Thursday, May 17, 2012

Bicycle Maintenance: Tires and Flat-changing Part 2 - AQ

This is Part 2 of the 3-part series on Bicycle Maintenance: Tires and Flat-changing.

In Part 1, I talked about what to expect in my flat-changing clinics, held monthly and hosted by B+L Bike and Sport. Here are some of the questions that come up in my flat-changing clinics. Please feel free to add your own questions in the comments. :)


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 are the advantages 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.

Is there any disadvantage to removing the whole tire?
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.

"<= ROTATION" is stamped into the sidewall of many tires.


What do all those numbers on the tube box mean?

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.

    Are bike measurements in inches or metric?
    Road bikes are most commonly measured in metric, mountain bikes 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 at your local bike shop which tire is best for your riding style and goals.
      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 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. 

      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. 

      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.

      Next week I'll have Part 3: What's in your saddlebag? Items you should have with you when you ride.

      Wednesday, May 09, 2012

      Bicycle Maintenance: Tires and Flat-changing (part 1)

      This is Part 1 of the 3-part series on Bicycle Maintenance: Tires and Flat-changing.

      When I first started cycling, my mechanic in New Jersey encouraged me to attend a flat-changing and bike maintenance clinic put on by the parks department. I remember following all the steps the instructor told me, but still being so confused, and feeling like I only got through the flat-changing part because someone more knowledgeable than me was there to help.

      Since that clinic in Feb 2003, I've tried to learn as much as I could about bikes and bike maintenance. Being something of a compulsive teacher, I naturally have to pass on what I've learned, so I started teaching flat-changing clinics with women as the target audience.

      Now I teach a flat-changing clinic at B+L Bike and Sports once a month. This past Sunday afternoon, I taught at the Solana Beach store where we had nine women attend. It was a great afternoon!

      Jenny and Robbin watch as Monica pulls the tube out of the tire in a simulated flat.

      It's important that everyone actually work on a bike and not just spectate. Doing it yourself boosts your confidence, and reinforces the notion that you can, in fact, do this yourself. We always work on rear wheels, with at least ten minutes spent removing and replacing the rear wheel, until everyone is comfortable doing so. As with most things, there are tricks to making removing/replacing a rear wheel easy. 

       Monica continues working on her tire as Bev (background) looks up from her work.

      Depending on space, there will be 4-6 bikes to work on. Attendees will work singly, in pairs, or even in groups of three to get the job done. Taking turns, everyone gets a chance to practice removing and replacing the rear wheel, removing the tire, getting the tire back onto the rim, and inflating the tube with CO2.

      Heather and Megan (left) and Patti and Jennifer (right) work in pairs  to install the tube.

      Everyone gets a chance to practice using CO2, thanks tosupport by Genuine Innovations. I remember being somewhat skeptical myself (read: afraid of it) at first. But once I realized how easy it is to use, and how I could eliminate ten minutes or more of exhausting frame pump arm work on the side of the road by using a CO2 cartridge that costs as little as a vanilla latte, I was sold.

      Jan and Bev line up the CO2 to inflate the tire. Special shout-out to Genuine Innovations for providing MicroFlate Nano heads and CO2 cartridges for the women to practice with.

      In part 2 of the blog Bicycle Maintenance: Tires and Flat-changing, I'll answer 
      frequently asked questions, including:
      • What do all those numbers on the tube box mean? 
      • How do I know I have the right size tube?
      • Do I need to take the whole tire off?
      • Why are some tires perfectly slick and others have ridges (tread)?
      • Is the rim and the wheel the same thing?
      Please feel free to post your questions below! If I can't answer it, I'll find the answer from someone more knowledgeable than me.

      Patti checks to make sure the MicroFlate head in lined up square to the rim for best air flow.

      Thank yous are in order to all the attendees of my most recent clinic in Solana Beach: Monica and her friends Robbin and Jenny, Bev, Jan, Heather, Megan, Patti, and Jennifer. Thanks to the guys at B+L Bike and Sports Solana Beach: Tom, Scott, Gisan, and especially Kevin who stayed late for us. Thanks to Mark of B+L Bike and Sports who invited me into his shop and is hosting these events. And big thanks to Genuine Innovations, who supplies the MicroFlate Nano heads and the CO2 cartridges we use in class. These San Diego Flat-changing clinics exist because of your efforts.

      Next clinic:
      Sunday, 5/20/12, 3:45 PM

      B+L Bike and Sports in San Diego (Rosecrans).
      RSVP on