So you have a flat, eh? The following is an introduction to the workings of pneumatic tires and how to fix them.
The average bicycle wheel is covered in a tire: that thick, textured external rubber that makes contact with the road. Underneath the tire is something called a tube. The tube has a valve and is filled with pressurized air. Its purpose is to enhance ride quality. The tire protects the pressurized tube and grips the ground. If a foreign pointy object manages to get through the tire, it may create a hole in the tube. A hole in the tube is called a puncture and results in a flat tire. Obviously, nails and glass can create a puncture, but other objects such as blackberry thorns have been known to ruin a tube’s integrity as well.
However, a puncture isn’t the only reason that your tires may be flat. Remember what happens to latex balloons a week after your birthday party? Just as helium balloons naturally loose air over time, bicycle tubes will go flat even without a puncture. Though with bicycle tubes they should hold air stay inflated for at least a month if they are in good working order. So, if you haven’t pumped up your tires in over a month or so and they look flat, do not fret! Pump them up and hope for the best. If they remain plump then you do not have a puncture.
If it looks like your tube is punctured there are a few options. The best option in our opinion is to replace the tube entirely. This provides you with the best chance of not getting another flat in the future.
Alternatively, there are “fix-a-flat” solutions (like Slime) and patch kits; both of these options attempt to mend the broken tube and neither are guaranteed. We’ve found that patch kits only work four out of five times. We don’t like those odds and prefer to only fall back on patches in emergencies like on-road repairs. Slime and similar products impregnate your tube with nasty goo that enrages bike mechanics when the tubes eventually have to be replaced. Moral of the story: keep your bike mechanics happy and put in a new tube right off the bat :)
Tires Go Bad Too
For the safety of the rider, we cannot instal a tube on a “bad” tire (and we don’t recommend you do either). At the time of writing, new tires for youth bicycles (<26″) start from $13 to $17.50 and adult tires (>26″, 700c) are $17.50 on up. As always, we are happy to just sell you the part, though if you would like us to install it there will be a small additional labor charge.
Especially on bikes ridden by speedster kids, tire tread is worn down excessively due to locking up the brakes and skidding to a stop. The result is what we call a bald patch or a skid. Here, the tire is weak and especially prone to allowing punctures. The real worry is that the next time Little Johnny decides to skid to a stop, the tire will be worn right through and the tube will blow out of the tire. Not only may this startle the kid, but it can also result in a loss of steering control, scrapped elbows, or worse. We recommend installing a new tube (and taking time to teach proper braking technique) before the tube blows out.
If the side of your tire looks as cracked and crinkly as a slice of baclava, it is about time to get a new tire. Over time (we figure eight years give or take), air disintegrates the rubber compound of the tire, especially the sidewall which is thinner and under relatively more stress than the tread. Just like skids, the tire has simply lost its integrity and is not safe to ride. When ridden to oblivion, the tire may separate from the bead or simply blow out the side.
The last common demise of tires could happen at any time and is not (usually) the fault of the rider — a split cord. Symptoms of ‘split cord syndrom’ are a bulge or other inconsistent protuberance which is obvious when looking at the tire and can be quite often felt while riding as a oscillating “bump”. While the cause varies, in general split cords are found on tires that suffer from manufacturing defects or were not installed correctly. Whatever the case, functionally a tire with a split chord is just as dangerous as dry rot: high risk of a blow out.