Join Date: May 2008
Location: Westchester, NY
Measure distance between spring pad and edge of bumpstop cup (not jounce bumpers). Measure distance from tires to fenders. Measure distance before shocks bottom out. Add bumpstop extensions till first measurement is equal to or less than other two measurements.
Edit: Oh, yeah, also need to check your steering in front at full bump. Depending on where you have axles positioned, what trackbar you are running, what diff cover you are running, etc. you may need more extension to prevent interference there.