Schrader valve extensions - will they work?

Bendy_House

More to the point, HOW do they work?! 

When you pump up a tyre, I understand that the pump's air nozzle will depress the tyre valve's 'pin' to allow it to be inflated, AND deflated/detect the tyre pressure, yes?

So, if I get commonly-available valve extensions to screw on, what do they do? Do the screw-on ends keep the car's valve permanently depressed (open), and the actual 'valve' job now passes to the extension's filling end? Or, do the extensions NOT press the tyre valve's pins, so there's now effectively two functioning valves, and the tyres can only be inflated, and not deflated?! Or, do the extensions not even have valves in them at all, so it still relies totally on the tyre's valves?

I hope that makes sense!

Thanks.

(These are potentially for a Transit minibus, where the valves - especially the rear doubles - are a pig to get to.)

peter3hg

The ones I've used have a long pin so they actuate the original valve stem, they don't have a valve of their own.

I've never left them permanently attached as it unbalances the wheel, but I assume it would be ok if you had the wheels balanced with them attached.

sevenhills

Some of our double wheel Crafters have these extensions, I believe you just leave them in place and check the tyre pressures as normal. If you couldn't do that, what would be the point of them?
I would guess having proper wheel balance only matters on the front wheels? The wheels should be fitted with the correct length valve to start with, so extensions are just making them the normal length.

sevenhills

Bendy_House said:

(These are potentially for a Transit minibus, where the valves - especially the rear doubles - are a pig to get to.)

Health and safety would state that you need to be able to check the tyre pressures. Get the right length valves or get the extensions.

Bendy_House

Thanks all.

It makes sense that they have this long pin, so activate the existing tyre's valves.

Some of these extensions are flexible, tho' - do they have a flexible pin?!

Yes, the idea would be to have them permanently fitted. I was imagining that their very small weight, compared to the massive weight of these big steels wheels and chunky tyres, would make little or no difference to the balance. I guess I could always glue another one to the other circumference of the wheel to balance it!!

The rear doubles are awful, and I've yet to FIND the inner valve, even tho' I've been told it's accessed via one of the wheel cutouts. Must get a torch and knee pads...

sevenhills

Bendy_House said:

The rear doubles are awful, and I've yet to FIND the inner valve, even tho' I've been told it's accessed via one of the wheel cutouts. Must get a torch and knee pads...

When the valves are too short, it's impossible to check the pressure. When they are the correct length, it's fiddly and difficult.
You should check your tyres visually on a daily basis, but it's almost impossible to know if they are ok, so a gauge must be used regularly.

peter3hg

Bendy_House said:

Thanks all.

It makes sense that they have this long pin, so activate the existing tyre's valves.

Some of these extensions are flexible, tho' - do they have a flexible pin?!

Yes, the idea would be to have them permanently fitted. I was imagining that their very small weight, compared to the massive weight of these big steels wheels and chunky tyres, would make little or no difference to the balance. I guess I could always glue another one to the other circumference of the wheel to balance it!!

The rear doubles are awful, and I've yet to FIND the inner valve, even tho' I've been told it's accessed via one of the wheel cutouts. Must get a torch and knee pads...

I've only used straight ones, not sure about the bent or flexible.
I had them on a motorbike. On a car or van the weight may not be an issue in terms of wheel balance but it was noticeable on the bike.

Bendy_House

Thanks again. I'll investigate the different types, and ask the sellers how they work.

Cheers.

SteveJW

Get yourself down to your local tyre depot
Get the correct length valves fitted
If they do not stock different sizes, not much of a tyre depot

Bendy_House

SteveJW said:

Get yourself down to your local tyre depot
Get the correct length valves fitted
If they do not stock different sizes, not much of a tyre depot

You mean they can fit over-sized valves? Becuase, afaIk, it's the 'correct' ones that are fitted, but these are notorious for access. In fact, even the outside rear wheels cannot be inflated by many portable pumps that have a straight connector. That's becuase the outside valves actually point inwards, towards - and close to - the wheel centre! It's just nuts!

In any case, 6 wheels with new valves must be well over £100 to have done? If I can get screw-on extensions, then it's something I can do, and save the organisation a bit of money.

SteveJW

It's the way twin wheeled vehicles have been built for ages
Are you trying to use a portable compressor that runs of the cig lighter, never seen one of these with the correct connecter for twin wheels
You need a connector the same as in the picture for twin wheels
And believe me I've blown up plenty of twin rear wheels