Stupid questions about tire pressure



RossB

New Member
Aug 20, 2003
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I bought my first road bike on Sunday - a Trek 1500 - so this will be the first in a series of stupid questions.

The Trek comes with Bontrager tires, which the LBS told me to pump to a pressure of 100. I have no reason to doubt this, but how do I verify what the correct pressure should be for these (or any other) tires? Is this determined by the tires or the inner tube?

Also, when connecting the pump, the meter starts at zero and goes to 100 after a few pumps. Shouldn't the meter be reading the pressure already in the tires, and wouldn't this already be close to 100 if they were only pumped a few days ago?
 
Originally posted by RossB
I bought my first road bike on Sunday - a Trek 1500 - so this will be the first in a series of stupid questions.

The Trek comes with Bontrager tires, which the LBS told me to pump to a pressure of 100. I have no reason to doubt this, but how do I verify what the correct pressure should be for these (or any other) tires? Is this determined by the tires or the inner tube?

Also, when connecting the pump, the meter starts at zero and goes to 100 after a few pumps. Shouldn't the meter be reading the pressure already in the tires, and wouldn't this already be close to 100 if they were only pumped a few days ago?

Most every tire will have the manufacturer's recommended pressure on the sidewall. If you've bought tubes to match the tire, then simply inflate the tube/tire to the recommended tire pressure. Tubes are made of a porous rubber compound, and consequently do leak air over time. That's why you need to check tire pressure before every ride.
 
About the meter not reading right away, until you stroke the pump once or twice the presta valve has not been depressed yet so you will not get a reading on the guage.

A tube is a tube (provided it is the correct size) so inflate it to the recommendation on the tire side wall.

Good luck with the new bike enjoy it..............................
 
Originally posted by Wally
About the meter not reading right away, until you stroke the pump once or twice the presta valve has not been depressed yet so you will not get a reading on the guage.

A tube is a tube (provided it is the correct size) so inflate it to the recommendation on the tire side wall.

Good luck with the new bike enjoy it..............................

Thanks, that's helpful. I couldn't find the pressure specified on the tire side wall. If the recommended pressure was 100, what would the tire typically say?
 
It would be pretty clear on the sidewall. My Continental tires say "Max inflate to 120 PSI." That's for pounds per square inch. I can't imagine any tire not having that info on the sidewall. I would think that it's required, just like a car tire. FYI, tire pressure is a matter of personal preference. It will depend on your weight, your goals for the day (racing, strolling, etc.) and the road conditions, among other things. Don't go just by what your shop says. Try out some variations and see what feels best for you. Personally, 100 PSI would be way too soft for me, so I would change my brand of tires if I bought that bike, but again, it's personal.
 
In addition to pumping the tires to your preferred pressure, I always let air out of the tires after every ride. I live in Michigan, and it doesn't get as hot here as other places, but still have had tires blow when they've gotten too hot. - and I put 120 psi in my tires too.
 
Before adding air, I always bleed off a few seconds of air pressure. This allows for pumping up to the desired pressure.

Michelin Axial Pro tires have a graph on the package that details recommended air pressure vs weight. For example 8 bar @ 80 kg.