A few thoughts on the subject. -and the following pertains to almost all 240 Wagons sold in the United States. The Sedans have smaller tires so don't use these numbers, just the websites mentioned.

You've got a wagon, and I'm betting that your stock tire size is 185R14 (look at the tire placard by the door latch on the passenger side door). If it says 185R14, then your car was originally equipped with the OLD metric style tires. In the new P-Metric format, this converts to something like 185/82R14. -and this is not a functional tire size in the new sizing system. Unfortunately, when replacing old metric tires, many tire shops simply use 185/70R14 and think it's good to go. However, this is a smaller tire will throw off your speedometer by about 12%. (the smaller tire makes your speedometer read 12% faster than your actual speed of travel)

For compatible tires that will make your speedometer read correctly, here are your closest options (assuming you still have the factory equipped 14-inch wheels on the car):
205/75R14 (makes the speedometer read 0.6% slower than actual speed)
195/75R14 (makes the speedometer read 1.7% faster than actual speed)

If you've taken a set of 15-inch wheels off a 240 Turbo, or a 740, then you're probably shopping for the following tires. The percentages listed are pretty close, but they vary slightly depending on tire manufacturer.
185/75R15 (about 0.4% larger, thus making the spedo read 0.4% slower than actual speed)
195/70R15 (about 1.0% smaller, thus making the spedo read 1.0% faster than actual speed)
205/65R15 (about 1.7% smaller, thus making the spedo read 1.7% faster than actual speed)
205/70R15 (about 0.8% larger, thus making the spedo read 0.8% slower than actual speed)
215/65R15 (about 0.5% larger, thus making the spedo read 0.5% slower than actual speed.)
Consider the 215/65R15 tire if you're looking for a wider/performance tire, which is probably why you bought the 15" wheels to begin with. If my memory serves me correctly, the 205/65R15 is the stock size for 240 Turbo Wagons (this is also the tire size that tirerack.com recommends when upgrading from 14-inch wheels to 15-inch wheels).

Volvo recommends the use of speed rated tires, and these are designated by letters of the alphabet. A speed rating of "S" or better should meet the manufactuers specs, but check your owners manual and tire placard. You probably won't see this designation on the tire itself, but the computer at the tire store will have the speed ratings of all the tires that they sell. FYI, an "S" rating equates to 112 mph.

The two following websites will be able to help you further. The first is a webpage that describes much of what I've just mentioned, but goes a bit further into what tires Volvo put on the cars in the various North American markets. The second is a tire calculator for determining size differences and how far off your spedo is going to be when changing tire XXX into tire ###. Make sure you look at the tire placard on your car, then at the tires on the car, and then use the tire calculator to determine how far off your spedo is. If the placard says 185R14, then use the 205/75R14 as your factory size when using the tire calculator.

http://www.sonic.net/~zipzippy/volvo/volvo%20240%20faq.html#tires
http://www.miata.net/garage/tirecalc.html

Lastly, it is possible to swap in a speedometer from a 240 Sedan and thus use sedan sized tires. Just below the needle on your wagon speedometer, it should say K9800 (which correlates to the number of counts per mile). If you take a speedometer from a Sedan (K10042), then you could use the smaller sedan tires like the 185/70R14, but check the placard on the vehicle that you're pulling the spedo from to be sure.

Print this page and take it with you the next time you go to buy tires. If you've just bought tires and they are the wrong size, go back and ask to have the proper size tires put on the car. They should have checked what the proper size was before selling you a set of tires. (they may offer you a prorated or discounted replacement cost) If they refuse to replace them or offer a discount, consider contacting the Better Business Bureau. (www.bbb.com)

God bless,
Fitz Fitzgerald.

P.S. If you could, please post what size tires are currently on the car, and what the size is stated on the tire placard. I'm curious what the tire shop sold you and how far off it is.

P.P.S. I tired to make this posting as complete as possible so that everybody who owns a wagon can save this in their archive folder for future reference. Click on the SAVE tab just above the subject message line to add this to your personal Brickboard archive.

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'87 Blue 245, NA 220K