I have a 2009 Ford F-150 XLT (w/ Chrome Package) Supercrew 4x2 with P265/60R18 Michelin LTX A/S tires and chrome-clad aluminum wheels. (I don’t like my wheels.) If anyone is curious, the exterior color is Royal Red Clearcoat (Maroon). I want to change out the tires and wheels to fill up the wheel wells for a better appearance.

My Ford Service Advisor told me that I would need to have the computer reprogrammed to have the speedometer and other data to be accurate if I changed from my OEM tire size. He also stated that Ford only supplied dealers with the ability to program the computer for the following sizes: LT245/70R17, LT245/75R17, P255/65R17, P265/60R18 or P275/55R20.

I thought I wanted to move up to a 20” wheel with the P275/55R20 tires, but the calculator at http://www.miata.net/garage/tirecalc.html shows that the diameter increase over what I have now is only 1.4 inches. That is not a significant change. In addition, I have read here on the forum where folks have stated that the 20” wheels have too harsh a ride and were actually going back to their 18” wheels. Others have mentioned that they are moving down from 18’s to 17’s and using larger tires to get the same effect I’m after, filling the wheels wells up.

Now add into the mix that many of you are adding leveling kits, yet mention that your goal is to also fill the wheel well space.

I don’t want to add anything other than new wheels and tires if possible. I don’t want to add fender flares for sure. I have not selected new wheels or tires yet. I’m just getting started. I still need to get more educated on backspacing, etc. I found a wheel I like, but it is a 20” x 10” and it is noted that it is for 4WDs only. It has 7.125” of backspacing. I suspect this is the reason that is for the 4WDs only.

1. What are y’all doing in regards to tire diameter and speedometer calibration?
2. What is the maximum amount of backspacing allowed with the stock components?
3. What is the maximum amount of offset I can have and not protrude beyond the fender wells?

Please help me from making an expensive mistake!

 

get some 32s, they will look nice!!

 

Sounds like you want a street truck look but are unsure about how to accomplish it. I'd suggest going with a 305/40-22 or 305/45-22. Personally, I'd add a set of lowering shackles out back to lower the rear 2 inches and level the truck. As for reprogramming the computer to correct the speedometer, it is a good idea but you don't have to. If you don't, your speedometer and odometer will be off. How much depends on the height of your OEM tires vs. the height of your new tires. If you buy an aftermarket computer tuner, you can recalibrate for any tire height and gain a little performance.