FGT Caster Adjustment
Jason,
Understood on your caster and lack of shims at the front lower pivot. Lowering the car 1” at the front should have increased caster just under 0.5 deg. So between manufacturing tolerance and lowering the car your static caster makes sense. I don’t think this should be too significant and there is not much you can easily do to adjust it with the lowered car. You are just at a new point on the kinematics curve with the lower car. You may be able to adjust the caster back with shims at the upper arm, but I am not sure you will have the adjustment there depending on shims and camber. You could also shim the other 3 pick up points (Both uppers and rear lower) out to achieve the caster, effectively increasing track and reducing fender clearance causing another possible problem. Probably not worth it.
Pros and Cons
Like almost everything, you rarely get something for nothing. There are some pros and cons of having more caster than stock. (Yours is reasonable though, the following is more for guys to think about as cars are modified.) One potential pro the guys mentioned was a little more camber with steer angle, however, this will be very small even at high steer angles and actually may be negated by the fact that the caster trail has increased a little as well. Caster trail is the effective fore-aft lever arm distance from the imaginary caster intersection with ground and the fore-aft distance to the wheel center on the ground. This is 28.5 mm stock on the FGT and it looks like just over 34 mm on your left front.
More caster will give you a little more straight line stability on a smooth road. However, more caster can also give you more wheel fight on bumpy or truck rutted roads. Have you noticed a difference in wheel fight or truck rut following since before the car was lowered? However, increased static camber with lowering would also make these worse and likely a bigger factor depending on your static camber settings.
In addition, increasing caster increases caster trail as noted, which will tend to reduce the change in steering torque felt as you approach the limit. Therefore, higher caster trail typically means it is a little harder to sense the limit in the steering wheel torque. This is something to worry about on higher caster changes (+1 deg or more), but I think you should be OK at your current settings.
I can give you more detail on this geometry and kinematics stuff if you would like.
Scott
