Why am I getting flat tires on my bike?

September 1, 2016 9:02 AM

The flats I am getting are not punctures and they’re not pinch flats. I get holes right next to the valve, soon after inflating the tires. It happens on both my front and rear wheels. Sometimes it happens overnight when the bike hadn’t even been ridden; sometimes it happens while I’m riding; sometimes I bike into work fine and when I leave for the day both tires are flat. There are no burrs/ rough spots on the rims. I have shown this to two different bike shops and they are also baffled.

It’s a Trek mountain bike, 26 by 1.75” tubes. I inflate them with a floor pump.

This began happening when I switched to different tires. But when I switched back to the old ones, it kept happening (though not as constantly). (Longer probably irrelevant story: I switched my knobby tires to more road-appropriate ones since I only ride on roads. I kept getting punctures in them because urban biking involves a lot of glass, so I switched to ones with somewhat deeper treads. Punctures mostly stopped but post-inflation flats started happening. I switched back to the knobby tires, which I’d never before had any kind of flats with, and am getting the holes by the valve still.)

Things I have tried unsuccessfully:

Different tires
Self-sealing tubes
Different brands of tubes
Lining the rim with an old tube

I’m going to borrow a different pump to see if that helps (I hope it does!) But other people use my pump without problems and I used it for years without problems, so I don’t think that’s going to solve it.

I’m not excited about the idea of buying new wheels because it doesn’t seem likely to help (since this is happening on both front and back) but will if convinced.

Any theories/ solutions would be enormously helpful. I used to bike commute daily, but haven’t been able to for a couple of years now because I am constantly getting flats. I hate driving. Help!

posted by metasarah to Travel & Transportation (19 answers total)

Do you have rim tape on your rims? You said lining the rim with an old tube - but the proper thing to use is cloth tape that bike shops sell, so that the tube doesn't encounter the sharp edges of the spoke hole or the valve hole. It's slightly adhesive, so it doesn't shimmy under pressure.

I've had a few brands of tubes that tend to come apart where the valve meets the tube. There are bad batches out there.

But my guess is that you need rim tape that costs just a couple bucks at the shop.
posted by entropone at 9:07 AM on September 1, 2016 [5 favorites]

If the punctures are happening at the same spot I'd preemptively apply a patch on the new tube in that spot. If it is some sort of weird pinch puncture that should prevent it. If it is happening where the tube meets the stem you can punch a hole in the patch and stick the stem through it.
posted by Mitheral at 9:11 AM on September 1, 2016 [2 favorites]

This probably isn't the cause, but I've always hated most bike pumps because the act of shoving the whatsit onto the tube valve and then removing it post-filling can be really hard. Every time I have to yank to get it off I worry that I'm tearing something. So if you're thinking of getting a new floor pump anyway, I highly recommend ones that screw on to the valve instead of just forcing it on/off. Mine is a Lezyne and it's freaking great. Takes a few more seconds to thread it on and off but I never worry that I'm putting stress on the tube at the valve.
posted by misskaz at 9:13 AM on September 1, 2016

I would try 1) Rim tape, yes. That's essential. 2) if that doesn't work, yes, try new wheels. Maybe you can get used ones or a shop will let you try some for a couple days in the name of troubleshooting? I would ask around. Maybe even a friend has some you can borrow. This sounds like a hassle but less than not being able to ride your bike.

(Once you sort it out: Gatorskin tires are amazing and since I finally shelled out for them I've had no flats whatsoever aside from the once-a-year or so giant puncture from glass or a nail.)
posted by jeweled accumulation at 9:14 AM on September 1, 2016

How tight a fit is the valve in the rim? I've seen this happen when people have presta inner tubes in schrader-drilled wheels - the inner tube moves around too much and the rim cuts the base of the inner tube. Apparently it can also happen if you don't tighten the presta lock nut at the base enough and the valve moves up and down in the hole.

Could something like that be happening? The rim wouldn't need to be sharp, it's just friction.
posted by tinkletown at 9:19 AM on September 1, 2016 [8 favorites]

I thought presta inner tubes in schraeder/woods-drilled wheels, too. You can get a very cheap metal inserts that fit in the valve hole so that presta valves fit properly.
posted by scruss at 9:24 AM on September 1, 2016

Bad rim strip. Get Velox, try that.
posted by fixedgear at 9:37 AM on September 1, 2016 [1 favorite]

My thought was also that the valve stem isn't fitting the hole in the rim correctly. I would try applying something (electrical tape, a patch, whatever) to either the hole or the tube, or both, to make things fit better and move around less, and to cover up any sharp edges that might be bothering your tubes.
posted by Anticipation Of A New Lover's Arrival, The at 9:44 AM on September 1, 2016 [1 favorite]

In my shop, I remove the plastic or rubber rim tape that comes on a lot of wheels and replace it with some good cloth tape like Velox.

But before I put the cloth tape on, I'll deburr the valve hole with a tool exactly like this.

Also, if your valve hole was drilled too small, I'll ream it with this tool before I deburr.
posted by spikeleemajortomdickandharryconnickjrmints at 9:55 AM on September 1, 2016 [4 favorites]

A simple test would be to try a new front wheel. See if you can borrow one from a friend or bike shop and do all your normal things with it. I have had this happen before with one of my wheels and tried everything mentioned above. Nobody could figure it out so I assumed the wheel was just haunted!
posted by oxisos at 10:01 AM on September 1, 2016

If this is at the root of the stem, and you've got presta tubes, I'd try screwing down that little nut that comes with the tube to stop it from creeping, which might be a cause. I second the reccos for better rim tape and Lezyne pumps. Schwalbe also makes very high quality tires, tubes, and rim tape.
posted by adamrice at 10:26 AM on September 1, 2016

Does this happen just as fast when it's the bike shop who installs the new tube and inflates it? That would rule out anything about your pump or your methods of pumping or of tube installation.
posted by aimedwander at 10:31 AM on September 1, 2016

Response by poster: I do have rim tape! But can try an upgrade.

I use Schraeder tubes, but will carefully examine the hole in the rim anyway to make sure there's no motion.

This has also happened when other people installed my tube, but they've used my pump. I'll hassle a friend to do it for me; good idea!
posted by metasarah at 10:56 AM on September 1, 2016

I had very similar holes when a certain bike shop near me changed my tube twice, both before and after they changed my rim tape. Same guy each time. When I did it after that, they were perfect. My guess (once you've checked for burrs) is technique-- could be that the stems aren't lined up perfectly with the hole, so there's torque/pinching/pulling on the stem/tube interface. Make sure that once you get one tire bead on the rim you're inflating the tube enough to keep it in place and lined up with the stem hole.
posted by supercres at 11:50 AM on September 1, 2016 [1 favorite]

Some bike shop convert presta to schrader by just drilling them out, maybe they used too small/large of a drill and the stem doesn't seat correctly. Too small an it will stick into the tire too far and maybe get a pinch flat next to the stem, too large and the tube may extend into the hole and get cut. I've also had problems with thick puncture-proof tubes combined with very narrow rims, they distort the area around where the stem attaches to the point that it fails. You should check to see if it is cut next to the stem, or has the stem come loose.
posted by 445supermag at 12:40 PM on September 1, 2016

When I had this happen for a while, in the exact same spot, the shop told me I was being too rough attaching and removing the pump. Now I try to be suuuupppper gentle, and haven't had any problems since. YMMV.
posted by megancita at 12:45 PM on September 1, 2016 [2 favorites]

After reading the thread: as convenient as it would be to blame a sharp surface for these repeated holes, I think this is probably due to you being rough with the valve stem in some unknown way. Try a different pump, or ask someone else to try installing and inflating the tube, and see if the problem persists.
posted by mosk at 12:59 PM on September 1, 2016 [1 favorite]

one thing that hasn't been mentioned is that you can get damage near the valve if the tyre is slipping round the rim (and dragging the inner, which puts strain on the valve because it can't move). typically that's only a problem if you're running very low pressures, but i guess maybe you could have a particularly slippy rim. you could mark on the tyre where it meets the seam of the wheel, and see if that moves...
posted by andrewcooke at 1:08 PM on September 1, 2016

Switch back to your slicks or inverted treads; you'll get more efficiency out of them than knobbies. When you switch back, try kevlar belts/strips between the tube and tire. That cuts out flats too, especially for us commuters.
posted by dlwr300 at 6:06 AM on September 2, 2016