In {TAIL ~ addition}, {HEAD ~ the skirt valve} typically lacks a spoke to hold the center of the valve in place, and therefore lacks the problems associated with the spokes catching foreign objects 
In
In { TAIL ~ addition } , { HEAD ~ the skirt valve } typically lacks a spoke to hold the center of the valve in place , and therefore lacks the problems associated with the spokes catching foreign objects
REL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH