There are multiple reasons to install wheel adapters on your Volvo 240. You may have spent a whole lot of money on racing wheels that ended up being the wrong size and now you can't return them. Perhaps there are some wheels you've had your eye on that are a different bolt pattern than the stock 5x108 Volvo wheels. Whatever your reason, wheel adapters will allow you to install wheels with a different bolt pattern than your factory wheels.
Wheel adapters, just like wheel spaces, place the wheel farther away from the stock hub location. This may cause excessive stress on your suspension if the adapters are too large. Also, very thick adapters may force you to roll the fenders of your car to keep the tires from rubbing against them.
Jack up the front of the car and place it on jack stands.
Use an impact wrench or lug wrench to remove the five 19 mm lug nuts from the front wheel.
Pull the front wheel off the wheel lugs and set it aside.
Place the wheel adapter over the existing wheel lugs, then install and hand-tighten the provided lug nuts.
Tighten the lug nuts to 85 ft-lbs with a torque wrench or impact gun.
Install your new wheels over the lugs of the wheel adapters and tighten the lug nuts to 85 ft-lbs.