This might be a strange question to ask on a gun board, but we seem to have people here who know something about everything. Did the outer diameter of Schrader valves change at some point? I'm having a strange issue with a tire pump. This begets something of a long story.

I used to have a tire with a slow leak. I also keep an electric tire pump in my car (that plugs into the cigarette lighter socket) to deal with just such issues. I had an old one that clamped onto the tire valve. I bought a new one that screwed onto the tire valve. That was a bit of a pita, but it worked.

Then I bought new tires. I bought them from Costco, who filled them with nitrogen. The car has a TPMS, and when I see the tires getting low, I've been going to Costco, and topping them off with nitrogen. I don't really expect the nitrogen to make any difference, but it's free.

Then I had a situation where I needed to pump up a tire and couldn't get to Costco, so I broke out the pump. This was the first time I used it since I got the new tires. But the fitting on the end of the pump hose wouldn't screw on the valve. I was able to get the tire pumped to an acceptable level anyway, and eventually got to Costco, and got everything topped up.

But I was annoyed that I couldn't use the pump, and that meant if I needed to use it in the future I'd have a problem. So I went on Amazon, and found a screw valve to clamp valve adapter. See link below

https://www.amazon.com/dp/B088...dt_b_product_details

When I tried to screw this onto the fitting on the pump, I had the same problem as I did trying to screw the fitting on the pump to the valve on the tire. The male end on the adapter was smaller than the inside of the pump fitting.

So now I have two items that should be standard Schrader valve screw threading that won't screw onto my pump fitting. But the pump fitting very successfully screwed on to the original circa 2010 tires on the car. So it seems that something has changed. But AFAIK nothing has changed with Schrader valves in something like a century. I'm having a what gives moment.

We have enough car guys here, including some pros, that if I am actually missing something, someone could tell me. I first though Costco put some sort of non-standard valve on the tires, since they planned to fill them with nitrogen. But then I wouldn't have a problem screwing the adapter on the pump.

Any ideas?

20 years ago, it was a very loose standard but most were interchangeable. I'm sure as more chinesium gets in the pipeline, it will be even worse, as you never know what measurement system/tolerance/material/process they will use.

Fun fact: In college my tire sales experience ended when I was fired from a corporate tire shop due to valve stems. We were out of valve stems for a week+, we had been buying/borrowing/stealing from other shops. Then boxes of a new brand showed up and we couldn't order the old ones. 3-4 days after we got the new ones (which felt cheap), I noticed a car that we'd just put tires on that looked low. I carried a decent digital gauge - ~10psi low on all 4. We only had 1 guy in the shop that evening & he wasn't an idiot. We checked others, all about the same amount low. We had a car with old valve stems, pulled a tire, aired it up on the tire machine & it was OK. Tried one with the new valve stems & it the gauge showed 32psi with the hose locked onto the stem, but the tire was actually at 20-22psi. Repeatable on both tire machines. I gave the tech my gauge to use & started pulling cars back in and then calling all my customers for the day to come back & let us fix the screwup. A couple showed up in like 15 minutes. I grabbed a new, identical gauge off the rack, tore the box open & started using it to fill tires up outside. Kept that one as mine was tethered to a tire machine. I closed that night, left the MGR a note explaining the situation & was off for 2-3 days.
Came in Sunday morning & the loss prevention lady said 'come with me' and she didn't have her normal smile. Some corporate wonk had the package to the tire gauge I "stole", as well as the note I left for the manager. He talked in circles for 45 minutes, then told me I had to leave for the day so they could make a decision. Called MGR next day & he still knew nothing about me being fired or the valve stem problem. After hearing nothing before the 2nd shift I'd miss, I gave up. That store was down 30% year over year for at least the next 2 months, which should have been busy. Guess who was ~30% of sales?

Interesting question and interesting product. I like the concept of a locking chuck - my hands / fingers get tired when putting air into the truck tires, especially when filling from 20psi (off pavement) back to 43psi (on pavement).

Sorry to the OP for a side track but related question, if I may be so indulgent.

Will this locking chuck (so that I can inflate tires hands free) work with this pressure gauge / inflator?

Milton chuck:
https://www.miltonindustries.com/lock-on-grip-chuck
I don't know what this means "Will not function as a standalone air chuck"

Intercomp gauge / inflator:
https://www.intercompracing.co...ure-gauge-p-203.html

If the threads and stem are smaller it may be a model made for bicycles with high pressure tires (Presta Valve or other).
Here's an example.

https://www.bicycling.com/repa...-valve-and-a-presta/

quote:

Originally posted by konata88:
I don't know what this means "Will not function as a standalone air chuck"

Most likely means doesn’t have a valve, just attaches to the valve stem.

I’m gonna go with most likely will work fine together. They most likely will be the same thread/fitting size, and the correct “gender”, but if they aren’t it should be simple to adapt.

quote:

Originally posted by 220-9er:
If the threads and stem are smaller it may be a model made for bicycles with high pressure tires (Presta Valve or other).
Here's an example.

https://www.bicycling.com/repa...-valve-and-a-presta/

Never seen a Presta on a vehicle though. Only on skinny road bike tires.

I tend to doubt Costco would use bicycle valves on car tires. They have to be one f the biggest tire retailers in the country. If it weren't for the fact that I've used the pump successfully on tires before, I'd think it was just that, but I have. And I now have two different devices with Schrader fittings that won't work with this pump, so it can't just be the tire stems.

It'w just weird.

quote:

Originally posted by P250UA5:

quote:

Originally posted by 220-9er:
If the threads and stem are smaller it may be a model made for bicycles with high pressure tires (Presta Valve or other).
Here's an example.

https://www.bicycling.com/repa...-valve-and-a-presta/

Never seen a Presta on a vehicle though. Only on skinny road bike tires.

Could this be a SAE vs Metric thing?

Google say both exist…

External thread

Metric: 7.7 mm OD, thread root diameter is 6.9 mm × 0.794 mm pitch.
Imperial: 0.305 in OD, thread root diameter 0.271 in × 32 tpi (threads per inch)

quote:

Originally posted by cparktd:
Could this be a SAE vs Metric thing?

Google say both exist…

External thread

Metric: 7.7 mm OD, thread root diameter is 6.9 mm × 0.794 mm pitch.
Imperial: 0.305 in OD, thread root diameter 0.271 in × 32 tpi (threads per inch)

That “metric” thread spec is just a metric translation of the imperial thread spec you also quote.

You NEVER see weird non-round-number/decimal thread pitches like that (except very, very rarely when someone does something stupid on a custom one-off). An actual metric thread in that size and thread fineness range would be 0.75 mm pitch.

This is because the tools to make threads either are made to produce standard pitches (taps and dies which do one pitch, thread cutting lathes which use a gearbox to cut a fixed selection of standard pitches, thread rolling tooling that only works with standard pitches, etc) or are (relatively) incredibly expensive (either on a per-unit basis, like a CNC lathe, or on a setup cost basis, like fabricating new taps or thread stamping tooling).

As it seems to be the common factor, maybe the threads are stripped on your pump?

quote:

Originally posted by trapper189:
As it seems to be the common factor, maybe the threads are stripped on your pump?

Especially likely if it is a cheap plastic fitting like we see on a lot of cheap inflators these days.

Ditch the POS tire inflator. You need a normal one that pushes onto the valve stem, preferably with a mechanical locking lever.

quote:

But the fitting on the end of the pump hose wouldn't screw on the valve.

You never want this. What if the hose gets stuck or you fumble it in the cold or dark trying to remove it? You'd lose some, or even all, of the air you just got through putting in.

In working with tires ranging from bicycles to 18-wheelers spanning six decades now, I have never seen any variation in valve stem threads.

My guess is the pump was made metric and their conversion wasn't perfect. I've seen this with musical instrument electronics, where jacks, plugs, and knobs are just a titch different.

Another possibility is the thread of your pump being poorly cut or damaged. I have had several instances in the last couple years with bad threads from the factory and had to replace or repair the item. Cheap crap from Asia.

You can get an adapter that changes Presta to Schrader:

https://www.walmart.com/ip/Sli...l12=49934338&veh=sem

quote:

Originally posted by cparktd:
Could this be a SAE vs Metric thing?

Google say both exist…

External thread

Metric: 7.7 mm OD, thread root diameter is 6.9 mm × 0.794 mm pitch.
Imperial: 0.305 in OD, thread root diameter 0.271 in × 32 tpi (threads per inch)

That is the same thread diameter and pitch, just one is metric and one is SAE. Note the conversion factor is 25.4mm/inch and the minor differences are due to rounding errors on both Metric and SAE dimensions. On the SAE side the original OD was probably 39/128 inch, yeah the Imperial system was based on fractions at one time. So the OD is based on a dimension of 0.3046875 inch. Multiply that by 25.4 and you'll get 7.7390625 mm. Round both numbers and you'll see 0.305 inch and 7.7 mm are based on the same diameter.

I've had a few of these over the decades, and this one is the highest quality of them. The threads of the scraper fitting are metal, and don't look stripped, but I'll check again.

FWIW, here's the pump...


https://www.amazon.com/gp/prod...04_s00?ie=UTF8&psc=1

quote:

Originally posted by egregore:
Ditch the POS tire inflator. You need a normal one that pushes onto the valve stem, preferably with a mechanical locking lever.

quote:

But the fitting on the end of the pump hose wouldn't screw on the valve.

You never want this. What if the hose gets stuck or you fumble it in the cold or dark trying to remove it? You'd lose some, or even all, of the air you just got through putting in.

In working with tires ranging from bicycles to 18-wheelers spanning six decades now, I have never seen any variation in valve stem threads.