Should You Fill Your Tyres With Air or Nitrogen?

You've just bought new tyres. Then the retailer asks you if you want to fill them with nitrogen. Do you say yes or no? Or, possibly the retailer tells you nitrogen's numerous purported advantages. Does using nitrogen in your tyres actually stack up?

With competition in the tyre marketplace forcing retailers into margin-slashing to remain competitive, tyre retailers are under increasing pressure to add value, just to stay afloat. Brake and damper assessment and servicing, wheel alignments and the like are good incremental profit earners for tyre retailers, and a good idea for the increasing numbers of car owners who don’t give servicing a second thought. Another offer on the table is the ‘opportunity’ to fill your tyres with nitrogen, which is often touted as a performance optimising enhancement.

It’s sometimes advised that nitrogen has a lower specific heat than air, so it expands less than air for any given heat input, causing less pressure rise as the tyre is pushed hard. It’s also ‘anhydrous’, which just means ‘without water’ in the form of humidity.

The bottom line is that any benefit is bound to be immeasurable on the road, and barely measurable even on a race track – maybe good for a few hundredths of a second a lap. The air you breathe is about 80 per cent nitrogen anyway, so you’re already getting 80 per cent of the benefits of nitrogen when you fill your tyres with ‘regular’ air.

If you decide to fill your tyres with nitrogen, make sure the fitter ‘double purges’ them. This process flushes the air out, ensuring you don’t end up with the gaseous equivalent of a shandie.

For most car owners filling tyres with nitrogen is a total waste of money, and will yield -- at best -- negligible benefits. Save those dollars for something worthwhile.