Ive just discovered that the wheels I bought (newage subaru wheels) for my classic have two scarily unsafe tyres on the front - well hidden but deep cuts in the sidewalls.
The set of 4 tyres on there are 215 45 17's
I have two good tyes on another set that have a lower profile of 40.
Would it be safe to put the 40's on the front and leave 45's on the rear for the time being??
Need a quick fix that wont break the bank or the car.
Thanks for any help you can give.

 

NO, don't do it! You'll break your diffs, as the front axel will turn at a different speed to the rear! (I'm assuming the 40 profile tyres are 215/40/17).
The 40's will travel 1897cm in one revolution and the 45's will travel 1964cm in one revolution. Which is apprx 1% difference. Doesn't sound a lot but I woudln't risk it!

 

Had a thought that would be the answer! Thanks chap.
So the next question is should I chnage to 40 profile or stick with 45's??
The kumhos on the back of the car at mo (45's) are a little worn on the inners and the 40's on the spare wheels are Events?? - Im pretty rural so maybe I should stick with 45's for the sake of not scraping the wheels?? or....?

 

that will give you a difference of 3.5%. Is that acceptable? I really don't know.

a good site to use: www.willtheyfit.com

Also, you might want to consider the wear of your tires. Does the 40 sidewall ones have more thread depth than the 45 ones ? that could help you compensate the sidewall height difference.

 

Thanks for the quick replies guys! went straight down and got 2x 45's not worth bodging the job and dont fancy puting my family in the hedge or trashing the drivetrain!
All balanced up traking to be done on Monday - sorted!
Thanks for being so quick as I only had half hour before my booking at the tyreshop.