The 2015 Ford Focus rims have the right bolt pattern, but it's FWD, so those rims have too much backspacing and will sit way inside the fenders, likely interfering with the suspension, not to mention brake clearance. There's also centre bore size to consider. You need to do more research on the rims.
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1992 745, >500k km (now gone, but not forgotten)

To test offset quickly on 15' wheels, you need a straight piece of wood just under 30 inches long and a ruler.

Lay the piece of wood across the rear of the wheel rim and measure down to the contact surface of the wheels in question.

This does not tell you what the offset is, but you can tell if two sets are the same.

Front wheel drive wheels often have a much different offset than rear wheel drive wheels.

The tire size is fine(it will be taller & wider. speedo will read slower) but if you are planning on using the Ford rims. They have a different offset. Not sure how much difference you can have. You'll have to google that. Or someone smarter than me.
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Post Back. That's whats makes this forum work.

Caliper and hub clearance?

Small hole for the alignment pin on 1991 740 hubs?

Offset? I guess should be +20-25 mm?

I don't know, though hope that helps you.

Wheels and Tires page entry on the brickboard Volvo 700-900 Series FAQ:

https://www.brickboard.com/FAQ/700-900/WheelsTires.htm

Hope others here can help you further.

MacDuff
"Just Say NO to dark or black brake fluid!"
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Give your brickboard.com a big thumbs up! Way up! - Roger Ebert.