Will 225/40/R18's damage my transmission?, Tire shop says so....? Options

[CanadaCelica]

Hey everyone, I tried searching for a topic similar to this one already in the forums and on the net. No luck so I hope someone can give me a little insight here.

Yesterday I purchased a rim & tire package from a local dealer around here. I told them I wanted 225/40's for the tires, as I figured this would make my drive a little more comfortable and help me from scraping my front everywhere I go. Also it fills the wheel gap for a way better look.

So today I had the rims put on but I noticed that the tires were not as I asked, they were 215/35's. I asked the guy why he switched the tire sizes on me, and he told me that the 225's would cause my gearing ratios to be all screwy and it would hurt my transmission. Now I don’t know if this is true or not since I’v never heard of this from anyone else putting larger tires on. I know it would mess with my speedometer a little bit but I used that miata tire site and it’s only a 5% difference.

The guy said if I really want the other size put on then he would switch it, but he just doesn’t want to see me ruin my trans. Now this car is a daily driver and I don’t drive it hard ever. I just enjoy cruising around town.

So what does everyone think???