Hey guys. No one EVER answers questions in the Wheel and Tire forum, so I'm re-posting the question here since I've got an SC. I just got a set of ISX50 Rims for my SC400 (18" x 8"), Whats the best tire size to fill in the wheel wells sitting at the stock ride height? Should they be offset? like thinner tire in front wider in back, or both front and back the same? or what? I've never had to put tires on wheels that didnt already have the tire on them when I got them. Thanks for any help guys!

 

front and back the same will be same since it aint a staggard set, id put 225s honestly, u can put 245s if u want

 

225 45 18 height should be equivalent to the stock 225 55 16

 

im running 245-45 all the way around!! it fills out nicely it is equivalent to the stock ride hight

 

I have a set of IS350 wheels and they came with 225's stock. I had them on when I was at stock height, slammed, and with a mild drop and they were fine. If you can fit wider tires on like 245's, go for it. Keep in mind that the wider you go, you may rub if you make hard turns too fast.

 

run the 225/40/18 on the 8" and 255/40/18 on the 8.5". thats stock IS sizes.

 

I believe 225/45/18 and 255/40/18 are probably closest to the factory SC wheel/tire setup for staggered. This sizing is still a bit taller than the stocks, but not as far off compared to going via the smaller route of 225/40/18.

Though 245/40/18 is closest (assuming that sizing is available); just not sure if you'd want it on an 8" wheel.

 

Do this. Just remember, a thicker sidewall is not a substitute for a lowered stance.

 

225/55/16 will give an overall outer diameter (wheel and tire) of 647.5mm
245/40/18 will give an overall outer diameter (wheel and tire) of 646.0mm

Thus, the 245/40/18 will be the closest to OEM stock sizing. However, it will look too small in the rear. I have 245/40/18 front on 18 x 8 front and 265/40/18 on 18 x 9 rear wheels. The overall outer diameter is slightly larger than stock on the rear but it looks nice. The 245/45/18 setup will give you 670.5mm final diameter which is the equivalent of one inch larger than stock. Thus, you will have speedometer error and possibly rubbing at full wheel lock on turns even at stock height.

 

Well the wheels aren't staggered, they are all 8" wide I believe. I'm thinking that 225/40 front and 245/40 rear? Should suit the wheels well you all think? And I shouldnt have any rubbing issues with the wheels turned all the way?

 

ISX50 rims are staggered 18x8 and 18x8.5 normally. Do you have fronts only or did you get rims from an AWD IS250?

 

i have 225 40 in the front and 245 40 in rears on 18 x 8's all around. looks just fine

 

I forgot to mention they are from OEWheels. They aren't OEM rims. So they are all the same 18x8. I could never find any for sale anywhere so I gave up and bough them brand new. I'm defiantly happy with the quality of them as well, very nicely made.

 

Thats what I was thinking. Just some that are a little wider in the rear and a little thinner in front for good clearance when turning.

 

+1 Not to mention a loss of acceleration off the line and an increase in gas mileage when cruising.

Adjusting tire diameters does more than fill a wheel well; it effectively changes your final drive ratio, much the same as swapping diff gears would (although most likely on a lesser scale).