Tire failure of S03 at 80 mph, Bad Valve stem?

[tsuter]

Holy tomolly!!!! You mean there are actually people who drive these cars 80MPH or over or at all WITHOUT valve stem supports????



I think I'll go clean my valve stem supports with a Q-tip!!!!

[CarreraS2]

Originally posted by rdane
I have never seen another production car delivered with valve stems supports as OEM equipment.

Which years/models 911s were delivered from the factory with those valve stems supports?

[rdane]

Anything with 5 spoke Fuchs on the car.

[ras911]

most 911s on the board see 100mph at a couple of times a year

Let's see that about 5500 in 3rd ? MMMM! I may have hit that a couple of times last year

I better go check my valve stems

[rdane]

Yes most will see 100

For those that like to see the top end of your car a tire failure is the one thing most likely to ruin your day in a semi controled environment.

[Bill Verburg]

Only the wider wheels use them, 8s and 9S w/ some 7s getting them but not all.

The stem on the wider wheels is at more of an angle, subject to centrifugal loading.

Same reason to use caps w/ seals, the shrader valves are also subject to opening a bit at speed, heat makes it worse.

[Drago]

Originally posted by rdane
...and most 911s on the board see 100mph a couple of times a year.

My goal is daily.

[randywebb]

I thought all the tire dealers had steel stems. (?) Les Schwab and America's Tire do for sure.

I always get them... and I've never run anything wider than 6's or 7's -- it just makes sense...

[89911]

I'd go with steel. The supports may be usefull but I find them ugly and a big dirt trap. At least on the photo shown.

[CRH911S]

rdane, my point was that the supports and steel are really not necessary for street use but might be under certain circumstances. For example, a proper street car set up for Willow Springs where high speeds and extreme braking is creating heat at a level not experienced under normal driving conditions.
As an after thought it's worth mentioning that the BS S02 and S03 are excellent tires but don't necessarily see a long life. In 89911's situation we're looking at 24 months and 3 thousand miles and the wear down the middle suggest the tire has seen its useful life and it's time for replacement. What does the short tire life suggest to you?

[89911]

I think the gobbled up tire is a bit misleading. This picture on inflation shows the tread isn't too bad.

[Formerly Steve Wilkinson]

I use metal valve stems. The rubber-stem supports are cute, but the sticky-tape glue quickly melts on the track wehn the wheels get hot.

Stephan

[Emission]

From TireRack's site:

"Michelin recommends the use of metal valve stems in wheels used for competition, but recognizes that many wheels require additional machining or preparation to accept metal stems. Inspect all valve stems for cracks, signs of aging or other damage whenever changing tires.

The valve in the stem is there for the purpose of inflating the tire, and not as a safety system. In hard use at high temperatures (particularly at high speeds that generate high centrifugal loads on the valve) the valve can weep small amounts of inflation pressure. Enough of these tiny momentary leaks can decrease the tire’s hot operating pressure to a level that can lead to tire damage. The best result from tire damage in a competition setting due to underinflation is that you cannot use the tire anymore. The worst result is obvious.

Regardless of the stem material, (metal or rubber) Michelin recommends a good metal cap that is equipped with a high-temperature gasket. With such a cap providing the primary seal, if the valve fails, the internal pressure of the tire is still contained. Why metal? Michelin engineers have seen plenty of plastic caps melt right off of a stem that has been exposed to serious brake heat."

[Harlan Chinn]

Both my 7's and 9's had factory supports on them before I had them polished. Group 2, who have done my most recent tire installation and balancing have and install metal stems.

[NoLift911]

I would ditto the metal stems and save the supports for the local concours circuit.

As an aside - not that anyone here does but... those boutique "metal" show caps with Porsche crests on them or other insignias are a recipe for disaster on a rubber valve stem...once everything gets hot and spinning real real fast...kinda like having a fishing weight on the end of yer jimmy while doing battle in the trenches.

(I hear alot of people running to their cars to pull the caps - must be all the Targa and Cab guys )

Just a thought - and kidding of course - well...no... not really

-Jeff

[randywebb]

"boutique "metal" show caps with Porsche crests on them... kinda like having a fishing weight on the end of..."

A bit of hyperbole...

Wt (lbs.)
0.007 valve stem cap, metal acorn head
0.005 valve stem cap, metal Porsche crest

[NoLift911]

Randy just say bs...those of us with GED's would appreciate it.

I have a set that someone gave me as a gift and they are heavy - at least equal to the weight of a nickel...that strapped to the top of a rubber valve stem id bad news hyperbole or otherwise...

-Jeff

[CarreraS2]

How much does a standard plastic cap weigh?

[rdane]

Originally posted by 89911
I think the gobbled up tire is a bit misleading. This picture on inflation shows the tread isn't too bad.

As to the tire wear comments. I once had a 3.4 in my car. SO3s went pretty fast. The rear tires did less than 7K miles to the wear bars running a consistent 34# in the rear on a light car. The center tread was gone in that time.

Too much fun to spin the tires at your every whim with that much torque low in the rev range. Soft tires aren't going to last if you drive like I do.

Bill mentioned the angle of the valve stem on the 8s and 9s Fuchs which seems to most of the problem. "The stem on the wider wheels is at more of an angle, subject to centrifugal loading."

Additional weight makes it worse. I have seen a picture of a rubber stem under centrifugal loading and the stem is flat against the wheel at 100+. Extra weight would make that happen at even less speed.

Easy to see why you'd want a support or steel stem on the bigger Fuchs.

[Rikao4]

Happened to me on the Dunlops 9000 ,new,while installing the "twit" removed one the support gizmos, replaced same and went to steel stems..no issues.
Rika