Looking to see what problems popped up and what didn't if you changed stock tire size.


I have seen a few posts about navigation and speedometer issues and wonder how far from stock size is safe to go. Plus what was needed for leveling for those that went even bigger.




Just a general info, what size was stock, what size went to and any problems (and fix if you had one)


Not a this tire last longer, or is better in the mud, or looks better in wheel well thread (unless you want to give some background)

 

This is actually a great thread starter and will serve to b e extremely helpful.

I changed my tire size from the stock 235-17 to another stock size, 265-17 and lost about 1-1.5 MPG's. No issues with the speedo or anything else.

 

I had navigation issues BEFORE a tire change.
Disconnecting the neg battery cable worked for a few weeks, then it came back. I finally had the dealer reflash the GPS module around December and I haven't had any issues since.

I have a 1.75" increase in ride height up front via BOSS coils. I'm +1" out back via RAS.

On March 1 I went from the stock 275/55/20 to a 275/65/20 BFG KO2 (2" increase in size, 15lb increase per tire). My truck is re-calibrated for the rotations via a SCT Livewire TS+. My speedo is accurate within 1mph at 80mph (GPS checked). My mileage around town has taken a 1-1.5 mpg hit depending on my driving habits. My highway mileage is down just about 1mpg. My navigation issues have NOT come back since the tire change.

I track every fillup via Fuelly.com on hand calculations and noting the octane (I run 89 since it's lightly tuned) and noting what the lie-o-meter states on the truck. The hand calculations are typically 0.6-1.1 mpg LOWER than the lie-o-meter.

 

Went from P265/70-17 (38 lbs.) to P285/70-17 (51 lbs.)

Braking immediately changed and requires more pedal effort. Fuel economy has been dropping since installation. Acceleration is noticeably more labored and the truck holds lower gears now. From a practical standpoint it was a terrible decision. But I like the way it looks and I am no longer scared of cutting a flimsy sidewall in the middle of nowhere.

Cons - Less practical, not as safe to drive, more fuel

Pros - Factory calibration of "fuel economy" display is notoriously optimistic. The slightly taller tires slow the odometer down just a tad and it brings the fuel economy display into reality. Also, less likely to have a flat and less likely to get stuck while not on pavement.

 

2013 F150 FX4 5.0 with 3.55 gears
I went from stock P 275/65R18 tires to LT 275/70R18 tires. The LT offer a firmer ride but the 1" larger diameter messed up my on board navigation. I used a Hypertech speedo calibrator and put in the new 33.25" tire diameter. The Navigation still doesn't work correctly all the time, just sometimes, but I noticed this last weekend that the truck is traveling at 76 (Garmin gps) when the speedo is showing 80mph. I think I should hook the calibrator back up to be sure it did the tire size change correctly.

 

WXboy....what gears are you running in your truck? I was thinking of making the exact same change on my 2011 EB with Max Tow and 3:73 gears. But I tow trailers all the time. The heaviest being 8200 lbs. I don't want to sacrifice my performance too dramatically.

 

I went from stock 31.9" tires to 34.45" tires and after recalibrating the speedometer with my SCT tuner my navigation is still spot on.

 

I don't understand guys touting a drastic difference. I lifted mine 6" and put on 35s (actually 34.5") up from the factory 265/70/17 and it does have a different feel but I'm not experiencing any significant loss on acceleration or braking, while I'm sure there is a loss it's minimal and not seat of the pants noticeable. My mileage is down about 2 mpg from previous average and on open highway will still push 20 mpg......this is with 3.55 gears also I've left on the air deflector on bottom of front end alot of guys take it off for looks after they lift it doesn't bother me and probably does still help.

 

Forgot to mention my speedo is about 5 off now.

 

Some good info so far. I didn't know there was a SCT tuner to recalibrate tire size for the F150. I knew Mustangs did this, don't know why I didn't think the trucks would too.


Also I guess the navigation is not linked to the wheels size? I figured it might be as a "check" to location, but looks like maybe not with whats posted so far.

 

I'm pretty sure the tire diameter is used in the navigation system. Many folks have had the issue after increasing the tire size.

 

I've got 3.55s. There's really very little difference between 3.31-3.55 and 3.55-3.73. It's such a small difference that in overdrive it won't even register on our tachometers. Guys get too worked up over gear ratio.

My advice when buying tires is to buy the lightest tire you can find that still serves the purposes you need for your truck. That's why I stuck with P285 and didn't go with LT285.

 

I had thought about going to a taller tire would help gas mileage but I guess not. I got stock 265/70/17s

 

I went through this going from P275/55 R20 to LT275/65 R18.
It will affet the tire revs per mile.
Up to a certain size, Ford can change the TCM parameters. I don't know what the limit is.

SCT and some other devices can allow you to manually change the revs per mile setting.

There are a lot of factors in setting the correct rev per mile setting.. 1010 tires seems to have the best calculator according to Mike at 5Star Tuning http://http://www.1010tires.com/Tool...ize-Calculator This calculator seems to adjust for "tire squish" and provided me the best adjustment until my local Ford dealer finally got it right.

The Ford dealer looked at the tire size provided by running the VIN# and didn't actually put the actual tire size in the TCM. Once I found a tech to actually look at the tires and read the tire size, all went welll. The other alternative is to use the SCT or some similar device.

 

Didn't know Ford could adjust for tire size also. Good info.