Valve Stem Extensions

[Jon Wehrenberg]

I have always advised against valve stem extensions. Unfortunately because I kept procrastinating I never got around to pulling them off my bus when I got it.

Today I pulled the drive axle outer wheels so I could access the forward air bags. I'm glad I did. The attached photos are of my drive axle, inner wheel valve stem extensions, and one of the wheels showing the hole the extensions go through.

Michelin at one time spoke against extensions because of the fact that eventually the valve stem would fail at the bend due to fatigue from centrifugal force. What they failed to stress was if the valve stem does not fail due to fatigue, the extension would eventually wear a hole in itself and the inner tire would lose its air.

[Coloradobus]

Oooh Ouch, Jon.
I use them but replace them annually. The mag-chloride for snow removal on the roads here degrades them fast. I also use a rubber grommet that fits into the wheel slot. Seems to help with "extension wobble" you appear to have.

[Jon Wehrenberg]

I should have added that I have the grommets on both wheels. At the end of a trip, invariably I have to push the grommet back into the hole.

I got along quite well without extensions on my other coach.

I use hex shaped valve stem caps. I used a 3/8 deep well socket and extension and I could reach in the appropriate hole (always 180 degrees from the outside wheel stem) to remove the cap. I checked pressure or filled the tire with straight foot tire gauges or fill valves.

A second reason I don't want to use extensions is it is just another joint with the potential to leak, and if you ever get a blowout because of the slow leak the worst wheel for that to happen is the inner drive. It is the hardest to check, replace, and tears up more when it fails.

[win42]

Jon: This is another one of those reasons for us all to be here sharing. The smallest thing can cause major problems. I felt bad because they only put one extension on after polishing the wheels. Now I'll remove that one. The hex stem caps sound like the way to go, are they readily available. It may be a good post to display the air filling and checking devices you use Jon and others. Those inside duals are always a worry.

[Jon Wehrenberg]

Now that I am finally following my own advice I'm going to be checking and filling tires as I have for years on the last coach.

In the attached pictures I have shown the tools that I use or have used.

Since the tags, outer drive and steers all have the valves easily accessible almost any straight or angle chuck works. But rather than using different tools I have used a Milton valve with a straight chuck that reaches through a hole on the outer drive wheel and with a little practice easily finds and slips on the valve stem for the inner drive wheel. The Milton fills the tire when you squeeze the trigger, and when you let up, lets you see tire pressure in the little window.

I ran across the one with the round gauge at Walmart for about $15, and replaced the angle chuck on it with a straight foot chuck and this one is my favorite. It also reads lower than the others so when I fill it to my desired pressures I am either right on the pressure or a little high which is OK.

I replaced all valve caps with the hex type. I install and remove all caps, including the inner drive with the 3/8 deep well socket and handle. I only put them on hand tight. I will throw out the caps at the first sign the seal is not functioning. The valve stem is the first seal against a leak but the cap is the final seal. I have loosened a cap in the past and heard a baerly detectible hiss when I did that, indicating a slight leak in the Schrader valve core.

I show in the photo a pair of valve stem extensions screwed together. If you have them and remove them, they work (as a pair) very well for also filling the inner drive wheel. Just remove the valve strem cap, screw the extensions on hand tight, and fill away. When the pressure is good, unscrew the extensions and replace the cap.

FWIW, I have had my share of leaks in tires. No blowouts, but just leaks and in order of frequency, they show clearly what stuff you may want to keep in your kit of spare parts.

Most frequently I end up with a Schrader valve stem core that leaks. That is followed by the actual seal at the valve stem where it passes through the wheel, and a distant third in frequency is something in the tire such as a nail or screw. If the core leaks, caps are essential. If the stem seal at the wheel leaks, the fix is almost always as simple as deflating the tire, pressing the tire off the bead at the valve stem, and reaching in with a wrench and tightening it up a little. For punctures I carry the tools and materials needed to put a plug in the tire.

[JIM CHALOUPKA]

Jon, I think you are boyond this fix for your situation but it might help someone else wanting a quick and if not a permanent one, something that could take the worry out of the situation until other measures would be implemented. Here it is. Slip over the stem extension a length of nonferrous spring or a piece of heat shrink tubing or even rubber or plastic tubing. This would eliminate the wear on the stem caused by the contact with the wheel. I also have a question I will ask here even if it is not in the correct place From your photo of the worn stem I think that I see that the inner drive wheel is steel. Is that so? If I am correct what is the reasoning and is that standard or common practice. If it is have you seen any coaches that have 8 aluminum wheels. Please someone elaborate on this topic.

[garyde]

Jon, I think you are boyond this fix for your situation but it might help someone else wanting a quick and if not a permanent one, something that could take the worry out of the situation until other measures would be implemented. Here it is. Slip over the stem extension a length of nonferrous spring or a piece of heat shrink tubing or even rubber or plastic tubing. This would eliminate the wear on the stem caused by the contact with the wheel. I also have a question I will ask here even if it is not in the correct place From your photo of the worn stem I think that I see that the inner drive wheel is steel. Is that so? If I am correct what is the reasoning and is that standard or common practice. If it is have you seen any coaches that have 8 aluminum wheels. Please someone elaborate on this topic.

Yes, on all of the coaches I have owned, they use steel Rims on the inner dually. Gary

[JIM CHALOUPKA]

I have been under the impression that the lower the unsprung weight the better. Is this a cost thing where the converter doesn't think the clientell would know the difference, or what?

[Jon Wehrenberg]

For race track handling you are correct about unsprung weight. According to Prevost, when the change to 315R 22.5 size was made they went to steel inner wheels to stay within the width requirements. I'm just reporting what was said so address all comments to Prevost.

The coaches with 12.00 22.5 tires had a pair of aluminum wheels.

[lewpopp]

FWIW My 90 has 8 aluminum wheels. Still can't get it over 95 MPH.

Lew