Clarky879

Anyone got any idea why I keep getting puncture bottom of valve 4 times in a row, I have taking inner tube out etc and looked but can't see anything, sanded it down around the hole with sandpaper

TiHabanero

Have never been able to fully figure it out, but have seen it hundreds of times at the shop. Provided the issue is not caused by installation and removal of a pump head, I have found putting electrical tape over the valve hole area in the rim plus coating the tube in talc HELPS prevent it from happening with great frequency. Another trick I have resorted to is greasing the tube two inches out from the valve stem in either direction.

Clarky879

Hi mate, yeah it doesn't make sense, just don't understand it at all, tempting just to buy whole new wheel/tyre, will try your tricks first though thanks

freeranger

Schraeder or presta? If presta and you're using the stem nut, either remove the nut or place it in the middle of the stem, don't tighten it down on the rim. Or, what Ti said.

BobbyG

A few years back I had the same problem, maybe once every 18 months. It was very difficult to find. I even submerged the inner tube in water to watch for bubbles, but it wasn't until I put pressure on the inflation tube that the bubbles appeared from near the "collar" of the presta inflation tube.

After wearing out the hub (cheap build plus daily commuting) I replaced the wheel and the problem hasn't returned, so in my case it may have been a rough hole.

Iride01 

Presta valve? The air chuck on my pump was not releasing easily when I aired up my tubes and after enough time of having to yank the chuck off the valve the boot around the stem would develop a leak.

If you have a Schrader valve doing this, then I wouldn't suspect that as they have a stronger boot around them where they go into the tube. If you run with such low air pressure with them that the tube creeps in the tire and the stem doesn't stay straight and perpendicular to the rim then that might be wearing a hole in it.

Other things too. More info is really needed. All we can do is generalize about something that has many causes. Put a pic of it in your gallery and we can find it if you tell us it's there.

Welcome to BF

79pmooney

This is usually from mis-handling the valve chuck when inflating. Possibly stressing the valve by pushing sideways with a frame pump. Possibly by the antics to remove the chuck. If you use a frame pump without a hose, wrap your left hand fingers around the spokes at the tube valve so you are pumping against your hand, not the the valve. (I've been doing this 50 years with the Zephal HP and HPX pumps and can count on my fingers the valves I've damaged.) Removing the chuck - the time honored way is to deliver a sharp blow to the pump where your left hand had been to cleanly and quickly slide the chuck off the valve. Pump chucks with a lever that can be released are a big help here.

(In my pump references, I am assuming you are right handed; pump with your right, left hand at the valve end of the pump. Pumps with hoses alleviate the side force issue - as long as you don't pull on the hose - but may not disengage as easily. I am a huge fan of the Zephal pumps partly because the pumping action is so easy, the "spoke-wrap" grip so easy to do and the engagement/disengagement so easy and clean. They got it right a long time ago. The patents expired long ago so there is no excuse for others not copying what simply works.)

cyclezen

All as noted by 79pmooney, and proper handling of the pump...

Proper handling of small portable pump when inflating... Important to support and steady pump/pumphead with hand, FOREFINGER and THUMB. Then 'unlock' pump and give a sharp downward tap on pump, near pump head, to detach from valve... no wrangling of pump during use or removal !!!

Other option is to use a pump with a small screw-on hose, but if you're not quick getting the head unscrewed, quite some air pressure can be lost in the removal.
If it's presta, I recommend 'losing' the small round valve nut. It really serves no purpose, but overtightening is a primary cause of tube failure around the valve base.
Other issue is a sharp edge on the valve hole, which eventually cuts/wears thru the butyl. I always use a small cut piece of old inner tube, with a small center hole just big enough for the valve stem to slide thru. This becomes a protective, thin shim which protects the tube/valve area. Gets transferred to any tube swapped into the wheel.
You can also use 2 small sections of duct tape, applied to the rim/valve hole area - puncture tape with a small hole, big enough to allow the valve stem to slide thru...
If the tube needs air and is greatly deflated, put your thumb on the tire at the valve area, press inward, and then apply the pump head to the valve.
Ride On
Yuri
EDIT; If it's Schraeder , it's prolly because of valve hole edge.
Both value types... If the tube is not installed 'square' to the valve hole, over time an angled valve will put undue stress on the butyl base, and there eventually will be a 'failure' of the butyl.

KerryIrons

As others have noted, it might be technique of removing pump head, but you haven't explained it clearly enough for me to guess. Smoothing the valve hole is an obvious step if the location of the leak is right at the base of the valve. If a rough valve hole is/was the issue, you would think you could see some abrasion of the rubber at the leak point. It might take a magnifying glass to see.

Clarky879

Hi thanks for all the replies

Clarky879

I will take some pics, also I used, car electric pump is this a bad thing maybe I should just use hand pump?

Clarky879

Will check which valve it is

Clarky879

I'm new to the forum so need 10 posts before I can upload pics typical

Clarky879

The inner tape inside doesn't overlap the hole maybe this has something to do with it?

N2deep

I experienced the same issue and solved it by adding multiple layers of rim tape. This issue drove me crazy for a while. I took the rim, tire and tube to the LBS for inspection to see if they could spot the issue and they did not see a problem. Apparently the tube was trapped between the rim, spoke holes and tire, pinching it slightly to cause a micro-leak. I have not experienced a flat since I replace the rim tape.

Best Wishes.

JohnDThompson 

Are you perhaps using a narrow presta valve in a rim drilled for a wide Schrader valve stem? If so, there are grommets to deal with this.

Iride01 

You could just upload them to the gallery here on BF and just tell us they are there.

Clarky879

Hi thanks again for all reply and help, I have posted few photos in my gallery as someone suggested maybe it will help