Firstly Tire is the American spelling and Tyre is the English spelling.
If you cannot carry 2 of each spare then don't get flats, simple OR you can repair them in situ with a simple easy to use kit, nail in tyre you jack up wheel, inflate tyre, prepare plug, remove nail, score nail hole, with extra glue ram plug into hole, reinflate tyre, have a beer then lower jack and drive off, job done spare still on rack. These simple kits are available at Supercheap,Repco etc, have been using them for over 30 yrs and never leave home without one.
Now if you rip side out of tyre or blow it to pieces then you use spare, if spare already used because the same has happened before, choose better tyres !!! carry a spare tyre under van, cut off old tyre from rim, liberally smear straight dish washing liquid over bead of new tyre and slam onto rim, using big rubber hammer and 2 x tyre levers pop tyre onto rim, note: you must put tyre on so bead drops into dip in rim first or you will be there for ages. Advise to wear boots not thongs, is easier than it sounds really, if you have CDF is even easier.
Removing a buggered tyre from rim,now that requires skill...try Mr Google he's bound to have something but drive over the tyre on rim works sometimes, but be prepared to look in the bush for your rim when it takes off.......lol.