Hi, Is there such a thing as low pressure valves ?. The reason I am asking is that I have found that my rear tyre valve holds air with no problem at 25 psi however when I reduce this to 4 psi to do a trial the valve leaks. I have replaced the valve with another and it also leaked the same. If a low pressure valve exists where do I find them.

Many thanks in anticipation,

Lincol1

The answer is no.

Your valves are either badly made, the seal has been damaged or there is dirt preventing it sealing fully. Try holding the valve open and letting the 25 psi out - that should shift anything.

If indeed the valve is the problem.

Thanks for your reply, I have never had this problem before. I noticed the problem last weekend when I removed the valve cap to blow up the tyre prior to leaving. Prior to a trial today I replaced the valve thinking it was a faulty/damaged valve and blew it up to 25psi to transport to venue. At the venue I reduced the pressure down to 4 psi and was amazed to find that the valve continue to pass air. I rode the trial with a tightly fitted valve cap which worked ok.

I can only think I have two duff valves or should I be using a different sort.

Also your valve caps (preferrably metal ones) should also have a seal inside should the valve leak.

The caps need to seal well as the low prsssure sometimes does not shut the valve properly.

You might have a leak somewhere else that is affected by pressure, I suggest a big bucket of water and some patience

Proper diagnosis is key, of course you could use the old spit on the valve trick to see if it leaks

Spit is a diagnostic tool

And once you've discovered if it's leaking using spit, you can get a little widget (some fancy valve caps have them built in) which will tighten the inside of the valve up.

Like this: http://www.google.co...83&tx=122&ty=96

Michelin do heavy duty tubes which come with metal caps that have valve keys built in. Try googling valve key cap? I did and came up with this http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=1&ved=0CE0QFjAA&url=http%3A%2F%2Fwww.halfords.com%2Fwebapp%2Fwcs%2Fstores%2Fservlet%2Fproduct_storeId_10001_catalogId_10151_productId_564275_langId_-1_categoryId_255241&ei=uL4nUKu7HYel0AWE7oCACw&usg=AFQjCNHPvdJOJW9aOWeA6aTvUx3MpoI3hA&sig2=xxJN40wKci3eKzbqr0Afdw

Not only can you tighten the valve or remove and replace it you can tighten these properly and rule out leaking caps. It also help at tyre replacement time as you can completely remove the valve.