I have a 2000 F150 XLT 4x4 4.6l with 3:55 rear end. I tow a 25 ft travel trailer. I just put new tires on and went to a little bit bigger tire. LT265-75-R16 Original tires were LT255-70-R16. I have noticed a little loss in power. Are my new tires making that big of a difference?

 

Yes it does.

Go to:www.bncoffroad.com

That site has a good calculator to show the difference. Although unless you tow everyday, I don't think I would change anything.

Good Luck.

 

That link doesn't even work. Maybe it's my pirated copy Windows.. hehe

 

Nope its not your windows. I couldn't get it to open either. Any other suggestions on where to get that info?

 

Yes, your "new tires making that big of a difference?"

Compare the towing capacity of your truck with the 255/70R16's to a "Off Road Package" , which has 3.55 and 265/70R17's. The 265/70R17 and 265/75R16 have almost the exact diameter.

 

Is the only way to adjust for that is change gear ratio? Or is there something else that can be done?

 

In order to bring back your truck to it's "stock" ratio, you'd have to put in some 3.73 gears. That being said, it's not really that much of a change IMO. Why Ford didn't just install 3.73's as standard, I'll never know!! My buddy has a 1999 4x4 ORP with the 17" wheels and he has the 3.73's, but I think it was an option.....

Have you recalibrated your speedo/odometer to "adjust" for the taller tires? (You have to have your computer adjusted. 97 and 98's use an actual gear in the tranny.)

This is just from my own experience, and I have a 97 with the 5.4, so it may not really apply, but once I fixed my VSS gear to make up for my taller tires, I noticed the truck drove much better. It shifted like it did when I had the stock tires on and actually felt better coming off the line too. I've not towed anything yet, but have had the bed loaded down a number of times, and it pulled pretty well up the hills I encountered.

Here is where I go for that "calculator":

http://www.bncoffroad.com/tire_gear_cal.html

 

Thanks Mitch for fixing the link.

 

Thanks for all your help. Just installed 3.73 back to normal now.

 

Ah man... you missed a good opertunity to go with 4.10's! Oh well....

 

I know, but the price was right for these so it was hard to pass up. 4.10's will be on my super duty when I buy it next year!