tyre size for spare

[adam ant]

as above i was wondering if my spare 18 inch mo compomotive wheel would be ok on 205 or 215 width tyre,the reason i am asking is beacuse i have just fitted a rear strut brace on my car and i cant put my spare in the boot now it has 225 tyre on at the moment and it wont clear past the strut brace,now bear in mind that i wont be using the spare tyre unless it is an emergencey any ideas on this?

[richyx]

you need to keep the same rolling radius to stop the transfer box burning out, but you may get away with as long as its just a short journey to the tyre place etc

[TREVCOS]

If you let some air out of it will it go? Assuming you carry a pump.