Tire tube valve stem cap

[noelf]

I just finished putting new tires and tubes on my -6A. The old tubes were the originals from Van's (Aero Classic Leakguard). These had a valve cap that needed a 3/8" socket to remove/install.

The new tubes I installed were the Michelin Airstops. They require a 10mm socket to remove/ install the valve caps.

I had also ordered a couple of caps from ACS ( p/n 2525, MS20318-1B) and they require the 10mm socket also.

This is not a real problem, but did require me to swap out the 3/8 socket for a 10mm socket I keep in the aircraft. This note is just FYI for anyone else that may need to know.

[az_gila]

Originally Posted by noelf

I just finished putting new tires and tubes on my -6A. The old tubes were the originals from Van's (Aero Classic Leakguard). These had a valve cap that needed a 3/8" socket to remove/install.

The new tubes I installed were the Michelin Airstops. They require a 10mm socket to remove/ install the valve caps.

I had also ordered a couple of caps from ACS ( p/n 2525, MS20318-1B) and they require the 10mm socket also.

This is not a real problem, but did require me to swap out the 3/8 socket for a 10mm socket I keep in the aircraft. This note is just FYI for anyone else that may need to know.

A MS20318-1 valve cap should be 3/8 across the flats. None of that metric stuff...

http://everyspec.com/MS-Specs/MS2/MS...S20813F_39268/

Could it simple be a paint build up on the hex part of the cap?

Thick paint layer of 0.010 (inches, not mm) would make it look like a 10mm wrench would be needed.

[Rupester]

I installed my original Aero-classic tubes in 2010, and the only socket that would fit the valve stem caps was a 10mm. I just installed a new tire/tube on the L side; the 10mm socket works on that too. Didn't try a 3/8" on the new one.

[noelf]

The caps that came with the Michelin tubes are chrome plated and definitely 10mm. The new ones from ASC are painted yellow and also require the 10mm socket.

I did not need to change out my nose tire / tube. The valve stem cap on that one is painted yellow and takes the 3/8 socket. I just replaced that one with a 10mm cap so I would just need to keep one common socket in the aircraft.

On the plus side of this, the battery terminal bolts on the PC 680 and the nut on the back of the alternator also use the 10mm socket size.

[az_gila]

Originally Posted by noelf

The caps that came with the Michelin tubes are chrome plated and are definitely 10mm. The new ones from ASC are painted yellow and also require the 10mm socket.

I did not need to change out my nose tire / tube. The valve stem cap on that one is painted yellow and takes the 3/8 socket. I just replaced that one with a 10mm cap so I would just need to keep one common socket in the aircraft.

On the plus side of this, the battery terminal bolts on the PC 680 and the nut on the back of the alternator also use the 10mm socket size.

Then it doen't sound like the yellow caps from Spruce are really MS20318-1 parts....

Are there any identifying marks on the cap? If you look at the Skygeek picture it shows the Mil Spec number on the part -

http://www.skygeek.com/military-stan...FQ9rfgodqMACgQ

Note that the Mil Spec linked earlier requires marking just below the hex portion.

[noelf]

Gil, I assume you transposed a couple of numbers.

The older yellow valve caps: USA MS20813-1 SCHRADER

The ACS yellow valve cap: MS20813-1 SCHRADER

The chrome Michelin valve cap: I will have to look the next time I go to the airport.

[az_gila]

Originally Posted by noelf

Gil, I assume you transposed a couple of numbers.

The older yellow valve caps: USA MS20813-1 SCHRADER

The ACS yellow valve cap: MS20813-1 SCHRADER

The chrome Michelin valve cap: I will have to look the next time I go to the airport.

Yes... the errant fingers will be told off and a stern letter will be issued...

The links are correct though.

It almost sounds like the real Mil Spec part is getting substituted with a common auto part which would be metric sized.

Again, a true MS part will be marked in some way.

[noelf]

Just to close this out. The chrome Michelin valve caps have NO markings at all and require the 10mm socket.