New tires, bad MPG

[spitfire5454]

Hey guys, i noticed that ive been getting bad MPG since putting on my thornbirds. They are the same hieght and a little wider and probablly heavier, but my gas light came on, i put in 5 gallons and it comes on again 50 miles later. Ive done this 5 gallon thing three times, so its not a fluke. Any suggestions? i love the tires, i was just wondering if this was normal. I have noticed like others have, b/c of its tread, it tod kicks me in to 4w all the time. I was thinking that this may be why my mpg sucks, would i benifit from hooking up a disconnect? Thanks.

btw-i havent gone on the road yet, but i was getting about 360 miles per tank before. Based on this, ill only get around 230.

[thebear54]

Hey Spitfire,
When you change tires to a bigger, wider or heavier off-road tire your mileage will suffer. You are not alone with this problem. The laws of physics applies here. Putting the stock size tire back on will bring your mileage back to where it was before but it's not as cool
John

[VX crazy]

Thornbirds are one of the heaviest tires, even a different larger tire will affect your gas milage! Thats the price you pay to run larger beefier tires....

[yal^]

And ease off the gas LOL
TOD behaves a bit differently with heavy tires. It'll go crazy if you keep racing everyone and everywhere. Taking off abruptly with heavy tires makes the whole system work much harder. Since VX strugles a bit to spin your new tires TOD thinks you are slipping and kicks in automatically.
Try for once taking off slowly and watch your TOD - it won't kick in until you actually reach a steady speed, maybe around 5-8mph. Then watch as you slowing down. With stock tires TOD basically would stay on until you completely stopped your vehicle. With beefy shoes TOD will turn off way before you hit the brakes.

Somebody correct me if I'm wrong.

[Tone]

Double check the dimensions of your tires compared to the stock ones. Thornbirds are some of the heaviest tires out there (even tho they are bias tires) but they look wild! Taller will definitely make mileage numbers appear lower.

[tomdietrying]

What size tires are your Thornbirds? I'm thinking about going a bit taller and wider before Moab, but if it's going to do that to my MPG I'll have to think twice about it.
Peace.
Tom

[spitfire5454]

Thanks for the info. Mine are 30x11.50R16. And as tone said, they look awsome! Here is a spec comparison to the stock tires:

Stock Thornbird

Hieght: 29.7 30.0
Width: 9.8 11.50 (probably less b/c 16x7 wheels)
Weight: 35lbs 55lbs

I purposly didnt get taller tires because i really liked the performance of the VX. This is worse than when i put 33s on my amigo. Today i will fill up and see how much i get to the tank.

Brian

[JAFO]

I been researcing for new tires and I just read an article in Consumer Reports at Lunch that said that heavier lug tires (mud/snow) have higher rolling resistance.

5 gallons / 50 miles = 10 MPG

Wow, mine gets 18-20mpg on stock R18 Duelers. Big change.

[t2p]

Spend any time on a bicycle .... especially on the road ....
.
and you will quickly see the difference tires can make ...... weight, width, tread pattern ......
.
There is a good reason 'Triathlete' .... Billy .... is riding those skinny tires !

[Tone]

Bias tires like the Thornbirds will get lower MPGs than radials as well - higher rolling resistance, more rubber on the road in this case and more weight and sligthly taller height.

Your speedo and odo are off by3% - 60 on speedo is really 62mph. Your mileage is slightly better in town than 10MPG and of course will always be lower than highway.

[JAFO]

I also forgot tire pressure. Your not running them at 5psi with bead lockers are you? :bgwg: