I just replaced my 17" rims with 18" rims with 40 series tires is my MPH going to be off? If it is then by how much? I was told that i would be going 5 mph faster from my friend but he's always stoned. anyways some help would be nice, here are some pics of my car.

http://members.cardomain.com/clanbluntz

from what i have experienced, yes your MPH's will be off. do a search for a trie calculator, i know i saw one here before....that will tell you how off your MHP would be. as far as 18's, let me ask you....do they rub in the rear?? left, right, or both sides?? im not talking about a rub all the time, but when you have weight in the back. the reason im asking is i switched my 17's to 18's recently and my rear driver side rubs when taking a hard corner or when i put someone in the back. i no longer drive with anyone in the rear, but i just wanted to know if yours rubbed. if i find that link i will post it here for you.

heres one link you can try....

http://www.eunos.com/tirecalc/

from what i have experienced, yes your MPH's will be off. do a search for a trie calculator, i know i saw one here before....that will tell you how off your MHP would be. as far as 18's, let me ask you....do they rub in the rear?? left, right, or both sides?? im not talking about a rub all the time, but when you have weight in the back. the reason im asking is i switched my 17's to 18's recently and my rear driver side rubs when taking a hard corner or when i put someone in the back. i no longer drive with anyone in the rear, but i just wanted to know if yours rubbed. if i find that link i will post it here for you.

Yes my tires did rub when i first put them on. They would rub when taking a full left turn and also rubbed in the back. I figured out that the front was rubbing against the front wheel wall which i was able to pust back and its fine now. But the rear i had to take my spare out and bend the fenders a bit so that they would not rub. My friend he had a bad rub on the back when he upgraded his rims, what he did was go to automotivve shop and bought these risers for the rear springs, they are kinda like reverse clamps which you can adjust, you put em between the coils, they were like 12 bucks for 2 i think.

Ill try out that calculator thx.