Your stock tires should be 185/70R14 for a 244.
You could pick up 15-inch wheels from any 240 Turbo, 740, 760, 780, 940 or old 960 and use those, with a 195/60-15 for a good size match.
The speedo will read right with that combination.
If you can find them, the 16-inch wheels that were on 1990 740T and 91-94 940T cars (5-spoke alloy, called Hydras) allow a 205/55-16 tire fitment. With any of these sizes, you could certainly go up one size with a small effect on the speedo reading.
All these wheels are good options for the car:
http://brickparts.d--r.com/wheels/index.htm

Very wide tires will run into clearance problems in the inside of the rear wheelwell- they hit the wall of the trunk. Tall tires will run into a limit up front hitting the bottom of the strut spring perch. With really large tire fitments or other wheel offsets, clearance to other parts will be a problem.
--
Rob Bareiss, New London CT ::: "Roterande Fläkt Och Drivremmar!"

Yes, you can put larger tires on your car that won't mess up your speedo. You
didn't mention wheels and tires so I going to assume you meant stock 14" wheels.
A really good tire size recommended by Paul Grimshaw in the Volvo performance
book is a 195/65-14. I've tried this and it is a great size. Better braking
and handling. The tire is 99% of the stock size so the amount of change is
so minimal it doesn't matter. After all your speedo could be off 2% or more.
Dave 82 242ti

Hi
You can't really put bigger tires without changing the speedometer, but you can put larger tires on. The previous owner of my car put 215/75r15 tires on my ar and they fill the wheel well nicely. The come close to rubbing but don't. This is the highest profile i would go. The stock tires for the 240 I think is 195/60/15. The profile system of tires is simple. If you go up 10 in profile it changes your diameter 1 inch and increasing by 5 increases the diameter by 1/2 and inch. Each time you move your wheel size up an inch you need to decrease the profile by 10. hope I answered your question.

Charles 1985 245ti 133K

Find the tire size on the sidewall and write it down. Then go to tirerack.com and look at options. I believe they have choices up to 16 or possibly 17 inch rims.