Might seem a silly question this one - but i was checking my spare tire the other day and realised it was only 15" and wondered is that actually going to work if i put it on my car when all the wheels are 18"'s? it has body kit etc and i can just c it damaging the car if used.

The wheel will probably be OK, as long as you haven't put big brakes on.

The wheel is smaller but then on your everyday wheels you have a lower profile, so the spare wheel will have no trouble replacing your existing wheel.

 

I've seen so many car driving round with a space saver on. The whole purpose of these space savers is to get you and your car to the nearest tyre place to repair replace your problem wheel/trye. Too many people just drive around with one on with the I'll get it sorted later attitude. The tyre on the space saver doesn't really have a rating and has problebly been sitting in the boot for many years, so it's not a safe wheel to use as a casual wheel.

 

You won't have any problems using it, but just make sure you get it sorted asap to get your proper wheel back on.