emerges. This time, it's the probability a Ford Taurus Sedan will be stollen in Texas. Next time, it's the chance a Toyota SUV will roll over in a sideswipe. Life can be so rich. But the majority of these calculations focus on the standard makes and models of vehicles on the road. If you fit safety features above and beyond the manufacturer's specifications, you will be rewarded with discounts. But what happens if you customize the vehicle for different reasons?

For some people, the vehicle they drive is a statement about who they are as people. It must signal to the world that this owner is someone with a particular lifestyle or values. So they fit alloy wheels, rims and tires, tint the windows and think about a music system that will broadcast bass-boosted alt-rock to the neighborhood. If it stops at this point, the money invested is still quite small and the replacement values are within easy reach of the standard policies. But when you start thinking about modifying the engine and suspension, not only does the cost of the work go up as the power of the vehicle is increased, but the cost of insuring it is also taking off like a rocket.

The first rule of insurance is good faith. You have a specific duty to inform the insurer of any changes to the vehicle before you insure it. If you are proposing to make modifications, you should get quotes before you authorize the work. You may find the premium rates a deterrent. If you fail to tell the insurer of any modifications, you will find the policy cancelled immediately the insurer discovers what you have done. So let's take this as a three-step mambo. Starting with the rule you must tell the insurer of any customization, you are likely to find cosmetic changes costing less than $1,000 will probably be waved through. But if you are spending serious dollars on a custom paint job or any other fixtures and fittings not changing the performance of the vehicle, you rates will definitely go up. The real rises come when your modifications enhance performance, e.g. fitting a turbo, rebuilding the chassis, and so on. It becomes a different vehicle and you will be quoted a special rate.

So before you spend any serious money on customization, get multiple car insurance quotes to find out roughly how much the premium rate is likely to rise. Note the "roughly". The insurance company is going to ask you for a very precise description of the proposed work and may well delay confirming the quote until it has a chance to inspect the end-product. Some people tweak the ride after getting the quote. So companies often give conditional car insurance quotes, awaiting the completion of the work.