Tires, Tubes, and Inflation

(Reprinted here from the Monday Missive by popular request.)

Tires are wonderful things.  They are actually quite simple, and yet…

The majority of flats we fix at the shop can be traced to under-inflation.  I don’t think I’ll ever understand this.  

• The range of inflation values is embossed on the side of every tire.
• Tires lose air pressure.  They aren’t very thick.
• If you don’t ride them often, they will go flat.  Pump them up before you ride.

The “roadie” mistakes:  Most “roadies” ride on under-inflated tires, unless they have recently over-inflated them.  Many road riders seem to be products of our society.  Like most Americans, they tend to think that if a little bit of something is good, then way too much must be almost enough.  Here’s the problem:  Under-inflated tires are flat-prone and make your bike slower.  Properly inflated tires roll more smoothly and don’t get as many flats.  For that reason, many roadies will run tires at the maximum inflation rating.  This is a bad idea, and it’s counter-productive.  An over-inflated tire is harsher.  It doesn’t roll smoothly over imperfections in the road, but rather bounces and vibrates.  Bounce and vibration are lost energy.  In other words they are slower.  Add to that, there is a risk of the tire exploding, or worse, of the over-pressure tire causing a failure of the wheel rim.

• Always stay at least five pounds less than the maximum value on the tire.
• There is an ideal inflation pressure for each tire width, and rider weight.  For most riders a 700 X 23 tire can be run safely and efficiently at pressures between 100 and 105 psi.

Common scenarios: 

1)  We have recently repaired a tire for a customer.  (Recently here is defined as less than a week.)  The customer comes back in with the same tire flat.

• If the customer is angry, in almost every case, we will find a puncture.
• Sometimes the recurring flat is our fault.  If it is, we fix it for free.
• Occasionally (rarely) there is some underlying cause for recurring flats.  This could be a sharp drilling at one of the spokes, a failing rim strip, a sharp piece of something embedded in the tire.

2)  “My tire keeps going flat!”  We ask,  “When did you last inflate it?”  If the answer is, “I don’t know, just recently.”  Then the tire has not been touched with a pump in the last three months.

3)  “I took this out of the shed and pumped it up.  I haven’t ridden it in a while.  Do you think the tires are okay?”  The tires in question are crumbly with dry rot.  The answer is an emphatic NO!!

4)  “I haven’t ridden the bike in over a year.  You guys did a lot of work on it, but things just happened and I didn’t get a chance to ride.  So when I went out to ride the bike the tires were flat, and I pumped them up, but they expolded!

Here’s what happened.  The bike was sitting on the tires.  The tires lost air.  (See above)  The bike settled on the tire, and the tire was forced “off the bead.”  So the tire was not well seated on the bead, and then the bike was rolled to the compressor.  (This made matters worse.)  The compressor started inflating the tire, and the owener didn’t notice the huge bulge of unsupported tube.  BANG!

Find out what pressure is right for your bike, and riding needs.  Check, or inflate, every time you ride the bike.  Be careful.