Hey Mister Rik. Good advice here so far. Don’t pay attention to the people bashing you.
My Wife does full IronMans, and I’m her Sherpa for those occasions. At first, the Presta valves where a pain in the ass. More so for my Wife because she has some weak hands from surgeries and accidents.
MODERATOR WARNING
Here’s your second warning in this thread for insulting the OP.
You won’t get another.
I’d suggest not posting any further to this thread.
samclem, moderator
But isn’t the whole point of prestas that it allows for a smaller opening in the rim and thus preserves structural strength with a narrower rim?
More like one year. Or longer.
I bought the bike while I was still without a driver’s license (I went without driving for 14 years). My past practice had been to buy a $200 “mountain bike” from Target or Wal-Mart and ride it until it broke, then go buy a new $200 bike. I finally found myself in a job where I was making more money than I was used to, and decided, “Dammit, I’m going to get a decent bike!” So I bought the Specialized … and then, less than a year later, I got my license back and got a car. Since then, I’ve found it difficult to motivate myself to ride regularly. So my bike sits, and the tires go flat.
It doesn’t help that I live in an area where “in the winter you freeze and in the summer you fry”. Riding a skinny-tired road bike in the winter is kind of out of the question. Then, if I don’t start riding in the early spring, and getting back into shape, the next thing I know it’s July/August with 100-degree weather to deal with on top of being out of shape, and … bleh.
For what it’s worth, I’ve never done this. On my race wheels I can’t do it as the valve isn’t easily accessible and my training wheels don’t have sticky valves so it hasn’t been necessary, but it’s hardly a hassle having to blip the valve, you’re already there loosening the nut anyway.
Yep, you get to spend more money. 
My cite is common sense. We don’t know what the wheels are & it sounds like this is a second hand bike so they may not even be the spec’d wheels. They could be carbon, but I doubt that. It does sound like they are aero wheels. Aero wheels have less of a cross section than flat, boxy wheels; therefore, you’re removing a larger percentage of the flat surface.
I’m not saying it can’t ever be done, but I am saying, in general, it’s a bad idea to alter the structural integrity of equipment, especially when you don’t know the design characteristics. I wouldn’t do it myself, & I sure as hell wouldn’t advise a newbie to medium/high end equipment (no offense intended at the OP) to do this either.
Mister Rik, another possibility is that the rubber O-ring in the pump is worn. Next time I wear one out, it won’t be the first (or second) time I’ve worn out a pump this way (think on & off the tires 2-3 times a week over a couple of years & you’ll wear out/stretch a cheap rubber gasket). If you can find the right replacement part, it’s a 50¢ or $1 repair. However, frequently, you can’t get the correct size so you need to buy a new pump. Head over to your local bike shop with both the bike & the pump & they can look at it & tell you how to fix. Parts are dirt cheap, new tubes, with longer stems are probably around $6-$7, & worst case scenario, a new pump can be bought in the $30 range.
If you mean mine, nope, it was purchased new, and has the original wheels.
Nope, it’s practically a brand-new* pump and hasn’t been used much. I did disassemble the chuck to check the O-ring after I started this thread (mainly to see if, perhaps, it was one of those that you need to flip over depending on valve type), and it’s in excellent condition.
*I bought the same pump in 2007, along with the bike, but that pump was in my ministorage unit when it was burglarized in 2012. My current pump is the replacement I bought.
It seems to me that the crucial point here has been mentioned, and acknowledged, but then talked around and ignored (underlining mine).
The valve receding into the rim is a HUGE, CRITICAL problem in terms of getting the pump chuck to attach properly, and may even be a factor in the high resistance to pumping air into the tire. I thought all Presta valves came with stem nuts, as shown here (nut halfway down to show how it goes on, not fully installed yet) and here (nut tight against the rim). Since you don’t seem to have these nuts, get some and secure the valves to the rim. I’m confident that when your Presta valves stay up to where the chuck can grab them, you’ll find them very easy to air up. Just don’t forget to screw them open before pumping and screw them shut afterwards.
No, not as far as I know. The presta valve lets our less air when pulling the pump head off. That is not a big deal for the average rider, but it benefits riders who are concerned with maximizing performance.
I agree with what you say to a point, but my views are shaped by years of experience in the industry as well as talking to many people with many more years of experience in the industry. Also, what I have read online from reputable sources is also consistent with those views. Furthermore, what I have read about wheel building and the physics behind the strength factors of a wheel are also consistent with the notion that it is safe to drill the hole slightly larger on rims that are not carbon. Also, if what you are saying is true, you would have some significant difference in the amount of failure near the valve hole; there is no significant increase in failure near the vale hole. Wheel failure happens somewhat more frequently at the seam.
I did say earlier that the best thing to do is go to a bike shop, so I agree with not having people just fiddle with their equipment that way if they have a place to go to that has experienced people who can help.
Why would nitrogen leak more slowly? First, air is 70% nitrogen. Second, oxygen is a bigger atom that Nitrogen. Is it to avoid oxidation of the inner tube, that oxidation presumably leading to higher leakage?
You mean oxygen is a heavier atom, learjeff, it is actually smaller in size than the nitrogen atom - high school chemistry right?
The oxygen molecule is slightly smaller than N2, IIRC, but not by much. Regardless, losing pressure from a tyre is a question of permeation (not diffusion, as is sometimes stated), and molecular size is just one parameter. It’s a bit like considering how ‘soluble’ a gas is in the solid rubber polymer matrix - many factors in play. It turns out that O2 permeates faster than N2, so an air-filled tyre will lose pressure (slightly) more quickly than a nitrogen-filled one.
What this means for inflating bicycle tyres I have no idea, as I’ve never heard of anyone putting nitrogen in their tyres as some sort of psi quality control. I believe it’s a consideration for some vehicles, like trucking companies might do it, but even then I don’t know if it makes much of a difference.
Not all presta stems are threaded for the little nut. Some ultra light tubes leave off the threading and nut to save a gram or two. Here’s an example of a Michelin tube: https://images.coloradocyclist.com/product/800/m/micfwxga.jpg
I was one of those silly weight weenies who left off the nut. After tearing a few tubes at the presta valve, I started using the nut again. I also found that my floor pump head was really difficult to remove from the valve. I bought another pump, a Specialized, that is super easy to install and remove plus auto-adapts to both presta and schrader valves. I haven’t torn a tube since.
Before you drill the rim make sure you can get as header tube that fits you tire. I don’t think I’ve ever seen a 700X21 a header tube.
It would be a real bitch to drill them out and not have tubes available.
Trucks use N2 for reasons of longevity (oxidation is an issue for tires filled to 100 psi that need to last several hundred thousand miles with retreading) and to reduce pressure loss rate (it takes a long time to check/refill 18 tires, so it’s beneficial to minimize that).
Commercial aircraft use N2 for fire safety.
Air leaks out of a typical butyl-tubed tire at a rate that’s about 1.6 times that of pure N2. So if you use N2 in your bicycle tires, you’ll need to refill only about 63% as frequently. OTOH, it’s generally a pain in the ass to track down an N2 source, unless you buy your own bottle and put it in your garage; usually much easier to just grab a foot pump.
Honestly, I don’t even know. I should say here, (I probably should have said it before) the bicycle industry is so full of products that have some sort of basis in half truth in science if you tried to unravel it all and devote your life to it for the next 50 years and never know a whole lot for certain.
Even with the stupid valve, it’s kind of silly that presta valves are as prevalent as they are given how much trouble they cause people and how much time you have to spend if you work in a shop showing people how to use them. And another thing about the valves is that yeah, part of the appeal of presta a while ago was that they worked with really narrow rims. But now, because there are clinchers that can rival the performance of tubulars, and also because people do not ride on 18mm tires (they used to think narrow was better, but then too narrow meant not enough absorption of surface anomalies), there are more wider rims on the market. But, people probably associate presta with high performance so entry level bikes come with presta for no good reason; or I shouldn’t say no go reason, but for the reason of consumer perception - which is important, actually more important than anything in bicycle retail.
So, really, the products on the market are the result of pseudo science mixed with marketing and traditions that take to long to die being developed within the framework that requires pricing that is palatable to the consumer.
You can see here how much discussion is involved in a friggin valve stem, just imagine what happens when you start getting into something crazy, like a hub. It’s just endless discussion that never gets resolved really. I got into accounting after over a decade in the industry, it’s a lot simpler.
