Have a 2000 F150 4X4 that have P235/70R16s. The tires look pretty small and I was wondering how big I can go on the OEM wheels? Would 265/75R16 be okay?

The truck's used mostly for on road, towing a horse trailer on weekends. Thanks in advance...

 

If you go from a 28.9 (235/70) up to a 31.7 (265/75), you'll see a pretty good drop in perceived power, especially when towing. I went from a 30 to a 32 and I can really feel the difference. I don't mind but you might. Breaking effectiveness and gas mileage will go down as well. You're speedometer will be about 6 mph low at 55mph also. Some things to consider.

 

Yes, no problem, would match (width and height) of the "off road package". With the higher sidewalls I would recommend getting a LT, Load C or D, 6 or 8 ply tire, for firmer/safer handling.

 

Thanks for the sppedy replies, guys. But now you have me concerned about speedometer recalibration and more importantly, changes in performance.

So, if I go to a bigger tire, is there going to be a performance hit?

 

Yes, due in large part to changes in effective gearing ratios, and in small part to changes in rotational unsprung mass (heavier wheels/tires).

You are lowering your effective gearing by about 10%. This is the same as going from a 3.73 rear end to a 3.39, or from a 3.55 to a 3.23. You could compensate with a higher geared rear, such as a 4.10.

The other physics involved can't be as easily compensated for. To compensate for the larger rotational diameter you can mount F250/Lightning rotors. The effect on ride quality is difficult to fix. You could go with a softer sidewall of a "P series tire to allow more flex, but this also negatively affects the load capability, durability, and handling.

If you do go with larger tires (especially +10%), be sure to have the dealer burn a new calibration code for this tire size into the ECU. It controls the shift rpm points, timing, A/F ratios, etc.

I, too, like the look of a beefy tire filling out the wheel wells. I just don't like the performance hit I'd take in doing so.

 

I just upgraded to LT rated tires from the lame 235/70 stock due to the fact that I tow a 5K# 5er. The ones I settled one were BFG 245/75 and although I haven't towed yet I was surprised that the power loss was minimal. I am running 45PSI when not towing and they will take 80PSI. I did like the way the smaller bumps were taken and it firmed up cornering some.

Next is shocks.

 

I put BFG All Terrain TA 285/75/16s on my 97 F150 w/ no problems at all other than the fact that my speedo is off somewhat. I notice no performance hit at all.

The BFGs w/ that much tire on the road give me unbelievable traction in rain (needed here in FL). The goodyear 235/70s I had prior were crap and my rear end was always in the other lane around corners in the wet.


Here's a pic


https://www.f150online.com/galleries...=9377&anum=976

and one from the side

https://www.f150online.com/galleries...=9403&anum=976

w/ a 4x4 i doubt you'd have clearance problems if i don't

 

Normally I would agree 100% with this post however. . . . .

Ford specifacation for 16" OEM tires on the F-150 WAS 255/70-16s. The only thing they changed other then tire size was the speedometer calibration when they made the change to 235/70-16.

The reason that Ford changed the size spec was:

1. Firestone problems, when Ford had it's massive tire recall it also discontinued the use of Firestones on all it's North American market vehicals. Ford had the other tire manufactures step-up and supply them with tires (255/70-16 was among these) Of course there were MILLIONS of tires involved in the recall.
In order to help relieve the pressure on the tire manufactures (of coming up with so many tires in such a short period of time (for the recall vehicals as well as NEW models) Ford made a switch to the less poplar but readily available 235/70-16.

2. This switch also cuts cost as the smaller tires are cheaper.


Go ahead and make the switch to some real tires.

It drive me nuts to see an otherwise fine F-150 running around on tiny little econo car size tires anyway.

 

How do you calculate the power loss for tire changes? I like the way the 285/75/16 tires look on this truck, and I am considering this size for my 2001 4x4 Supercrew. The current tire is 255/70/16.

Snoopy's comments about power loss worry me though. I do some towing, and do not want to sacrifice power for looks. I am also considering 265/75/16 tires which have almost exactly the same diameter as the stock 265/70/17 tires on 2002 FX4's. I dont hear any 2002 owners complaining about power. Whats the deal? The Ford specs must be different for the 4x4 Supercrews with the 4.6L

 

i have a question about this myself would a 33x12.50 be too wide for the stock 16 in rim my truck is a 97 4x4

 

My truck has 285/75 BFG's and I tried to get all the dealers in my area to reprogram the computer for this size, but they told me that these are considerd "illegal" tires, and they can not do it. WTF is up with that?

 

When I changed to my ProComps I did not bother to get anything calibrated. I noticed a small decrease in power and I just kept in mind that my speedo was about 10% slow.

As far as your tires being illegal, I think they are full of manure.

 

the only law i could think of that you'd be violating is the law in some states that the tires cannot extend beyong the fender...

50% of the states dont have that...i dont know about wisconsin...i do know that in texas, its as big as you can get it...and you can apparentely get away with 52" military tires legally (as wide as you want)...see recent post...

 

I think what your tire dealer is refering to may just be company policy regarding tire manufacture recommended rim widths.

For example the tire manufacture may 'require' that a 285/75-16 tire NOT be install on a rim that is any narrower then 7.0" and no wider then 9.0"

It's a liablity thing that concerns then, and rightfully so. There have been many a lawsuit filed against tire manufactures and dealer on behalf of the families of 'victims' that experianced catistrophic failure that according to the lawyers was due to the tires. Doesn't matter how it was a veriation from the OEM, ie. speed rating, size or being mounted on a under or oversized wheel, they are just plain afraid of the lawsuits.

 

OK... I just found several calculators for gear ratio, actual speed etc. with tire size changes with the help of another member in a different thread here. www.intercotire.com

When I go to the gear ratio calculator and plug in my old tire diameter (16") and new tire diameter (17") and the factory gear ratio (3.73) it states:

the actual ratio = 3.51

the high ratio = 3.61
the new ratio = 3.96
the low ratio = 4.32

What does all that mean to me and my truck? I do know this about gear ratio, I had a 1978 camaro with a low gear ratio and I could burn rubber for miles, I sold it and bought a 1971 Z28 with 4.11 posi and could burn rubber for several feet at every gear for miles.

Please help.