Not rocket science but I thought I'd write this up in case it helps someone.

Bought a 2000 V40 a year and a half ago for my son to drive. Car was in generally good shape with low miles (77,000) but it had a classic wheel balance-type vibration at 60 to 65 mph on the highway. I thought it was a front wheel vibration but was not 100% sure.

Had all four wheels balanced. No change.

Looked hard at the front suspension, thought the problem might be a drive shaft due to what looked like to me a fair amount of slop in one inner CV joint.

Before touching the drive shafts I thought I'd try some new tires. So off came the fairly worn Continentals, on went a set of Michelin Primacy MXV4 195/60R15 88V tires. Big improvement, vibration 80% reduced.

In the process of mounting the Michelin tires the installer noticed two rims were bent. So I bought two new (used) rims and reinstalled two tires on the straight rims. So now the car has four new tires and four straight rims. Problem was now 95% solved.

The last step? Dialling in the front wheel alignment (toe). I do this myself by eyeball and road feel. Car originally had slightly too much toe-out, which I overshot to slightly too much toe-in. Then got it perfect. Front wheel vibration is now completely gone.