Reducing unsprung weight/mass

**HDTboy** · 28th March 2006, 13:18

Can anybody see any obvious problems with filling ones tyres with Helium? Other than the cost

**justsomeguy** · 28th March 2006, 13:20

How much weight will that save?

**SimJen** · 28th March 2006, 13:27

Race teams use Nitrogen because it keeps a more stable pressure than Helium.

**bugjuice** · 28th March 2006, 13:28

not a lot..
I thought they use Nitrogen or something else.. that cold stuff, I thought..

reducing unsprung weight would be things like magnesium, titanium or cabon fibre wheels, all of which are fragile to curbs and the like..

you could always just try a diet, tubby

**WRT** · 28th March 2006, 13:32

Besides, your still not reducing the mass. Sure, filling the tyres with helium will make them lighter in relation to gravity, but will it really have an effect on how quickly the suspension moves in relation to the road and the bike? Someone with an engineering degree might be able to confirm or deny, but in my laymans train of thought, I cant actually see it having any difference what so ever.

**skelstar** · 28th March 2006, 13:34

Did I hear that Helium will leak out of a rubber tyre wall due it being smaller in particle dimenisions (compared to air that is)?

**svs** · 28th March 2006, 13:34

won't save you much weight. probably not worth it

Some race teams use nitrogen, but that's mainly for consistency with no contaminants from the air and consistant humidity etc. which means there is less variation in tyre pressure when it heats up, and partly cos sometimes it's easier to carry a nitrogen tank than a compressor.

Me, I'll stick with with plain old air, I doubt my gauge is accurate enough to notice the difference anyway.

Oh and helium diffuses very rapidly through rubbery materials -- the cause
of the short life of helium filled party balloons

**SimJen** · 28th March 2006, 13:41

Carbon or Superlite magnesium wheels will make a far bigger difference.
I gather you've already tried making the bike lighter in other areas? if you haven't then why are you bothered.

Make the fairings from only a few layers of FG
Only put the thinnest coat of paint on
Make sure you take a good dump before riding
Fill your lungs with Helium, it will also make you lighter albeit squeeky
Remove the lights/indicators
Put a lightweight full system on
etc

**sAsLEX** · 28th March 2006, 15:15

Originally Posted by WRT

Besides, your still not reducing the mass. Sure, filling the tyres with helium will make them lighter in relation to gravity, but will it really have an effect on how quickly the suspension moves in relation to the road and the bike? Someone with an engineering degree might be able to confirm or deny, but in my laymans train of thought, I cant actually see it having any difference what so ever.

a box of helium weighs say 1kg and a box or air weighs say 2 kg, now you tell me if there is a difference trying to swing them about

**bugjuice** · 28th March 2006, 15:17

how would you stop the helium escaping out the box? It's bad enough just trying to keep air in it..

**The Stranger:Me** · 28th March 2006, 15:21

Remove the brakes, all those heavy discs and calipers can't be good for unsprung weight.

**froggyfrenchman** · 28th March 2006, 15:22

Originally Posted by skelstar

Did I hear that Helium will leak out of a rubber tyre wall due it being smaller in particle dimenisions (compared to air that is)?

As far as i know, you are right

**HDTboy** · 28th March 2006, 15:32

Originally Posted by sAsLEX

a box of helium weighs say 1kg and a box or air weighs say 2 kg, now you tell me if there is a difference trying to swing them about

saslex is following my train of thought.

I'm aware of the use of Nitrogen for stability, the Helium thought was because it's a shitload cheaper than aftermarket wheels

[QUOTECaN]Remove the brakes, all those heavy discs and calipers can't be good for unsprung weight.[/QUOTE]
True, that's why we have alloy callipers and disc hats