This is my third flat tire in a month. I don't think it was a pinch flat this time as both my tubes were inflated to 125 PSI (maximum) when they were previously at 90 PSI.

This time I had just gotten off a trail (paved) and left my bike at home overnight. Then I disassembled it by taking off the front tire and I packed it all into my car.

When I take the front tire out my car it is flat. The rear tire (still on the bike) is fine.

What could have caused this flat? I'm pretty sure it isn't a pinch flat because the trail I was on was paved and relatively well-maintained and wouldn't a pinch flat cause instant deflation? Could it just have been a thorn or other debris from the trail? Or maybe something in my car got to the tube?

Is there something I can do to permanently prevent flat tires? High PSI seems to be working for pinch flats ... how are those "Slime" tire tubes? What about injecting tire sealant into the tire? I have never removed a tube from a wheel before ... I tried once with a fork but got nowhere ... and I'd rather not pay the mechanic again (if only to save myself the embarrassment).

Most likely a pinched tube. Not the same as a snakebite flat. In a pinched tube, the tube/tire wasn't assembled quite right and the tube was stuck under the tire's bead someplace. Once inflated, the tube eventually worked its way out and, without the support of the tire, it exploded. You'll probably find a star-type hole blasted in the tube where it happened and possibly the tire will be blown off the rim.

To avoid pinched tubes, put everything together normally and inflate the tire to about 5 psi. Then working your way around both sides of the tire, push the bead away from the rim and look down inside. You shouldn't see anything except the rim strip because the tube should push itself up into the tire. If you see the tube, that's a problem that you need to fix. When you get done with both sides, one final step is to push the valve stem up into the rim as far as you can and let air pressure pop it back out. It's VERY common for the valve stem reinforcement to get stuck under the tire bead. Then you can inflate normally.

I've heard slime isn't especially effective at those high pressures.

Quite possibly a thorn or other debris from the trail.



Flat tires are a part of cycling ... learn to change them with the appropriate equipment. If you're not sure what to do, there might be classes in your area, or ask your mechanic to teach you.

Thanks for all the replies. I suppose that later I will have to visit Wal-Mart to purchase some cheap tire irons and practice on the busted bikes I have in the garage and hopefully eventually wrestle the tube off my main bike. Any suggestions for tire irons? Or will any do?

Also the tires are "700c x 23" ... and the local Wal-Mart has tires only in inches (i.e. 27 in). I think a 27 in tire should fit, but what about the diameter? 1 and 3/4? Or what?

You may not need tire irons; watch a YouTube how-to video (or two) on flat repair. Get quality tubes from a bike shop.

Go to a bicycle shop. Talk to the people there. Ask them to show you how to change a tire.

And you don't want "tire irons" ... try tire levers. They're usually plastic, although some may have a steel core to keep them from snapping when working with particularly difficult tires.

You might try tire levers like these, for example: Park Tool TL-1 Tire Lever Set

Tire Sizing Systems

When I got my bike from the LBS, they asked me if I knew how to change a flat. I did, but it had been years and I was used to coaster brakes... I had to go back to the shop because I couldn't figure out how to "break the knuckle" on the v-brakes .

FWIW, you're asking the right question.

Take out your flat inner tube and inflate it to about 4X it's normal size. Try to fins where it's leaking air. Sometimes it's hard to find the leak and you have to dunk it in a tub of water (or the toilet).

If the leak is on the opposite circumference from the valve, you have a puncture from a thorn or piece of glass or wire or something. Make sure it's not still caught in your tire before installing a new or repaired tube.
If the leak is on the same circumference as the valve stem, you have a rim strip issue. Make sure that every tiny little arc of rim hole is covered.
If the leak is on the side of the tube, you pinched the tube under the tire bead while installing it. That's easy to do if you're not real careful.
If your valve is leaking, you need to tighten the valve or replace the tube.

If I lived in an area where they have goat head thorns and I punctured multiple times per week, I MIGHT consider using "Slime" or some similar puncture sealent. I don't so I don't. I think the sealents are yucky.

SOmetimes multiple flat tires in a short period of time is just bad luck, but sometimes it is because the cause of the first flat tire was not discovered and fixed before re-installing the tube.

Your job as the rider of the bike is to determine the cause of the flat so that you will likely not experience a fl;at for the same reason again. Every time you get a flat tire, use tire levers to remove one side of the tire from the rim and leave the other in place. Then pull the tube out and find the puncture. Then, using the valve as an indicator, you can trace the leak back to a particular position on the tire or rim and figure out what caused it. If flats 1, 2, and 3 are caused by a thorn, a pinch, and a piece of glass respectively, it is just bad luck, but if all three are at the same place on the tube then you have a mystery to solve.

Definitely learn how to change your tubes. It's absolutely necessary if you're going to be riding bikes with any sort of frequency. It's super easy, just get yourself 2-3 tire wrenches/levers. I personally like this one from REI.

crankbrothers Speedier Tire Lever

It seems to work a bit better than the typical $1-$2 ones you buy all the time. Plus it somewhat protects you knuckles. Watch a youtube video on it. Once you do it once it's really simple. There also may be something pointy on the inside of your tire/rim that's continually poking the tubes and putting holes in them. Yes, any competent mechanic would check that, but who knows if they did.

Also, depending on the type of tire you have, you MAY be able to pull it off by hand. If it's a wire bead tire/really tough bead tire, it'll be hard. It's still possible, but hard. Here's a video of an oldish man changing a known tough to change tire by hand without levers. I've tried doing this... it's not easy, but it IS possible.

SOmetimes multiple flat tires in a short period of time is just bad luck, but sometimes it is because the cause of the first flat tire was not discovered and fixed before re-installing the tube.

That would be my thought as well. There could be a sharp edge on the inner rim that is causing these repeated flats.

I was reminded of this when I watched a documentary of a young man who biked around the world and set a time record (which has since been broken). I believe there was a sharp edge to one of the spokes ... or some minor manufacturing flaw that was not filed down and that was the cause of his repeated flats. I believe he had two flats in a short period of time and that got him thinking.

i have had two flats in two weeks. one front large thorn .then the rear couple weeks ago i dug out piece of glass that did not go thru the following day rear tire is flat found sharp pebble in same hole as the glass was.. had to replace tire and tube as you could now see tire cords in the hole. now running original tire in front and a nimbus armadillo on the rear. first flats in over two years

Some May hate the added weight , but I fitted Heavy duty Thorn Resistant Tubes in a few bikes , and go Years without Punctures ..

My 10 month tour from SW Ireland to NE Scotland , in '97 was Puncture free, and The tire was a Suomi Finn Utility type, not a Schwalbe Marathon Plus.

I did the same thing after getting a flat based on the LBS suggestion and have been flat free! The extra weight is not even noticeable.

Okay, I definitely know how to use tire irons, as I managed to remove the tubes from two other tires lying around in my garage no problem. These aren't cheap irons either; they actually are iron (with plastic on the outside). I think the problem is that I have Kenda tires ... and I've read a lot of people complaining about how tight they are. The fact that my bike was purchased from someone who left it sitting around for the last 10 years untouched probably didn't help ... I'd imagine that the heat in the garage would have affected (slightly shrunk) the tires.

As I see it, there are two options: Get used to changing flats, or get puncture resistant tires.

The first option is really pretty good. Changing flats is not a big deal, and after you do it a few times it becomes pretty routine and doesn't cause too much stress. It turns from "I had to change a flat! " to "I had to change a flat! " pretty quickly. Actually, there are times when it's rather relaxing - I remember riding over Trans Mountain Road (El Paso if you know it) and had a puncture pretty close to the top. I changed the flat (replaced tube) as I watched the sunset in the west - enchanting.

The second option -- Several tire companies, one that I have used, make puncture-resistant tires that work. Continental has their Gatorskin, plus a line of tires with what they call their "plus system". This is what I use - I currently use Continental Touring Plus and have used Continental sportCONTACT, (or SPORTcontact I don't remember lol) and have not had a flat since the summer of 2008 - 6-1/2 years @ app. 1500↑↓ miles per year. Schwalbe Marathons are rated equally as strong although they are a little more expensive. If you absolutely hate changing flats, this is the way to go.

But I like Machka's answer - probably the best thing to do is just get used to doing it, because it's part of bicycling.

Alright Deontologist you"re making this too serious, changing tires and fixing flats is not that serious of a task relax and do it slowly paying attention to what you're doing, it'll be alright, if you're gonna ride you're gonna fix flats! and remember,,, Good tools are not cheap, and cheap tools are not good,,,,,,,,,,,

I feel compelled to pass on (again) a link about the inner tube that doesn't require you removing the wheel from the bike ...

That's pretty neat; I've not seen it before. I wonder can you feel the butted ends when rolling?

I would very surprised if you could - just as you cannot feel patches, properly applied tire boots, thick or thin spots in the tube...

The only thing you can always 'feel' is a tire with damaged cords or warped casing, or an improperly mounted tire. The tube has no effect on the shape of the tire.