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Flexible Valve Stem Extension

June 15, 2017, 11:23:56 pm

New tires, asked for all new extensions, seals.  The result:

a.  The outer dual tire stem moved from inward facing to outward facing, as I asked, so two new stems
b.  The front stems were replaced as well.
c.  One driver side inner dual stem was kept as it only a year old, said in good shape.  The original had failed after five years.
d.  The passenger side original inner dual stem was not good and was replaced but it had lasted a year longer than the other side.
e.  Steven, the mechanic, explained that on the inner steel wheels the valve stem passes through is sealed with rubber rather than a stronger neoprene material used on the Alcoa outer Al wheel with smaller valve stem holes.  Due to that, he admonished to be very careful if I tighten the nut that holds the valve stem on the steel wheels, do not over tighten

f.  Now to the curious part.  The passenger inner dual valve stem extension was changed to a flexible one by Herman Power.  It is  harder to get a psi reading, my straight gauge just did not get any pressure.  I changed to a different gauge and the sliding psi reading tab slowly came out and stopped at  92 psi.  Heretofore, with the old steel stem, the tab popped right out.  Seemed odd.

Returned to talk to Herman Power.  Said would replace with straight steel one but had had no problems with the flexible.  However I need to get the length of the steel one needed and they would order it.

As a side note, a friend also had the flexible stems, said to be kevlar, installed but he was not good with that.  At FOT he bought a package of two extensions which included the rubber support disk that is used on the outer dual wheel to keep the inner dual valve stem from moving around in the wheel hole.  He apparently did not have the rubber support disks.

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Re: Flexible Valve Stem Extension

Reply #1 – June 16, 2017, 03:43:36 am

On my GV I had 4in metal extensions and one failed when it broke off at the threads of the wheel fitting. Never again.
I was saved by the TPMS that I had just fitted, and it gave a warning before I ruined a tire.
Speedbird 1.

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Re: Flexible Valve Stem Extension

Reply #2 – June 16, 2017, 07:18:52 am

You should not run a TPMS system on a flexible valve stem extension - you need a rigid stem that's well-supported or you're risking a blowout.

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Re: Flexible Valve Stem Extension

Reply #3 – June 16, 2017, 07:59:21 am

Herman has  had a one piece valve stem in the past that is long enough to reach all the way out to the outer wheel. You still need the rubber support plug even if you don't have a TPMS.  Seems like there was even a part number for these valve stems posted 4 or 5 years ago. 

Pamela & Mike

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Re: Flexible Valve Stem Extension

Reply #4 – June 16, 2017, 09:49:55 am

Pamela, mike and michelle....

Greg told me they no longer carry the steel extension due to need for so many different lengths....that seems very strange, but even so I wish they had asked my choice.  Anyway, after got coach and expressed concern they will switch.  I will try FOT for the right one (length) or use my old one from the other dual to get one at Kelly Truck......

Michelle, think it wise you pointed out danger of the flexible with a monitor.  I may return to a TPMS since I removed the pressure pro couple years ago. 

Speedbird, you just airing the inner dual via the normal valve stem, able to use the straight chuck (which I highly recommend as best chuck desugn for these high pressure tires) thru the outer wheel hole?

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