Ive got the stock 275 65 20's, but im interested in going up to maybe a 295 or similar to fill out the wheel well a bit. wanna keep the stock rims also. will my speedo and odo be affected as usual? or is there a way to keep all the numbers accurate?

 

If all is as it was in the past, your dealer can adjust for tire size. A tuner can do the same.

 

dealer...great. as for tuners. i know very little on that subject. is that something i just plug in to the obdII port and can change settings there?

 

Yes, but I've only used them to upload tunes. Never did any settings myself. I'm sure someone who knows more than me will chime in....

 

thanks for all your info so far. youve been very helpful, especially with the bilstein deal

 

Anything I can do brother!

 

Your dealer can definately do it.
I thought most tire shops could do it these days?

And like Karl said, if you have a tuner you can do it yourself.

And adjust your TPMS pressure.

And looks like my truck needs a bit of cleaning / dusting, yikes

 

Actually, the dealers can no longer recalibrate speedometers outside of what is offered as factory equipment. I just went though that issue with my dealer. I have a 3.31 axle ratio. I went from 265/70-17 to 275/65-20. My speedometer/odometer were 7.8% slow (checked w/GPS) after changing wheels and tires. I thought this would be easy. The technician set up my new tire size. We went for a ride to check speedometer accuracy, speedo was right on. During the ride back I got a check engine light. The technician connected the laptop and discover that I had a transmission fault code. A quick google search turned up others that tried to do what I was trying to do. It was suggested to set the axle ratio to 3.55 to get rid of the trans check fault light. That worked. We got the fault code because Ford does not offer 20" wheels with 3.31 axle. Went for another ride to check speedo, speedometer is back to being 7.8% slow. We played with different factory combinations of tire and axle ratios to get the speedometer closer. Finally got the speedometer within 4% slow. We played with so many combinations, I do not remember what we settled with.

Long story short, you are limited to what is on your truck as factory option for speedometer calibration. The tech said they used to be able to set any combination of tire size and axle ratio, but on the newer trucks that is no longer possible. You can also use a Tuner to recalibrate your speedometer, but then there goes your warranty.

Hope that helps.

 

Thanks, that does help, I did not know that.
Learn something new here almost every day

 

is that something id have to leave installed in the truck at all times? or can i just "tune" things then store it away in my tool box or such

 

I'm actually not sure if you can unplug it or not. I use it to track EGT and a couple of other things so I never even though about un plugging it.

 

Why does egt matter in a truck? I use egt when flying to lean my fuel mixture control. But when driving i dont havr control over such things...so?

 

It means the same thing. And if you have a tuner you DO have control of it. I defuel at 1450F so I don't melt anything.

 

If you are towing with a tune or using a hot tune, if your egt gets to hot, you will be re and re-ing a turbo and possible heads. Egt is meant to warn you to back out a bit before all the carnage.

 

....so isnt that just a reason to keep it stock?