WARNING to those who have rubber valve stems on their wheels

[Keith Carter]

I don't recall this ever being mentioned on the forums before and I figure it's worth a post since we all share the things we learn about here. A valve stem failure happens once, it's a fluke... failure a second time and it's a real problem. We had rubber valve stems on a set of our OZs when we got them and mysteriously had one fail at Grattan a couple of years back. I was lucky enough to feel the tire go down and adjust my driving accordingly to finish the race. We thought it was a fluke and went on with our racing lives. This past weekend at the Sprints I had another one fail and didn't find out a tire was down until I was in the braking zone going into T8 at Road America. I didn't know what happened at the time since the car got crazy out of shape and I lost all braking power and shot off the end of the track missing the tire wall be several feet. It could've been MUCH worse/expensive if it was to happen elsewhere on any track. Do yourselves a favor and replace all rubber valve stems with metal ones. It may save your neck and your pocket book later on.

[formulasuper]

Keith, Can you tell us how/where the stem failed?

[Paul LeCain]

And when you put in metal ones, make sure they're as short as possible.

I touched a pylon once, and it tipped inward and sheared off the metal valve stem. Very unlikely, but it happened.

[Keith Carter]

I can't say for sure what caused it to fail. Possibly just of old age/UV exposure? When we tried to air up the tire again after the failure occured it was leaking fron underneath the surface of the wheel at the base. We're guessing that the combo of old stems and the centripetal force on the stem when the car was at speed caused the failure. I don't know if they automatically change the valve stems when you have tires mounted, but we had never changed them since we mount our own tires.

[JHandley]

Thanx for the timely post, Keith.
I am in the process of re assembling my compomotives and was wondering which valve stems to use.
Should anything be placed on the seal at all or just bolt them in?
Jeff

[Keith Carter]

There should be a rubber grommet that comes with the metal ones. Other than that I don't believe we do anything else.

[JHandley]

Thanx, Keith.
Kinda thought so but wasnt sure

[akilcoyne]

The bolt in metal type stems come with a rubber seal.

In my experience, I don't like the metal stems for the exact reason that Paul stated. They can be broke completely off with contact. I like the idea that if there is contact that would cause a rubber stem to tear, it would be a slow(er) leak and not an instantanious flat. I replace the short rubber stems every other time I change tires. Cheap insurance imho.

[formulasuper]

Note: One thing I've noticed when changing stems is sometimes there will be a little corrosion or crud around the seating surface of the stem on the inside of the rim where moisture can get trapped. Of course this should be cleaned & smoothed to allow for a good airtight seal against the rubber seal on the stem.

[TedV]

The rubber stems bend out from centripetal force and tend to crack at base near rim when old or damaged. When changing tires or from time to time, squirt with soapy water and bend stem out like it will when racing. Look for bubbles. If you see dry cracks, replace, even if not bubbling. I have seen cracked stems that would hold air at rest, but bleed air when bent. The shorter the rubber stem the better.

Another problem I’ve seen is valve cores. There are some very long valve cores with external springs that have to engage a lip inside the stem. If there is no internal lip, air pressure will keep the valve closed until the wheel rotates at speed, slinging the core open, letting out the air. You come in the pits air tire back up, it holds till next session, then repeat the air loss. Mostly see this on metal stems when a local tire shop uses the long cores out of a rubber stem.

Metal stem with nut on outside is best of metal type. If nut comes loose, you can tighten it without busting the tire bead. You usually discover it's loose on the way to race grid. Use the proper size of grommet whose lip will engage the hole in the rim, usually 2 sizes to choose from. Most formula rims use the small grommet, except FV, big hole.

[Rick Kirchner]

Also check your trailer tire stems. Trailer rims are notorious for being really cheap stampings. They leave a sharp burr arond the stem hole and when the stems are installed, they are frequently cut. I had a couple of slow leaks until the hoosier guy out here tipped me off to the problem.

I've never seen rubber stems for rims as thick as mag OZs. Could it be that the rubber stems are really not meant for this application?

[carnut169]

FWIW we replace stems everytime we mount up a set of tires... now street tires last for a long time but stems are pretty cheap. I'd say install new 1x a year and you won't have to worry.

[Avon Racing Technical]

Just chiming in here,

We would always recommend the use of a metal valve cap with integral rubber seal as even if the valve core fails / vibrates / is loose, you don’t loose air. If you don't, at best, you could end chasing odd hot pressures, and at worst, your tyre would deflate and could destroy your weekend and more.

As reported above, the rubber valves do bend outwards at speed so the shorter they are the better. Short metal ones are a good option if you can get them to fit your wheel, provided they don’t protrude over the edge of the wheel as ‘carroting’ is a real risk if racing is er, close.

Perhaps more subtly, rubber valves (in particular) can suffer if tyres are fitted such that the bead of the tyre is dragged over the base of the valve. Basically, the valve should be opposite the fitting head as the fitting process starts. The last bit to slip over the wheel will be by the valve, and hence the tyre is never dragged into the well, over the valve. Do this for both beads.
Stripping the tyre requires the opposite, in that the valve should be under the fitting head. When you insert the tyre lever, you will find that the point opposite the fitting head will be dragged down into the wheel well (that’s what it’s there for), so if the valve were to be in that position, it could easily be torn and you may not see it.

If a metal valve is used, the same process applies, but this time to save the tyre bead as it’s VERY easy to tear the sealing lip of the tyre.

Regards,

Pete

[kea]

Keith C.,
Good topic to bring up.
I've been around racing so long (70's), I just took it for granted that everyone used metal valve stems and kept the caps on during a race. (I leave them off for pracitce/qual, so that air pressure changes are easier).
Keith A.

[Bob Coury]

Trying to replace the rubber ones on my front Dymags. There is not enough "flat" area on the wheel surface for the nut to fit flush as it "bridges" the radius area between the bead and the spokes. Are there any all metal stems with a smaller nut or are these pretty much standard?

[Brian]

This is why I switched to rubber stems, frankly. I have several sets of wheels that the stem hole is in a tight or curved area, and the metal stems don't work. On the outer side, you can fumble up spacers or sleeve nuts - but not in a Hoosier dealer on the way to the track when your lathe is 600 miles away... On the inner side, you just have a poorly compressed rubber seal that is prone to leaking.

I'd love to know what the advice is to solve this. I use the rubber stems, but like a lot of people I just don't quite trust them as much as metal. OTOH, I've only had one fail when I know I rubbed it hard and tore it.

Brian

[TedV]

there are some skinny shanked metal stems usually seen on Fiskie and BBS rims Ive seen around the track. The nut is on the outside of the rim. you do NOT want any valve stem nuts on the inside of a rim. Appalachian has been trying to keep some in stock, but I just found out they are out and looking to get some more. They are a little long, expensive, and can get clipped on contact if the valve is towards the outside of the rim, like most formula rims. There are super short rubber valve stems, about 1/2" to 3/4" long, usually seen on lawn tractors that seem to work well on formula rims. I can't remember the exact part numbers for them tho. sorry.

I go with metal stem if it will fit in the rim and is deep enough in the rim not to be sheared off in contact. Rubber if real close to a bend in the rim, or if it sticks out and can hit something. Just do the soapy water spray bend test and replace when they feel hard or bubble.

[Roger Eade]

There is nothing wrong with them, in fact they maybe better than metal in most cases, people who think that metal stems will never fail should think againl in a lot of cases where you are in a position to get a stem wacked, I would go for the rubber every time ( remember what your Daddy said about rubbers) it will give, in a lot of cases, whereas the metal one will snap off, so IMHO, it is up to maintainace of your wheels, and regular replacement of the valve stems that will safe guard against any failure, at least with a rubber stem, it may not go down in one hit, which it will do with a metal stem.
Roger

[DaveW]

There is nothing wrong with them, in fact they maybe better than metal in most cases, people who think that metal stems will never fail should think againl in a lot of cases where you are in a position to get a stem wacked, I would go for the rubber every time ( remember what your Daddy said about rubbers) it will give, in a lot of cases, whereas the metal one will snap off, so IMHO, it is up to maintainace of your wheels, and regular replacement of the valve stems that will safe guard against any failure, at least with a rubber stem, it may not go down in one hit, which it will do with a metal stem.
Roger

I use rubber valve stems for exactly this reason. I've had a few leak a little, but never fail. That's a lot more than I can say for the metal ones. The last time I used metal stems was in the 70's when I had one snapped off in a mild wheel-to-wheel contact. I do use the shortest ones available (I think they're made for golf carts or something similar - about 3/4" sticking out of the rim). I replace them every year.

[dmiller]

Do people just use "regular" valve stems? Anything different from the ones you get at Pep boys than the ones I need for my OZs?

[Brian]

I get mine at NAPA down the street. Nothing special, but I'm sure there are varieties. One variety has a brass core and is rated to high PSI for truck tires.

Brian

[M.Sauce]

All valve stems should be as short as they can be ,metal or rubber.I have run 200 National races and never had a rubber valve stem fail.I have rubber because of exactly the issues Dave W raised.I do inspect them quite often and I usually have new tires on every or every other race weekend so they don't go uninspected for very long.I sell Goodyear tires in SW Division and we inspect the valve stems all the time when changing tires.I have more issues with metal stems than rubber in most applications but for a FC and an OZ wheels a metal valve stem is best,the shorter the better.Many wheels especially Kodiak 8 X 13 in. 3 piece wheels will not have an adequate sealing area for a metal stem.Inspection on a regular basis is the best solution to failures in my opinion.