Hello
I have a good sucess rate in the car tyres, Currently i have peas,beans,onions, & carrots in tyres and in a old frezzer i had have my spuds and the the old fridge another lot of carrots.
In the tyres around the fruit trees i currently have more onions
Just use a good top soil (wickes 5 for £10) and compost and a little sand and manure or chicken pellets
Cheers
Brogusblue