What should be the correct tire pressure for a road bike especially when racing?
There is no one correct answer to your question. The proper pressure depends on how much you weigh, and the surface you are riding on. Most people think they should pump their tires to iron like hardness to reduce rolling resistance. In a perfect world this would work great, but, we don't live in a perfect world and you should resist the temptation. First, a couple of comments about rims and tires...
Beleive it or not, rims are not necessarily able to handle as much pressure as tires. In fact, many high end rims are limited to pressures way below what even the least expensive tires can handle. So, you may want to look on the website of your rim maker to see if there is a limit. Tires too, will have a maximum pressure rating. Be sure not to exceed it.
Road surface makes a big difference. The smoother the surface the more pressure you can run. On a rough surface, though, more pressure will actually slow you down. How can this be, you ask?
You need to think of your tire as a spring. When you hit an obstruction, your tire, just like a spring, compresses. Then like a spring, the tire rebounds. If you have too much air in the tires, you will find your bike bouncing off every little obstruction instead of smoothly rolling over them. Insofar as your wheel meets an obstruction somewhat before bottom, dead, center, you are actually rebounding back! In other words, that bounce is actually a braking action which is slowing you down. Furthermore, too much air will also cause fatigue as ever little bump in the road is transmitted through your bike into your body.
Of course, too little air in your tire will cause you to get a pinch flat because the rim will pinch the tube against the obstruction making a pair of holes that look like a snake bite.
The perfect amount of air will cause your tire to conform to an obstruction and roll over it with minimal rebound. Obviously, it will prevent pinch flatting, as well.
So, what is the perfect pressure? Well, one thing for sure is it much less than the stated maximum on the tire or the rim. I weight about 165 lbs. On a really smooth road, I'll use around 100 lbs. On rougher roads, I ride with around 90 lbs. If you weight more, put a bit more air in. If you weigh less, try a bit less. In a few rides, you should find the pressure that seems to suit you and the roads you ride nicely.
There has been lots of discussions of tire pressure in the Road Bike Rider Newsletter. Your may want to check out the
Road Bike Rider Website:
Here is a discussion of tire pressure:
Hope this helps you understand the ins and outs (or prehaps the ups and downs) of tire pressure.
Dec 21, 2010 |