Hello All,

I recently had some new tires put on my 2003 F150 Supercab 4X4 5.4 and they are a little larger. I went with the P285/70R/17, they look really nice and the truck rides better. My question is I have seen posts about getting one of those "tuners" which will help adjust for larger tires etc., it it worth me getting one since I have the larger tires or should I not worry about it? Am I going to notice worse mpg or notice any shift changes?

P.S. I went with the Bridgestone Dueler REVO tires. I no longer "slip and slide" in the rain like I did with the Goodyear Wranglers.

 

I have the exact same tires as you.....they are really a great tire for everything I found.
If you had 265's on before you are gaining just over an inch in height (31.4 - 32,7) so your speedo will be out about 3-5 mph, so if you are cruising at 50 mph , your true speed will be slightly higher. A tuner will correct your truck and Ford could recalibrate it for a fee, I personally would go the tuner route.

What gear ratio do you have? The bigger tires will cause slower acceleration from a stop, and the shift points will change slightly from the added stress of turning a bigger tire. If you have 3.55's like me and the larger tires you will feel some power loss, another reason to get the tuner I think.

 

Thanks xtrford for the response. I have the 3.73 gear. I have been looking at the tuners but most of them are $300-$400 bucks. Not sure if it's worth investing in that or not. Maybe I will ask the dealer next time I'm in for service?

 

Tuners can almost pay for themselves since they can read the codes that trigger a check engine or ABS light. That, and your tire issue would be a simple adjustment with a tuner and then you would be set.

 

I have the same tires on my 1997 4x4 and yeah I think they are great as well! Your speedo is actually off by 2%
So at 100 its off by 2 mph
at 50 its off by 1 mph
If you check your mpg w/out compensating for the 2% then you will notice a difference because if you got 300 miles on a tank then its off by 6 miles. But if you compensate ie add 2% to your mileage when you fill up & divide by the gallons the difference is so small...

I looked for the calculator that said 2% and I could not find it, it used the actual tire dimensions ie compared 265.70.17 to the 285.70.17 and gave me 2%
I found a few that were all 3% but they used the less exact inch measurement.

Either way its 2-5 depending on what you believe. Just add w/e % you believe to your mileage and check it. I doubt it would be any real difference.

 

It is little bit more than you think. I found this from a previous thread, the site does all the calculation for you after you enter the numbers.

http://www.1010tires.com/TireSizeCal...?action=submit

came out to 3.5% comparing 265-285 p-metric tires.

 

We've been down this road before. IMO before you start playing the numbers game you'd be wise to do a Real World-Reality Check. My absolutely stock '98 odometer reads 3.4% off right out of the box, when compared to interstate mileage markers. I'd hate to have the computer reset for bigger tires, based solely upon the numbers, & possibly end up adding another "3.5%" error, when in reality it might have nearly zeroed it out!

Establish a baseline for comparison by checking your odometer against interstate mileage markers. A minimum of 10 miles, but much better to check against a 100 mile trip, in order to judge just how far off your odometer actually is. If you decide to reset the computer you should also confirm the accuracy of the change in the same way. It is the odometer reading that's used for MPG calculations, not the speedometer, which is a bit trickier to check. Interestingly, I circled & drove through a 50 MPH construction zone radar setup 3 times & could not see any difference-both indicators were right on 50.

I wouldn't worry much about "any shift changes" based soley upon the relatively small change in tire sizes, especially w/"3.73 gear". FORD invested plenty tuning things just the way they are. If you've got an extra "$300-$400 bucks" burning a hole in your pocket it might be worth it to invest in a tuner to monkey around with to 2nd guess FORD. I'd thought modern FORD computers were somewhat 'adaptive' adjusting to the way an owner drives? Judging by the generous size of the wheel wells I think FORD expected owners to put bigger tires on. When FORD tuner fans start consistantly boasting convincing numbers for significantly improved fuel economy I'll get interested. At this point most of the tuner bravado seems focused on higher RPM shifts that gobble gas & shorten drivetrain life.

 

No one here has stated "signifigant" fuel economy gains. Stick to the subject matter before you go off your wild tangents.

Shorten drivetrain life? Please, spare us from your pitiful logic of adaptive strategies and on Ford tuning.

 

larger diameter tires will let the motor run at a slower RPM dwon the road at a constant speed MPh. you would think that would relate to better milage. but turing those big tires will probably negate any increase in milage. probably will acutally be somewhat worse... try it first, at 3% off, probably not worth reporgraming the computer.

 

I'd suggest that you "stick to the subject matter" yourself & "spare us from your pitiful" attempts to suppress others' on topic opinions. Also try to quote members correctly. What I posted was: "When FORD tuner fans start consistantly boasting convincing numbers for significantly improved fuel economy I'll get interested."

You apparently struggle to read or spell & failed to quote correctly when you wrote "signifigant". IMO "here" happens to be a big place, not limited to this thread & "fuel economy gains" have been claimed both on this forum & by tuner peddlers. So far, documented "gains" remain fleeting & unconvincing, most often swept under the rug by excuses like; you'll be unable to resist stomping on the gas, thus erasing any "gains".

That, all other factors remaining equal, drivetrain life is directly related to how hard equipment gets used is not my "pitiful logic"-its a simple mechanical fact of life. FORD develops conservative compromise tuning that provides for power, economy & longevity. Monkeying w/tuning for power "gains" sacrifices economy & longevity.

Quantifying odometer accuracy against interstate mileage markers is very sound advice. If you think such valid comments are "wild tangents" on this thread, it is a reflection of your poor judgment, not mine. You can very easily "spare" yourself in the future by simply not clicking on, reading or responding to my posts.

 

i know in my 02 crew with the stock tire size my spedo was off by like 4-5 miles an hr but with my bling bling 22's its right on the money, verified by my gps. i wonder if my rear end gears have ever been changed by a previous owner hmmm??

 

Well, I have gained 2mph with my Predator tuner and have more power to boot. I have also cranked up the transmission global pressure and all shift firmness settings are at 100%. This eliminates the slippage between shifts and lengthens the tranny life. It was the best money that I have spent on the truck. Better mileage, more power, better shifts and tranny life, adjustability and live data diagnostics, it's a no brainer for me. If you can afford it, I would definately recommend it.

 

Club Wagon and xtrford.

I would like to make you aware of a feature in our forum called "ignore", so I suggest you click on each others profiles and select it

 

lx man (i miss my 1992 gt :.( can you give some more info on that tuner? does it help with towing? i pull a two place snowmobile trailer and sometimes my 5.4 seems underpowered, do you think a tuner would help?