I drive a 2004 Nissan Maxima SE, the tires are an R18. I recently bought replacement tires and the dealer installed R17 tires. What is the impact of this? Should I complain? Does it really matter?
The impact is that you have been downgraded to cheaper rims (and possibly tyres) without your permission. As others have said, 17" tyres do not fit on 18" rims, so the rims now on the car are smaller than what you had.
You should ask for an explanation and, yes, probably complain that the rims were downgraded without your permission. I shouldan't make allegations, but it might be worth checking the mechanic's staff carpark for cars with rims that look like your old ones ;)
Does it matter? Well, if the 17" tyres are good quality, the performance could be about the same. However, if the outer diameter (also known as rolling diameter) is different, your speedometer will read incorrectly. Also, there may be issues with your insurance policy if your tyres are a non-OEM size for a 2004 Maxima.
How in the hell did he manage to get the tire on the rim in the first place? There's a whole inch difference between the two rims. But be that as it may, the impact is that your traction control system is going to freak out because the tires aren't the same diameter, and to the traction control system it's going to look like the R17 wheels are losing grip. Unless all four tires were replaced, in which case the TC won't notice.
Yes, you should complain. The R17 tires are narrower than the R18's, which makes them slightly more dangerous because you lose a tiny amount of contact surface (on paper anyway), but mostly there is a huge price difference between 17 inch and 18 inch wheels (for some reason). If you paid for 18's, you should get 18's.