two different sizes
 

i went to stanard auto wreckers and pick up some tires...all in mint condition...or so i thought...i pick a 185/70/13..but the guy said that one tire was no good so he put on a different one...but its a 175/70/13...so now i have three the same size and one different....would this cause any problems...ex- performance, suspension, or gas and so on??? :shrugs:

it will have a smaller overall diameter so your car won't sit properly weighted for that corner and it will not perform the same...
general rule is if you want a different size tire match the fronts to each other and the rears to each other

i did do that....but the guy said one was no good and he went into the back and picked one....he didnt even ask if i want that one

that's just no good at all.... tires should at a minimum be matched in pairs.

its like blowing a tire and using your doughnut spare :p