Tire valve stem

When valve stems leak, it is normally the core that leaks. Cores can be replaced or tightened even. You just put some spit on your finger and cover the valve stem hole with the spit to check for leaks.

It is common practice at 'good' tire shops to replace the valve stem with new tires. It 'should' be done because they do rot over time.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 (More Off Road album links at bottom of the view page)

While valve stem will eventually rot, what is the time frame? I have farm equipment with 30 year old valve stems - they haven't rotted out yet. In over 38 years of driving, I've never had a valve stem fail. I won't say it can't happen, but it is not a high risk item. I have had valve cores fail, but only on water filled tractor tires.

I've argued over charges for valve stems in the past. In the not so distant past, many tire stores liked to replace them becasue the fastest way to empty a tire was to use a pair of dikes to cut off the old ones. One store was going to charge me $2 per tire for valve stems. I told them I liked the current ones just fine and wouldn't pay for new ones. The service writer repeated your line about them rotting. I said I'd take my chances. He finally took the charge off but said they'd replace them anyways. As expected the tire installer cut the old ones to let the air out.

These days, the better tire machines have provisions for pumping the air out of the tires. Plus many new vehicles have pressure monitors with "steel" valve stems. I wonder if they try to charge you for replacing those?

Ed

When I worked in garages, we examined the valve stem by bending it sideways. If there were weather cracks or it was dry and hard, we recommended changing it. These were the days when folks regularly switched from winter to summer tires so an inspection happened often. New got new usually for free, places still advertise that here in Canada.

I did run across a fair number that had wear cracks from sun or salt or age, who knows, but there were more than a few over the years, that's for sure. There were different quality replacements also....

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 (More Off Road album links at bottom of the view page)

I agree. New stems with new tires are cheap insurance.

Stems are inserted into the rim hole from the inside, and pulled into place from the outside. There is no glue or anything needed to keep them in place, and they have nothing to do with the tire. (I'm talking steel rims, and tube-less tires here...) If a tire is 'busted' loose from it's rim for any reason (like patching, or damaged stem replacement), it needs to be rebalanced. It's for all practical purposes impossible to get a tire back on in the exact same position.

A couple of quick thoughts on stems... I like rubber stems over fancy metal ones any day. Rubber ones simply flex out of the way when struck by curbs or road debris.

If your hubcap situation requires long stems to ease tire service, be sure the shop installs long stems... those valve extension things cause a lot of valve core leaks by allowing dust and whatnot through. If stem length isn't an issue, get short stems. You'd think tire shops would do this automatically, but it's not always the case.

Erik

If the core is leaking, you can purchase metal caps that screw into the stem in place of the cheap plastic ones, which seal them pretty well against slow leaks. A couple buck solution.

--scott

A new core is also only a couple bucks....

Bicycles used to come with metal caps that have the core removal/change tool on them as well as some car ones did. You can still buy that type of cap, it has a point with two prongs on the top.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 (More Off Road album links at bottom of the view page)

As others have already posted, leaks are often at the valve core, and sometimes just tightening the core will stop the leak. A slosh of soapy water on that area will usually tell you if it is the valve stem area that is the problem.

But I had a tire once that was leaking down over time, and the valve stem was suspected. The tire shop aired up the tire and placed it under water to find the leak, but found nothing.

Still, over time, the tire would lose pressure, normally slowly at first, and then faster and faster.

To shorten the story, the sealing surface of the rim was the problem. The seal was pretty good when the tire pressure was high, but as it leaked very very very slowly, the pressure seal deteriorated, and then the tire went quickly flat. (That is why checking it under full inflation actually hid the problem)

I checked the rim for bends, dressed the pitted sealing surface with fine abrasive, painted the rims, and stopped the problem (which could have recurred even with new tires).