Wanting to switch to 285/75R16 or 255/85R16???

[TRodney]

Will my mpg decrease if I switch to the larger and heavier 255/85R16 tires? Also, I have noticed that the selection is a lot larger if I switch to the 285/75R16. I would appreciate anyones experience with running either of these size tires with respect to there milage. Both of these tires will be heavier and I am assuming that the larger diameter (approx. 33") will increase my milage, but I am not sure about the additional weight.



Getting ready to purchase some 285/85R16, please let me know if I should do this?



Thanks,

Tim

 

[jsimpson]

Check with your tire dealer's charts. 285's are way to wide for 6" rims. The center of your tread will wear rapidly.

 

[TRodney]

I thought the same thing until I noticed them on a few different trucks with stock rims.



I contacted Discount Tire and they said that they will fit without any problems.



Has anyone running 285/75R16 on stock rims observed any wear problems??



Thanks,

Tim

 

[ChesterRam]

I too am interested in the MGP ramifications of the 33 inch tires.

Does it make any difference?



Or are the folks running these bigger tires mostly after "cool looks" and "horsepower?"



Chris

 

[BK]

my tire guy mentioned that they will fit no problem too... but may see more wear on the center ribs of the tires with ~6" rims.

The narrowness of the rims, pulls the beads in, pulls the sidewalls in and trys to pull the edges of the tires in, causing the center to buldge a bit.



Each tire manufacturer, for each model and size, will recommend a minimum wheel width.



Bob

 

[TRodney]

Come on Guys (and Gals)! We can always run the 255/85R16s or buy new rims, but we are mainly interested in the MPG results of running these larger tires.



Can someone running these larger tires let us know about the MPG??



Thanks,

Tim

 

[BK]

My past experiance when changing from stock size Radials to to 33x12 size radials was that I lost about 1 - 1. 5 mpg. This was on all gassers. V8's, V6's and 4bangers...



I havent put a set on my Ram yet due to $$ issues...



With the larger tires there is more rolling resistance, usually the tread pattern is more aggressive causing even more rolling resistance. Since these tires are wider tire their contact patch is bigger, with less psi to the ground patch... to make them better in the rain the compound is usually sticker, so again, more rolling resistance.

All this out ways the fact that you've raised the gear ratio and would expect better gas mileage. . (making 4. 10 seem like 3. 75 by making the tire taller)



With all the low end grunt on our oil burners, I too wonder if the use of some of the un-used torque (while not towing) will show up as more fuel being used... .

I know I saw it on my gassers... . but with the oil burner. . ?

I see no reason it should be any worse than the gassers.



Bob

 

[TRodney]

Yes, I agree that bigger and heavier tires on the gas trucks which have less torque and power cause a decrease in MPG.



But, what about the MPGs for our diesels?



Also, any information on the milage for the 19. 5 tires, which are similar in height, would be appreicated.



Thanks,

Tim

 

[BK]

For my use, which is towing offroad and need floatation, I dont like the 19. 5" tire.



For towing on road I see some great advantages, mostly in a more rugged an stable sidewall.



Not sure about tire weight Vs rim weight...

I know there's less mass to the tire, but the rim grows...



If the overall tire/wheel combination of the 19. 5" rims reduces the spinning weight, sounds like it would be a win/win all around for an on road towing combination.

 

[BCFAST]

tall tires

It seems to me that if you go from a stock tire up to a 33 or so, you are looking at fewer revolutions per mile and thusly less engine RPM at 70mph (the same effect as an overdrive unit). You will lose low end pulling power, but we all have wonderful torque and unless you're running around at 20k lbs, it shouldnt really be a biggie. As someone above mentioned, there is the issue of rolling resistance; the taller tires have a LONGER contact patch, and wider tires have a WIDER contact patch. Something to be conscious of: with tall sidewalls, you wont be able to hammer an on-ramp like you used to! It's the fulcrum length from the tire bead to the treadblock that will cause the sidewall to 'fold under' during too-hard cornering. Look at a Porsche or other sports car... the sidewalls are very short for that reason! The other thing mentioned above was weight. A heavy set of wheels/tires will make a vehicle ride very smooth... absorbing road imperfections easily... . but they wont stop-turn-go very well... . important on a 2200lbs race car, not an issue on a 7000lbs truck.

 

[LSMITH]

The concern about uneven wear on the 285's with factory wheels is unfounded. I have over 60K miles on with BFG A/T KO 285/75/16's on. They wear great, over 45K on the first set. They fit fine on the stock steel wheels. "Things" have changed on my engine and I really don't remember what the MPG was like with the 245's so I can't tell you what it will do to your MPG's. I get over 20 MPG easily on the highway at less than 70 MPH now. I turn right at 1500 RPM at 60 MPH with the 3. 5 gears so if you tow heavy you will want to stay with a shorter tire if you have the 3. 5 gears.

 

[BK]

LSMITH,



Gald to hear it, my tire guy said that it may happen since the stock rim width is less than specified by BFG... but he never said he saw it. And it makes sense, but it's most defenitily a matter of degree, and you just proved that it isnt noticable on the stock 6. 5" rims.



Can you do me a very large favor, you are the only one I know with the 285's on stock rims, and the same year truck I have...



Are your rims the metal chrome 6. 5" wide ones?



If so can you measure the hieght from the ground to the top of the tire? can you also measure the trear width. . and kinda eye ball / measure / estimate the width of the side wall to side wall. .



would appreciate it.

I haven't found great coralation to BFG's listed size Vs listed real size VS what they really are.



thanks

Bob

 

[JSoloman]

I'm running 285's BFG MT's and am getting 20-21 mpg empty. I'm stuck on these tires, have been running them for years.



Jen

 

[CumminsAholic]

I gained almost 2 mpg when I went from my stock 245 75's to the 255 85's. That's the honest truth. BUT... I have 4:10 gears. I believe that is the reason I gained. It's like I now have a 3. 73 ratio. If I had 3. 55's I dunno what would have happened. I think I would have lost because I'd have too small of a ratio. When I first bought my truck, it had 22k, I got 15 mpg. Now (35k) with my mods, I'm up to 18, I can get 19-20 if I hold it at 60 for a full tank. The tires made the biggest single improvement out of all the mods. Can't wait to get a timing box, over 20mpg, that'd be great. FYI, I also gained a few mph in the quarter with the 255's. The only bad thing with the tires is because they're so narrow they wear fast. At least mine did, I had an offbrand 45k mile tire, well I'll be lucky to get 10k out of them. I'll never buy an off brand again. They were Chaparral, junk IMO.

Corey

P. S. I have a set of BFG 295 85's AT KO's in the garage waiting to go on, I'm interested to see how the width affects mileage. So actually I won't get 10k out of the 255's, they're gettin smoked off.

 

[MUDDY]

255s gave me no less mpg. just figure odo and speedo error and drive 60 on the speedo to go 65. i have 3. 55 gears. i do shift down out of 5th od sooner with the 33. 5 inch tires, when i am pulling a heavy trailer. a guy i know with 4. 10s gets better mpg since he wnt the 255 tires.



on some gas rigs ive had, mpg went to heck with the 255s cause you had to put the hammer down all the time. 36 inch buckshots on a ford 460 i had turned it into a dog. even with 4. 10 gears. even empty. bad deal. 36 inchers with a cummins with 4. 10s work great.



either a 255/85 or 285/75 work well for a great all around tire, either loaded or empty, on or off road. especially the BFG. imo

 

[Ted Constantine]

I have run 255's and 295/75s (currently) I am very happy with the 295 BFG AT KO. I used to be able to break my tires loose on a damp highway at full speed with my 255 bfg mts but the ATs grip like nothing I have ever seen. I have never lost milage as I have 4. 10s. They run at 3. 9ish with 33. 3 or 33. 4 tires repectively. I am worried about the 295's come winter



the gear ratios comparison is from my 265 stock tires

 

[Dave MacArthur]

I've checked my mileage every tank since new. I have had Dunlop Radial Rover RV 255/85's for about 11,000 miles. My mileage is exactly the same. Averages about 17 mpg (including 10% correction). I have a '99 auto with the 3. 54 gears. I am very happy with this combo. No difference cornering, excellent rain traction etc. No visable wear so far. They have a 60k mile warranty. Very impressive warranty compared to all the other tires I looked at.



Dave.

 

[Cooker]

Dave MacArthur,



Are you sure the RV's have a 60k mile warranty? I thought it was only the AT's.



Thanks,

Ryan

 

[DarrellB]

If you do

If you do put the 285/75/16s on the stock 6. 5" rim don't buy a cheap tire. I have a 99 quadcab 4x4 with 4:10s and a 5spd, when I bought the truck I got the biggest tire that dodge would let you get 245 something. I put about 1,200miles on them and traded them in at a local tire place for some summit wildcountrys. The summits were 285/75/16s and I only got 11,000miles out of them. I went and bought a set of 285/75/16 Big O BigFoot XTs and only got 13,000 miles out of them and with the 285s when towing heavy loads you could watch the sidewall roll on the rim in hard cornering. I now have 33/12. 50/16. 5 BFG Mts on 16. 5x9. 75 inch Weld RoadHawk rims and love the combo, works great when hauling or unloaded. I have about 27,000 miles on them and hope to get about anouther 13,000 or so out of them.



My fuel mileage has gotten better with the bigger 33s, getting around 22. 3 mpg unloaded running about 70 down the highway and pull less rpms at that speed to. The only down side is when you start to get these tires spining they get sticky and like to wheel hop.



Sorry for the long post but I thought it might be of help.

Big D

 

[DieselDoghouse]

Your Mileage may vary...

On a '98 with 4. 10 gears I found I did NOT change my mileage going from the stock 245's to 285/75R16 BFG AT/KO's. I suspect possible reasons:

1. Fatter, heavier tire should drop mileage

2. Larger circumference should raise mileage

3. Alloy rims are lighter, lower rotating mass should raise mileage

4. better tread = less tire slip, raise mileage??

So why bother? Handling is improved esp. on rough or grooved pavement. RPM's are down 150 - 200 at 'pike speeds. Reportedly, the 285's would give better life for SAME tread style in 245's.

I did use the Tru-speed unit to correct speedo and have had no erratic gauge, shift point, or flashing ABS problems. All connections were soldered into Duetsch automotive connectors while the Scotchlock connectors were thrown over the shoulder as far from the truck as possible!!!