Tire inflation access on wheel pants

[gasman]

Find the correct size vacuum cap to fit the stem. Pull off, push on with needle nose pliers.

Amazon and NAPA autoparts sell a flexible extension that will screw on even
when the stem is not in prefect alignment with the hole.

Ignore the 90* fitting.

[hpdmp3486]

Interested with the holes in the wheel fairings. My question is how do you mark the holes to match the valve stems to cut the holes?

[mburch]

Originally Posted by hpdmp3486

Interested with the holes in the wheel fairings. My question is how do you mark the holes to match the valve stems to cut the holes?

Remove wheel fairing, park plane with valve stem in desired spot, shine laser on valve stem, reinstall wheel fairing, drill hole.

[Larry DeCamp]

The laser idea is cool. I just drilled a piece of aluminum with two small holes . One was for the bolt in gear leg threaded cap, and the other was for a center punch or marker corresponding to the valve stem radius from the axle center.
Put he bolt in the wheel pant and mark the pant for hole location you want to access the stem.

BTW, no one responded to my question about “why plug the hole”. Obviously aesthetics is a personal priority. Is there a significant aerodynamic reason to plug it ?

[Scott Hersha]

Originally Posted by Larry DeCamp

The laser idea is cool. I just drilled a piece of aluminum with two small holes . One was for the bolt in gear leg threaded cap, and the other was for a center punch or marker corresponding to the valve stem radius from the axle center.
Put he bolt in the wheel pant and mark the pant for hole location you want to access the stem.

BTW, no one responded to my question about “why plug the hole”. Obviously aesthetics is a personal priority. Is there a significant aerodynamic reason to plug it ?

I doubt there is a measurable aerodymic difference by just leaving it open. If you haven’t drilled your holes yet, go fly and take some measurements, then drill the holes and see if you can tell. If you already have the holes, use some tape and let us know what you find. I have a friend with an RV8 with the open holes. He has no trouble keeping up with everyone in formation, but I seriously doubt he has done any testing.

[HFS]

The valve stem is very rarely aligned perpendicular to the face of the wheel pant at the extended "contact" point. What this means is that unless you allow (somehow) for that fact - if you drill the access hole in the WP based on where the end of the stem is, you probably won't have the alignment you expected after drilling the hole. You could drill a small "pilot" hole and then modify your alignment from there - assuming the correct alignment hole diameter still contains the pilot hole.

The solution I came up with (probably stole it from someone else, been so long don't remember) is to make a valve stem "extender" that projects the actual alignment of the stem to whatever distance is required to mark the same on the inside of the WP with a pencil. You can make the mark along the circular path made by rotating the tire slightly when marking. Then you can choose where on that arc you would like the hole for servicing.

The unit shown is make from some all thread tubing for lighting projects - but any thing that matches the diameter of the pencil you are using will work. I silver brazed a "retention" nut on one end to hold the pencil in place. But even this is optional - with a little care and a pair of heavy duty "tweezers", you can slide out the pencil, after installing the extender, enough to contact/mark the inside of the WP. I usually put some light masking tape in the area of interest, to help the pencil mark show up better.

YMMV - but this way assures alignment at the WP face.

HFS

[lr172]

Originally Posted by Bill Boyd

Not attacking (I'm on your team), but I'm clearly not understanding the perceived importance of valve stem caps. I ditched them about a decade into my 20 year RV-6A ownership and never looked back, tossed the next set in the trash when I was building the RV-10, and do not see any tragedy that may be lurking just because they aren't still in my way every time I want to check or add air. They may keep dirt out (never an operational problem in my experience) but they don't hold air inside if the Schrader valve is leaking.

I'm honestly not sure why we preserve this ritual. Is it like safety wiring an oil filter - we've just always done it and we can't seem to stop?

Have you ever examined the sealing mechanism in a schrader valve? It is a very small cap with rubber and a very weak spring. If any dirt particles enter the stem, they will be forced into the small gap at this rubber piece by the air pressure during filling and if they lodge in the sealing surface, you have a leak. It only takes dust to create a slow leak in a schrader valve and there is plenty of brake dust in that wheel pant. The caps prevent this scenario and cheap insurance from debris related leaks.

Further, the avaiation steel caps have a rubber sealing surface and if in good condition and tightened properly will hold 25+ PSI, providing a layer of limited redundancy for leaks in the schrader valve. I got a set of tubes once that had machining debris covering the surfaces that the schrader seals against. The tires would drop to 30 PSI in a few days and stay there indefinitely, due to the caps. This is different than the plastic auto caps that will not hold any pressure

Not saying that what you are doing is wrong, only that there are tangible benefits to the caps.

Larry

[Bill Boyd]

This addresses exactly what I was wanting to know, Larry.

Thank you for that explanation.

[rongawer]

I too quit using stem caps a long time ago. Just make sure you valve stems are well seated and clear.

I recommend the straight tube approach for checking/adding air. I bought a Milton straight nipple from Amazon years ago and then use either a 3/4" rubber hole cap, or a Camloc spring door, to cover a hole lined up with the valve stem on the wheel fairing.

This is quick and works very well.

TIP: paint a vertical white line (or use a tire marker) on the side of the tire to know when the stem is lined up with the opening.

[D-Dubya]

Regarding the value of having a screw-on valve stem cap, I remember way back in the last century when I lived in Buffalo, NY (much colder than where I now live). A buddy and I washed a car in his heated garage in the middle of winter. When we pulled the car back out into the sub-freezing temperatures, there was apparently some residual water in the one valve stem that didn't have a cap. It froze pretty quickly, and the expansion of the ice allowed air to leak out. In a couple hours, we had a flat tire. It took us some head scratching to figure out what happened. We had to get a hair dryer, thaw out the valve stem, blow the water out, then air it up again. Problem solved, and it never happened again.

Granted, the mechanism of failure wouldn't be exactly the same, but it could be possible for water to freeze when climbing to altitude. Far fetched? Maybe. Would centrifugal force expel any water that was in the valve stem? Probably. But that experience always stuck with me and I ALWAYS put the caps on my cars and my plane.

When I was debating the need for an access door during my build, I read a post on this subject (I think it was from Paul Dye). I don't want to misquote, but he basically said that it's not a bad idea to pull the front half off of the wheel pants and inspect everything in there on a regular basis, which negates the need for an access door to the valve stem. If you have good tubes like the Michelin Airstops, leakage is almost non-existent. So that's what I chose to do. It's not a big deal to pull the front half off.