Quote:
Originally Posted by flybouy
I'm suprised you didn’t "cover that on your tire blog with pictures".
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Sorry but since I cover 4 to 6 RV forums each day I do not have the time to write the same info on the same topics every couple of weeks. The posts that I am most amused by are the ones that start of with "I have searched everywhere and can't find the answer".
flybouy, I am wondering what your suggestion is on what I should do when I see posts and questions on a topic I have previously written about. Would you approve the following?
Thursday, December 3, 2020
Tire Valve core torque tool
I have mentioned valve cores in a number of posts. I even offered some advice on how and why you should avoid over-tightening the core
Here.
Last week, I learned about a low cost tool that I feel I can endorse as I purchased and tested this tool and was pleased with the results.
This is essentially a "clicker" type torque tool. You tighten the valve core in a smooth twist and it will click and release when the core is tight.
Using my calibrated In-Oz Torque wrench I confirmed the Slime unit worked at 3.5 In-Oz
which is in the range of 2 - 5 In Oz as specified by the
Tire & Rim Association, the organization that publishes dimensional specifications for tires, Wheels and valves as used world-wide.
It's the Slime Part # 20178. I got mine at a local auto parts store but I see it listed as available at a number of stores and on-line.
or this
Friday, March 22, 2019
Valve stems, cores, and caps "Oh My", and how tight is tight enough?
Yes, some rubber valve stems have a metal center and some valves are all metal except for a rubber gasket. The metal part of valves is almost always brass. Sometimes Nickle plated to look like chrome or to match aluminum wheels.
The two valves on the left are "Snap-In" rubber valves. The two on the right are "Bolt-in" metal stems. By "Snap-In" we mean the valve is installed into the hole in the wheel by pulling on the threaded part of the brass until the small rubber ridge "snaps" through the hole.
The best way to know for sure is to look for a nut that "bolts" the stem to the wheel. I would suggest a TR416 or similar as seen
HERE from Auto Zone. O'Riley's parts stores have a similar
short stem. You should be able to find similar in almost any auto parts store. These metal stems come in many lengths from less than an inch to 2" or longer (different lengths have different TR part numbers). The hole in your passenger, trailer or light truck wheel is most likely 7/16" Old VW wheels were 5/8" All 19.5 and 22.5 wheels should have come with a metal bolt in valves but those use the 5/8" rubber grommet/O-ring. Many metal stems sold at retail, come with two different rubber gaskets, one for each size hole. The gasket is just a snug fit and should just push into the wheel hole.
Note the nut has a torque spec of 25 - 45
INCH Pounds so do not over tighten the nut. I have found that a regular 9/16" wrench is just fine and you do not need a big ratchet wrench to tighten the nut.
Keep the stem short to lower the chance of the TPMS being knocked off if you get near a curb. There are some unique wheels that may require a bit longer stem to allow you to attach your TPM sensor. I suggest you have the sensors available when you install the bolt in stems to confirm sufficient clearance.
The main reason for metal stems when running TPMS is to prevent vibration of the stem which can fatigue the rubber stem.
While you are at the auto parts store be sure you have METAL valve caps. Plastic caps are IMO only good for keeping dirt and small birds out of the valve core area. Metal caps should have rubber "O" rings in them and can retain air if you are not running TPMS. Look in the thread end and you should see the gasket.
Each Fall, when I remove my TPMS for the Winter, I place metal caps on my stems. I will admit that one year I didn't do that and the valve core had a very slow leak but I ended up with a tire being damaged because it lost air over the 7 months between when I parked and when I was getting ready to go traveling.
I have a couple of posts that focuses on the valve cores. One on
why they leak.
One detail is how to know how tight is enough for your valve cores. Over-tight can cause the small gasket to deform and even split and under-tight will result in a slow leak. After 40 years of installing valve cores I consider my fingers to be close to "calibration" but it would be better if you followed a specific procedure.
I did a test that may help. The spec for valve core torque is 1.5 to 5.0-inch pounds MAX but I don't expect you to run out and buy a special inch-pound torque wrench as seen here.
To help you I devised this test. Using the test fixture I made when running my TPMS comparison I loosened a core till it leaked as seen here.
Then using my torque wrench I tightened the core till the leak just stopped. I then continued to tighten the core till I reached about 1.5 Inch Pounds (this was 1/4 turn after the leak stopped) I then continued to tighten the core till I reached 5-inch pounds (This was 3/4 turn after the leak stopped)
So I would suggest that you can simply tighten a core till the leak stops then rotate 1/2 turn more.
Here are sample core tools.
The one on the left is a "professional" tool but I have also used my home made core tool for many years. This is just an old scrap rubber valve stem with a cap that has the cut-out to fit a core.
I hope this helps you understand a bit more about valves and valve cores.
Friday, November 2, 2012
Why do tire valves leak?
Many people who experience a tire blowout insist they had checked their tire pressure and that their gauge was accurate. So they blame the failure on a defective tire. However, what could have been the culprit was a bad cap on their valve.
Now I must say that if you have a TPM sensor that is basically a screw on valve cap, this warning probably does not apply as long as you ensure the valve stem is not dirty or covered in mud when you remove or install the TPM sensor.
A good valve cap is metal and has a small gasket or O-ring in it to seal against the end of the valve stem. The cap serves two functions. Primary is to keep dirt out. Second is to be a backup to keeping the air in if the valve core develops a leak. A cheap plastic cap may work on a 30psi passenger tire but I doubt it will last too long on a hot high pressure Class-A TBR tire.
Lets take a close look at the valve core.
I have labeled the plunger that opens the valve to let air in or out "P". The gasket that seals the core inside the valve stem "S". Note the small indentation that indicates this core has been used but not over tightened.
Finally the location that opens when you press on the plunger "V" is a small circular opening.
To the right is a graphic from
Wikipedia showing how a
Schrader valve operates.
If you look closely you can see the valve opening letting the air out.
Now lets look at what can happen if you get a single piece of grit stuck in the valve area.
I included the head of a straight pin so you can see just how small that bit of dirt is.
Now lets see what happens if this valve core with the grit in the valve is used on a tire.
Now you see why using a good valve cap is important. You must keep the dirt out of the valve area. If you discover a leak as shown in the picture above, cranking down on the core will only damage the core seal (the black band in the pictures above) and will do nothing to stop the leak. It is best to simply replace the core with a new one.
Friday, July 3, 2020
Valve Stems and TPMS Part 2
As a follow up to
last week's post of why I recommend people NOT use rubber valve stems with their external TPMS sensors I decided to show some of the "guts" of valve stems.
Standard "rubber snap-in" stems like the TR413. If you look down the hole you can see the end of the brass part of the stem. More on this later.
These have been used for decades on hundreds of millions of tires. These can be installed by hand using a "puller" that stretches the rubber which makes the diameter of the stem small enough to "snap into place in the wheel hole.
Once installed the wheel "pinches" the rubber part of the stem to seal the air in. The arrows show the location of the wheel relative to the metal part of the stem. Note the part of the valve stem that goes into the air chamber was cur off before I took this picture.
You can see that the brass stops before it gets past the edge of the wheel. This makes installation easier.
Next, we have the "High Pressure" stems such as the HP-500.
Here you can see the brass part extends almost to the bottom of the valve and into the air chamber.
When the rubber is buffed off you can see that the brass part extends through the wheel hole (location shown with the arrows.)
Now when we look at a "bolt-in" stem, like this TR416s
we see the location of the wheel hole at the arrows. We can also see the much larger brass body (nickel-plated in this piece) that goes inside the air chamber and expands to a broad base. This type of stem needs to be installed through the wheel hole with the rubber grommet sealing the air. An external washer is used and the nut is to be tightened to specification to prevent air loss.
I am also including pages from the US Tire & Rim Association yearbook which publishes the "interchange and fitment" specs so all tire companies and valve manufacturers know what dimensions are required. This is the book where all the Load & inflation tables come from and might be considered the Tire Engineer's "Bible" and is used by tire engineers around the world when they are making tires that are intended to be used in the US.
Here we find the details of valve stem designs as specified by TRA.
Finally to show the attention to detail here is the spec for the little pin that sticks out of the valve stem. Not meeting this specification could be the reason your TPMS does not register your tire pressure. (Yes I have run into that problem)
I just wanted to try and give you a little understanding of the attention to detail tire engineers go-to when designing tires and when trying to understand the "why" for a tire to lose air.
Wednesday, June 24, 2020
Valve stems and TPM Sensors
I read the ongoing discussion on what valve stem to use with an external TPMS sensor.
A standard 65 psi max, rubber valve stem is very flexible as seen here.
Some people think the 80 psi max, "High Pressure"
HP 600 rubber valve stem is Ok to use with external TPMS sensors but you can see the HP-600 is still flexible.
Here is proof that an HP rubber stem can fail when a TPM sensor is installed.
IMO staying with any "snap-in" type stem is false economy given the metal bolt-in stems only cost $3 to $4 each. Not all tire stores will have the metal valve stems so check first. if they don't you can get stems at AutoZone, O'Riley's, Advance Auto Parts or NAPA or most any auto parts store or even on Amazon.
They are easy to install too.
Don't let the service center tell you installing metal stems is a lot of work. Watch and you will see.
https://youtu.be/sJB9wPsbBVU