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Anthony Marchand Bicycle Repair And Maintenance information And Tips

  • Place the bike on a smooth hard surface with the desired pressure in each tire. Using calipers, measure the shortest distance from the bottom of the rim to the floor. This distance should be a few centimeters in length.
  • Next (you'll need the assistant), sit on your bike with your hands on the handlebar and placing your shoulder against the wall. Have your assistant measure the same points, front and back.
  • Finally, for each wheel, divide the second measurement by the first measurement and multiply by 100. If both front and rear are 85 or slightly greater, you have ideal pressure for efficient cycling. If not, adjust the pressures accordingly not to exceed the tire maximum noted on the sidewall.
This method, which has some benefits, has been questioned by some for a variety of reason. The biggest is that tire construction has drastically changed since this was advocated. Supple and stiff tire casings vary in pressures that will give low rolling resistance and comfort. Lower pressures may actual give lower rolling resistance. But be warned, to low a pressure will subject you to pinch flats.7 However, my own tests with this method on Continental Gatorskin Tires with butyl tubes have correlated well with the "Rule of Thumb" below.

2. My Easy Rule of Thumb (maybe not ideal but gives a ball park figure):
  • Look at the minimum and maximum air pressure for your tire on the side wall.
  • If your a light weight (when fully dressed in your bike outfit and shoes and you weigh 100 - 120 lbs or less) aim for the lower end of the psi range, a mid weight (140 to 160 lbs) toward the mid range, and above 180 lbs aim toward the higher end of the psi range shown on the tire side wall.
  • Once you have selected an ideal pressure for you weight, adjust it to put about 5% less in the front and your ideal in the back (there is about 5% less weight carried on the front tire then the back according to my studies).
  • Do not go lower then the minimum or over the maximum on the tire sidewall.

For example ONLY, a tire with a minimum pressure of 95 and max of 120 written on the side wall of the tire:
Rider Weight (lbs) 100-120 120-140 140-160 160-180 180-120
Front Tire Pressure (psi) 95 psi 100 psi 105 psi 110 psi 115 psi
Back Tire Pressure (psi) 100 psi 105 psi 110 psi 115 psi 120 psi
Note:
  • Smooth road conditions allow for a slightly higher pressure and lower rolling resistance.
  • Lower the pressure by about 5 psi for very rough roads or wet conditions.
  • Raise pressure a few psi for cold outdoor temperatures.
  • Lower pressure a few psi for hot outdoor temperatures.
  • As noted, butyl tires drop about 1 psi per day which means to keep your desired tire pressure you need to fill your tire at least once or, even better, twice a week.
  • Experiment and find what's best for you.

References:
  1. Bicycle Tires and Tubes   from Sheldon Brown, Harris Cyclery.
  2. Tire Right Pressure   from Performance Bicycle.
  3. How to Select the Right Tire Pressure for Your Road Bike   from Active.com
  4. How to choose your tyre pressure  by John Stevenson March 8 2017
  5. Bicycle Tire Calculator   based on Jan Heine's work.
  6. How to Select the Right Tire Pressure for Your Road Bike  Tire pressure based on tire compression by Jim Castagneri For Active.com
  7. Tire Pressure Take-Home from Bicycle Quarterly, March 2016

Floor Pump & Tire Pressure
Anthony Marchand bicycle repair and maintenance information and tips

How to Use a Bicycle Floor Pump
How to Calculate the Correct Tire Pressure

So you think you know how to use a bicycle floor pump? Do you know the correct tire pressure you should be using? Well here are some tips for best practice with a bicycle floor pump.

Presta valves:
  1. Always turn the bicycle wheel to point the valve down so when finish and remove the pump you wont bend the valve head. Most bike pumps have a lever that pulls up to lock. You'll note that pressure on the pump gauge drops because air from the tire enters the pump cylinder.
  2. If when you start to pump, no air goes into the tire and the pressure goes way up – the valve is sticking. Remove the pump and tap the valve head again and start over.
  3. When pumping, try not to push the pump all the way down to where it clucks the bottom of the pump cylinder or you'll damage the end of the pumps plunger. So push about 9/10 of the way down.
  4. Pump to desired pressure. Even though the side wall of the tire states a minimum and maximum pressure do not over fill. The ideal pressure for you is based on your weight and bike weight as well as tires used. See Correct Tire Pressure below.
  5. Flip the pump lever and pull straight down on the pump head. The hiss you hear is not coming from the tire but the air inside your pump.
Schrader valves:
  1. Place the tire such that the valve is pointing down as above.
  2. If the bicycle tire has not been pumped for a while, let a little air out using a tiny screw driver (or your multi tool). This will unstick the valve.
  3. Some bicycle pump connections will screw into the schrader valve while others use the clamp type used for most presta valves.
  4. Proceed as above. When finished, carefully pull the pump head up and off.
Created by Tony Marchand

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Optimal Tire Pressure:
The tire pressure depends on weight of the rider, width of the tires and road conditions. There is always a trade of between tire width and pressure. There is a debate about whether rolling resistance increasing with wider tires and lower pressure (probably a myth), but the ride comfort and handling improves. To high a pressure leads to decreased handling ability and more discomfort on rough surfaces.1,2 Rider weight as well as weight distribution has to be taken into account (45% in the front and 55% in the back for recreational riders based on my own studies using scales under each wheel)3. Use of Jan Heine's grafts and calculators based on those grafts seem to give a far lower pressure then the minimal tire pressure on most of today's tire.4,5 Today's type of tires where probably not available when Jan wrote her article.

1. One Method for Measuring Correct Tire Pressure:6
Any method of determining ideal pressure takes the rider weight, bike weight, weight distribution and tires into account. Ideally, one should see a drop or compression of the tire to 85% or less. A number closer to 85% will give more comfort but one does not want to be below 85% because of the risk of pinch flats. A slightly higher compression of 90 or 95% may give lower rolling resistance but only on smooth road.