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> Valve stem failure
John2kx
post Sep 2 2003, 08:12 PM
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I'm running 5 lug Fuchs on my 914 and have had two valve stem failures since wheels were installed 6 months ago. Both failures have been on the front and on opposite sides. Failures both seem to be from shank section of stem and have shown up as slow leaks luckily and not total failures while at speed.

I use the best tire shop in town for mounting and balance and see many high end cars worked on there.

Is my tire guy missing something? The stems used are a rubber material. I seem to remember seeing some type of stem support back in the 70's. Are these required?

My car does see 100 mph on a regular basis and 130 or so on occasion if this makes a difference.

John
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ArtechnikA
post Sep 2 2003, 08:35 PM
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QUOTE(John2kx @ Sep 2 2003, 06:12 PM)
I'm running 5 lug Fuchs on my 914 and have had two valve stem failures since wheels were installed 6 months ago.

do you know the part numbers? check 'em out against Jeroen's Wheel Types page; i was surprised to discover that several of the wheels (including the part number i have on the back of the 911 right now) are listed as "tube type" wheels... donno if that's a factor, but it could be you're using wheels that were not designed to run tubeless...

there are racing-style screw-down metal shank valve stems i've used in the past, and even those i sealed in theor holes with a bit of silicone RTV.

past that - can't say ...
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Brad Roberts
post Sep 3 2003, 12:22 AM
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You nailed it Rich. He probably has the tube style Fuchs wheels. The bolt in valve stems may be the only cure John.


Its funny reading about someone who occasionally sees 130 mph.. LOL (In the 2.0 guy's dreams)



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John2kx
post Sep 3 2003, 01:54 AM
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Thanks guys for the information. I'll pull wheel this evening and get part number. Had a chart last year with all the Fuch info but can't find link now. Did a search on this BBS but did not locate either.

These are 16 x 6 Fuchs and the tire guy had a real time mounting the 205/50s on the fronts (rears are 16 x 7's and went on fine). He claimed it was due winter weather and shop/tires being too cold.

Brad- will my tire guy be familar with bolt in valve stems or is this something I'll have to purchase from a Porsche dealer? I'd prefer to go this route vs. installing tubes. Or is the bolt in valve stem part of the tube?

Safety is my major concern here plus the fact I don't carry a spare. Call me lucky but have never had a flat which required pulling a tire on side of road in 30 years of driving.

Thanks for information!

John
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John2kx
post Sep 3 2003, 02:03 AM
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I just found a Fuch wheel chart here and it only showed 14 and 15 inch wheels that required tubes. No such info listed for 6x16s.

Now to find a source for bolt in valve stems. I'll speak to my tire guy in a few hours. Feel sure this won't be greek to him.

John
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Brad Roberts
post Sep 3 2003, 03:01 AM
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yeah.. I forgot you had 16's.. only the 14's and 15's had the tubes (as you found out). I wonder why you are having this problem. Another thought: The tire guy's use a valve stem "puller" to install them correctly... well.. they stand a chance of scuffing the rim if they use this tool... so he may be shying away from installing them correctly with the tool. Ask him.


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Joe Bob
post Sep 3 2003, 03:24 AM
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A lot of stems are put in dry.....I always use a good lube and then spin them to ensure a good seat.
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ChrisFoley
post Sep 3 2003, 06:12 AM
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Are you sure he installed new valve stems? A lot of places stopped using new ones (IMG:style_emoticons/default/rolleyes.gif) to "save" you money. They never go bad, right? (IMG:style_emoticons/default/blink.gif) My wife's car has had 3 stem failures at the base, right after the Honda dealer changed tires. (IMG:style_emoticons/default/finger.gif)
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ArtechnikA
post Sep 3 2003, 06:21 AM
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QUOTE(John2kx @ Sep 3 2003, 12:03 AM)
Now to find a source for bolt in valve stems. I'll speak to my tire guy in a few hours.

the set i used was from Revolution Wheels, aluminum, very lightweight. long time ago, haven't seen anything like them in years...

also - different but related topic - where possible - use valve stem caps. "centrifugal" force works in the direction of pulling the valve core open. if the spring is a little weak, and the air pressure a little low, it can be pretty easy for that valve to collapse and let a lot more air out ...

i don't use them much on the street - but i like to have them on the wheels for track events. i think the last time i looked at the numbers typical wheel speed at the end of the straight was about 2400 rpm...
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campbellcj
post Sep 3 2003, 07:09 AM
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I have used metal stems in the past with good results. Supposedly they can slow-leak slightly more than rubber stems, but are clearly stronger. Also, those little valve-stem supports may be helpful at sustained high speeds. I think they were "required" by the factory on 7" and larger Fuchs.
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VegasRacer
post Sep 3 2003, 07:25 AM
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I have always used the metal valve stems on my race wheels.
I think they were required by SCCA in my race class several years ago.
I got a bad one once that would not allow me to add any air.
Never had any leaking problems with the metal ones.
Any good tire shop should have them available (for a small fee).
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DuckRyder
post Sep 3 2003, 07:44 AM
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BBS makes some metal bolt in stems.

Many of the BMW suppliers have them at about 7.00 each.
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John2kx
post Sep 3 2003, 03:04 PM
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Spoke with my tire guy today and felt he was honest when telling me he has had stem failure in the past.

I mentioned the metal stems you guys suggested and he agreed this was a good choice. He uses "Dell" stems and requested a part number if possible to prevent any error. He's been down this road before and mentioned the angle in which stem is seated into rim as a potential leak path if correct stem is not used. He's more than willing to help but would like to do this right the first time vs. experimenting with different size metal stems.

Does anyone have a part # of a metal stem for 6x16" Fuchs?

John
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