OEM Suspensions and Brakes

The suspensions:
Starting with the FE1, and then the changes with each up-level system

FE1 suspension
19-mm front stabilizer bar
16-mm rear stabilizer bar
Stamped steel front lower control arms

FE3 suspension
22-mm front and rear stabilizer bars
Cast aluminum front lower control arms
FE3 shocks and springs

FE5 suspension - 2005-07 years
24-mm front stabilizer bar
FE5 shocks and struts. The springs may be different from some FE3 models.
Larger front end links

FE5 suspension - 2008 and up years
24-mm rear stabilizer bar
NEW FE5(LNF) shocks, struts, and springs.
Updated front knuckle

The Brakes
Brake systems are independent of suspension system, even though many parts are dependant on each other

J41
Front disc; 256mm x 23.69mm front rotors, 50mm single piston iron calipers
Rear drum; 50mm single piston iron calipers, 9.06" rear drums
4x100 wheels
(LS/LT)

JM4
Same as J41 but with ABS
(LS/LT w/ABS)

5 Lug JM4
ABS front disc; 276mm x 23.69mm rotors, 52mm single piston iron calipers
Rear drum; (unchanged except for 5 lugs)
5x110 wheels
(LT w/ABS and upgraded wheels, LT2, 2009 LT2 Sport)

JL9
ABS 4 wheel disc; 296mm x 26mm frt rotors, 54mm single piston iron calipers
Rear; solid 270mm x 14mm rear rotors, 38mm single piston iron calipers
5x110 wheels
(SS/SC, SS/NA, 2.4L Sport)

JL9/LNF
ABS 4 wheel disc; 315.5mm x 26mm frt rotors, 38mm 4 piston Brembo aluminum calipers
Rear; vented 292mm x 19.9mm rear rotors, 40mm single piston iron calipers
5x110 wheels
(SS/TC)

The Cars
These are just Cobalts. If anyone can fill me in on G5's, Ion's or HHR's, I'll add that.

2005

Base, LS, LT - FE1 with J41 or JM4
SS/SC - FE5 with JL9

2006 - 07

LS, LT, LTZ - FE1 with J41, JM4, or (2007) 5-lug JM4
SS/NA - FE3 with JL9
SS/SC - FE5 with JL9

2008 (updated FE5 specs began this year)

LS, LT - FE1 with J41, JM4, or 5-lug JM4
Sport - FE3 with JL9
SS/TC - FE5 with JL9(LNF)

2009

LS, LT - FE1 with J41, JM4, or 5-lug JM4
SS/TC - FE5 with JL9(LNF)

Part interchangeability

So far, and to the best of our collective knowledge, every single suspension part is completely interchangable between models. Some rules apply, which are listed here:

1. If you change the front anti-sway bar, you must be careful to get the proper model year. The FE5 front bar mounting changed between 2005-06. It appears the simple trick it to just get the 2005 FE5 parts to insure compatibility.

2. You can change the rear FE1 axle to an FE5 axle. The FE5 axle has provisions for mounting rear disk brakes. So you either have to cut those off to put on your drums back on, or you have to convert to rear disks. Converting to rear disks does NOT mean you have to convert to 5 lug hubs, but you are going to have to find some 4-lug rotors!

3. Knuckles are the same on every suspension up through 2007. In 2008, the FE5 knuckle was updated with various improvements for bump steer. It is NOT interchangeable. You can still use the GM Racing knuckles for those earlier years

4. Every other part should be completely compatible. For instance, you don't have to use FE1 struts if you want to put on FE5 springs, and so forth.