Valve stem stabilizers...what

[BoaterAl]

After returning from the trip and looking over the bus I was unable to find the rubber valve stem stabilizer on one of the dual drive wheels. There are two on the drive axle. Each is a custom molded black rubber piece fitting over the long valve stem shaft from the inside dual but set in place on the outside dual.
OK, no big deal ...BUT... while reading about this part is extremely important to the longevity of the valve stem. On the Alcoa site they have all the different types available for there wheels along with available dealers.
According to Alcoa this seemly unimportant piece of rubber eliminates valve stem failure on the inside duals.
I ordered 2 new @5.20 each
In looking at the old verse new remaining rubber stabilizer stem hole is slightly larger showing some wear from movement.

[Bill Price]

AL:

Google up the site Dually valve. I put a set of these on a Monaco Dynasty and really liked the way they look and work. I have not replaced them on my Prevost but probably will do so this Fall. See what you think??

[Jon Wehrenberg]

I've said it before and I will say it again for those new to the site or who choose to not listen.

The rubber stabilizers or whatever they are called will not prevent the sudden loss of air due to a failure of the valve stem extensions. The extensions are for those folks who choose to not use a long straight foot tire fill valve. They being the valve stem to the outside dual. The rubber grommets are supposed to hold the valve stem extension so the centrifigal force from wheel rotation does not cause faitigue failure of the valve stem where it comes from the wheel and makes a 90 degree turn.

I knew about the extensions being opposed by Prevost in the early days and did not use them on the first coach. My current coach had the grommets and extensions and because I was lazy I did not remove them or the extensions.

Prevost Maintenance 016.jpg

When I did get around to seeing what was what this is what the extension looked like. Road dirt and grit gets between the rubber and the extension and it wears the extension. But in case anyone wants to think the grommet prevents flexing of the stem and faitugue failure Roger and I were shocked to see his extensions had worn a groove in his Balancemasters and the extensions and he was only a short time aways from a sudden failure of the extension.

Prevost Maintenance 023.jpg

I now use the fill valve with the red hose shown above for filling. My valve stem caps are the fill through the cap type.

Unfortunately the trade off is I cannot and will not use tire pressure monitoring systems that require the use of valve stem extensions because of the problem shown in the first photo.

[Sawbonz]

I don't get it, Jon. Can you label the picture and/or give some others so that I can get a point of reference here?

[BoaterAl]

Jon,
I had long straight valve stems installed on the inner duals tire change last year. In this case size and weight does matter. I'am not a fan of extra weight added with the screw-on extensions, hanging at the end of already piece of pipe.
The only sign of wear was on the rubber stabilizer.

[BoaterAl]

Jon,
How old is your Milton air chuck ? I'm a little surprised you are not displaying a digital inflater in your tool box.

[truk4u]

I'm with John on this one, NO extensions, they're not needed. I just changed out all my stems while putting on new tires and used the shortest stem I could find.

IMG_4121.jpg
This was before the tire change, inner dual with a 6" extension and Pressure Pro

Inner Dual_1.jpg
This is after the tire change, extension removed with Pressure Pro

[Jon Wehrenberg]

The top photo shows a flat spot on the valve stem extension where the extension went through the grommet or stabilizer. It was caused by dirt and grit getting between the extension and the grommet and the constant flexing while driving wore the flat spot in the extension. The remaining thickness in the extension is likely only a few thousands of an inch.

In case anyone wonders why the extension would be worn almost to the point of failure and the grommet not showing any wear the answer is shown by a technique used by folks who sand blast lettering and designs in stone. The grave marker industry makes a rubber stencil with the lettering to sand blast the markings on a headstone. They attach the rubber stencil to the stone and sand blast the letters in the stone. The rubber is unaffected, but the stone is sandblasted to created the lettering, often to a depth of 1/4" or more. The grommet functions the same way. Grit getting between the rubber and extension erodes the extension and leaves the grommet almost untouched.

When the extra weight of an extension is screwed on an inner dual valve stem that lever arm which appears held stationary by the grommet is in fact flexing towards the outside of the rotating wheel by a considerable amount. If I can guess based on the grooves in Roger's extensions and the Balance Masters that flexing could be 1/2" or more.

If you use extensions at the very least check for wear at the grommets often, and understand that even with the grommet the valve stem and extension is flexing and the potential for a fatigue failure of the valve stem at the bend increases.

[phorner]

Tom,

How hard was it to position your Pressure Pro sensor on the inner dual wheel without the valve stem extension?

Looks like it could be a challenge....

[truk4u]

Paul,

Very easy using either the special Pressure Pro tool (3/4 piece of pvc pipe with 3/4 coupling) or a socket with extension. If not using the Pressure Pro, then just a short quick extender like you bought me at NAPA in PSL. It wasn't free folks, he worked me like a dog for two days!