I have 18s and I am using 245 40s. I just need some tires to get on the road for a little while until I get the loot to buy new ones. There is a shop near me that has a bunch of used tires. I called them and said that I didnt really need 245 40 and that I wouldnt mind going a little wider and he said that "40's" were already wide enough, that sounds bass akwards to me. I thought the 245 was the width? Anyway my speedo is off anyway because of the gears so I really dont care what size I put on as long as its not too tall. So what sizes would be good? These tires will only be on for a little while so it is not ultra important, just to get me on the road. Also I plan on getting the 23 tooth speedo gear so what size would put my speedo back to normal with 3.73 gears? Thanks.