Lee Ann, Ideal Tire Pressure
Question:
I am confused. My friends told me that I need to put 130 lbs of air in my tires. They say it reduces rolling resistance. I am 5'2"" and weigh 110 lbs and am not strong enough to pump my tires to more than 100 lbs. Am I hurting my tires and are they making me slower?
Answer:
I am asked this Bicycle Tirequestion many times a year and the quick answer is, "No you are not hurting your tires." What you will like even better is, there is less rolling resistance and you will find other very good things about lower tire pressure. Allow me to get a little technical as there is more here than meets the eye.
First, people think that if a tire says "130 lbs max" on the sidewall that this is the minimum pressure. That is not the case. The real minimum pressure you should be concerned about is, having enough air in the tire so you don't get "pinch" flats. A pinch flat only occurs in clincher tires (not tubulars) and is a result of hitting a rock, pothole, curb, or other obstacle hard enough that the tube is actually cut by the flanges of the rim.
The way you can tell you have a pinch flat is 1) it probably happens right after hitting something, and 2) the tube will have two little holes that look like a rattlesnake took a bite out of the tube.
You weigh 110 lbs so the risk of pinch flats is very low. I weigh 207 and I put 105 lbs of air in a 700-23 clincher tire. That said, I have learned to lighten up, or even bunny hop, when going over obstacles so I never get pinch flats. I have seen people that weigh much less than me get pinch flats with 110 lbs of air, but they are hitting these obstacles much harder.
Another thing to consider is the size of the tires. The bigger the tire, the less pressure in PSI (pounds per square inch) is required to keep from getting pinch flats. For instance, my touring bike (700-28 ) gets 85 lbs, and a mountain bike gets 40-60 lbs. My tandem has 700-25 tires and it gets 120 lbs of air.
The other concept you asked about is rolling resistance. There is actually a point where more air pressure does not contribute to lessening rolling resistance. Additionally, higher pressures make for unstable cornering, rough ride and more flats!
Time trial bikes can use more air, up to 130 lbs, and track bikes can have up to 200 lbs, but for road riding, here are some suggestions, assuming that you are reasonably careful when avoiding nasty bumps.
Rider weight, under 150, try 90-100.
Rider weight, 150-200, try 100-110.
Rider weight, 200-225, try 110-120.
Over 225, try 120+
Kevin