Valves failing

Davidc

Guru
Location
Somerset UK
I'm getting worried about valves failing. All on my runaround - 26" with Schraeder type valves.

I've had 4 go since the middle of June. The first was on one of the tubes supplied by Ridgeback, in the back wheel. I put in one of my spare continental tubes. About 2 days later the valve in the front tyre failed. This time I thought at first it was a slow puncture as it took a day to let most of the air out. The tube was a continental, which had been in from new for about 8 months and 600 miles. I put in a panaracer bought locally. The valve failed within a week. The shop replaced the tube and the new one seems OK.

Now I've just had the back tyre go flat, and its the valve again. Its the continental I put in 4 weeks ago.

Its driving me mad!

Do I have a puncture fairy with a valve fetish hiding in my garage?

or am I just being unlucky?

Those tubes aren't inflated to any more than 35psi, as thats the recommended (and maximum) pressure for the tyres. Even worse is that I've since put one of the failed ones (the slow deflation one) on my wife's bike after a puncture. It has marathons on it and uses 90 psi, and it's stayed up for a week.

If this goes on I'm going to need the men in white coats ...............
 

ASC1951

Guru
Location
Yorkshire
Those tubes aren't inflated to any more than 35psi, as thats the recommended (and maximum) pressure for the tyres. Even worse is that I've since put one of the failed ones (the slow deflation one) on my wife's bike after a puncture. It has marathons on it and uses 90 psi, and it's stayed up for a week.
35psi is very low for a bike tyre, even for off-roading in mud, and would normally give you lots of pinch punctures. I have never seen a tyre rated so low.

There are of course several other immediate explanation for punctures. Sharp rims, ditto rim tape, tiny bits of glass lodged in both tyres, a bad batch of tubes, user error inflating them. Given that a "failed" one stays up when you move it to your wife's bike i.e. it isn't punctured but a valve issue, as you say.

Here is my explanation. Air leaches out of a tube at a uniform rate. If you lose 15psi out of a 120 psi road tyre you won't notice a great effect on the handling in everyday use; if you lose 15psi out of 90 psi, you certainly will notice; if you lose 15psi out of 35psi the bike will be unrideable. Furthermore Schraeder valves have no tightening nut and need a threshold pressure to keep them properly closed, so once you get down to low pressures you lose the last few psi quite quickly. Throw your 35psi rated tyres away and get some that will take normal pressures.. [I would then put Prestas in, but that's a personal preference.]
 
OP
Davidc

Davidc

Guru
Location
Somerset UK
35psi is very low for a bike tyre, even for off-roading in mud, and would normally give you lots of pinch punctures. I have never seen a tyre rated so low.

There are of course several other immediate explanation for punctures. Sharp rims, ditto rim tape, tiny bits of glass lodged in both tyres, a bad batch of tubes, user error inflating them. Given that a "failed" one stays up when you move it to your wife's bike i.e. it isn't punctured but a valve issue, as you say.

Here is my explanation. Air leaches out of a tube at a uniform rate. If you lose 15psi out of a 120 psi road tyre you won't notice a great effect on the handling in everyday use; if you lose 15psi out of 90 psi, you certainly will notice; if you lose 15psi out of 35psi the bike will be unrideable. Furthermore Schraeder valves have no tightening nut and need a threshold pressure to keep them properly closed, so once you get down to low pressures you lose the last few psi quite quickly. Throw your 35psi rated tyres away and get some that will take normal pressures.. [I would then put Prestas in, but that's a personal preference.]
Interesting - but I don't entirely agree. I did have a brain failure writing/ reading through the OP, it's 65 not 35 psi. (The tyres are Kenda Kwests).

I've never had a puncture on those tyres, only this sucession of valve problems with the tubes. Normally if I pump them up to about 65 they are around 60 four weeks later when they get done again, during the same time the tourer's and my wife's tyres go down from 90 to 80ish. I agree about the presta valves being better - but the mtb rims are designed for Schraeders so I'm stuck with them.
 

battered

Guru
A bit of a long shot: is there oil in your bike pump? Pumps that are oiled will blow oil in the tyres and the valves will suffer. Grease won't do this. As I say a long shot but worth checking.
 

tyred

Legendary Member
Location
Ireland
It's easy to replace a shrader valve and the tool cost pennies.

I've spent a lifetime surrounded by these on bikes, on cars, on tractors and other farm machinery and on lorries and have seen very few problems with them. If they do leak, you can uusually remove it, give it a clean and put it back in again. The only thing that might go wrong is the pointy bit which pushes down when you pump the wheel up can get bent and won't seal properly. Again, it can usually be straightened carefully with pliers.
 
OP
Davidc

Davidc

Guru
Location
Somerset UK
It's easy to replace a shrader valve and the tool cost pennies.

I've spent a lifetime surrounded by these on bikes, on cars, on tractors and other farm machinery and on lorries and have seen very few problems with them. If they do leak, you can uusually remove it, give it a clean and put it back in again. The only thing that might go wrong is the pointy bit which pushes down when you pump the wheel up can get bent and won't seal properly. Again, it can usually be straightened carefully with pliers.
I did wonder - where do you get them and the replacement valves?

I'm not sure its worth it though, as before this run of four the last valve I can remember failing had a valve rubber - one of the aincient type.

The contamination suggestion is interesting. I haven't added anything to either my hand pump or the electric one, and I haven't used the mini one, but that doesn't exclude the possibility. If I had one oof tyred's tools I could inspect the valves for foreign bodies.

The two Continental tubes were both bought at the same time so could be faulty, as Numbnuts suggests, but the other 2 weren't related to them.

When I wrote the post I wondered if anyone else had had this happen recently, but so far it seems no - just have to hope it stops.
 

tyred

Legendary Member
Location
Ireland
They should be available from any decent car accessory shop or Halfords. There are two types, one is slightly more sophisticated and would be used in a tyre centre or garage. The best one for your needs is like a normal metal valve dust cap with a a valve removal tool on the back of it (small circular section which pushes into the inside of the valve with two tabs to lock into the valve core). They are usually sold in packs of four. They are sometimes fitted to car wheels anyway so have a look around you car, you might already have one. 
 
OP
Davidc

Davidc

Guru
Location
Somerset UK
I'll have a look, thanks.

At least I could have a look at one and see if it's got any obvious cause.

I presume you can just put the valve back in afterwards. Didn't realise they came out, but as I said I wondered about it, which shows how reliable they usually are.
 
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