Different tyre valve stem sizes?

[Grahamm]

I bought a mini air compressor from M&P off eBay (see https://www.ebay.co.uk/itm/Stop-and-Go-M...2761018999 ) but I've just tried to use it and the screw fitting on the end of the hose appears to be too large for the valve stem.
This means it won't screw in place and make a secure seal, so the air leaks out and I can only get about 25psi.
I thought valve stems were a standard size, but are there different fittings? Do I need to get an adapter?
Anyone know what's happening?

[Jamieg285]

It should be standard.

Have you got a different vehicle you can try the pump on?  Also, you can try the valve cap from something else to check your valve stem.

[Grahamm]

Unfortunately I don't have another vehicle (and I think the neighbours might object!)

[Trebus]

Sounds like it could be faulty or needs turning to tighten an internal rubber grommet. Only two types that I’m aware of, presta valves like on a bicycle or schrader on cars / motorcycles.

[Grahamm]

Here's a couple of pics of it.

One shows the unit with the hose at the bottom, the other shows the end of the hose itself.

It's a simple screw fitting with a knurled outer, you're supposed to put it over the valve stem, screw it on and you're sorted, but the thread doesn't engage as it's wider than the stem.

You can see it on eBay at https://www.ebay.co.uk/itm/Stop-and-Go-M...2761018999

I did have the OEM valves replaced with 90 degree ones (similar to the ones in the third pic or here https://www.ebay.co.uk/itm/90-DEGREE-MOT...2387648017 ) but if it's a standard size, why should they cause a problem??

[His Dudeness]

stripped threads on the pump?

[Grahamm]

stripped threads on the pump?

Not as far as I can see and it's brand new.

[His Dudeness]

The ad says it comes with attachments for pumping other things. Do the attachments screw into the pump properly or are they loose? If they're loose the threads on the pump must be stripped. Are the attachments the same diameter and pitch as the valve stem?

[Trebus]

The seal looks loose as a goose from the picture

[Grahamm]

Ok, the problem has been solved!

It turns out that the replacement valves, having been on there for over 10 years, had got worn down due to regular pressure checking and re-inflating when needed.

This had caused the threads to become a little narrower such that the attachment on the hose from the compressor wouldn't actually engage with them.

A quick trip to Russ' Tyres in Portsmouth for a new set of valves and now everything is working fine :thumbup

Thanks for the comments and advice everyone