Jump to content

tire milage


Recommended Posts

Got a 2002 gmc 2500hd with 6.0 with stock tires.Noticed most people have gone to the 285/75/16. I will also put that size on very shortly, still researching which tire brand i want. so here is the question, if you put a larger tire on ,wont you go further with each revolution ,meaning you will get better gas milage? Just curiuos if this will occur?

Link to comment
Share on other sites

Apparently the brand of tire is more important that the size, when getting people's advice about whether bigger tires cut your mpg.

 

Some people, unlucky ones, report 1-2mpg worse after going to 285's. I don't know what brand of tires they are using.

 

I had *no difference* when I went to Toyo Open Country 285's from my stock 245's. I can still get 15 mpg on the highway if I need to, cruising 65 actual mph.

Link to comment
Share on other sites

Why would your milage go down?  I have this crazy idea in my head that your going further in distance with each revolution so you would increase milage. Why is this wrong?

 

 

 

 

There's three big reasons. First off is that you're increasing wieght in the worse way, rotating. It takes more power (fuel) to accelerate the extra wieght upto speed. It also takes more brakes to slow them. Secondly is the larger diameter reduces torque at the point of contact. We measure power in pounds of torque at one foot. Go past a foot and that power is less, less than a foot is more. So your engine has to work harder to acheive the same results with a taller tire. This is why towing is effected so much with larger tires. You're getting less power to the ground with the same engine power as before. Third is that the larger tires catch more air induced drag. Larger surface area being pushed at speed through air.

 

Now keep in mind that the first two things show up mostly in stop and go traffic where your fuel efficiency will take a big hit. Out on the highway at a steady speed it isn't as bad. But the third increases with speed and that along with the first two's role still means highway mileage is a wash at best.

 

You can regear your truck to increase driveshaft speed compared to axle to regain the lost torque but it won't undue the wieght penalty. Actually you add to the wieght because you're now spinning your drivetrain faster to acheive any speed.

 

RPM isn't as big a determining factor in fuel efficiency as power required to maintain that RPM. If you're turning 2000 on the highway and using 20 HP to maintain speed you're using less fuel than the same engine turning 1700 RPM but needing 25 HP to maintain speed.

 

If you have 4.10s now it won't be so bad but you'll really lug a 6.0 with 3.73's and 285's.

 

Vernon

Link to comment
Share on other sites

Thanks for the reply! After reading it about 3 times it finally makes sense. I do have the 4:10 rear so maybe ill still go with the 285s. Very interesting the facts though, thanks again

 

 

 

 

 

Well if you tow a lot then I would maybe go with 265's. But if not go for it.

 

I have a no low end grunt 5.3, with 3.73 that went from 265 to 285's, and I did notice a slight loss of take off power. It just feels very slightly sluggish around town. But after 2 weeks you don't even notice.

 

Now with a 6.0, and 4.10, I would bet it would be even less noticeable.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.



×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.