Eastlake girls practice changing a flat
We recently had a flat-changing clinic during one of our team meetings. After an initial demonstration, the kids tackled the bike, changed a flat, then learned how to use CO2.
If you’re on the Eastlake team and are not proficient changing a flat or using CO2, please talk to one of your coaches, and take advantage of the opportunity to learn when there’s no pressure, you’re not in the middle of a race, or on a trail ride minutes before dusk. Everyone who rides should learn how to change a flat!
Here are some Frequently Asked Questions about Changing a Flat:
Do I need to take the whole tire off?
No. You only need to take one side of the tire off so that you can remove and replace the tube.
What is the advantage to removing the whole tire?
Facilitates finding the thing that made you flat.
Removing the tire entirely will make it easier to find the glass, thorn, piece of wire, etc. Sometimes the object will remain in the rubber of the tire, slightly poking through the inside, just waiting to flat your new tube. With the tire removed, you can practically turn it inside-out.
Facilitates finding the thing that made you flat.
Removing the tire entirely will make it easier to find the glass, thorn, piece of wire, etc. Sometimes the object will remain in the rubber of the tire, slightly poking through the inside, just waiting to flat your new tube. With the tire removed, you can practically turn it inside-out.
What is the disadvantage to removing the whole tire?
Takes a bit longer to remount the tire. Possibility of remounting it in the wrong direction.
Takes a bit longer to remount the tire. Possibility of remounting it in the wrong direction.
Tires are often designed to roll best in one direction. Unless you know the direction of rotation, which is sometimes stamped into the sidewall of the tire, you need to either
a) pay close attention to decals and logos when you removed the tire, i.e., logos match up to the cassette /skewer nut side or the skewer lever side, or
b) know how to read the directional tread of a tire. Here’s the practical physics lesson of the day: Look at the tire from the point of view of the handlebar. The “V” in the tread should point away from you, with the point of the “V” pointing forward. This allows dirt or water to be directed away from the center of the tire. If there’s no obvious “V”, look for the slope of the lugs in the knobby tread. The more sloped side should hit the ground first, and the more cliff looking side should follow. Running it the other directing will induce drag.
a) pay close attention to decals and logos when you removed the tire, i.e., logos match up to the cassette /skewer nut side or the skewer lever side, or
b) know how to read the directional tread of a tire. Here’s the practical physics lesson of the day: Look at the tire from the point of view of the handlebar. The “V” in the tread should point away from you, with the point of the “V” pointing forward. This allows dirt or water to be directed away from the center of the tire. If there’s no obvious “V”, look for the slope of the lugs in the knobby tread. The more sloped side should hit the ground first, and the more cliff looking side should follow. Running it the other directing will induce drag.
“<= ROTATION” is stamped into the sidewall of many tires.
TUBES
What do all those numbers on the tube box mean?
Example: 700 x 18-28, 48mm (road tube)
Example: 700 x 18-28, 48mm (road tube)
- 700 = roughly 700mm rim diameter
- 18-28 Number of mm wide the tube will comfortably inflate. If the tire is narrower than 18mm, there will be too much flabby tube inside it. If the tire is wider than 28mm, the tube will be stretched too thin.
- 48mm length of the presta valve on a road tube. Deeper rims require longer valve stems. A short valve stem inside the rim may not allow you to attach the pump to inflate it.
Example: 26 x 1.9-2.125 (mountain bike tube)
- 26 = 26″ diameter rim
- 1.9 – 2.125 Number of inches wide that the tube will comfortable inflate.
How do I know I have the right size tube?
Easiest way: take your tire to the bike shop and tell them you need a spare tube. When you remove the tube from the box and put it in a plastic bag, tear off the end of the box with all the numbers and put it inside the bag with the spare tube.
Can I use a 26″ tube in a 29″ tire?
Yes. While it is not optimal, you can use a 26″ tube in a 29″ tire.
Yes. While it is not optimal, you can use a 26″ tube in a 29″ tire.
TIRES
Are bike tire measurements in inches or metric?
Road bike tires are most commonly measured in metric, mountain bike tires in inches.
Road bike tires are most commonly measured in metric, mountain bike tires in inches.
What is the “bead” of the tire?
The bead is the edge that hooks into the rim and holds the tire onto the rim. Tire beads are either wire or kevlar.
What is the difference between wire or kevlar bead tires?
Wire bead
- often less expensive
- harder to mount onto rims
- better for 230+ lbs riders (because the bead stays in place and won’t blow off the rim)
- adds 50-75g in rotational weight, which is fine for flat terrain, but more work in hilly terrain.
Kevlar bead
- often more expensive than wire bead
- easy to mount into rims
- fold-able (you can carry one in your back pocket if you need to)
- reduced rotational weight
How much air do my tires need?
Every tire is stamped with a recommended inflation. Road bike tires are high pressure, low volume, and are generally inflated between 95-125 psi.
Road bike tire recommended inflation: 115 PSI / 125 PSI
Mountain bike tires are low pressure, high volume, and are generally inflated between 30-50 psi.
Mountain bike tire recommended inflation: 36-65 PSI
Why are some road tires perfectly slick and others have ridges (tread)?
Perfectly slick road tires are most often used by racers, having the least friction and drag. Tires with more tread provide better grip and are better for directing water or mud away from the center of the tire. Ask your coach or at your local bike shop which tire is best for your riding style and goals.
MISC
Is the rim and the wheel the same thing?
No. The rim is only the hoop part with the holes in it. The wheel is made up of the rim, spokes, hub, etc.
What is presta and schrader?
Tube valve stems are either presta (below) or schrader (looks like the car tire).
presta valve in a mountain bike wheel
Unscrew the top (little gold piece) to inflate. Be sure to tighten it back down.
How often do I need to pump up my tires?
Check tires before every ride.
Properly inflated road tires should feel completely solid. If you can make any depression with your fingers in the sidewall at all, you need air. Use a good floor pump and knew for certain how much pressure is in your tires.
Comparing Apples and Oranges: If road tires are to be harder than an apple, mountain tires should be a bit softer than an orange. You should be able to depress the sidewall slightly.
Joel works to become the tire-changing master!
If you have additional questions or are curious about tubes or tires, please see Sheldon Brown’s website. Although Sheldon is no longer with us, his site is maintained by volunteers and remains a great resource for cyclists.
-Coach Drexler
Trails are located immediately next to Eastlake High school, and lead to exciting rides in Chula Vista including trails around Sweetwater River Valley, Otay Lakes, and the Otay River Valley.
Eastlake Cycling Team (ECT) 