I'm looking at putting the BFG 285/70/17's on my truck next week. Currently i have the 265/70/17 tires with the 3.55 rear end. Will i see a big difference in performance or only slightly? I drive some light off road but mostly highway.

Also, if i change to a 3.73 or the 4.10 diff what are the down sides of doing this? I was thinking the 4.10 would be turned into a 3.73 with the bigger tires. Is this correct?


Thanks,

 

I doubt if you will notice a difference, especially if you have a 5.4. You are only going from a 32 inch tall tire to a 33 inch tall tire.

 

If you install 4:10's and then go to a larger tire, you will ineffect increase the ratio (increase ratio - lower number). Now, I know you probably already know this, but it won't increase to a certain specific number like 3:73, but rather whatever it calculates out to. For each increase in tire size (10 MM) you are looking at increasing the ratio around 7. So you could go from a 4:10 to around a 4:03.

Based on that, if you are running 3:55's currently and went to a 3:73 setup and went up 3-4 tire sizes, you will be roughly the same as you are now..

Clear as mud?

 

I have some experience with gear swaps (had them done twice on my jeep). Anyways, I would probably advise you to NOT do what you are thinking. Playing with the numbers like that can be a real pain in the butt and unless you are spending some coin to have someone run all the numbers for you from the tranny drive ratios, to the axle ratio and then the tire changes, you will be in for some challenging times. It's not end of the world challenging, just can be a little frustrating and you might get into that "what the hell have I done!" mode..

I am also going to go with 285's on my next set of tires and I don't foresee too much of a difference.. It's only about a 3% increase in tire size, so expect about a 2-3% loss in performance..

You really won't feel that too much... Maybe when starting from a stop and some passing power, but not much...

 

Nice truck Wandell!!

what made you get the lift kit? Your truck looked great with stock height. Don't get me wrong it looks even better now...just curious.

By the way, thanks for clearing up the backspacing confusion that I can never seem to understand... more space= deepdish.

keep up the great work informing us fools(me).

B

 

Wouldn't that be less backspacing = deeper dish?
From the picture Wandell posted, it looked like he was measuring from the back side of the wheel.

 

I have a '03 Scab and went from 235/16's to 265/18's with no problems in the clearance department...but running a 3.55 L/S threw everything out of wack...Shift points,MPH on speedo.etc....That was corrected by the 9100 programer from Mike at Troyer Performance...It won't spin the tires off the line but 2nd gear goes a long way..raced a chevy the other day and he was going into 4th when I came out of 2nd and I just kept pulling away

 

Right, the LESS backspacing the have the more the wheel "sticks out" and the more "deep dished" the wheel looks. As for as my lift, I just couldn't stand the thought of the truck being at stock ride height like every other Screw in town. I just had to have the first lifted Screw in town.

 

The BFG AT KO weighs quite a bit more than any the OEM tires. More weight farther away from the center of the wheel means more inertia to move. I am not please with my 285/70R17 BFG's in terms of performance hit.

 

Thanks every one for your help!.

APT,
I know what you mean. Believe it or not I went from factory P265/70/17 tires to Cooper LT265/70/17's. I never would have thought that i could physically tell a difference in the weight of the two tires. Take off, braking and overall ride were effected. The tires just felt hevier. I guess there is more material in the tires to make them stronger than the passenger tires.

Thanks,

 

1sawtooth...
U went from car tires to real truck tires (LT). That is why you can tell a difference. i have a hard time understanding why Ford puts car tires on a truck....especially a 4x4.

I have 285 70 17 BFG ATko. I lost 2 mpg by going up 2 sizes and from "P" rated to "LT" rated. Gettin' those damned Goodyears off my ride was worth it. But, I got 1 mpg back by replacing the stock muffler with a 18" glasspack and 1 more mpg by using the SuperChips 1715 programmer.

I didn't notice any change in performance, only in mileage. Well....the performance of the tires was way noticeable. Waaaaay better with the BFG's. You can actually get traction with BFG's.

 

Oh yeah, someone asked about tire scrubbing and trimming the valence. I put the 285's on before I cranked the torsion bars and never had any scrubbing. I only cranked the bars to level out the truck.
You won't have to trim anything unless you go to 315's on the stock wheels. That will require cranking the bars and a little minor trimming. .

 

RebelYell,
Thanks for your help. The tires should be here by Friday and I plan to purchase the programer in two weeks. By the way, how do you crank the torsen bars?

Thanks again!

 

1saw... I have the same question as you:
Somewhere out there someone has to have detailed pics about adjusting the torsion bars. I looked all over, but couldn't find any pics. I'm new at all this stuff(don't laugh, I know it's easy, I just don't want to mess it up), hopefully someone can remember where good photo's and directions are so me and 1saw can bust this out and move on to our next challenge.

 

Nice lookin truck.

How wide is the tire tread on the 285's. Those tires looked pretty good on the stock wheels. I was thinking of getting 33" x 12.5" tires, but your tires look pretty good.