has anyone with 285/70/17 tires lost MPG noticablly???

 

How are you checking your mileage? Your odometer is now reading wrong unless you use a Smarty to correct for the increased tire diameter.

 

i've always checked my milege by hand, cause its always alittle off from the overhead.... beside, i aint got the 285's yet either..

 

ive run 2 tanks since ive had mine. correcting for tire size, its almost no change. it read alittle better the first tank and a little worse the 2nd. i wouldnt expoect dramatic changes in either direction


btw, thats hand calculated and adjusting the odo reading by 3.5%

 

Good to see that some people are still honest about MPG figures. Get's real old with "my tires are bigger, heavier, wider, more rotational mass and I picked up 10 MPG" thread's

 

I ran the stockers till 40,000 then switched to the 315's for 20,000 and switched a buddy for his new 285's since he was traiding it in, i have not noticed a difference other than getting some power back that the 315's robbed but the BDTD took care of all that,setting at 70,000 now...15-17mpg so far. The 285's work great for hunting where i live and chains for them don't break da bank or yer back.

 

my truck is new so not broke in yet. First tank of fuel avg 13.9 2nd tank was with 315's and avg 14mpg figuring 8% underdriven.

 

The only way i think you will see any differance is how your geared. If your running (410s) gears auto trans,I believe 315s should help on the road for as lowering the RPMs. I know my new (6spd) needed biger tires i was tacking way to high on the road (325s) did help mine Dont get me wrong here im talking highway not city here.

 

I don't think the 285s are enough bigger to make a difference, however, I don't care what anyone says, I picked up 2mpg unloaded at 70mph when I went to the 315s. It keeps the tack below 2k. You break 2k rpms and the mpg drops like a rock.

 

For auto trans, I don't think you'll see much difference, maybe less mpg unless you have 410 axles and do much highway driving. The auto is geared for good mileage.

What you may be hearing is that G56 manual and 315s produce a much better 65-70mpg driveline ratio for mileage, getting you into the CTD RPM 2000-2100 rpm sweet spot and these tires, pumped up to 60 psi, can improve mileage 10 to 20% at the same corrected MPH. Of course the driveline ratio causes many to drive 5-10 MPH faster, which negates most if not all of the mileage gain. I get a corrected 2.1 mpg improvement (19 vs 16.9) in highway 70 mph driving over about 5000 miles and several tanks of fuel. If I hold it to 65, there is about a 2.9 mpg improvement (20.9 vs 18). And yes mileage seems to drop like a rock once its pushed over 2000 rpm. I suppose with a better mileage tire than the agressive 315 BFGs, the difference would be even more significant.

Your mileage may vary

 

I had my computer recalibrated by the dealer to the 285's and didn't see much difference after the switch, it was a little better but I got the new tires at 1000 km so that might be due to break in as well.

 

So would 285's on a auto with 3:73's get worse milege u think???

 

I don't think so.
Many people think these trucks are geared too low, especially on the highway I wish I had another gear.
Going 100 KPH (about 65MPH) I'm revving around 2,000 rmp, I wish it would rev a little less (but that's with a std trans).

285's are not that big, the factory puts them on the power wagon models.

 

You won't see a decease with the 285's. But if you go 315's and you got 3.73's and auto trans.......look out. Good for the highway but every day up and down driving will kill you. I know it has for me. Going back to 285's after the spring.

But those 315's look so good.....lol !

 

I am running 295s, and in town I get about the smae mileage as the stock tires. On the highway I did see an improvement of about 1mpg.