Ok, so I’m in a Miller Lite haze prepping for an early morning group race (I mean ride). An odd thought entered my mind (and introduced it’s self to many others). Since some gasses are lighter than air and reasonably available (and yes, I know Hydrogen has a little bad history with that blimp thing), I was wondering what could be if you filled your tires with one of them.
Listen, I know this is a complete piss in the wind, but I’ve seen enough obsession in these forums over completely nonsense topics to think there might be a debate to be had over another nonsense topic. There is nothing else to do tonight, 24 and American Idol are over…and I know you’re not out on the town if your frequent these parts. Unless there’s a new Infinit bar in Boulder. Imagine if you could effectively lighten your rig by 1 lb…and 1lb of rotational weight at that. Hell, you could build an airtight frame and pump that sucker full the morning before the race. Hell, I’d externally route everything if I had a frame the came in a negative 2 lbs. Train heavy, race light.
3 more beers and I’m contacting the patent office. After reading how many people are ready to just pounce on a set of $1,200 brakes…BRAKES! I figure all I need is some sexy marketing (Guerrilla Marketing to be exact), some quotes from a Swiss scientist and pay some top pro to endorse it and it wouldn’t even matter if it worked. But just imagine if it did work…
Some track riders used to fill their tires with Helium. This was done at the Olympic level (due to the cost/inconvenience) and I recall that they claimed it saved 16g/wheel.
As for filling the frame…see how many helium balloons you need to buy to lift a full water bottle and you’ll get an idea why this hasn’t been done.
Correct on Nitrogen. The friction on the tire heats up the moisture in the compressed air and causes pressure to build creating pressure irregularities. Nascar and many other racing bodies have run Nitrogen for years to keep pressure and temperature buildup to a minimum. I am new to tri from running and have just started putting miles on my Trek, so not alot of cycling experience. Though, I have had similar thoughts and would be interested if there are any discernable benefits as the numbers involved are significantly lower than those of a race car.
to the other poster, same thing with us and playing paintball, we fill a lot of our tanks with nit and not compressed air to keep moister out and keep them from heating up.
Hydrogen and Helium molecules are tiny. If you use the best sort of tires/tubes – i.e. latex, the miniscule weight savings will be overridden by the rapid loss in pressure. Latex tubes save you several watts over real tubes. However, they lose pressure fast even with nitrogen. With He or H, you’d probably lose 10 psi in an hour or so.
thought the same thing man, however i came to understand if you compress He to say 100lbs in a tire then it doesn’t have the same affect/effect (i never figured out which was which) as is does being slightly compressed ie a balloon. You lose all those properties if you do that. Blimps and such, my understanding, have a low psi in them making them float. Once compressed the become heavier then air and no longer float. That doesn’t mean that a tire wouldn’t be a little lighter inflated with He or H but not in the way you arart thinking with 3 or for of those watery things you are drinking!
I fill my tires methane. It’s important that this is bean-based. Do NOT fill them with egg-based methane, as that’s been shown in the tunnels to be substantially slower. Lima beans have been shown to have the greatest elasticity and will aid in rolling resistance, plus depending on digestive system will lighten the wheels the most. All the top guys at Kona do it; it’s one of the shameful secrets that you don’t hear much about. Another being that when you’re highly hydrated your urine is low enough in salts that it’s perfectly digestible, so the top athletes will recycle as they go on. This is why you rarely see them asking for water at the water stops, despite constantly drinking and drenching themselves with it.
Helium has gone up a lot lately. You can do cheap balloon grade stuff for about $75/300cf, but once it’s under pressure, it doesn’t float any more, so there is almost no weight savings. You can run some combined gas calculator to figure the difference in moles between air and Helium.
We used compressed Nitrogen in aircraft tires, but mostly because they’re inflated to between 250 and 350psi in most cases and the N2 is more stable at various altitudes since wheel wells are not pressurized.
Honestly, both would be useless in a bicycle tire other than the placebo effect perceived by the rider. Air in 79% N2 anyway. You could also run your air through a dryer before compressing it.
Hydrogen and Helium molecules are tiny. If you use the best sort of tires/tubes – i.e. latex, the miniscule weight savings will be overridden by the rapid loss in pressure. Latex tubes save you several watts over real tubes. However, they lose pressure fast even with nitrogen. With He or H, you’d probably lose 10 psi in an hour or so.
Actually…it’s not so much the size of the molecule that matters, but it’s solubility in rubber (butyl or latex). IIRC, CO2 actually is a larger molecule than N2, but it “leaks” through rubber faster than N2 because it’s more soluble and thus diffuses through faster.
I’m not sure about the solubility of H, but I would think He probably wouldn’t be too soluble in rubber. I’ve got a reference at work I could check on Monday…
Nitrogen is big in car racing since the tire temps are changing by 100+ degrees .5 psi changes can alter the handling of a race car. They need a pretty fine level of predictabilty in psi and change vs temperature since they are filling the tires at room temp but racing on them at 200 degrees +. Probably not an issue on the bike The amount of moisture in whatever is in the tire will change how the tire pressure responds to temperature changes so using something with a predictable moisture content will make managing tire pressure easier.
I don’t think there is anything especially significant about nitrogen itself, its more that when buy a tank of industrial nitrogen, it has been processed to a consistent moisture state (and its fairly cheap too). The moisture content of compressed air is kind of a crap shoot. You could probably get the same affect using industrial oxygen or hydrogen but they explosive (and more expensive) so not a good idea.
The amount of moisture in whatever is in the tire will change how the tire pressure responds to temperature changes so using something with a predictable moisture content will make managing tire pressure easier.