bigger tires=better gas mileage?

[bagpiperjosh]

a friend of mine told him that someone had reccommended putting bigger tires on his diesel so it would get him better gas mileage (i guess changing the ratio at which the tires would spin).

does that actually do anything, or do you just THINK you are getting better because it would throw your odometer off a bit?

And if it does work, could I just put bigger tires on the rear of my truck being its 2wd?

 

[diesel dummy]

In my experience with 4x4s larger tires = more rolling resistance,harder to get the extra mass started rolling.I have never gained mileage with larger tires.

 

[The Warden]

Yes and no.

Taller tires = the truck will move slightly further for every tire revolution...so, unless you adjust your speedo gear, the odometer will actually be showing fewer miles traveled than you actually have, so any fuel mileage calculations will be low, not high.

With that said, if you're changing your tire size strictly for the purpose of better fuel economy, you want to get a tire that is as tall and narrow as possible. The wider a tire is, the higher its rolling resistance, which makes the engine work harder and in turn robs your fuel economy. With height, you also have to worry about increased wind resistance...so, all in all, it's probably not really worth it unless your primary goal is to get the RPM's lower.

Actually, if you have 4.10 gears and don't really tow much, you might do better with 3.54 gears...

 

[dgr]

Timing your IP would likely gain you some ;p
Larger diameter tires while keeping the rolling resistance down = 255 85 16. Only available in mud terrain which increases resistance. About $900 to $1500 a set.

I thought you had a 3.54 rear axle. What is your Mpg? How much is a t5 in your area? Would improve highway mileage

 

[bagpiperjosh]

Yes and no.

Taller tires = the truck will move slightly further for every tire revolution...so, unless you adjust your speedo gear, the odometer will actually be showing fewer miles traveled than you actually have, so any fuel mileage calculations will be low, not high.

With that said, if you're changing your tire size strictly for the purpose of better fuel economy, you want to get a tire that is as tall and narrow as possible. The wider a tire is, the higher its rolling resistance, which makes the engine work harder and in turn robs your fuel economy. With height, you also have to worry about increased wind resistance...so, all in all, it's probably not really worth it unless your primary goal is to get the RPM's lower.

Actually, if you have 4.10 gears and don't really tow much, you might do better with 3.54 gears...

seems like if i already need tires, it might be the easier route. But i dont know how much bigger i would have to go to make a difference worth while and not look stupid and actually fit

 

[94f450sd]

On the highway yes.around town, no.

 

[Wicked97]

Taller tires will help if the width and weight doesnt increase very much. I can tell you that going from a 235 85 16 with stock wheels to a 285 75 16 with old steel 8.5 wide wheels lowered the rpms at highway speed considerably but at the same time the added rollong resistance and double the weight slaughtered the milage.

 

[Devon Harley]

Timing your IP would likely gain you some
Larger diameter tires while keeping the rolling resistance down = 255 85 16. Only available in mud terrain which increases resistance. About $900 to $1500 a set.
Check craigslist theres a set of 255 85 16 2 year old new for 400 never mounted.

 

[dgr]

Timing your IP would likely gain you some
Larger diameter tires while keeping the rolling resistance down = 255 85 16. Only available in mud terrain which increases resistance. About $900 to $1500 a set.
Check craigslist theres a set of 255 85 16 2 year old new for 400 never mounted.

Down there or up here? My 4.10s are starting to get tiresome

 

[Devon Harley]

Here an all try an find the exactly 400 set. http://sandiego.craigslist.org/csd/ptd/3420529964.html

 

[PwrSmoke]

I've fought the "4.10-3000-rpm-at 70mph" blues for 28 years now. 55 mph= 15-16+ mpg. 65 mph= 14-15. 70 mph=13-14. That's pretty much been it for 28 years just like clockwork.

Tread pattern makes a HUGE difference, so a highway ribbed tire will do the best and a mudder the worst. The problem is there aren't really any readily available taller tires than the factory 235/85R16s that aren't also wider. The wider part kills much of the gain you might get going taller. Taller also usually makes your aerodynamics worse, so you lose part of what you gain, if not all. Gear change, overdrive or go slower. Nothing else you can do will deliver a significant change, except reducing the weight of the truck. FOr me the gear change is the cheapest option because I can set up gears. Even with a shop doing it, it still might be cheaper than an overdrive depending on where you go.

In the long run, though, you can spend thousands to save hundreds. Unless you plan to drive the truck a lot and for a lot more years, what you gain from the big bucks you spend may take years and years to get back. Swapping up to 3.54: gears would realistically deliver a 2-3 mpg highway gain at best. 15K miles per year @ 15 mpg @ $4/gal= $4000. 15K miles per year @ 17 mpg @ $4/gal= $3529. You save $471. A 4x4 gear change costs about $1000 full pop, out the door. 1000/471= 2.1 years to pay back the cost of the work in fuel savings. It works more in your favor the more you drive. And then, you might find a deal on the work. You can make it work for you but you should crunch the numbers. I watched a friend trade in a pickup in great shape that got 16 mpg and was worth about $5000 in trade for a $25,000 car that got 30 mpg.

 

[RLDSL]

If you put larger tires on around town you will inhale fuel and realistically, most folks spend a LOT more time on side streets than they realize It ends up taking a whole lot more fuel to get all that extra rolling mass in motion, and a lot more brake power to get it stopped THink of larger tires as adding 4 extra heavy flywheels. Yes they are great at storing energy once you get them going, but it takes a lot to get there and then once you get all that energy stored in them, it takes a bunch of energy to counteract the energy stored in them to get them to stop.

If you try to tow with larger tires you will really take a hit. BEst bet is to add an overdrive or Brownie. I have the best of all worlds, a full deep reduction range, stock range and over drive range ( double OD) with the ability to split all gears.. With a 4.10 rear I went from a best 14 mpg ( usually worse ) to 18-20 empty , and over 11 towing HEAVY ( better depending on the trailer )

 

[Kevin 007]

Taller tires will help if the width and weight doesnt increase very much. I can tell you that going from a 235 85 16 with stock wheels to a 285 75 16 with old steel 8.5 wide wheels lowered the rpms at highway speed considerably but at the same time the added rollong resistance and double the weight slaughtered the milage.

This is just what I did. went to a 285 75 16 and I wouldn't say the revs went down considerably but they did go down a bit. MPG stayed about the same, due to them being wider. I will be searching around for a set of maybe 265's that are taller.

 

[MUDKICKR]

Taller tires will help if the width and weight doesnt increase very much. I can tell you that going from a 235 85 16 with stock wheels to a 285 75 16 with old steel 8.5 wide wheels lowered the rpms at highway speed considerably but at the same time the added rollong resistance and double the weight slaughtered the milage.

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
235/85-16 7.9in 15.9in 31.7in 99.7in 636 0.0%
285/75-16 8.4in 16.4in 32.8in 103.1in 614 3.5%

i really cant say that would be a lot of difference, being the height of the 285/75r16 is only 1.1 inches taller, cause you would still divide that by 2 to get the height gain on the truck.

 

[MUDKICKR]

This is just what I did. went to a 285 75 16 and I wouldn't say the revs went down considerably but they did go down a bit. MPG stayed about the same, due to them being wider. I will be searching around for a set of maybe 265's that are taller.

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
235/85-16 7.9in 15.9in 31.7in 99.7in 636 0.0%
265/75-16 7.8in 15.8in 31.6in 99.4in 637 -0.2%


funny thing is is the 265s are shorter then the 235s, but not by much.