How to Fix a Flat Bike Tire

by Raymond Parker on April 30, 2011

in Technical

Recipe for roadside repairs

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A simple fix

If you ride a bike and you don’t have a special dispensation from the Polybutl Fairies, you’ll eventually be faced with a flat. Punctures are no big deal, if you’re prepared. With the right kit, you can fix a flat in minutes. Here’s how:

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Repair kit saddle pouch

Use tyre levers to remove the tyre. Pry up the tyre bead and hook the first lever on a spoke. Use the second lever to run around the rim. Pull the tube out. Don’t bother patching the tube at the side of the road, unless you have had the misfortune to have multiple flats. Better to save your punctured tubes to patch at home.

Carefully inspect the tire, inside and out. Remove the source of the puncture. Can’t find anything? Check the rim and rim tape. Is the rim tape in one piece and covering spoke nipples? Is there a metal burr on the rim? If the rim tape is broken, repair to your repair kit and patch with electrical tape. If you still can’t find the culprit, consider that the object went in and out, or perhaps the tube sustained a “pinch flat,” by hitting a bump. The tell-tale sign in this case will be a “snake-bite”—two small, adjacent holes in the tube. Avoid pinch flats by running correct tire pressure … and dodging potholes.

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Basic flat repair kit
(click to enlarge)

If the tire is significantly damaged, apply a “boot” between tire and tube. Boots can be cut from old tires or use material at hand—wealthy cyclists have been known to use folded paper currency—in an emergency. The idea is to stop the tube from bulging through the tire.

Re-install the tire (with bead on cogset side of rear wheel, open away from cog side). Take care to line up tire label with valve hole in rim, otherwise the cycling gods will be offended. Take a spare tube and put a puff of air in with your pump. Close Presta valves. Put valve through hole in rim and feed tube into tire.

Begin pushing open-side bead over the edge of the rim, working both sides evenly toward the valve. Try not to use tire levers to finish the job; use your thumbs. If the tire is very tight, check that the opposite bead is seated deeply into the well of the rim. If the tube interferes, let out a touch of air. Take care not to pinch tube.

Partially inflate the tire. Push around bead with thumbs, seating the tire evenly. Spin wheel to check eveness. Push the valve upwards, making sure the tube isn’t pinched by the tire bead at the valve stem. Tug it back down and apply threaded nut on Presta valves. Finish inflating to correct pressure. 

An ounce of prevention

  • Appropriate tyre pressure should consider road surface and account for rider weight. See Chart here
  • Examine tire treads regularly for embedded detritus—glass shards, stone slivers—that will eventually penetrate. Carefully dig them out. A significant hole/cut in the tread (that does not pierce the casing) can be filled with liquid rubber or trusty Shoe-Goo.
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Conor Ahern January 26, 2012 at 9:15 am

I remember way back in the dark distant days when the tubular tyre was the only choice available. Fixing a puncture took a needle and thread, puncture repair kit, a knife, tubular glue and a bench vise. Those were the days when you carried 2 spares correctly rolled under the saddle and held in place with toe straps, does anyone even know what a toe strap is nowadays? It was simple process of ripping the punctured tire of the rim, putting on a new one, centreing it up, pumping it up and hoping that the glue would hold until you got home.

Raymond Parker January 26, 2012 at 12:34 pm

Conor, I do indeed remember dimly. I also remember doing my first traverse of British Columbia on tubs. It was a great adventure (photo on the My Bicycles page) punctuated (or was that punctured?) by the nightly routine of patching and sewing, around the campfire.

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