I've read and hear of milage drops when going up in size from the stock 275/70/16's on a FZJ. Anyone have numbers to toss at that? Is it noticable with 285's or only at greater diameter changes of 305 and up?
MPG delta vs tire size
- Thread starter TroutBear
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Yea , go up a size you will not notice a big drop. Your more likely to see a milage drop with under inflated tires, or dirty air filter over one size larger. Its all the other stuff on the trucks that seem to make it added up. Like more weight , roof rack, ARB. The stuff you know you want but it will cost you in milage. You will see numbers from 12 - 14 but I would question anything more than that with the 285's.
get the tires LC's just look good with larger meats.
get the tires LC's just look good with larger meats.
C6H12O6
SILVER Star
I only have one tank on my truck with the new 285 Revos, and the mileage drop isn't that noticeable. Maybe a fraction of one mpg on the first tank.
They do look sweet, though.
They do look sweet, though.
Well I didn't notice too much of a drop. Kinda funny but my choice in oil caused more of a drop in MPG than the tires. The tires depend on weight and tread, I think an all terrain will fair much better then heavier blocked tread like my x-terrains. I have usally been getting around 11-12mpg average, city and highway.
I need to start a new thread after some more driving but I just want to point out my current switch from M1 15w-50 to Castrol 5w-50 has increased my MPG. Today was my first highway trip on the Castrol and already I've gone up to just over 13mpg on my drive to my parents home. I have not seen 13mpg since I bought the truck.
I need to start a new thread after some more driving but I just want to point out my current switch from M1 15w-50 to Castrol 5w-50 has increased my MPG. Today was my first highway trip on the Castrol and already I've gone up to just over 13mpg on my drive to my parents home. I have not seen 13mpg since I bought the truck.
cartercd
SILVER Star
The difference in mileage when switching to 285s is probably dependent on the type of driving you do. If you are in stop and go city traffic, the extra power required to get the larger meats turning will result in a mileage decrease. If you drive mostly on the highway you probably won't notice any difference and could even see an improvement. My commute is mostly on the highway, and I did not see a reduction in mileage when I switched to 285s - I still get 15mpg. Make sure you do the speedo correction mod (or use GPS) before comparing before and after mileage numbers.
Sorry to hijack but how many MPH will the speedomeer be off? I just got my 33's and if anyone would be willing to let me use their speedo, Id love to and would offer some payment for its use.
cartercd
SILVER Star
The stock 275 70R 16s have a diameter of 31.2". 285 75R 16s have a diameter of 32.8". This is a 5.4% difference, and thus your speedo will be off 5.4%. The Slee speedo correction gear is the easiest fix. For $40 you get a a speedo drive gear that has 31 teeth instead of the stock 32 teeth (a 3.2% difference). Your speedo will still be off by about 2%, so at 65mph your speedo will read 63.7mph. If you want your speedo to be right on, you would need to get a TruSpeed or Yellow Box (see write-up at http://www.ih8mud.com/reviews/fzj80-yellowbox.php)
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I dont really think the gear is worth it. And with the speedo being 200$, I think I can deal with the drag.
semlin
curmudgeon
the difference is based on tire circumference not diameter. for 285s it should be about 3.1% difference from stock. However, different types of tire vary in true diameter and your speedo is probably innacurate anyway. Using the highway 5 mile calibration my odometer is almost exactly 5% of on 285 BFG ATs
cartercd
SILVER Star
There is a linear relationship between diameter and circumference. So if the diameter is 5% larger the circumference will be 5% larger and the speedo will be 5% off.
NorCalDoug
problems solved daily...
my experience.
I'm running 315s right now.
On the highway, the RPM are lower. The speedo is low by 10% -- ODO is too.
I get better fuel economy on the freeway by between 1 and 2 MPG (based on GPS readings) than with 285 on the rig -- outfitted the same.
I'm running 315s right now.
On the highway, the RPM are lower. The speedo is low by 10% -- ODO is too.
I get better fuel economy on the freeway by between 1 and 2 MPG (based on GPS readings) than with 285 on the rig -- outfitted the same.
C6H12O6
SILVER Star
semlin said:
Not sure about this math. Where do you get the 3.1% difference? The circumference and diameter of a circle are proportionate (Dessert anyone? We're having Pi), so increasing the diameter by 5% does increase the circumference by 5%.
It takes a minute to wrap your head around the math of it all when figuring mileage the first few times after the upsize with the tires, but since the speedo shows a slower speed than reality by 5%, you need to add 5% more miles to the miles driven between fillups, no? If you drive an hour, you are really covering 60 miles, but the odometer only says you have gone 50-something. You need to add back in whatever the correction is for your individual tire/gear combo.
