presta valve woes. what am i doing wrong?

[jax13]

I'm having problems on both the clockwork & my commuter with valve-tear rather than punctures.

one source told me that (on the roadie based commuter) the low pressure (60psi) was causing a bit of tyre slip causing the tears at the base of the valve so i started running 80+ & it hasn't happened again as yet.

the clockwork is another story - realistically I can't run at 60+ psi off road on a rigid bike & i'm sure nobody else does but I still get the same valve tear, but why?

I make sure the valve is sitting straight & not at an angle, I seat the tire & only inflate slightly to check for pinches then blow up to running pressure, tighten the lockring down against the rim & away I go.

the tubes are the correct size for the rim, rim tape is brand new & fitted properly, no sharp edges etc.

please help - i'm losing patience & may resort to drilling the valve holes out if it continues!

 

[rocky ridge]

just drill the valves out and fit the different valves life becomes much easier then

are you saying the metal valve snaps near the rim alot

 

[lewis1641]

Try some talc on the tubes

 

[ishaw]

Sounds like your tyres might be the problem. I've had sets where the sidewall isn't as good as it used to be, and if the pressure is not high enough, the tyre can rotate on the rim, pulling the tube with it. This could result in your valve being pulled against the rim an tearing. I think talc might make the problem worse, as it will help the tube grip the tyre (or will it make it less likely to grip).

Are your tyres easy to fit on the rim?

 

[drystonepaul]

I think talc might make the problem worse, as it will help the tube grip the tyre (or will it make it less likely to grip).?

Talc acts as a lubricant between the tyre and tube, so if your tyres are loose fitting and rotate around the rim, then the tube is less likely to move with it.
It also improves the way the tyre performs and can lessen the chance of punctures, especially snake-bites.

You've already checked for sharp edges but it still could be worth using small file can be used to round off the edges even if they are under the rim tape.

Another trick I've seen is to use corn plasters to protect the tube at the base of the valve stem.

 

[Anthony]

Another trick I've seen is to use corn plasters to protect the tube at the base of the valve stem.

Good thinking, I hadn't thought of that!

I agree that old tyres can cause this problem, and that talcum powder on both the tyre and the tube should help.

I also unscrew the locating nut a bit after pumping up the tyre, as otherwise it might put a strain on the tube/valve join as the tube loses pressure over time and the valve wants to retreat back into the rim.

 

[MiniNinjaRob]

+1 for drilling rims and putting proper valves in.

Presta just aren't as durable. Fine for road bikes so you can put 100psi in but MTB's should be car type valves. Stronger, less affected by dirt.

 

[FluffyChicken]

tighten the lockring down against the rim & away I go.

This is not helping and wrong.
The ring is there to help you inflate it, after that it is redundant.
There should be not pressure pulling the valve stem.
Check the inner wall on the rim is also the valve diameter and not larger if it is ty and shim it to make it smaller.

The Schwlabe tech do download on there site has some good technical-ish info in it.
Try a different inner tube with reinforcing around the valve.


As for road valves, well last time I used one, it gummed up with mu and the valve tore off. So I wouldn't say they where better.


http://www.schwalbe.co.uk/_webedit/uplo ... 20Info.pdf
pg21

Other than that mentioned by people above, another one is to sand your rim a bit to make it drippier.
Of course, try using a different tyre that might fit a bit better.

 

[medoramas]

You not using some cheap innertubes, are you?

I ride rigid, tyres are big volume 2.1 Maxxis', the front is inflated 5 PSI below the recommended minimum (they say 35, I do 30...), I've never had that problem. Maybe it's about the tube's quality?

 

[hamster]

I agree - I found that the stock Specialized ones most bike shops carry are really awful for it, certainly there was a bad patch around 5 or so years ago. My really old tubes were lasting fine (one got retired after 16 repairs) but newer ones had the rip-out problem. Since switching to Schwalbe tubes I haven't had a bad one.

There was a lot about this on the CTC forum a while back - it was affecting road bikes too. People seemed to have cost-reduced the tubes and the valves were poorly reinforced.