I've seen alloy wheels being sold in sets of four, but if changing to a larger or smaller size what happens about the spare? Do people always buy five wheels in this case? I can see a set of four works when buying the same size but different style.

Just curious as I've not seen wheels advertised in sets of five.

Ive got 20"ers but my spare is a 19" alloy, it looks like it has never been on the car, just treat your spare like a space saver wheel, and get you original fixed ASAP. cheers. RANGE ROVER 3.6 TD V8 HSE ZERMATT SILVER BLACK LEATHER. AC COBRA 5.7 V8.................. LIVE FOR TODAY COS TOMORROW MAY NEVER ARRIVE,,,,

Even on a brand new car with 20" wheels the spare is always 19" WINNER - 2009 ‘Just Doing What It’s Designed To Do’ Award

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Depends!

If rolling circumfernce of spare is within 3 percent of other wheels no problem.

If like me you have changed the profile size, alters the rolling circumference and puts it over 3 percent you need another wheel.

EG:

4 wheels 18 inch 255x55x18 is acceptable with standard 19 inch rim fitted with 255x50x19

Howver swapped to 255x60x18 tyres and needed 5th wheel with same tyre as standard 19 inch fitment works out to have a rolling radius in of 8.5 percent differnce

Think its black cirlce tyres website that has arolling circumfrence calculator though of course worked all mine out manual

After posting the question I found the answer, well to be honest I was told the answer and realised I was being a bit stupid.

My RRS comes with 20 inch wheels and 255 * 50 * 20 tyres. The 19 inch wheels come with 255 * 55 * 19 tyres (I've bought a set of 19 inch wheels off a newish FFRR)). The difference in aspect ratio means the rolling circumference is the same, thus the same spare caters for both size wheels.

I'll be keeping the original 20 inch wheels and tyres for summer use and be putting winter tyres on the 19 inch wheels, probably Vredestein Snowtrac 4 Xtremes if I can get a set locally.

Thanks for the help.