225/45 R18 tire questions

[Rgurleyjr]

So two of my tires are shot, other two are like new. Bought the car 5 months ago and haven't had tire issues till now.

Just realized my tires are not factory size but a common size speed owners buy. I'm not a tire guy, never have been.

Since I have 225 45 18s on the back, going to stat with that size. Read something about the speedo being off.

Question is will I be going faster or slower than what speedo says and how many mph? Should these tires use same psi as stock?

 

[mangosmoothie]

My quick google comparing tire sizes shows a 3.6% difference. It's a larger tire, so the speedo will read about 3.6% low. When 60 is indicated youre going about 62-62.5.

I would run the stock pressure, but I'll let someone who knows more answer that one.

 

[Rgurleyjr]

My quick google comparing tire sizes shows a 3.6% difference. It's a larger tire, so the speedo will read about 3.6% low. When 60 is indicated youre going about 62-62.5.

I would run the stock pressure, but I'll let someone who knows more answer that one.

Thanks! Dang, I already drive fast, surprised I haven't gotten a ticket yet.