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For a definitive discussion on tyre pressures and economy have a read of this page on Barry's Tire Tech. This is probably one of the best sources of information on the web regarding tyres. You might want to check the authors credentials before reading the article:
Barry's Tire Tech
Anyway to the article: Rolling Resistance and Fuel Economy
And a follow up posting re tyre size and rolling resistance.
Rolling Resistance and Fuel Economy (Continued):
I won't cut and paste as the whole article needs to be read, because the recommendations are a trade off.
The article is at least partly at odds with what I've said in the previous post, but I'm happy to defer to expert knowledge.
For a tech explanation of the load vs pressure ratio I mentioned above the following paper contains detailed but readable discussion and formulae. For my personal use I've put together a spreadsheet based on the formulae to calculate trye pressures based on axle loading.
http://dawsengineering.com/linked_fi...ducedloads.pdf
cheers
Paul
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All good stuff here. Owners manual tells 28-38 on the front and 28-46 rear. I find the front tyres wearing more on their edges unless I keep the front 32 to 36. Possibly urban myth but the dealer (when I purchased) did tell me that 28 on the front was for comfort given the stiff anti roll bar in the D2.
Can't offer much tech info for 4x4 rolling resistance but on racing bicycle tyres, rock hard is only good for smooth tracks, on the rough crushed rock on top of tar roads around here dropping down in pressure a little allows more give over the stones and thus less rolling resistance.
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Thanks for the links, Offtrack.
What I found interesting is that whilst increasing tyre pressure from 24psi to 40psi reduces rolling resistance by 21%, for city cycle, rolling resistance is only 4% of total energy use, hence in total it reduces only 0.8%.
Thus for 15,000km/yr, 13L/100km, one uses 1950L which @ $1.50/L is $2925/yr. A reduction of 0.8% is only $23.40 per year. Not worth the loss of traction or decreased comfort in my view. Also insignificant cost of ownership of a landy.
