I have 18" wheels on my s2k.
I know you're not suppose to use the OEM spare tire when you have bigger wheels.

My question is I have spare wheels and tires laying around from my other car and was wondering if it will fit on the s2k as a spare.

Wheel specs are 18x7.5 with a +45 offset.

Can I used this as a spare?

 

Well, if the tire swap was done right, the diameter of the tire should be the same as the old 17" stock wheels. If that's the case then using the factory spare is fine.

Typically you plus size which means the bigger wheels get thinner tires so, the total height of the tire remains the same. I'd measure the total height of the 18's and compare it to the total height of the stock 17's

What you don't want is a stagger between the left and right on the rear because it'll work the LSD to death.

 

It is very important NOT to place the emergency spare in the rear even with OEM tires. The emergency spare in NOT the same diameter as the service wheels. As it states in the owners manual, in the case of a rear flat, first mount the spare in front and move the front tire to the rear position. Assuming you are not running different diameter front and rear aftermarket wheel, this will prevent damage to your differential.

 

So I can use these (18x7.5 with a +45 offset) in the front but not the rears?

Will these even fit in the rears and clear the calipers?

 

A full size spare (a normal wheel and tire) will almost completley fill your trunk.
Do you want to drive around with it?

An 18x7.5 +45 offset wheel doesn't say that much.
About the tire you have on it?
The tire determines the circumference and that determines if you are able to use it on the rear or front.
About the center hole?
About the bolt pattern?
About if it will fit and clear the calipers?

 

Aren't you making an assumption here? He didn't say it had a tire on it. Maybe he's just driving on the wheels.

 

I tend to just keep a can or two of fix-a-flat in the trunk.

A complete tire plug kit's only about the size of a paperback book. Keep one of those, some needle nose pliers and fix-a-flat (or small compressor) in the trunk and 95% of the time you can fix it and drive on.

 

I drive 40 miles to and back from work everyday.
It would suck to have a flat without a spare especially during rainy season coming up.

The tires are 225/40/18
Bolt pattern is 5x114.3

Not sure if it will fit the calipers... That is a good question.

 

Front and Rear both????????????

 

You can use the OEM spare on the front unless you have done something funky like install a "big brake kit" or the like.

Unless you have done something funky with your tire circumferences (actually the key parameter), you should still be able to use the front tire on the rear in case of a rear flat, and then put the OEM spare on the front.

Then just drive slowly to the nearest tire shop and get it fixed ASAP.