Why does fitting wider tyres increase a car's emissions?

In your column 14 January, MV of Thatcham stated that "larger diameter rims increase exhaust emissions," but did not say why. I can see that average engine revs will be lower for the same journey average speed but I, and I expect other readers, would welcome further explanation.

Asked on 21 April 2012 by DT, Abingdon

Answered by Honest John

Because the rolling circumference of their tyres is about the same so they invariably come with lower profile, wider tyres creating more drag and increasing the CO2.

Tags: wheels and tyres low profile tyres co2 emissions

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