Rear inner tube valve failure at speed

[jacksonracingcomau]

Umm? Why do people insist on tightening the valve stem nut against the rim?

The nut should be used as a lock nut for the cap, not against the rim. If the nut is used to clamp the stem in the rim you won't see it begin to cant over if the tyre starts to 'Creep' on the rim and the first you'll know about it is when the valve stem rips out of the tube as I suspect occurred here.

Pete

 :1:
That and/ or low pressure explains it
Almost impossible otherwise

[Mike Harper]

One major cause of a valve stem being ripped out like that is that the tube had been installed incorrectly unless it was a centerline tube in a center line rim.  We see it all the time where the stem and the rim hole  are not properly aligned during installation.  Ie  the tube is backwards  and the stem is bent over to reach the  hole.

[John A]

It was hard to hire a good tire guy that would take the care tires deserved and the regular mechanics didn't like doing tires. That was my experience as a service manager so many years ago it makes me cringe!

[Groover]

I have those same rims on my 81 G5. I ended up converting them to tubeless; So far so good. 2 years later, all is well.

You have two choices for valves that I'm aware of that are a direct fit to those rims without modifications:

- Parts Unlimited Part# VS-1218R - https://www.denniskirk.com/parts-unlimited/all-metal-valve-stem-vs-1218r.p54155.prd/54155.sku

- Napa Part# NTH 90426 - https://www.napaonline.com/p/NTH90426

I ended up using the Parts Unlimited VS-1218R, but with one rubber only as the Napa part is shown. I test fitted both, but I preferred the quality of the Parts Unlimited one so I went with that one, but really both will work.

Notes:

1) I had to shorten the metal valve caps about 1/16" otherwise they would not tighten down to the seal when using the two locking nuts. You could use one nut like the NAPA one shows, but that didn't put my mind at ease enough, so I went with the two in locking setup.

2) I didn't do this on this first installation, but now that I am convinced this is the way to go with those rims (no leaking and such), I will I think next time drill/machine a flat spot where the rubber sits for a better seal. The way it sits now, the rubber has to form to the concave shape of the inside of the rim (that's the whole point of the rubber, but it's close and the seal could be better by making it flat). I did use a touch of NAPA Bead Seal between the valve rubber and the rim ( https://www.napaonline.com/napa/en/p/BK_7101204/BK_7101204 )

3) Not all tire places will install a tubeless tire without a tube on a tube-type rim, so you'll have to find someone whom will do that for you. It has to do with liability I think - Anyway, I researched those particular rims a lot along with rim types and profiles of TT vs TL rims - My conclusion was that not only will those rims work for tubeless setup, but IMO tires are actually less likely to come off the rim because of the seating profile they have. The rims you and I have, have a WM marking and CP (Conrtre Pente) which indicates a reverse 4 degree angle) that actually locks the tire on the rim in the event of total air loss better than a true tubeless rim which does not have the reverse angle. Anyway, that's my conclusion and works for me, but do at your own risk and research it until you are comfortable with doing the conversion < that's my disclaimer.

Rim markings on mine (81 G5)


Tubeless Conversion Valve, Parts Unlimited VS-1218R on same bike (after restoration):


Hope that helps, and good luck.

[Triple Jim]

It was hard to hire a good tire guy that would take the care tires deserved and the regular mechanics didn't like doing tires. That was my experience as a service manager so many years ago it makes me cringe!

I think the problem is that the tire guys are considered the lowest guys in the shop, and their pay reflects that. 

The best tire mounting and balancing work I ever had done by a shop was done by a skilled mechanic who happened to be the only guy left in the shop that day.  I could see he was irritated that he was asked to do my four van tires, and he got even with his boss by taking a long time to do the job.  He wire brushed the rim beads, lubed the studs, got the balance just right, and I think he even used a torque wrench on the lug nuts.

[Gliderjohn]

For autos I am blessed with a local rural shop operated by a father and son team only that are 2nd and third generation mechanics. Besides skill and experience they still have all the old machine tools for engine rebuild/overall although usually not cost effective anymore. They also sell parts and tires.
They even test drive after an oil change and put back on the lift to check of leaks. They will work on your late model car or your 1948 Case tractor and about everything in between.
They also let me shelter my Guzzi there if I am coming home from and trip and it is raining so I can't get to my house on dirt roads at that time.
GliderJohn

[Kentktk]

What problem are you imagining now?

 Language discrimination as a way to determine ability.

[Sasquatch Jim]

Okay, I am curious.  They said the valve itself failed.  You said there was a cap on the valve at the time of the incident.  The valve was separated from the tube when they gave it back to you.
  With these facts, I would like to know how they tested the valve to come to the conclusion that the valve itself failed.  Also, even if it did fail, did the cap also fail?
  Someone is telling fibs to cover something up.

[sdcr]

Okay, I am curious.  They said the valve itself failed.  You said there was a cap on the valve at the time of the incident.  The valve was separated from the tube when they gave it back to you.
  With these facts, I would like to know how they tested the valve to come to the conclusion that the valve itself failed.  Also, even if it did fail, did the cap also fail?
  Someone is telling fibs to cover something up.

Jim,

I cannot tell you how they "tested" the valve. When they gave me the part back, I had to ask again, if they knew what caused this, as it may help me avoid a repeat incident. The SW answer, " using a high pressure pump, or the tire may have hit a bump" was all that was offered Yes, there was a metal cap on.

[sdcr]

I have those same rims on my 81 G5. I ended up converting them to tubeless; So far so good. 2 years later, all is well.

You have two choices for valves that I'm aware of that are a direct fit to those rims without modifications:

- Parts Unlimited Part# VS-1218R - https://www.denniskirk.com/parts-unlimited/all-metal-valve-stem-vs-1218r.p54155.prd/54155.sku

- Napa Part# NTH 90426 - https://www.napaonline.com/p/NTH90426

I ended up using the Parts Unlimited VS-1218R, but with one rubber only as the Napa part is shown. I test fitted both, but I preferred the quality of the Parts Unlimited one so I went with that one, but really both will work.

Notes:

1) I had to shorten the metal valve caps about 1/16" otherwise they would not tighten down to the seal when using the two locking nuts. You could use one nut like the NAPA one shows, but that didn't put my mind at ease enough, so I went with the two in locking setup.

2) I didn't do this on this first installation, but now that I am convinced this is the way to go with those rims (no leaking and such), I will I think next time drill/machine a flat spot where the rubber sits for a better seal. The way it sits now, the rubber has to form to the concave shape of the inside of the rim (that's the whole point of the rubber, but it's close and the seal could be better by making it flat). I did use a touch of NAPA Bead Seal between the valve rubber and the rim ( https://www.napaonline.com/napa/en/p/BK_7101204/BK_7101204 )

3) Not all tire places will install a tubeless tire without a tube on a tube-type rim, so you'll have to find someone whom will do that for you. It has to do with liability I think - Anyway, I researched those particular rims a lot along with rim types and profiles of TT vs TL rims - My conclusion was that not only will those rims work for tubeless setup, but IMO tires are actually less likely to come off the rim because of the seating profile they have. The rims you and I have, have a WM marking and CP (Conrtre Pente) which indicates a reverse 4 degree angle) that actually locks the tire on the rim in the event of total air loss better than a true tubeless rim which does not have the reverse angle. Anyway, that's my conclusion and works for me, but do at your own risk and research it until you are comfortable with doing the conversion < that's my disclaimer.

Rim markings on mine (81 G5)


Tubeless Conversion Valve, Parts Unlimited VS-1218R on same bike (after restoration):


Hope that helps, and good luck.

Groover,

  Thanks for posting this. All very helpful. I have owned this bike for about 5 years, and each tire change, considered to the swap to tubeless. I asked a couple of local shops if this would be feasible, but they did not want to do this. Liability, as has been mentioned. I am looking for a smaller, maybe a one man operation that may do this.

[atavar]

I would be upset if they were selling me tubes that can't survive hitting a bump.  LOL  I would have had fun with that statement.

[Charles in Lake Charles]

A 1/8" NPT Nickel Plated Brass Air Compressor Tank Fill Valve Schrader can also be used to convert to tubless

[rodekyll]

Language discrimination as a way to determine ability.

Not biting. Go back under the bridge.

[bigbikerrick]

 Btw, the bike that we are talking about is a 83 Le Mans with the cast, hour glass wheels.


I dont know why I thought you had a bike with wire spoke wheels...DUH! 
With your LM III wheels its a piece of cake to go tubeless, and a no brainer IMHO. You got some great technical information here though.
Thank you for correcting me,
Rick