Do I need a full-sized spare for my X-Trail?

I have just bought a Nissan X-Trail Tekna for towing a caravan - the tyre sizes are: 225/55R18 on 18x7J rims, whereas on the Acenta they are 225/60R17. Why is this and what are the advantages and disadvantages?

Also I was surprised that it did not have a full size spare wheel, as you cannot tow with the 'get you home wheel'. I am thinking of getting a full size spare wheel, are these available in steel, or will I have to bite the bullet and pay for an alloy, which no doubt will be expensive?

Asked on 3 December 2012 by K Newton

Answered by Honest John
Bling. Idiots want the fancy big wheels and low profile tyres that wreck the ride quality, don't last as long and cost a fortune to replace. Tyremakers sell fancy tyres cheap to carmakers knowing they will make the money back on replacements.
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