not sure if this photo worked but for the 3rd time in as many months I've got a hole right at the base of the valve. This one was Schrader but the last 2 were presta.
Feels like maybe the tube is shifting inside the tyre and rubbing on the edge of the valve hole. I put electrical tape over the valve hole last time (though oddly can't find it now)
I've had it on a bad batch of tubes before. I guess they're being pulled round by the tyre under braking
rubbing on the edge of the valve hole.
Sounds plausible - can you feel if there are any sharp edges you could file down?
Some new / thicker rim tape might help or you could try putting a suitably sized o-ring on the valve stem first so that is what is up against the hole.
[url= https://i.ibb.co/dfjcR9c/PXL-20240125-090209288.jp g" target="_blank">https://i.ibb.co/dfjcR9c/PXL-20240125-090209288.jp g"/> [/img][/url]
Thanks scotroutes.
I tried a different brand of tubes last time so it's not just a bad batch.
The rim tape does appear to slide round the rim easily. I'll try some thicker tape but can/should I stick it down to stop it moving?
Velox tape is sticky back fabric and really excellent if old fashioned.
Do you run fairly low pressure with tubes? I've seen issues with tyres being dragged round because of being soft and causing similar issues.
more talc on the tube and file off any rough bits on the rim - or maybe consider "shimming up" the tube away from the rim hole by putting a second lockring/nut right down onto the valve before putting the tube into the wheel ?
<adds>: if the tyre's really loose on the rim and able to rotate, say under braking, you need to address that with more/better tape
Used to happen to our group a lot when we first moved to disks. The combo of powerful brakes and poor fitting tyres meant the tyre rotated on the rim dragging the tube and stressing the valve. Had about 6 in one day out once and used all our spares. The long term fix was better fitting tyres but the short term bodge/fix was a few dots of super glue on the bead. You put some on one side and you can still change the tube from the other side and it peels off to change the tyre.
Sometimes I’ve cut out the valve stem and slid a section of net tube over a new tube valve before replacing for extra protection. It’s likely due to over vigorous pumping rocking the valve around and causing the tube to puncture on the rim hole.
Thanks, I'll try all of these suggestions at once.
My wife's tyre started slipping on a ride once and it killed 2 tubes in about a mile. I wrapped the bottom of the valve on the last tube we had with lots of electrician's tape and jammed it into the rim. It held for about 4 years!
It was one of the reasons I went tubeless. The valves were moving under braking seemingly.
Are the rims drilled for car valves? The extra space used to kill my tubes that way. You can get inserts that cured the problem for me. <br /><br />
I found that over-tightening the valve nut was causing this problem.
It stops the inner tube from having any wiggle room.
Not had it happen since keeping it loose.
Credit to TiRed.
A slight variation on their idea works for me.
Cut a circular piece from an old inner tube, about 40mm diameter. A couple of small cuts in the centre, and push that over the valve and against the tube.
Fit the tube as normal, making sure to tuck the edges of your 'washer' inside the tyre so that it doesn't foul the bead.
TL:DR: put a mark on your rim and a mark on your tyre and see if the tyre is rotating on the rim. If it is, and you don't have a ton of talc, then it will drag the tube with it and decapitate the valve just like in the picture.
There are other reasons why it might happen that are explained above, but this way you can either prove or discount this particular cause and move on to the next.
Mrs Udder's infrequently used bike as this same issue, as does one of the Udderlet's 24" wheels. I swapped Mrs Udder to a set of tubeless 26" wheels we have spare, but can't do that with the 24" wheels, which use drilled trials rims. I found more air pressure helped there - I'd purposely been running those soft on account of him not weighing very much.
I also had this years ago with Panaracer Fire XCs. It seems like the beads stretched slightly (Surrey Hills singetrack back then wasn't very hard on tyre treads, so they tended to last a long time). The tyre would start to rotate on the rim under hard braking, pulling the tube with it. Lots of talc between tyre and tube had some effect, replacing the tyres outright completely solved it. At the time I was running my other bike tubeless with the early Swiss and Stans stuff, and the bike with the valve issues quickly followed it.
For me this was old tyres with loose beads. New tyres and the problem went away
Baggy beaded tyre especially on a wide rim.
We've a set of old Ritchey off centre rims that with certain tyres ate valves like that at a scary rate. The 2 mile ride to the gym cost us two tubes once.
Building up tape and/or less flappy tyres was probably the answer if I hadn't swapped in some other wheels and put the Ritcheys on the spares pile.
In the Olden Days, when fitting new tyres we used to make sure a good squirt of talc was rubbed in the inside of the tyre to stop the tyre sticking to the tube. It stopped this kind of thing (basically the tyre is moving n the rim, the tube is stuck
to the tyre, so the tube gets ripped at the valve.
I still do it on tubed tyres, indeed using the same 25 year old pot of Superdrug basics talc.
I've noticed on some rims(even Hope) theres a little bit of a sharp edge/burr around the valve hole. I remove this using a drill countersink. You could use a file, or emery paper. I use a countersink because I have them to hand and it does the job well.
I've had this before on a couple of bikes. My theory is the tyre gripping the tube when you brake hard causes the tear. A combination of patching round the valve stem (old inner tube round the base) and lots of talc when installing the tyre mostly fixed it for me