Caster change by "rake"

[j-c-c-62]

This has been a topic mentioned on a few threads here recently regarding changing the cars rake in having an effect on front caster settings. I thought it best if real numbers were agreed upon so everyone can be on the same page.
There is one minor assumption here, that the front ride height is adjusted to remain the same after raising the rear ride height. Because raising the rear ride height transfers ever so slightly more weight to the front, causing it to lower, and a small tweak on the front TB will easily and quickly return to the original front ride height.
So as an example on a 116" WB car, raising the rear 3", will reduce front caster by approx 1 Degree.

 

[Kern Dog]

With no other changes, switching from a 295-45 to a 295-35 series tire, the alignment guy was able to go from 4.5 degrees to 5.5 degrees with my car.
Many people don’t know that as the front is lower, the caster increases. Front ends lose caster as they rise up.
Here are two charts plotted on the common disc brake spindles/knuckles we mostly use for disc brake conversions:

Just look at the gain in caster as the suspension compresses and how much it loses on extension/rise.

 

[j-c-c-62]

Which all goes to show IMO, the loss of 1 degree static caster from say 3" of increased "rake" really is almost insignificant with the dynamic changes measured in a typical Mopar IFS.

 

[RemCharger]

And don't forget when you jack the front back up you lose even more caster.
My solution to that way back was a 295 50 shorty on the back and big front tire . Gets the front spindle back where chrysler wanted it.

 

[j-c-c-62]

Not exactly, if you are referring to my comment about after raking front ride height restoring, you aren't "losing" anything when you are returning to the static setting you began with by changing the preload.