Tires On Sc400

mclinton · March 25, 2008

I am trying to buy new wheels and tires for my sons 93 SC400. Does anyone know if 245/40-17 tires and 17x7 wheels with will work. The dealer is telling me that his book says that 245/45 - 17 will work but he does not know about the 245/40 -17. The 245/40's are almost the same heigth as the orignal tires and 1.19" wider, while the 245/45's are 1.1" taller and 1.19" wider. It would seem that if the 245/45's would work than the 245/40 would work since they are not as tall?

Brendon Bosy · March 25, 2008

245/40R17's are much too small for our cars. They have diameter of 24.72", which is over an inch smaller that stock. If you want to go to a 40 aspect, you'll need 18" rims. A general rule of thumb tire dealers use is not to go more that 3% larger or smaller in diameter from stock. Doing so can severely alter your speedometer and suspension/handling. Here's a list of what can safely fit on our cars for 17":

OEM = 225/55R16 (25.74")

215/50 (25.46")

225/50 (25.86")

235/45 (25.33")

245/45 (25.68")

255/45 (26.04")

265/40 (25.35")

275/40 (25.66")

285/40 (25.98")

As for the rims, it depends on the offset and width. Stock offset is +50mm, which looks pretty sucken in on our cars. From what I've read, you can go as low as +38mm before the fenders need to be rolled. The lowest offset you can go is +22mm with your fenders rolled. Rim width wise, 10" is the widest you can go on stock +50mm. Tires above 285 series will require rims wider than 10", which wont be able to clear the suspension unless you lower the offset. Offset can be lowered by either the rim's original design, or by putting on spacers. As far as I can tell, 11" is the widest I've heard being successfully fit on our cars, though by that point you're probably not going to find tires designed for anything less than dry pavement. The 285 series is the widest I've seen availible in all-season.