I'm in need of 2 new front tyres which are 215/45/17 but instead of buying 2 i was going to buy 1 and use my spare wheel instead. The things is, my spare has a 245/45/17 tyre so would i be able to buy another 245/45/17 and run those on the back with the 215/45/17's on the front?

Cheers chaps.

Yes you would as long as the rim is wide enough for a 245 tyre Craig. What rims are you running on? If they are standard 17" Lexus rims, 245 seems very wide for a 7.0jx17 rim...........

Oops my mistake, the spare has a 225 tyre on it - so that would be ok then, 225's on the back and 215's on the front? The reason i don't want to buy 2 new tyres is because i don't plan on keeping the 17's for long