[TRIZ]

So answer me this... a 14 inch rim and tire, will that weigh less then a 16 inch rim and tire? Common sense would say the 14 incher would be lighter with a tire, because rubber is ligther then metal.

anyone have any info/data on what real life tradeoffs would be as far as weight and speed are with increasing rim size?

[Eyger]

That's weird I didn't even notice that this was a second page to your original post.

I accidentally posted. I donno man.

just a random thought, what do you think would happen if you put helium in your tires? Ha ha, that would be weird right. Do you think it would reduce the weight of the wheel and tire combo?

Edited:
After searching the web for this idea turns out:
This was a stupid idea of course. Anyways, Guess I'll just stick with nitrogen

[Zzyzx]

Originally Posted by Eyger

That's weird I didn't even notice that this was a second page to your original post.

I accidentally posted. I donno man.

just a random thought, what do you think would happen if you put helium in your tires? Ha ha, that would be weird right. Do you think it would reduce the weight of the wheel and tire combo?

Edited:
After searching the web for this idea turns out:
This was a stupid idea of course. Anyways, Guess I'll just stick with nitrogen

Helium.... for starters the tire would lose Psi at a much greater rate. (Helium, He2, is a very small molecule)

Tires already loose Psi over time as the oxygen & argon slowly leak through the rubber.

Nitrogen would be a better choice here, as its natural state is a much larger molecule and therefore less seeps through the tire. Which is the prime reason why some tire shops offer it.

Other wise, it wouldn't matter, as I know you were thinking that Helium is lighter then "air" so wouldn't that make the tire lighter.... Problem here is that you are putting the gas under pressure, a good deal of pressure. which means a higher concentration of He2 because its so small, which means more weight. (You don't see tanks of He floating away do you?)

[emjay]

5zigen fn01rc .. the ones i have are pretty light ...i think bout 12 lbs a wheel

[Zzyzx]

Originally Posted by TRIZ

So answer me this... a 14 inch rim and tire, will that weigh less then a 16 inch rim and tire? Common sense would say the 14 incher would be lighter with a tire, because rubber is ligther then metal.

anyone have any info/data on what real life tradeoffs would be as far as weight and speed are with increasing rim size?

the 14" setup could weigh less, or it may weigh about the same as the 16" setup.

The important part here is that the main mass, the wheel its self is closer to the center of rotation, which reduces that wheels rotational Inertia


The basic formula for estimating Rotational Inertia of a hoop goes like this.. I=m(r^2)

I = Inertia
M= Mass (weight)
r = Radius

So, compiring a 14" that weighs say 15lbs Vs a 16" Wheel that weighs 15lbs

15lbs = 6.8kg
14" = 35.6cm
16" = 40.6cm

so for the 14"
I = 6.8(17.8^2)
I = 6.8*316.84
I = 2154.512

for the 16"
I = 6.8(20.3^2)
I = 6.8*412.09
I = 2802.212

A 24% difference in rotational Inertia from just the wheel its self!



Now, as far as the upside of larger wheels. Well, most street tires have fairly flexible sidewalls which means the tire will distort more while under cornering loads giving you less overall traction then you could have had. Replacing this flexible rubber with relatively inflexible metal means the tire flexes less and you have the potential to make more traction.

So larger wheels will hinder acceleration & braking, but can help with cornering... if you are running tires with soft sidewalls.