going from 265 to 285s

[fennsz]

I was thinking about going from a 265 to 285 tire. I know about the clearance issue and alignment. but can I expect worse gas mileage and any loss of power? Also considering a mud tire, does that make a difference?

[nhkid28]

I depends on if your truck came with 265's and which gears you have. My guess is that yours came with 265's because it is a Z71 so you will probably not notice any difference in power.  As for the gas mileage, if you have 265's and 3.73 gears and you change to 285's then you are changing your effective gear ratio to approximately 3.60 which would give you slightly better mileage but the bigger tire size negates that.  In other words it would probably stay the same. My quess is that the a more aggressive tire, such as a mud tire, will not alter the mileage by much at the most 1 mpg.

 

[fennsz]

thanks,

My original is 265 and I run 3.73 gears.

[mka18]

I use to get around 380 miles per tank of gas when I had 265's.  After the 285's I went down to around 320 per tank.  I have the 3.73's and drive pretty hard.  I'm thinking of switching to 4.10's here pretty soon to get back around the stock ratio.  If your an easy driver and don't tow anything the difference will be minimal.  However, if you have a lead foot and tow like me, you'll see a decrease in mileage.  The benefits out weight the loss in gas money though...  I didn't by a truck to save on gas money... :thumb:

[Shaners]

When you go to larger tires and if you don't reprogram your speedo/odometer, then you are actually traveling a further distance than you are recording on your odometer.

 

Your odometer will be off 3-4% so for every 100 miles you record on your trip meter, you will actually have gone approx 104, so you have to make the computations when you figure out your gas milage.

 

With that said, and if you make the correct adjustments to your miles.  Then I would say your highway MPG's should be close to what you are getting now (maybe 1 MPG less).  Your city driving would suffer more due to loss of torque at launch.

 

An aggressive tread, and a wider width will also reduce your MPG's.

[mka18]

Dang!  I've changed to larger tires on my last two trucks and never even thought to add the extra distance the tires will take me to my gas mileage.  I always assumed the tires I've added decreased my mileage that much.  I must have been so excited about saving a couple of miles on the odometer because of the bigger tires, I forgot the obvious.  I guess that's what the forums are for though.  Everyone needs another to make ‘em feel stupid every once in a while...

[RyanbabZ71]

also add in added weight of the tires.  I know my bfgs weigh more than the stock f stones.

[nhkid28]

I have heard that the speedo's in our trucks are not that accurate.  I have also heard of some people using a GPS to check the accuracy of them.  It would be interesting to see if there is a difference.  

 

If anyone has done this please post your results.

 

[Firetiger(MN)]

I have used a GPS to check my speed, but that was after I put on larger tires so I can't say if the speedo was accurate with the stock tires.  

 

By calculating what my speed should be and actually measuring it with the GPS, it does look that the speedo is very close.

[BDBWTE]

No probs going to 285's.  #### on a 2500HD I went from 245's to 285's and I noticed a little power loss.  But with 4.10's and a stick shift I bully the truck into it's power band and we move out smartly..

[WhiteHorse]

I got 285s on my 2000 LS extended cab.

5.3 with 3.73

they work great

they look great

[timk49]

I checked the speedometer with my GPS unit with the stock 245's  and it was right on at 70 MPH. I checked it again when I put the new BFG 285's on and when the speedometer reads 66.5 mph  I'm really going 70 mph. I have 4.10 gears and don't feel much loss on the low end but then I don't try spin the tires much anyway.