Wednesday, April 14, 2021

The B.O.G. Series: How To Repair A Flat Tire

  Welcome to the Basics of Gravel Series (B.O.G.)! In this series I will attempt to bring a very foundational knowledge of gravel and back road riding to anyone reading that may be curious or a beginner in riding off-pavement, but not wanting to be mountain biking. There will be a new entry every Wednesday until the series is complete. To see the schedule, click this LINK. Thanks! 

The author fixing a flat tire.

One of the many skills a bicyclist should concentrate on acquiring is how to repair a flat tire. This is a skill which is especially handy for the rural cyclist. To become a 'self-supported' cyclist, one that can maintain their own physical prowess during a ride and be able to overcome minor mechanical setbacks, is a key to being a successful rural cyclist. 

The flat tire repair I am going to cover today will concentrate on the tubed tire type set ups. This is the sort of tire/wheel combination found on most bicycles and the type most beginners will encounter first. Last week I covered what items make up a simple flat repair kit. You should go back and review those items at this link if you missed that or need a refresher

One thing to note here is that you may want to add certain special tools to your particular kit depending upon the bike you are using. Some wheels are attached using various systems that may require special wrenches. You also may want to consider adding something like a sharp awl, a small pair of pliers, or a small knife for removing embedded objects. 

Now I will go trough the steps to properly diagnose and repair a flat tire. 

  • Diagnosis- Part 1: First, the obvious- your tire won't hold air, or it suddenly goes flat while riding. Now the important thing to find out is why did that happen. This is very important because if you don't understand what made your tube fail, your chances at fixing the problem are going to be very low. So, the first thing to do is to visually inspect the tire. Look for foreign objects protruding from the tire. These could include bits of metal, glass, or sharp thorns, so be careful when handling the wheel. You may see a slit where a tire may have been cut. Sometimes the flat will be caused due to a tire casing failure, where the bead of the tire has been separated from the rim. In most of those instances- where the tire has been damaged- repair in the field is probably either impossible, or beyond a beginner's skill. At that point you may need to call for a ride/help. We will assume from this point that the repair is possible in the field. 
You may need to add special tools to your kit to remove your particular wheels.

  • Wheel Removal: This part is something you should practice and be familiar with before you have to do it. First off- you need to understand what attachment system you have on your bicycle. You'll probably be dealing with either a bolt-on, 'quick release', or possibly a through axle. Next, you need to understand whether or not you will need to adjust the brake to allow for wheel removal. Many bikes have an adjustment, or a way to 'release' the brake, to allow for the tire to be passed through the braking mechanism. This is for a rim brake system, if you have disc brakes, this does not apply. So, know your attachment method, understand your brake release mechanism- if applicable- and then, finally, stow away any tool you may need to get the wheel off the bike. In some through axle situations, this may be a 6mm or 5mm hex key. In the case of a bolt-on wheel, you will need a box end wrench to fit the nuts on the axle. (Usually 15mm, but it could be something else- check this carefully) Make sure you stow away the proper tool. Quick release axles don't generally require tools, but do understand what you have and that it may have its own quirks. Finally- A Tip For Removing a Multi-Speed Rear Wheel: Shift the rear derailleur into the fastest selection (smallest cog) to move the rear derailleur the furthest outboard that it can go. This will make wheel removal much easier. NOTE: Internally geared hubs, coaster brake equipped bikes, single speeds, and other unusual set ups may require special techniques and tools for rear wheel removal. See your local bike shop for tips in these cases. 
Pressing inwards with your thumbs in this position will help to dislodge the tire from the rim.

  • Now I'll assume that you know your bike, you understand and have practiced wheel removal, and we're at a point where you actually need to fix a flat or find out why your tire looses air in a very short period of time. So, wheel in hand, take your valve cap off, (if applicable), then use the corner of the tire lever to depress a Schrader valve core, or open the Presta valve and depress the manual core shaft to fully release as much air as possible, if there is any to release. Completely flat already? Then don't worry about that step. Next- Holding the wheel with both hands by the tire, use your thumbs to push the sidewall of the tire away (inwards) from the rim edge. (See image above) Make sure the tire is separated from the rim edge all the way around on both sides. Next- Take a tire lever and pry the tire up and over the edge of the rim. You may need to do this with two or three tire levers, spaced a couple inches apart, before the tire comes off freely. 
Tire levers have a hook which grabs a spoke so you can 'park' one as you apply another to get a tire bead over a rim.

  • NOTE: YOU DO NOT HAVE TO FULLY REMOVE THE TIRE FROM THE RIM. One 'side' of the tire should stay inside the rim and not be pried off. This will speed up repair and help us to determine where the flat happened. Now reach in a gently pull the tube out of the tire casing. Next- Note where the valve stem was in relation to the tire. This is important for the next step. 
It is important to note where your tube's valve is in relation to the tire before you remove the tube.

  • Diagnosis- Part 2: This is the next critical step in completing a successful flat repair. With the tube out, (try to keep the tube oriented in the way it came out of the tire for best results here), use a portable pump (frame or mini-pump), to air up the tube. In cases where there is a big hole in the tube, the tube won't hold air at all, and you may have to really pay attention to where that big hole is to find it, but you will find it. If the hole/puncture is smaller, and the tube airs up seemingly well, you may hear a hiss, in which case your search will become easy. But you may not hear that. In this case I over-inflate the tube to a ridiculous size, then I pass the tube, rotating it in my hands slowly, by my ear. When I feel airflow or hear a hiss, I then have found the problem with the tube. 
Inflating the tube to a cartoonish size will help you find the leak in some cases.

  • Next- Orient the tube valve stem to the point noted earlier on your tire. Then note where you found the problem with the tube. Let's use the valve stem as a '12 o'clock' position and then look where we heard the hiss, or saw the hole in the tube and see at which 'clock position' it was on the tire by holding the tube against the tire with the valve stem aligned with the valve hole on the rim. Now you have a smaller area to look at inside the tire for a foreign object and you will not have to search the entire tire casing for that possible problem. If you don't use the clocking procedure, you'll be left with no other option than to search the entire inner tire casing for the possibility of an embedded foreign object.  
Holding up the valve in the '12 o'clock position and aligned as it came off the wheel allows for quicker detection of embedded objects in a tire.

  • NOTE: If the hole in the tube faces the tire/rim interface, you may have just pinched the tube and tire down on the rim and caused a 'pinch flat'. Many times you'll note two holes directly across from each other. If this is the case, you may be able to skip the next step. If the air is rushing out of a hole facing the inner rim well, you may have a rim strip problem. This may not be repairable in the field. When spoke holes are revealed and can rub against the tube, that causes a flat eventually. If possible, re-orient the strip correctly and install a new tube. In some cases tubes fail at the valve stem. Just replace it then.  Next- When looking for possible embedded bits in a tire casing, it helps to use a rag, or cloth and to sweep the inside of the tire with that. This rag will snag on anything inside the tire casing that is sharp and sticking into your tire. This will keep you from cutting your fingers and makes short work of finding small bits that could otherwise escape detection. Use a small hex key, sharp tool,  or a small pliers to pull out or push out anything you find. If you don't find anything, use you eyes to visually inspect the area. If you see the hole, or small cut, and cannot detect any foreign objects, you should be okay to install a new tube. 
When replacing a tube it is best to have enough air in it to give it some shape.

  • Installing A New Tube: Now assuming we have gotten the proper diagnosis and have gotten any foreign objects out of the tire, (if any were detected), we can now replace the tube. You could patch a tube in the field, but unless you enjoy sitting around in the middle of nowhere, it is better to just do that later and replace the tube for the time being. The first thing to do is to make sure you add a little bit of air into the tube- just enough to give it shape- not enough to stretch the rubber at all. Never put a tube in as it comes out of the box. That's a recipe for a pinch flat. First, feed the valve stem through the valve hole in the rim. Then carefully stuff the tube up into the tire, being careful to place the tube in the rim well and not in a position where it will get pinched against the outside of the rim and the tire as we start to place the tire bead over the rim edge and back where it belongs. Next: Start pushing the tire bead up and over the rim edge while keeping an eye out for the tube, so it doesn't get pinched. The last three to four inches of the tire bead will be the toughest to get over. At this point you may gain an advantage by doing two things. First, let a little bit of air out of the tube. Then, make sure the bit of tire you already have pushed over is as far into the middle of the rim as you can manage it without pinching the tube. This may be all you need, but if things are still not budging, I find that instead of pushing up on the tire bead with my thumbs, a rolling motion, using my hands and pushing the entire casing over sideways in the direction I want the bead to go, works well. 
  • Finishing Touches: Now that you have the bead in where it belongs, it is time to air up that tube. I like to introduce a small amount of air, maybe up to 20psi, and then stop and inspect how things are going. At this point you have enough air in the tube that you can see if things are wrong before the tube blows up. Things like a bead starting to pop off one side, or if your tire seems to be stuck down lower into the rim at one spot. Here you can manage to manipulate the tire a bit by pushing and pulling as necessary, or start over by deflating the tube and making corrections as necessary. If you reach this point and all looks good, then go for it and air it all the way up to pressure. If you have a Presta Valve, don't forget to manually close it. Replace the wheel, reattach brakes, if necessary, and spin the wheel to make sure, one last time, that everything looks good, and you are off......almost!

Now is the time to make one final sweep of your repair area. Got any litter to carry out? Definitely pick up after yourself, and of course, you are taking that old tube with you! Don't you dare leave THAT out there! Check to make sure you grabbed all your tools, and then make one last check to make sure you zip your bag shut which you are packing everything in. (Don't laugh! I and others have been bitten by forgetting that one!) 

I recommend doing mock flat tire repairs at home to familiarize yourself with the procedure. The more comfortable you are with the tools, concepts, and processes, the more chances for success you'll have when you really need to do the job out in the Styx. Plus, practicing may bring questions to the fore which you can get answered before things are at a critical state. 

Learning flat tire repair is liberating and empowering. Anyone that rides a bike can probably master the techniques necessary to do this task. With careful observation, patience, and with the correct tools and procedures? Yes, you could be a self-sufficient cyclist. 

Next week: How To Lubricate Your Chain


Nooge said...

I think it’s good to mention that a bell wrapper or dollar bill can be used as a tire boot (cover for a hole in the tire). It’s not ideal, but can get you out of a jam. There are purpose made boots that have adhesive, but I carry the money since it serves double duty.

Also, you mention it, but I would really emphasize that getting the tire on can be tricky and proper technique makes a huge difference. Tire beads do not stretch. The only way to get the tire over the side of the rim is to have the tire bead to sit down in the middle of the rim as much as possible all the way around. I find it’s much easier to leave the valve stem of the tube and that section of tire for last when mounting the tire, because the stem pushes the tire bead out of the center of the rim channel.

Finally, many people underestimate what can cause a tube to fail. The tube actually moves around a bit in the tire as you ride. So any little thing in the tire or edge on the rim that the tube touches will wear right through it.

Tomcat said...

Nice comprehensive guide, Mark!

Guitar Ted said...

@Tomcat - Thanks!

baric said...

A few more observations and experiences with and about tubes over the years since I still use them and as you say tubeless tires, their maintenance hassles and expense are not for everyone. Started out with 26"ers. The bike came with Schrader valve single wall rims. Tacoed the rear rim badly in an unseen, weeded over hole in an old sidewalk. Bought a new, fairly inexpensive double wall, bladed spoke, drilled for Schrader valve, complete with cheapy plastic rim strips wheelset. I highly recommend buying and using the best rim strips you can find, Velox cloth or whatever or now adays maybe a couple of layers of Gorilla tape as the plastic strip eventually wore thru and punctured the tube at one of the spoke web holes. I also have three Velocity wheelsets of various sizes, a Dually and two Blunt 35's which I use their Velocity Veloplugs in the spoke web holes. Lighter weight and reusable, no rim strip needed. I likeum. Bought a set of nice 26" balloony tires [ they're the Apple of my eye and I'm still using them] and the prerequisite Schrader valve tubes. Well my new rims chewed the rubber around base of the valve stem at the valve stem hole of my new tubes to pieces rendering them completely useless. The fix was Presta valve tubes, an appropriate size rubber grommet in the base of the valve stem hole and a Schrader to Presta stem adapter in the outer rim. I now use Presta tubes exclusively on all of my bikes, mostly for convenience, but for the above reason also. BUT only use Presta tubes with REPLACEABLE valve cores. Why? Because if you change tire pressures often or check your air pressure before every ride, which you should, that little brass screw stem which tightens and loosens the seal occasionally will get bent or break off from fatigue and need replacing, just like a tubeless stem does from gunking up. I've had to do this a few times. When that happens to a non replaceable stem tube there's no fixing it, rendering that perfectly good tube unsealable, unless you can maybe figure some way to rube up some kind of Schrader gizmo to it. Not a good fix! Plus you still have the rest of that little brass screw seal thingy floating around inside your worthless tube. Not good.... I've got a couple of these perfectly good worthless tubes around here somewhere. Enough of this Blather!