So I'm watching Myth Busters and they are checking out how far a football will travel fill with air and filled with helium, and the helium went further.
And when I close my eyes some nights I can still read what Tex says about light rim/tire como it is the 2nd best way to improve acceleration oops I mean fuel economy...
So can we bust this one or do you think it will actually work?? It did for Larry Walters

 

Now THAT is a great question Mike!

I would be genuinely curious about this as well. It would seem to make sense. But at the same time I would have reservations because we are dealing with a pressurized fluid, so we don't have to overcome the moment inertia or friction inside the tire because it can stay relatively stationary as the tire and wheel move around it. Granted the stem to fill the tire and the TPMS sensor, and any flaws or weighting will stir things up a bit.

But I would be concerned about first finding out how helium expands and contracts due to ambient weather while under ~34psi in the tire.. This is why nitrogen fills are popular in many applications

At the same time, being that it is still unsprung weight it may not change the acceleration, but it could improve your suspensions ability to deal with keeping the wheel in proper contact with the road with less mass to manipulate.

 

Supposedly, one advantage people say of nitrogen over "air" is that it leaks less (a nitrogen atom is large forcing molecules to be large). Helium, on the other hand is TINY in comparison, in both atoms and molecules that can form (the reason for the weight differences is the same reason for the size difference, neutrons and protons, or lack of)... It will leak out VERY FAST.

If, and ONLY if you can reduce the rate it leaks... Then it would be useful.

 

Excellent point on molecule size.

This is all true.. but I think there could very well be some merit to what Perrenoud is getting at with a helium fill. But maybe with the precaution of putting an extra dab of tire sealant on when you mount them on the wheel to help avoid leaks.

It could go either way as far as acceleration and mileage, but if it checks out as safe for use in street cars I could see it helping the suspension do its job more effectively, maybe even help with controlling wheel hop if nothing else

Either way, this is an interesting topic Mike!

Edit: on further thought at the very least it is less mass for the engine to push around, which would lead to better fuel economy and acceleration for that fact alone.

Would it cut down on rotating mass? I don't know how much windage exists inside our tires, so it is tough to determine!

 

Nitrogen has no water in it, not sure if helium would work in the tires because of heat. But its interesting anyways.

 

That is my main concern, but otherwise it certainly seems plausible!

 

Helium also freezes, if you ever had a balloon and took it out side in winter it would contract and go flat. They use nitrogen because there no water in it and since water is corrosive it can damage the tire shortening the life of the tire. The only problem is it cost 20 or so to fill with nitrogen, and what do you do when you need more?

 

Yup. Like aluminum, lead, copper or steel.. nitrogen, helium, and "air" (which is mostly nitrogen) expand and contract at different rates.


You can get a nitrogen fill in a surprising amount of places, like anywhere that supplies paintballing equipment or airports.

 

Actually, the "leak" I was talking about, is through the rubber of the tire itself. I forget the site that was talking about it concerning nitrogen vs "air."

I agree with SilverBullet about the contracting, Helium is too vulnerable to temp changes.

 

Nitrogen is suppose to be better but its still mostly opinion. Theres pros and cons to both.

 

My guess is that helium filled tires won't make a measureable difference. The tires aren't that big. Beside, helium may change the weight of the wheels by a small amount, but not mass.

 

You could also fill your trunk with helium balloons. And in both cases the difference would be negligible. You'd accomplish about the same thing by never filling the washer fluid container more than half-way...

 

I use a special 78% nitrogen blend. It's kinda expensive, but the mechanic tells me it's the best.

 

you are assuming that it requires the same MASS of Helium as Nitrogen (or "Air") to produce the "PSI."

it requires the same VOLUME... but the mass of 1 L of He at STP is NOT the same mass of 1 L of N at STP.

*warning* that's all the warning anyone is gonna get.

at STP, an "ideal" gas takes up 22.4L for each mole. that is regardless of the gas.

1 mole of any gas, is 6.02 x 10^23 atoms (or molecules).

so, in that 22.4 L... Helium weighs about 4 grams... Nitrogen weighs about 14 grams. Therefore, Nitrogen weighs 3.5x Helium.

 

I know that the Olympic cycling team filled their tire up to 140PSI with helium in the 80s... I am not sure about how it was determined to be too their advantage to do so but it was said that it reduced rolling resistance but it's molecular structure allowed it to leak out of tires quickly at that pressure

 

I just fill the cabin with helium. It makes a huge difference with acceleration.

 

now... combining plain physics and "racing" physics... you are talking about... sprung weight.

the helium in the tires would be unsprung weight. and as I'm sure many would agree... any unsprung weight difference has more effect than sprung weight differences.

But really, the question is... just how much weight difference is there in a nitrogen filled tire vs a helium filled one? Which ultimately depends on how much you can stuff in there.

googling here and there, finding conversion calculators (cause frankly, i'm to f-ing lazy to try and remember stuff from 15 years ago)...

the best answer I can come up with (rough guessing sizes, rounding numbers here and there)... there is about a TOTAL (I mean all four tires) weight saving of... less than 2 lbs... or is that the weight of Helium? Making the savings something like 4.5 lbs (a bit over 1lb per tire)?

It's past 5 am, and I haven't slept... forgive me if my process is madder than a hatter.

Maybe... not so worth it.

Well, I did say it was "useful"... just hadn't thought about HOW useful.

Let's remember, the advocates of using "pure" Nitrogen say its not for weight savings... but consistency (slightly less pressure leak and fluctuations). And if we stick to those two, there's no reason to use Helium.

 

my buddy had a torque monster nova when i was in high school. he filled up the front tires with helium and the rear tires with pure oxygen. he normally could only do a wheel stand a few inches off of the ground but with the helium and the oxygen, he got about 4 feet off the ground.

my main concern with putting helium in the tires is the reduction in traction you will suffer when the helium is fresh. also, you would have to change the helium every day or two to make it effective.
helium gas atoms have a higher velocity compared to normal air particles. the helium particles are also smaller than oxygen or nitrogen making it easier for them to escape through any pore in the tire. the helium they put inside of balloons is a mixture of O2 and helium. when you keep a balloon for a long time, it shrinks and stays at a certain size because the helium escapes and the oxygen is left inside of it.

all in all. i dont think helium is a feasible substitute for good old fashioned air.