This is from another thread I posted on but I thought it apt given
@Terri Gorder just bumped this thread.
Being too far back on your heels after heel lifts can be a symptom of too much heel lift, too much boot forward lean, too much binding ramp delta, or too much boot ramp angle, or some combination of the four. It's not what those things do, it just means it's too much. Fixing any one can fix the problem expecially if you understand the setup.
Ramp angle leans you forward and moves your center of mass forward with out changing your boot geometry. It works well for people who's femur/lower leg proportions are high and have short torsos and relatively long femurs. Too much and you will reactively lean back. Can cause increased quad burn.
Bindings are all different and there is no standard and no standard reporting. Tyrollia PRX bindings have 8mm of Ramp Delta, PRD have 5mm. The bindings (from another thread) that one of our members was struggling with had 7mm. The old volkl bio-logic setup gave negative ramp delta. Knee bindings give you the option of 3mm or 6mm of Ramp Delta. New women's Atomic Vantage skis have + ramp delta of unknown quantity.
Heel lifts lean you forward but bend your foot at the ball and open up your ankle joint and cause you to be relatively more upright in whatever boot you are in so they work well in people with limited dorsiflexion. Too much you will reactively lean back. If you have a high arch they can cause increased pain because they decrease the available space for your arch.
Reverse binding ramp delta or toe shims can help center people who need heel lifts for the increased dorsiflexion or are in boots with too much forward lean and are therefore sitting back or are in some of these bindings with too much + RA.
Lange Boots have 12 degrees of forward lean and they advertise a natural stance, Head Boots have 16 degrees of forward lean. They both have 4 degrees of ramp angle in the boot. Dodge boots have variable forward lean. I don't know about other brands. Spoilers can be added to increase forward lean.
Too much for your particular anatomy or geometry can push you too far forward, cause you to reactively lean back, and decrease the available dorsiflexion you can access in your ankle. Too little can keep you centered behind too far back and require too much boot flex to move forward.
Solid sole boots can usually be modified to adjust ramp delta by about +/- 8mm. Comfort soles can usually be adjusted +/- 3mm. Higher the forward lean more the quad burn.
Boots that are too big will decrease the amount your leg is leaning forward, no matter what the actual cuff angle is. A tightly buckled cuff will make the angle more upright as well, as compared to a loose cuff. As liners pack out and the cuffs are tightened down it will pull your lower leg straighter relative to where it was before the packout.
It would be nice if we could also keep track of what the different skis/binding manufacturers were doing so if someone change a setup and had a problem we had a database here where they could look up their skis, bindings, or boots. Every bit of information I provided above was acquired the hard way. It would be nice if we could pool data for future use.
What I wrote was acquired over my years of trying to fix me, so is specific to things I've used. What other data do members have that might be helpful?