ok so i got 245/40/18 on the back of my ss/sc. my question is will they fit on the front without rubbing? or should i just get 235/40/18 thanks

 

are you doing 8 or 8.5" width on the back.. those 245's will be a kind of big for 18x7.5

 

We got some 17" rims for my brothers SS/SC with 245/45/17 Blizzak WS-50's. They only rub if you turn the wheel all the way to the side and go over a bump (like turning into a driveway). And when they do rub it is very little. The 245/40/18 is very slightly taller then the 245/45/17, so it would rub more if anything. The 235/40/18 is actually slightly shorter then the stock tire, not to mention 10mm thinner than the 245's. I'm just about positive people don't have any clearance issues with the 235/40/18's.

Long story short, the 245/40/18's will probably rub, but only a little bit. The 235/40/18's should clear fine.

Something else you might want to look into is how having 2 different sized tires might affect the ABS. I'm not sure how the Cobalt ABS is setup, but the different sized tires might reduce it's effectiveness.


If you care to look through all this I'll post it up hehe:
Stock Tire - 215/45R18
Search Tires Tire 1 - 245/45R17
Search Tires Tire 2 - 245/40R18
Search Tires Tire 3 - 235/40R18

Section Width: 8.46 in 215 mm
Section Width: 9.64 in 245 mm
Section Width: 9.64 in 245 mm
Section Width: 9.25 in 235 mm

Rim Diameter: 18 in 457.2 mm
Rim Diameter: 17 in 431.8 mm
Rim Diameter: 18 in 457.2 mm
Rim Diameter: 18 in 457.2 mm

Rim Width Range: 7 - 8 in
Rim Width Range: 7.5 - 9 in
Rim Width Range: 8 - 9.5 in
Rim Width Range: 8 - 9.5 in

Overall Diameter: 25.61 in 650.49 mm
Overall Diameter: 25.68 in 652.27 mm
Overall Diameter: 25.71 in 653.03 mm
Overall Diameter: 25.40 in 645.16 mm

Sidewall Height: 3.80 in 96.52 mm
Sidewall Height: 4.34 in 110.23 mm
Sidewall Height: 3.85 in 97.79 mm
Sidewall Height: 3.70 in 93.98 mm

Radius: 12.80 in 325.12 mm
Radius: 12.84 in 326.13 mm
Radius: 12.85 in 326.39 mm
Radius: 12.70 in 322.58 mm

Circumference: 80.45 in 2043.4 mm
Circumference: 80.67 in 2049.0 mm
Circumference: 80.77 in 2051.5 mm
Circumference: 79.79 in 2026.6 mm

Revs per Mile: 812.1
Revs per Mile: 809.9
Revs per Mile: 809.0
Revs per Mile: 818.8

Actual Speed: 60 mph 100 km/h
Speedometer1: 59.8 mph 99.7 km/h
Speedometer1: 59.7 mph 99.6 km/h
Speedometer1: 60.4 mph 100. km/h

Speedometer Difference: -
Speedometer Difference: 0.271% too slow
Speedometer Difference: 0.383% too slow
Speedometer Difference: 0.825% too fast

Diameter Difference: -
Diameter Difference: 0.28%
Diameter Difference: 0.39%
Diameter Difference: 0.82%

 

i already have 245/40/18 on the back. thanks guys

 

So why don't you mount them on the front and tell us how they fit?

 

you know what thats a good idea. smart man. why didnt i think about that thanks.

 

lol That was good.