Tyre Valve Cap Thread Size

Post by **alanworland** » Wed Jan 21, 2009 10:18 pm

Anybody know the thread size for valve/cap?
I bought some nice hexagonal caps from our local 99p shop (cheaper than the £ shop)! but the thread needs tidying up - should take them back I suppose!

Post by **bmcecosse** » Wed Jan 21, 2009 10:29 pm

Schrader valve - could be 3/8" UNF ?? Same as brake pipe fittings, and wheel nut thread - to be honest I'm guessing!! Hardly worth going back for 99p.

Post by **alanworland** » Wed Jan 21, 2009 10:57 pm

Suppose you get what you pay for!

Post by **PSL184** » Wed Jan 21, 2009 11:12 pm

There are many types of Schrader valve - I bet you didn't know that, did you

Anyways - Dimensions and threads as follows....
Schrader valves are classified by their material, diameter of intended rim hole, length, and shape.

TR-4 - straight metal stem (8 mm dia.)
TR-6 - straight metal stem (8 mm dia.)
TR-13 - straight rubber stem (11.5 mm dia.)
TR-15 - straight rubber stem (16 mm dia.)
TR-87 - short 90° metal stem (10 mm dia.)
TR-87C - tall 90° metal stem (10 mm dia.)
The standard Schrader valve has the following threads:

External thread

Metric: 7.7 mm OD, thread root diameter is 6.9 mm x 0.794 mm pitch.
English: 0.305 in OD, thread root diameter 0.302 in x 32 tpi (threads per inch)
Internal thread (to accept the threaded valve core)

Metric: 5.30 mm OD x 0.706 mm pitch
English: 0.209 in OD x 36 tpi.
For refrigeration, a 1/4" male flare fitting is used, with the same internal thread as above.

Post by **mike.perry** » Wed Jan 21, 2009 11:18 pm

That's real anorak information. I shall dash out to the garage tomorrow morning and check my tin of valve caps

Post by **PSL184** » Wed Jan 21, 2009 11:31 pm

Metal or plastic caps Mike ;-)

Post by **toginthemog** » Wed Jan 21, 2009 11:34 pm

why would you need to know that sort of info you must have to much time on your hands. Bless you

Post by **PSL184** » Wed Jan 21, 2009 11:36 pm

I'm not THAT sad - I just copied it off Wiki

Post by **alanworland** » Wed Jan 21, 2009 11:42 pm

Blimey! Learn something every day! Thanks

Post by **mike.perry** » Wed Jan 21, 2009 11:53 pm

Plastic and metal caps, a few core removing caps and a nice set of chrome hex top caps on the MM.

Post by **alanworland** » Wed Jan 21, 2009 11:59 pm

And I have been known to wear one too!

linearaudio · Post by **linearaudio** » Thu Jan 22, 2009 7:19 pm

Sounds, through all that jargon, as if what the gentleman needs is a 5/16" UNEF plug tap!!
Also happens to be the same thread on the end of your grease gun, if you are thinking of making a hydrogas pump (frankm83)!!

Post by **bmcecosse** » Thu Jan 22, 2009 8:18 pm

My grease gun is 3/8" UNF. Fits brake pipe connection on brake cylinders perfectly - handy for unsticking seized cylinders.

Post by **mike.perry** » Thu Jan 22, 2009 8:56 pm

Ref your earlier comments BMC, valve caps are different threads to brake pipes, much finer thread. If this topic goes on much longer I will have to get my thread gauges out.

Post by **bmcecosse** » Thu Jan 22, 2009 10:54 pm

Yes -I see that from the comprhensive data (phew) listed above. Just making the point that my grease gun is NOT 5/16 " UNF - and i don't think it is any way unique! Standard nipple connectors screw on very nicely to the 3/8" UNF thread.

Post by **alanworland** » Thu Jan 22, 2009 11:04 pm

Just had a measure:- it is 0.300in OD ? with a 32 TPI pitch, whitworth form, altogether a very strange thread, think I am unlikely to find a tap.
Thanks everybody - TOPIC ENDED!

Post by **mike.perry** » Thu Jan 22, 2009 11:15 pm

Bet you wish you had never started!!

Post by **bmcecosse** » Thu Jan 22, 2009 11:44 pm

All this for 99p - great value!

Post by **leyther8008** » Mon Jan 26, 2009 12:54 pm

Just to add my fourpeneth! I bought some lovely blue annodised aluminium hexagonal caps for the wifes KA, one month later when I came to check a tyre pressure (yes I know it should be every week) the things had corroded solid and I mean solid. eventualy realising that a mini socket would fit nicely over the new caps all I suceeded in doing was tearing the valve stems out of the rims with the resulting whoosh of smelly compressed air on two rims, then a trip to the local tyre depot for tyre removing new valves and fitting again, he told me he's seeing up to four cases a month now.
I will stick to boring black PLASTIC from now on.