PF keeps visiting around valve-am I doing something wrong?

mrtuk

Had a visitation this morning (in the rain!!), put a 'new' (repaired) tube in, pumped it up and as i put valve cap on, heard air coming out, and felt it around the valve. Took tube out and noticed a tear around the bottom of where the valve is attached. I have had a few of these, so wondering if I am doing something wrong? A couple of potential theories I have:
1. I'm screwing the valve in too much ... i.e. the little wheel that you can screw down the valve shaft keep it poked through the wheel properly. I generally screw it in before inflating (so it holds the valve out enough to attach the pump), and then when type is pumped up there is a gap, so i screw it down further ... could this be pulling the tube out so when i go over a bump it stretches the tube near the valve join?
2. Connecting and disconnecting the pump is straining the valve - using hand pump when repairing roadside it's hard to keep it still, so i am probably wiggling the valve around as i pump. Even with track pump at home though i find i have to pull fairly hard when pulling off after inflating to 100psi as i want to get pump of as quickly as possible to avoid the loss of air/pressure.

Any help appreciated.

Thanks

andrewc3142

Washers are definitely not allowed (Rule 60).

Seriously, though, it sounds like pinch punctures. Make sure the tube isn't between the bead and the rim - after you've put the tyre on push the valve to make sure it's moving freely and it's also a good idea to check all the way round.

Also helps avoid them if you slightly inflate the tube first.

Very, very unlikely to be connecting/disconnecting the pump [Edit: Unless as commented below you're using one of the pumps that don't have a flexible hose]

Best vid I know for putting on a tyre is: https://www.youtube.com/watch?v=-XUFVrl0UT4

The other thing it could be is a sharp edge at the valve hole and/or rim tape needs replacing.

tangled_metal

I always slightly inflate then push the valve into the tyre a bit before fully inflating. Never known why but I guess it could be to do with your problem. Before even inflating I run something around the loose tyre to make sure the inner tube is fully inside the tyre to prevent punctures from the tyre / rim squeezing the tube. Never had this issue so either it is working or I am lucky. Try not screwing the washer but having it loose or looser at least. I personally only screw that up when I have almost completely iinflated the tyre.

keef66

1) Throw away the little screw thingy.
2) Check for any sharp edges around the valve hole, and smooth down with a file / emery paper if required
3) Get a pump with a flexible hose.

I've read lots of reports of people ripping valves off tubes using mini pumps that clamp directly onto the valve. Worse still if the valve is already tightened into the valve hole by an enthusiastically tightened nut.

Observing these 3 precautions it's never happened to me.

mrtuk

keef66 wrote:

3) Get a pump with a flexible hose.

I've read lots of reports of people ripping valves off tubes using mini pumps that clamp directly onto the valve. Worse still if the valve is already tightened into the valve hole by an enthusiastically tightened nut.

I think this is the first step as don't want my roadside repairs to be the cause of more problems.

Also, forgot to mention, but I have 700x28 tyres, but the guy in the bike shop said i could use 700x18/25 tubes (rather than the bigger 700x28/35) ... could the extra expansion lead to the tubes being over stretched and more susceptible to visits?

andrewc3142

My 2 cents, if you're shelling out on a new pump worth looking at the Lezyne ones, which screw on rather than clamp on. Their track pumps are really good and their mini foot pump will easily get you to 120psi on the road. A little more pricey than some others but last forever.

And you're right, it may not help using the wrong size inner tubes.

The Rookie

The tubes will be fine and are less likely to pinch twixt tyre and rim than the fatter tube.

Tubes stretch a lot without issue, inflate one out of a tyre to see!

keef66

andrewc3142 wrote:

My 2 cents, if you're shelling out on a new pump worth looking at the Lezyne ones, which screw on rather than clamp on. Their track pumps are really good and their mini foot pump will easily get you to 120psi on the road. A little more pricey than some others but last forever.

And you're right, it may not help using the wrong size inner tubes.

I just bought the cheapest version of the Lezyne pressure drive to go with my summer bike. Flexible hose which screws on to the valve. £17-ish I think.

If you use eg Continental inner tubes with the removable valve cores, it's worth making sure they are screwed in tight before using a screw-on hose, otherwise you can inadvertently unscrew the valve core when removing the hose

Winter bike has a Topeak Road Morph permanently mounted on the seat-tube. Flexible hose which clamps onto the valve. Operates like a mini track pump so you're exerting no pressure on the valve. It even has a little inline pressure gauge. ££'s several, but very good.

I doubt the size of the tubes is the cause of the tears at the base of the valve.

MichaelW

Take the edge off the valve hole.
Fit good (Velox) rim tape.
Only use extended length valves in deep rims.
Support mini pumps on the rim with your thumb.