09-14-2007, 02:21 PM
Two months ago I replaced the original equipment tires on my 04 AWD with 225/70R16 BFG Long Trails. Since the change I have experienced a decrease in mileage from 23-24MPG to 19-20MPG and have noticed that breaking at freeway speeds is much less responsive. Is this typical? Please advise if there are changes I can make to improve the braking and mileage with my new tires.
09-14-2007, 02:44 PM
First off, when you "upped" the size of your tires, you made them wider and taller. This can and does, translate to more rolling mass and more friction along with rolling inertia.
Fix #1: Bump up your tire pressure, this'll decrease rolling friction and possibly improve MPG.
Fix #2: Change your brake pads. Upgrading your pads over OEM replacements, will net you more gripping action for the discs thus stopping the increased rolling inertia created by the oversize tires. Check for brands like Hawk and EBC.
I'm unfamiliar with the tires you put on, but if they have an "aggressive" tread, this will affect the aspects of your vehicles performance as well.
Chunky tread blocks are great for off-road traction, but don't fare so well for highway cruising, thus decreasing your MPG. Also, despite their size, off-road tires have less rubber meeting the road which will decrease stopping ability and increase stopping distances. This is due to the "chunky" tread, which has large gaps between the tread blocks to allow for better traction in snow, mud, gravel, etc. Think of the difference between Formula 1 car slicks versus Bigfoot's tires and you'll get the idea.
Hope this helps.
09-14-2007, 02:51 PM
I was writing this as Elemen-O-P was answering also, itís pretty much the same, but since I took the time, hereís my response too.
The decrease in mpg is probably due to a few things. The tire is 2% larger than stock so when your odometer says 300 miles you have actually driven 306 miles. Your mpg calculation should be adjusted also by adding 2% to 19 - 20mpg so itís actually 19.38 - 20.4mpg. Try adding 2% to your odometer reading next time you calculate mileage to see if that gets you closer to what you were getting. If you have a GPS you can verify the odometer difference over a few trips.
Thatís not much of an increase in mpg so the additional loss of mpg is probably due to the actual weight of the tire compared to the stock and the increased rolling resistance of the BFG tires.
The weight of the tire and larger diameter (larger centrifugal force) would explain the braking difference also since it will take more energy to stop or slow those tires down compared to the stock.