General comment on extensions. When I was racing I towed with 1-Ton dually and had steel braided extensions. Ran about 78,000 miles with no problems. When I got my Class-C my first add-on was TPMS followed by steel braided extensions. With only 16,000 miles no problems.
Now there are TWO main things that I would consider a MUST. First you need bolt in metal valves. Second you need a hard attaching point on the outer end of the hose to prevent movement of the hoses. The hoses come in different lengths so you should run the shortest hoses that allow you to easily bolt the end down and you need to support the end of the hose when pushing on it with your tire gauge or air chuck.
I can only guess as to why a metal valve would fatigue as without significant movement of the hose there should not be enough to stress the valve stem. Metal valve stems should be replaced or at least have all the rubber O-rings and gaskets replaced whenever you change a tire. The rubber parts age just as the rubber on your tire ages. Replacing when you replace tires eliminates the need of keeping track of the age of the O-rings and seals. There is a rubber interior to the hose and this will also age so when I replace my tires I will get new hose extenders along with new valve rubber parts.
I have seen spring clips that are supposed to retain the steel braided hose but they don't look too solid to me. I have not looked at the rubber "grommet" that fits the hand holes but have to wonder if they hold the braided steel line solidly. Clearly they do not support the hose end so there will definitely be some movement.
You can see in my set-up that I have the hose firmly attached to my hub cap. I do hold the extender hose when ever using a gauge or air chuck.
Retired Tire Design and Quality Engineer (40 years experience).
Retired Professional race car driver.
Retired Police Driving Instructor.
Member, FMCA Technical Advisory Committee
Delivered Tire Seminar for RV owners & two seminars on Genealogy at FMCA Bowling Green 2009, Madison 2011 and Indy 2012
Am planning on Perry, Ga and possibly Redmond in 2014 if FmCA wants me to talk.
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