Difference between revisions of "Tires and Tubes Teacher Training"
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- Inspect sidewall for rips, holes, or damaged rubber and casing.
- Inspect sidewall for rips, holes, or damaged rubber and casing.
- Inspect wire or Kevlar ® tire bead for damage.
- Inspect wire or Kevlar ® tire bead for damage.
==Repairing inner tube==
==Repairing inner tube==
Revision as of 09:22, 31 January 2017
Tires and Tubes—teaching youth to fix a flat
- EaB instructors will be able to identify the parts attached to the wheel of a bike and the tools and supplies needed for tube repair
- EaB instructors will be able to remove and install wheels with bolts or quick release
- EaB instructors will repair a flat tire
- EaB instructors will consider possible Academic content of this lesson:
- EaB instructors will be prepared for the common problems that students have with tire and tube repair
- Students will be able to recognize the pressure measurement on the tire and articulate the difference between pressure (pounds per square inch) and weight (pounds)
- Diagram that includes parts of wheel
- Tire levers Most are typically plastic these days. Advantages are that the plastic levers are less likely to damage a tube or tire bead. Metal levers are stronger and longer lasting. They must be used with more care. NBW uses Pedros levers made or recycled materials. Some plastic levers also have the advantage of having a scraper area that can be used to rough up the tube
- Glue. Bulk glue in a can is best. Innovations brand is the most economical that NBW has used in the past. There is not difference in glue quality between brands in our experience. Buy the cheapest. (This does not apply to patches)
- Patches. NBW does not recommend using commercially available patch kits in class. These materials are over 10 times as expensive as buying in bulk. Rema Tip Top are the best bulk patches available. They are good quality and reasonable price. Cheaper Taiwan or China brands tend to be more flexible and more difficult to use. Innovations patches are good. If possible get some with a plastic sheet over the top of the patch, not paper. The paper-like sheeting that some brands use is hard to take off if you have more than one hole close together and need to overlap patches. (Bike shops never use patches, so they will not necessarily give good advice about this)
- Wrenches for non-quick release type wheels that use axle nuts
- Floor pump and gauge
- Quiz, if appropriate for your class
Ideally, bikes with tires that need to be fixed. If you have a fleet of bikes and have pumped tires up when donations are delivered If not available, bikes that can be used for wheel removal and restoration drill, plus tubes to fix separately. In the worst case scenario, you can always pucture tubes with a pin
Fixing a flat:
Lead the teachers through the activity of repairing a flat tire.
How many times have NBW (co-op)staff offered to help youth with a flat because it was such a simple job only to become mired in complexity because of damaged axles? Most bike manuals will not go into the murky territory of fixing bikes that are constantly abused by pre-teens riding two (or more) on a bike. Our experience is that there are many ways to damage the axles of a bike that will make it hard to get the wheel back on. If possible check this out before offering to help a youth with a flat tire. If you confidently take the wheel off only to find that it is impossible to reinstall the wheel the bike club might instantly go from being a Good Samaritan to a bad guy… So, if working on a youth’s bike do the following inspection first:
- Are the axle nuts close to being equilateral hexagons? If they have been rounded by the application of vise grips, pliers of wrenches of the wrong size, you may not be able to get them back on tightly. Only work on the bike if you have a selection of axle nuts so that you can use to replace the damaged item
- Are the screw threads of the axle damaged? If the threads look anything other than even and similar all along the axle then it could be hard or impossible to get the nut back on if you take it off.
- Does the bike have axle pegs (pogos)? If so, the axle is probably bent unless it is a really high quality bike. Look at the bike from the front or back. Does the axle seem to describe a straight line, or does it droop at the ends, as if making a sad face because it has been ridden by more than one person at a time… Also, the threads are more likely to be damaged. NBW (co-op) will often refuse to allow youth to install pegs on their bikes in the shop. We can’t stop them doing it at home, but we can make sure that the bike leaves the shop in as safe a configuration as possible
- If the axle is especially bent, is it broken? If you think the axle could be broken, pull the dropouts apart. If they move, then the wheel is being held on only by the strength of the frame pressing in on the hub. The bike should not be ridden until a new axle is installed (at a minimum-a wheel may be necessary).
- Are the dropouts in good condition? Often when youth give their friends a ride on their axle pegs, the pegs bend the axles and the dropouts. You can see this by looking along the sides of the dropout. Is it flat, or is it uneven? If it is uneven, you may have to spend some time with a large pair of channel locks and/or a large adjustable wrench and a hammer—and that’s only if the frame is steel. If it is aluminum, you could be totally out of luck since frames of that metal are less repairable.
Quick Vocabulary Lesson
- Sidewall - Tread - bead
- Valve stem; Schrader (fat like a mug) or Presta (thin like a wine glass)
Teachers should follow the steps in the lesson plan, paying special attention to the following points:
Wheel Assembly Removal
- Release brake quick release, if any. See figure to the left. (Figure 2.1)
- Release wheel quick release by pulling quick release lever outward OR loosen both axle nuts outside of dropouts.
- Make sure that youth keep nuts on axles whenever possible—the natural tendency is to loose them.
- Guide the wheel through the brake pads and out the fork ends/dropouts.
--- Make sure that students do not force the tire through the brake pads and loosen or damage the pads. If the tire won’t fit, it should be further deflated. ---
Tire and Tube Removal
- Remove Tire and Tube from Rim –
- Check the "clocking" of the valve stem to the tire. Industry standard is to put the manufacturer's name at the valve stem. Note what it is. - Common errors with this are that youth will start the process next to the valve. Start opposite the valve. - Tires can be tightly fitted to the rim. Use tire levers to tire bead up and over rim sidewall. **** Do not use screwdriver, knife, or other sharp object, which may damage tire or tube. ****
- If you do not have a flat tire and you want to change your tire, deflate tire completely before removing from rim by pressing down on valve pin.
- Lay wheel flat on lap or on work bench.
- Check the bead is broken from the rim and on many tires, that the bead by the valve stem is pushed all the way to the bottom of the rim.You may need to use the heel of your hand to push on the sidewall all the way around on both sides. - Engage one tire lever (the ‘spoon’ side) under bead (edge wire) of tire opposite the valve stem and engage the hooked end onto a spoke. - Engage second tire lever one hand’s width or five spokes away from first lever. The bead should be loosened. Students will often want to force the tire lever around the rim, a trick which can be gotten away with in the case of loosly fitting tires, but will damage tire, tube, lever or hands on occasion!. - Starting opposite the valve, pull the second bead from the rim by pulling up on the tire to get the bead over the rim and then pulling it down. Use the heel of your hand. - Inspect inside of rim for spokes poking out or other sharp points.
Tube Repair and Tire Inspection
- Inspect the tube protector
- Inspecting the Tube and Tire
- Quickly check a Schrader valve for cuts (caused by low inflation and the tube slipping inside the tire during braking). - Re-inflate inner tube, if possible, until tube is about twice its normal width. If the tube will not re-inflate at all and has a large hole or a number of holes it is probably not worth repairing. - Anything much more than a pin hole or 1/8” slit is too much to patch. If holes are too close together they can be too hard to patch.
- Water generally isn't available trail-side. A leak large enough to quickly deflate the tube probably won't be hard to find.
- Inspect tube for air leaks by running hand gently over the tube, or by holding the tube up to the sensitive skin of your face to feel any air escaping. - Move the tube around its circumference starting and ending with the valve. - If these steps don’t work, submerge the tube in water and watch for bubbles to tell you where the hole is. - Once you have found the hole, use the repair kit scuffer/ abrasion tool to mark the hole. if you do use a pen, mark the leak with a long thin ‘X.’ Youth will very often want to scribble on the tube with the pen. Emphasize that a long thin X is the best. More than two lines will make it more difficult to find the hole again
- Inspect remainder of tube for any more holes.
- The type of cut or hole in the tube will help determine the cause of the flat. Common causes of flats are: - Cut at valve: Misalignment of tube in rim or riding with low pressure. Be sure tube is mounted straight and check pressure before riding. Usually not repairable - Large shredded hole or long cut or rip: Blow out, usually not repairable. Check the tire and the rim as well. Use care when seating tire during installation. - Tube hole on the rim strip side: Rim strip failure. Inspect inside of rim for spokes poking out or other sharp points. - Single puncture or small hole: Thorn, glass, tack, etc. Almost always repairable. Check tire for thorn, glass, tack etc. to make sure nothing is still embedded in the tire. - Double holes or slits: Rim pinch. Tube was pinched between rim and object in road/on trail due to too little tire pressure. Increase air pressure or use wider tires.
- Now use the tube "clocking" to find the most likely area of where the tire was penetrated. The tube usually gets miss-oriented, but still there will only be two primary spots to check.
- Inspect tire for what caused flat by pulling the beads apart – inspect both the outside of the rubber tread and the inside casing.
- fully inspect the tire for glass or other foreign objects that may have punctured your tube. - Squeeze any cut on the outside to see to look inside for objects such as slivers of glass. - Only after a good visual inspection, carefully run your fingers along the inside casing while looking at the outside. You will want to start and finish at a recognizable point, typically the brand name label on the tyre. - Inspect sidewall for rips, holes, or damaged rubber and casing. - Inspect wire or Kevlar ® tire bead for damage.
Repairing inner tube
Locate hole marked during inspection. Using sandpaper or the scraper on the side of a plastic tire lever, lightly sand an area around the hole that is slightly larger than patch size. The tube is coated with a substance that allows it to be removed from the mould when it is manufactured. This substance prevents patches from sticking and must be removed.
Apply a thin coat of glue and spread evenly around the sanded area using a clean finger or the back of the patch. Do not ‘glop’ on the glue. We tell students to thinly coat a large area.
Allow glue to dry. This make take a few minutes. This is a good time to inspect the tire for damage. If you want to test the glue, only test the perimeter area not where the patch will contact. Students will almost always want to apply the patch too soon. Hand out patches only when glue is dry Peel patch from patch backing. Handle the patch only by the edges. Center patch over the hole and lay patch on tube pressing down on patch, especially around the edges. Continue to apply pressure to patch for several minutes.
Rim strip: the wheel rim is made with holes between the rim sidewalls for spoke nipples. A rim strip covers the holes or nipples and protects the inner tube from sharp edges in the base of the rim and from spoke ends and nipples that may puncture the tube otherwise. The rim strip can be made out of fabric, rubber or plastic, and should be wide enough to cover the bottom of the rim, but not too wide that it interferes with the seating of the tire bead. Inspect the rim strip whenever changing a tire or inner tube. Look for tears and rips, and make sure that rim strip is centered over the spoke nipples.
Reinstall tube in tire and remount tire on wheel. Note any directional arrow/directional tread on tire sidewall. As far as NBW is concerned the jury is out as to whether this makes any difference, but people expect the arrow to be pointing in the direction that the wheel rotates.
Inflate tube enough to give it shape and reinstall tube in tire with valve next to air pressure recommendations written on tire sidewall.
Lean rim vertically against your legs with valve hole facing up, or lay flat in lap. Lower tire and valve into rim valve hole and align valve so it is pointing straight toward hub. Make sure it is not crooked as this can lead to an un-repairable flat tire. Install one bead at a time – begin with bead next to your legs/closest to you. Work the bead onto rim with hands – avoid using tire levers even if bead is tight to get back on since using tire levers for this purpose will pinch the tube and give you another flat. Work tube over rim sidewall and into rim cavity. Install second bead onto rim in same fashion as above starting at the valve. Roll tire bead into rim with the heel of your hand if your thumbs are not strong enough. Resist the temptation to use levers. It is better to take some time with this step than punture the tube with a tire lever and have to do the whole job again.
Inspect both sides of tire for bead seating and for any sign the inner tube is sticking out. Reseat if necessary. The valve is attached to the inner tube with a thick piece of rubber. Make sure that this thicker piece of rubber is inside the tire, and not jammed between the beads of the tire and the rim.
Inflate to low pressure and inspect bead again on both sides. Look for molding line on both sides above bead – this line should run consistently above rim.
Inflate to full pressure (according to the sidewall specifications) and double check both beads all the way around the rim same as above.
Reinstalling Wheels on Bike
Many people find it easier to install a front wheel when the bike is on the ground versus in a stand, so that the axle will be fully in the dropouts. The quick release skewer must be fully tight against the dropouts, or the wheel may become loose or even fall out while you are riding. If it is a bolt-on wheel, check that the axle nuts are loose enough for the axle to fit into drop outs. If quick release, check that the quick release skewer is in its “open” position (perpendicular to the fork blade and parallel to the ground). Check that the brake caliper’s quick release mechanism is open. Place front wheel (front axle) in dropouts. If quick release, make sure the lever is on the left side of the fork (from a rider’s perspective). Pull wheel fully into dropouts. For non-quick release wheels (wheels with axle nuts), the washers go on the outside of the dropouts. There may be some washers with hooks on them designed to stop the wheel from falling out of the dropouts if the nuts are not fully tightened. If everything has been left on the axle in the same order and orientation in which it was found, you will be OK.
For bolt on axles, tighten axle nuts down very tightly (both clockwise), while making sure that the wheel remains centered in the fork. You should tighten one side a bit, then the other a bit, until both sides are tight. Do not tighten one side all the way while the other side is loose—this can cause the wheel to become crooked in the fork. Close brake quick release mechanism.
For quick release wheels, line up quick release lever to that it will close just in front of left fork blade so it can fully close. Adjust closing tension of the skewer by holding the lever steady and turning the adjusting nut clockwise until its finger snug against right drop-out. Push in lever – the lever should meet resistance half way through its swing towards the drop-out. You should need to hold on to the fork blade for leverage to close the lever all the way, and the lever should leave a mark on the palm of your hand. If not, then open and tighten the adjusting nut a bit more, and try again.
Make sure wheel is centered in fork. If necessary, adjust wheel centering by either opening the skewer and moving wheel left or right until it looks centered (go by the rim not by the tire), or by loosening axle nuts and moving wheel until it looks centered. To secure wheel, close quick release skewer, or retighten axle nuts. Close brake quick release mechanism. pin wheel and check brake pad alignment to rim. If brake pads are not centered to wheel, you will have to adjust the brakes… another section.
- Bike with gears
Your aim here is to center the wheel in the bike frame and tighten the wheel onto the bike. Check that the quick release skewer and brake quick release mechanism are in the open position; check to see that rear derailleur is in outermost position. Pull back rear derailleur to open chain and place freewheel sprockets between the top and bottom sections of the chain. If in doubt about how the chain is supposed to wrap around the sprockets of the rear wheel, looking at another bike is often helpful. Guide wheel in between brake pads and rest chain on smallest sprocket. Guide axle up into the dropouts and pull back or up on wheel, depending on the style of dropouts (horizontal or vertical) and hold wheel centered in rear triangle (center by the rim, not the tire). Orient quick release lever so that it will close between the chain stay and the seat stay on the non-drive side of the bike. Close skewer with same force as described for front wheel Close brake quick release mechanism (or tighten axle nuts clockwise) and check brake pad alignment to rim by spinning rear wheel. If brake pads are not centered to wheel see the lesson on brakes!
- One speed bike
This is harder than the job with gears, because reinstalling the wheels requires three things to be done: Centering the wheel, tightening the axlenuts and tensioning the chain. On bikes with gears the derailleur takes is a silent partner in the wheel installation process. It takes up the slack in the chain for you.
Loop the chain to the outside of the right rear dropout, then place the axle in the dropout slot. Pick up the chain and place it over the rear sprocket. If the wheel has coaster brakes (foot brakes) attach the coaster brake strap to the brake arm on that extends from the left side of the rear hub. A bolt will go through one side of the strap, through the arm and then through the other side of the strap. Tighten the nut and bolt so they will not fall off, but not fully. You will need to be able to move the hub around as you tension the frame. Make sure the chain is correctly seated on the front sprocket and pull the wheel back with one hand, while tightening one axlenut with the other. Look at where the wheel is sitting between the frame and make sure it looks like it is in the middle. Check that there is only about 10mm (3/8”) of play in the chain. As with the derailleur bike, don’t tighten the nut all the way. Do one side a bit and then the other, ending up with both sides as tight as you can go. If the bike is a coaster brake bike, then fully tighten the coaster brake strap bolt. Here’s another point about bikes that are not good quality or have been treated roughly: the chainring (front sprocket) will often be bent. This means that on a one-speed bike the chain will tighten and loosen as the sprocket goes around. In cases like this you will have to set the chain tension so it is never too loose or too tight by sliding the wheel back and forth in the dropouts and testing for the best chain tension. If this is not possible, you might have to straighten or replace the chainring.
Have teachers try out the quiz for the youth
Take questions and comments