different brands of tires are very different rolling resistances, which is commonly called Crr by engineers
tread depth of the rubber on the tire also greatly affects rolling resistance, with new tires with deep tread rolling much harder than used tires with shallow tread left
as said above, high air pressure will reduce the rolling resistance
the "Ram Pickup MPG Improvement FAQ" has a whole section on name brand tires and how they vary in rolling resistance.
In just a few months the sidewalls of USA-sold tires have to have a new stamp rating their rolling resistance
You can measure your own tire rolling resistance (and aerodynamic coefficient of drag called Cd)
with this handy archived JAVA calculator from a racing team in England:
http://web.archive.org/web/2004080307322...tDownCalcs.htmlbe aware in the above online calculator that even if you use Miles per hour and square feet in your inputs the output they give you called
'A times Cd'
has the A part in square meters, not square feet.
Tire rolling resistance definitely has an effect on MPG. Here's a quote the Ram FAQ:
---
" Fuel mileage at a price. Some tires roll with less drag than others. The
lower a tire's rolling resistance, the more fuel you can save. Those savings
can be significant. {Pickup and SUV} Tires with the lowest rolling resistance
delivered nearly 2 mpg more at a steady 65 mph in our highway tests {2003
four-wheel-drive Ford Explorer XLT 4x4} than those with the highest rolling
resistance. The catch: While some high-scoring tires had low rolling
resistance, most tires with the lowest rolling resistance also had lower
overall scores."
In their 11/2004 Pickup & SUV tire test CR the
lowest rolling resistance tires rated 'excellent' were the:
Bridgestone Dueler H/T (D684)
Michelin Cross Terrain
Continental ContiTrac
BF Goodrich Radial Long Trail T/A
The Pickup & SUV tires with the worst rolling resistance were the:
Pirelli Scorpion STA
Kelly Safari Signature
Yokohama Geolander H/T-SG051
A tire with a 'very good' rolling resistance and high scores in other handling
and braking tests was the Hankook DynaPro AS RH03
Hankook recently announced that they had spent $10 million developing a
tire called the fx-Optimo that has even lower rolling resistance and can
give up to a 3% MPG improvement:
http://www.moderntiredealer.com/t_inside.cfm?action=news_det&storyID=5961Michelin has also recently introduced an ultra-low rolling resistance tire for
use on diesels in Europe that is available in 15 and 16 inch sizes:
http://www.autoblog.com/2007/09/07/michelin-creates-energy-saver-gas-conserving-tire/In another test of "All Season" tires in November 2005,
CR rated these tires as 'excellent' for low rolling resistance:
Michelin X Radial DT
Michelin Agility Touring
Michelin Harmony
Hankook Mileage Plus GT H707
Kumho Touring 795 A/S
Toyo 800 Ultra
Sumitomo HTR T4
In the same November 2005 issue
'All Terrain' tires were also tested
but only the
Continental ContiTrac TR
got an excellent rating for low rolling resistance in this group.
