When I was younger, I only had a bike till I was25. I am trying to get back into biking again. I bought a vilano performance hybrid roadbike and it came with 700 x 28c tires with presta valves. Now, its been a long time, but what was wrong with schreider valves ? Anyway, I know tubes loose air pressure over time, but I only rode the bike In the parking lot once to see how the adjustments were, one week later, I went to ride the bike, and both tires were completely empty, I pumped them back up to 85 psi, and a week later they were completely empty, I tightened the nuts after and replaced the caps, I expected to lose some pressure, but not all the pressure. Am I doing something wrong? Thanks for any help.
You don't need to make either the nut on the tip of the valve or the retaining nut very tight. That won't make it hold air better and too tight could damaged the valve or tube. I suspect that if the tires are losing air that fast, they are probably just cheapo tubes.
Once you get used to them, prestas are a bit easier to pump up. But unless you always have a hand pump with you, I'd recommend picking up a presta adapter ($1-$2) to keep on the bike. That way you can pump up at a gas station if needed.
You'll lose pressure faster with CO2. And those pressurized CO2 inflator things are a pain in the @ss.
With tires going completely flat in a week you have a air leak, either the valve, or the tube was pinched on installation and you have a slow leak. Screw down the lock screw and put a bit of spit or soapy water on the valve and see if it bubbles. If that does not leak pull out the tubes fill them with air and immerse in a water through , put some pressure on them with your hands and see if you spot leaks. Replacements are not expensive. I suspect valve issues. Finger tight is adequate BTW...
Like I said I am not a fan of these valves as a former Mountain Bike Unit rider I always carry supplies to help other bikers. I came upon a rider with a Presta valve and we could not fill the tube, another time I came across a Schrader valve that did not fit my pump.
As Dave said some Cheap stuff out there.
I added a Presta to Shrader adopter to my tool kit. Most bike pumps have reversible nuzzles.
Never Give Up!!!
Ok, thanks. I will check that. As this is a new bike, tubes and tires came with it, so I dont know what is in there and I was thinking they would be using quality parts from the manufacture. First time with presta valves, so I thought I might be doing something wrong.
I ride only Sclaverand valves (I guess Presta to the Francophobes) and as George commented (but worth stressing!) a likely mistake is that the valve core is not screwed in properly (apart from installation errors of tube and tyre). Plus tubes all lose air - the light weight butyl ones more than heavy duty butyl tubes, and latex tubes even more. On a road bike with latex tubes you lose 1 bar per day. It is good practice to check air pressure often, you'll find out how often you will need to check (daily for my road bike and cyclocross, weekly to bi-weekly for the tourer).
The caps and the valve nuts have nothing to do with the problem, I don't even have them on my road bike (the latex tubes (Michelin) do not have outside threads on the valves = no valve nut). In the rear I installed an adapter so that I have one in case I need air... (like many suggested).