Tyre pressure anomalies

[problemchild1976]

Re: Tyre pressure anomalies

I have a barrel of snake oil in the garage - I use it daily!

JJ

[lil.smartie]

Re: Tyre pressure anomalies

I've run 30psi all round on both 135's and 145's for as long as I've had Smartie and never had any issues or odd wear patterns. She has leaf springs.

Kate

[tolsen]

Re: Tyre pressure anomalies

I've run 30psi all round on both 135's and 145's for as long as I've had Smartie and never had any issues or odd wear patterns. She has leaf springs.

Kate

Thanks for the info Kate. I am now running 1.6 bar at front and 2 bar at rear. There is quite an improvement in comfort compared to 2 bar front and 2.5 bar rear. Have not yet established whether there is more wear and any higher fuel consumption with the reduced tyre pressure. Fuel consumption could in fact drop as considerable amount of energy is wasted boneshaking the Smart and driver when running on rock hard tyres.

[Evilution]

Re: Tyre pressure anomalies

Did always wonder about that - so what's the benefit?

For the seller - profit.
For the user - the local snakes will be a lot less oily.

[problemchild1976]

Re: Tyre pressure anomalies

Damn - gonna try helium then instead as a "weight saving" measure

JJ

[tolsen]

Re: Tyre pressure anomalies

Damn - gonna try helium then instead as a "weight saving" measure

JJ

Unsprung mass reduction by filling helium in tyres:

Air density 1.3 grams/ litre @ -2 C.
Helium density 0.18 grams/ litre @ - 2 C.

Front 145/65 R15
2.0 bar tyre pressure
Tyre volume 6.49 litre
Unsprung mass reduction per front wheel 21.8 grams

Rear 175/55-15
2.0 bar tyre pressure
Tyre volum 8.04 litre
Unsprung mass reduction per rear wheel 27.1 grams

Total unsprung mass reduction 97.8 grams. Obviously those with fat tyres will gain higher weight savings.

[problemchild1976]

Re: Tyre pressure anomalies

Plus if I leave the dust caps off - 98grams

Over 100k miles - that may nearly pay for the gas

JJ

[madDan]

Re: Tyre pressure anomalies

great techno waffle simply ignoring the fact the Helium with permeate through the rubber!

[problemchild1976]

Re: Tyre pressure anomalies

Haha! Obviously but that wouldn't have made for a bit of a giggle!

Oh well...

JJ

[Doofus]

Re: Tyre pressure anomalies

Nitrogen has bigger atoms/molecules/bollocks so it doesnt leak out as fast as "Air". Used in motorsport where tyre temperatures are higher than a Smarts will ever get to. The tyre walls are more porous, apparently.
Be aware that in a big accident, your tyre pressures will be checked! The police and your insurance company will want to penalise you. One will want to prosecute you for failing to maintain your car correctly, the other will want to get out of paying vast sums to a no fee lawyer who is on to a certain winner as your tyre pressures were "not in accordance with the car makers recommendation".

[tolsen]

Re: Tyre pressure anomalies

Dry air contains roughly (by volume) 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases. Using Dalton's law of partial pressurs one will see that loosing 50% of the oxygen in a tyre only results in a modest loss in tyre pressure. Repeated topping up tyre pressure with air would, if previous poster is right, result in concentration of nitrogen increasing getting near to 100% over time. Therefore no point inflating tyres with nitrogen. As he says, oxygen and other smaller molecules leak out thereby increasing concentration of nitrogen anyway.