Topic: Tube Valve Stem Nut Practice

[wdhewson]

I keep my tires pretty hard with lots of pressure, normally about 36 psi, so I've never had a tire slip on the rim and pull the tube valve off on an angle.  Or pull it right off the tube!

But, in my recent work on the CB350F, the valve stem is loaded with 3 nuts and a cap.  The cap is a nice metal piece with a quality rubber cover on the valve stem tool to keep it clean.

Of the 3 nuts, two were locked on the outer side of the rim, and I don't think they were drawn down onto the rim with much torque.  However, 1 nut was on the tube side of the rim spun down onto the metal base of the tube stem. So, from inside to outside, I had, the stem base "washer", a nut, the rim tape, the rim, the second and third nuts locked, then the cap with rubber protector.

It seems to me that the nut under the rim is a poor practice and does not let the rubber of the tube fit nicely into the space when the tube is inflated.  The above rim double lock nuts seems excessive.  What about one nut, a bit more than finger tight?

The cap, of course, is properly positioned.

So the question is, what is the best accepted practice for tube valve stems on our wire wheel SOHCs?  Thanks, Don

[ekpent]

I thought I read where 754 does not use any nuts on the outer or above rim section of the stem.Keep the tube from being pulled - damaged if there is tire slippage.

[gane]

Don, Of course, there are many tube configurations, But, ... Tubes which come w/cupped washers generally come w/ 2 nuts, and if you back 'em off & look at the tube "body" you'll probly see that the "valve stem" portion is a seperate piece..  I install tube w/ washer & 1st nut just snug. then w/ all assembled install 2nd nut on outside of rim just tight enough to keep stem from re-entering rim when airing. this will allow valve stem to "cant" and warn you in advance if tire should "slip" on rim before ripping valve stem from tube. This must have been a major concern of manufacturers in the day, as witness to the # of rim locks & rims pre-drilled for screws to tires. luck G

[754]

 Usually I run a double nut about 1/4 above the rim.

[crazypj]

The theory behind it is this.
 At high speed, the valve stem could centrifuge through rim and deform tube enough to come out of tube causing a blow out, that's the reason for nut on outside of rim.
 On street bikes, I use single nut nipped against rim (finger tight).
On MX bikes, run nut up against metal valve cap because tyre will move even with double rim locks
 It may have been true in 'olden times'  but modern tubes are more flexible and possibly better made?
 I remember my father having Dunlop tubes from 1950's where valve stem was actually bolted in place, I'm pretty sure when they got copied in Taiwan they copied everything even if they didn't know why

[wdhewson]

Thanks guys.  Good information.

For a bit more clarity I've included a photo.

Gane, do you mean by separate valve stem the metal part bonded to the rubber, or the larger black rubber oval bonded to the tube?

Is this typical construction?  Don.

[gane]

W, I was refering to the larger rubber pad. In many cases it & the metal valve stem are vulcanized to the tube from the inside of the tube, & is not apparent form the outside. G