mcours2006

I had a flat this morning and had to sit on the side of the road to replace the tube. Took a good 20 minutes b/c the valve stem wouldn't seat properly. This is the third or fourth flat on this particular tire/tube/rim combo. It got me thinking, what's the most likely cause of the flat? Tire manufacturers claim 'flat-resistance', but how does tire prevent a puncture from inside? The road I was on when I got the flat had lots of debris like sand, gravel, and salt on it from winter road maintenance.

trailerpark

What kinda stems are you using? On Schrader valves I've found it best not to pull them out.

Bad luck is the cause of all flats.

mcours2006

I've got the presta value stem. The puncture is not near the stem, though.

Yeah, I agree about the bad luck.

I think it's the narrow tires. I've never gotten a flat on my hybrid with the 32mm city tires nor the 35mm studded tires.

wolfchild

When changing your tubes on the side of the road, you need to be very careful that no road debris, sand particles or little stones get inside your tire.. It's very easy to get new tubes and the insides of your tires contaminated with road crap when doing roadside repairs.. You need to make sure that your tube and the inside of the tire is clean and free from any road debris, because if it's not, then your tube will get punctured from the inside after you pump your tires up.

mcours2006

Thanks, that's good advice. I was off on the grass area of the road, fortunately, and well out of the way of traffic, so I think the contamination was minimal, if any at all. And 50km later it seemed fine.

dynaryder

Where are the punctures? If they're on the outer part of the tube(facing tire),then it's from something that got through the tire. Always turn your tire inside-out by section to ensure nothing's still embedded in the casing. If the puncture is on the inner part(facing the wheel),then it could be a bad spot of rim tape,or a sharp edge in the rim. Check your rim tape,and either use a cottonball or carefully run your finger around the rim to ensure everything's smooth.

willhenry

Many flats are caused by pinching (between tire bead and rim). It's usually because people install the tube almost flat and a bit of it gets pinched when the tire is levered back on. I always partially inflate the tube before installation to reduce the chances, but it happens.

I'd also inspect the interior of the rim for burrs (carefully, as @dynaryder suggests). Makes sure your rim tape is in good shape.

TransitBiker

I have had flats where something innocent got into a tire hole created by a nasty thing i rode over. You could put some masking tape over the hole inside of the tire if it's a concern for more FOD infiltration.

Always check the tire & rim for pokey non-smooth stuff when possible.

As for me, i'm going to be switching to thorn-proof tubes, as the peace of mind is worth the bit of extra cost & few oz of weight

- And.

sirtirithon

I have had issues where a small piece of wire was embedded in the tread and could not be felt by running my hand around the inside of the tire yet when under pressure from inflation and riding it managed to puncture the tube again. Talk about frustrating. The best way to deal with that is to use a sharpie and make a reference mark on the tire where the stem of the tube is in relation to the tire, locate the puncture and then closely inspect the tire, folding it and probing around for anything embedded in the tread.

bowlofsalad

I imagine the most common causes of flats on bicycles relates to things puncturing the tire.

There are a pretty incredible range of tires to choose from, and you neglected to mention which you use. The tire you use can make a massive difference in how often you get flats.

Pinch flats are from when the tire is compressed so deeply and hard that the inner tube is cut. Wider tires can help with this.

Schwalbe marathon plus tires are very likely to alleviate any flats, the world of bicycle components looks very different when you look to it for reliability rather than going fast.

79pmooney

The trick to very quickly blowing up the tube to the perfect pressure for mounting? Blow it up by mouth. Blow hard. (You can; you're a cyclist!) Much faster than messing with a pump or canister.

Ben

tjspiel

A trick I learned here was to find the most prominent logo on the tire and center that over the stem. It's the same concept as your sharpie... without the sharpie.

79pmooney

Yeah, the 21st century cyclist's curse, automobile tire reinforcing wire. Pieces of very sharp wire can get picked up by your tire that are shorter than the distance from tread to inside of cord. But they will travel through to your tube. That is a good reason for patching tubes. When patches start appearing in the same place, you know exactly where the issue is. You can find hidden wire when you know ahead of time it's location within an inch.

Ben

ThermionicScott 

+1. And if one doesn't want to use their lungs, I prefer pushing in the air by mouth, if that makes sense. I can get a little more pressure that way without straining anything and getting light-headed.

Big Lebowski

Until 2 years ago, I had the same issue with road sand causing flats. I was using Gatorskins, but a sharp flinty stones that get dumped on the roads during the winter still got through it. I've since switched to a Kenda tire with a small tread and I have had no issues.

prathmann

Did you push the valve stem a little into the rim before inflating the tube to be sure you didn't get the section near the valve pinched under the tire bead? Easy for that to happen and it'll keep the tire from seating properly near the valve stem and can also cause a blowout flat if it dislodges the tire bead.

As to the cause of flats, the only thing that matters is what the cause is of *your* flats - and only you are in a position to determine that. Whenever you repair a flat check the old tube first to determine where the hole is and then check the corresponding area in the tire and rim to see if you can determine the cause (like a glass shard or thorn in the tire, a rough spot or missing rim strip coverage in the rim, or a pinch flat from hitting a bad bump with an underinflated tire - this last usually shows up as two little lines on the tube where the rim edge bottomed out against the tire). Once you know the cause then you can decide how to avoid future flats (i.e. higher pressure or wider tires prevent pinch flats, better rim tape coverage if the flats are on the inside part of the tube, tires with better Kevlar or similar belts that resist glass cuts and most thorns, etc.).

CliffordK

It is hard to say what caused your flat(s).

For me, I think it is:WET WEATHER APPARENTLY MAKES THEM WORSE.

Whenever I get a flat, I try to pull off the tire and tube off together, then blow up the tube to locate the flat before removing the old tube from the tire. Then investigate the cause of the flat before inserting a new tube.

Periodically I'll pick all of the glass and wire shards out of the tires in a vain hope to prevent future flats.

Flat prevention strategies by companies:

• Tire tread thickness: This seems to be the main method employed by Schwalbe in the Marathon tire. If one has tread thicker than the size of the piece of glass or metal shard, then it may never work its way down to the tube, especially if a person periodically picks the glass out. This is also a key part of the resistance in the heavier MTB and X-Cross tires.
• Belted (Kevlar). Hopefully prevent the glass or debris from cutting its way down to the tube. It is hard to say how effective different brands are. High density thread count may also help, at least if using durable threads.
• Rubber compounds formulated not to pick up the glass in the first place. At least a couple of brands advertise that they are better at preventing the tire from picking up the glass.

Here is a picture of the piece of glass that came out of my Marathon tire causing a flat in the first 50 miles.



It cut through the tread. And through the blue stuff. But, only a small part actually penetrated the cords. The end of the glass was still sticking out when I found it. Had it not punctured the tube when it did, perhaps it would have eventually sliced through all the cords. As it is, the actual hole is small.

It is my opinion that Schwalbe made a small error in that they should have added a little extra depth below the cords. So, the glass would have had more distance to penetrate after reaching the cords.

ItsJustMe

On my route, I rarely get punctures. Almost all of my flats are due to pinch flats or some such. Only on the road bike with 23s though. On the winter bike running 35s, never a problem.

Interestingly, it actually seems to make things a bit worse if I pump up over 80 PSI. There seems to be a sweet spot around 80 PSi where flats are minimized for my setup. Seems weird that a higher PSI would result in more pinch flats.

I'd say I have an actual debris puncture maybe 1 time out of 10. I flat about once a month on the road bike, and I can't even recall the last time it was due to a foreign object. Mainly it's the ****ty roads around here. Luckily the county seems to have dredged up some money this year because they're repaving like crazy this spring.

Leebo

Looking for some more info please. Tires, tube, rim width and pressure used? Rider weight? Worn tires?