Tyre (Tire) Valves

[Guest aironepony]

Recently I noticed that my front tyre was loosing pressure over a couple of days. I thought that maybe the rim seal or the valve core was the problem.

 

I duly pumped the tyre up to about 50 psi and painted some soapy water around the rim and valve. No problem with the rim. The valve stem at the point of entry into the rim was bubbling nicely. Then....pop!.... off flew the valve, sheared at the rim.

 

On inspection I found that the break in the aluminium stem had evidence of an old fault. Part of the sheared stem was clean and bright, but about half of the cicumference of the shear was of a dirty blackish "granular" appearance.

 

The local dealership say that they have experienced this with one other customer. It happened to him whilst riding!

 

I have replaced the item with a stainless version...............

[Guzzirider]

I have had a slow front puncture for a couple of weeks now, with no obvious cause, and had a new stem put in last week.

 

This did not cure it so I dropped my wheel off at the tyre shop yesterday and the mechanic figured it out- the aftermarket chequered valve cover was pressing down onto the stem causing the release of air!

 

Back to the cheap plastic originals!

 

Guy

[al_roethlisberger]

We've seen this at least once before.

 

I couldn't find the old thread off-hand, but a more diligent search would probably turn it up.

 

 

I think the other owner was in Europe, and he thought the stem was magnesium that failed. I suspect it was the stock aluminum unit.

 

Anyway, his cracked as well.

 

But this is the only other example I know of. So I don't think it is a common failure.

 

al

[belfastguzzi]

We've seen this at least once before.

 

I couldn't find the old thread off-hand, but a more diligent search would probably turn it up.

I think the other owner was in Europe, and he thought the stem was magnesium that failed.  I suspect it was the stock aluminum unit.

 

Anyway, his cracked as well.

 

But this is the only other example I know of.   So I don't think it is a common failure.

 

al

49223[/snapback]

 

Yep. This was me. Sort of on the edge of Europe, Al.

Looks like exact same problem as hairypony has.

 

I've had 2 failures.

 

One was a cracked stem on a Ducati wheel (possibly the same valve as Guzzi use? Certainly looked like the same material.). The crack is not visible. It allows slow deflation of the tyre. The solution was to replace it with a steel valve. The tyre guy knew what the problem was straight away as he has seen it plenty before. The second problem was when my v.11 tyre deflated on the road. I thought is was a puncture and rode on slowly. Later, on closer inspection I saw that the nut holding the valve to the rim was gone. Valve cap was still on, so only explanation was that the nut split and came off. This allowed the valve to drop into the tyre when enough air had leaked out and then there was rapid deflation.

 

The tyre guy called it magnesium. It looks like some sort of megnesium alloy to me. It's yellowey, not like aluminium. Seems to me that this is the wrong material to use for such an utterly crucial part and that the valves should be changed for stainless steel.

 

PS it seems that those aftermarket caps are bad news for a number of reasons. Back to cheap black plastic indeed.

[Guest aironepony]

Heaven knows what the material is; I call it Sh*tite. It's an alloy of Sh*t and aluminium.

 

Interesting that Beltclaspguzzi has had a similar failure. Should these valves be in use, I wonder. I have have changed the rear one now before it fails in use....