im fairly new at this...i have a 2007 cobalt ls 5 speed 2 door and was wondering if i could put 18's on it without recalibrating my speedometer? if so what size tires could i go with?

 

I think you will be fine, maybe about 2 or 3 mph off, nothing i would worry about.

 

well lets start with what size tires u have now?... and i believe that the 215-40-18's from teh stock ss/sc will work fine... just tell me ur tire size and i'll tell u wut size to get

 

i have the hub caps...yeaaaa.......195/60/15...the tire shop i used to work at said the biggest i could go with is a 205 40 17 but since the ss's came with 18's i was wondering if i could do the same

 

The SS/SC ride on P215/45ZR18, while the SS rides on P205/55HR17. You could put P215/35ZR18's on it and maintain your speedo calibration because that size 18 is the same diameter as the original P195/60R15's. Unfortunatly its not possible to reprogram the speedo in our cars, only the aftermarket tuners have that kind of access.

 

The dealer can re cal the speedo.

I have 225/40/18s on my 2.2 and they fit perfectly. at 80mph (on the guage)I am really doing 82.5 its not that far off, so I don't really care

 

If putting 18's on a Cobalt, the consensus is to use a 225/40R18. GM uses a 215/45R18 to give a little more sidewall. To answer the original questions, yes, it will fit perfectly. You can even lower the suspension (like the SS FE5) and still be perfectly fine. And yes, Dealers do have the ability to recalibrate the speedometers, but only to a degree. All the same, you can get it VERY close, to within 2 MPH.

Try this site to compare wheel sizes:

http://www.miata.net/garage/tirecalc.html

I just tried it using the numbers you provided and at 60MPH indicated you would be traveling 62.2, but like I said, the dealer can get it even closer.

As a comparison, I have the stock 16", which come with 205/55R16's. The difference with that tire is 0.5 MPH. I am lowered (Prokits), and have an absolutely perfect ride.

 

thx for all your help guys...it'll be taken well into consideration

 

Last I knew the reprograms we can do are only recalibrations for proper ABS function. When we reprogram the vehical its the EBCM that gets recalibrated, the speedo in the IPC is unaffected.

 

i think mine is way off, i got pulled over for going 72 when it said 65. i went to the dealership and they said they cant do it.

 

For 18's you should run 225/40/18. Even the stock SS 18's would work without your speedo being off.

Rim gets larger, tire gets smaller. overall diameter is the same.

 

ss/na has 205/50/r17 not 205/55/r17, at least thats what mine came with stock

 

i went to a 40 series 18" tire on my SS na, and my speedo is still exactly accurate.

 

Yup I have 18's and I got the eibach prokit springs w/ 45 series tires and they fit great, speedo is only 2.5-3 mph off and they look great!!! go with 40s if you get sportlines tho.