In my old Mustang, if you switched the wheel size, in order to get an accurate speedometer/odometer you were supposed to switch a gear behind the gauges. I believe the RPM gauge was electric, but the speedometer was cable driven.
How is it in the Cobalt? If both are electric now, would you need to have the computer updated?

Thanks.

 

both are electric. you have to try to match the tire diameter. stock on the ss is 215/45r18 with a tire diameter of about 25.6. the tire size i plan to go with on my ss is 245/35r19 which has a tire diameter of about 25.7. you can find tire size calculators online just do a search.

 

Yeah he's right. Both are electric and the computers can generally be reconfigured easily.

Here's a tire calculator that I've used:
http://www.miata.net/garage/tirecalc.html

 

Dont be concerned about upgrading the wheels on the cobalt s/c ... there is no aftermarket support for a 5 x 110 lug pattern.

 

do you guys think a 235 or 245 /45/18 will be fine on stock wheels on ss/sc

 

Upgrading a wheel size to about an inch bigger doesnt really mess with the speedo. Anything more should be checked out.

 

Whats the stock tire sizes ?

 

215/45/18, just want to go as wide as i can

 

215/45 is about as wide as u can go on a 7" wheel... 235/40 on an 8" wheel would be the next step up with the same diameter.