Ok.. I have a 2004, f150, ex cab, fx4. I just replaced the ****ty American Generals with Nitto Terragrapplers (295/70/17). by the way the truck does not have a leveling kit yet and doesn't rub a bit! After doing this I have some questions. I should have asked before I installed...haha

Q1- The tire dealer said to run 40psi in the tires even though the recommended pressure on the gas door is 35psi (for stock tires). Is this true??

Q2- Is my speedo off now?? It feels like it!

Q3- The f150 was never the quickest truck on the road but now its embarrassingly slow!! Is this normal and what can I do to fix it???

Q4- I think my shift patterns are off. Is this normal and what can I do to fix it??

Q5- I have been hearing a lot about piggy back systems like banks and bully dog... Whats the best bang for your buck out of all the piggy back systems?

 

Q1 - No, but he is a little low also. I would run them at 45 as they are a LR D with a max of 65. The 35 on the door is only for the same type of tire that came OE. A P series tire with a max of 35.

Q2 - yes your speedo is off. You can go here and find out by how much. http://www.discounttire.com/dtcs/infoTireMath.dos

Q3 - Yes, as you went to a larger tire, you now have a higher gear ration, meaning slower on acceleration.

Q4 - If you get the computer reprogrammed, with the correct tire size, this might help. However, you will probably have to buy a programmer as the dealer can only input certain sizes, and I believe the largest is 275/65R18, a good bit smaller than your tire.

Q5 - can't help.

 

Thanks