5 Most Common Flat-Causes

While nobody likes getting a flat, almost all riders love the chance to play detective and solve the mystery of the missing air! While you’re on the sidewalk swapping in your spare, almost every rider who stops to offer you a hand will also offer their best guess at the tire-tearing culprit. In today’s post, we’ll walk through the 5 most common causes of flats, so you can do your best to avoid them (and take an educated guess next time you see someone struggling with a mystery flat of their own)! Let’s roll. 


Glass is a beautiful, practical, nearly magic material. Strong, transparent, and equally suited to artistic purposes as well as practical applications. But once it’s shattered into tiny shards on the road, glass quickly becomes some of the most despised debris around.

Shattered glass will usually be found on the shoulder, but occasionally makes its way out into the lane – or you’ll find big patches of it in intersections where there was an earlier accident. Besides rocking Thickslicks or Gatorskins, the best thing to do when you come across glass on your path is to avoid it. Keep your head up while you ride so you’ll see the telltale glimmer of glass in the road ahead of time, and you can make whatever necessary moves to avoid rolling right through it. And, if there’s no safe way around, consider hopping off your bike to carry it across the dangerous patch – riding through it will put a ton of weight on the tire/glass contact patch and that can increase the likelihood of a puncture.


Before I started riding regularly, I had no idea what goatheads were. Thorns? Sure, like on a rose bush. Plant-born spike-balls? Yeah, I remember playing with those mini-maces in elementary school. But goatheads? I’d probably assume they’re what you’d find mounted on the wall in the den of an experienced goat hunter. But the truth is worse. Goatheads are gnarly little natural caltrops that live for the opportunity to stick your tires.

Spend any amount of time on the road, and you’ll eventually encounter some wild goatheads. More common on bike paths, trails, and anywhere that plants and transpo exist side by side. They’re not very easy to see at speed, so just do your best to avoid riding on the edges of the path/trail, and try to keep your wheels as far from the wilderness as possible. And, if you do find your tire stabbed by one of the prickly problem-makers, leave it in until you get home! Pulling that goathead out is a great way to unplug the hole it’s made and let all of the air out of your tires. Do your best to finish the ride before you start pulling these puppies out. Something I wish I’d known before popping one out at a stoplight only to go completely flat a block later :(.

Pinch Flats (Underinflated)

Also known as “snake bites” because they show up as two tiny little punctures, side by side on your tube, pinch flats are the result of your tube being pinched between the road and your rim while you’re riding.

Pinch flats are usually the result of an underinflated tire, because there’s not enough pressure to keep your rim off the road when going over bumps. The typical pinch flat usually goes something like:

7:00am: “Hmm, my tire’s a little low. I’ll pump it back up when I get to work”.

7:15am: “Here come those speed bumps. Just another ordinary commute”.

Bump-GRANK (<-- that’s the sound of your metal rim hitting the pavement)…

Hissssssssssss (<-- and that’s the sound of the air sneaking out of those two fresh holes in your tube.)

Just make sure you’re all aired up properly before you roll out, don’t go hopping huge curbs or anything on thin tires, and you should have no trouble riding pinch-flat-free.

Bad Spare Swap

Surprisingly, one of the most common causes of flats is messing up on your last swap. Unsurprisingly, riders will almost never immediately assume it was their own fault, and so this one usually only proves itself after an autopsy of the old tube.

Basically, it’s pretty easy to accidentally pinch the tube when you’re seating the tire bead, or when you’re using tire levers under to remove/replace the tire. The only real steps you can take to avoid these kinds of flats are just to take your time when installing new rubber, make sure everything’s going in pinch free, and be careful with those levers – hard plastic plus soft latex can equal some pretty quick tears.

Tire Wear (Tumors and Cords)

And, last but not least, the most well-earned of all flat causes, excessive wear!

Tires ridden down to the cords will have much less rubber protecting the tube within. Weakened sidewalls on old tires can bubble out (tumoring) creating a weakness and the perfect pinch point. Once your tires start getting up there in age, get thinking about replacements.

It’s always easier to swap an old tire for a new one once, then it is to keep swapping tubes week after week, just to get some more life out of that tire.

And that’s it, the 5 most common causes of flats! So next time you stop to help someone making a mid-ride patch, or swapping a tube, throw your detective hat into the ring and see if you can diagnose the cause!

And ride happy. We’ll see you out there.