When I ordered my truck it came with 17" alloy rims and the street Pirelli tires. I hated the way it looked so I got me some factory 20" on flea bay and put BFG AT TA KO 285/65/20 E's on them.

These tires are shown to be 34.7" in dia. The tires that Ford puts on the 20" are only slightly smaller than that, but these tires are some what bigger than what I had stock.

I am going tomorrow to have my speedo re-calibrated. Should I have anything else re-programed? Like the transmission or anything?

Thanks

 

I believe if you have the dealer recalibrate for the tires, that should cover the shifting too.

 

Thanks, I just don't want to have to go back for another trip to the dealer because I missed something.

 

leave it alone...it wont make any noticeable difference plus these trucks read high from the factory as it is. if you take it in they will probably use the bigger tires as an excuse to refuse warranty work in the future

 

yea i wouldnt bother if it isnt that far off. i mean mine hasnt been recalibrated and i have 37's, its like 10% off or so but since i tend to speed i just go the speed limit on my speedometer.

 

Heh...from what I've gathered here in the forums, you are right on the line. The computer has a low-end limit of 600 tire revolutions per mile (TRPM). Your new tires look like they clock in at 599 tire revolutions per mile.

I, personally, would suggest getting the reprogram done. The TRPM value is used in calculations throughout the entire operation of the vehicle. Not only are your speedometer & odometer linked to it, but there are also those "behind the scenes" systems like ABS, transmission operation (torque converter slippage, as well as shift points). Depending on the dealership, they will probably hit you for 30 to 60 minutes of shop labor...for what is actually about one minute worth of work, if the person with the computer knows what to change.


The dealership needs justification before they can refuse warranty work.

Yes, the tires are slightly larger than the factory (34.1" vs. 34.6", 609 vs 599 TRPM, 64 vs 68lbs.), but it is a pretty minor change. The dealership would be hard pressed to truly build a case on that. And, they must be able to build a case that the aftermarket product in question was directly responsible for the failure of an OEM part/assembly.

If it ever did come into question, I think that just about anyone could get their dealership to see how similar the OEM optional 20" tire & the tire that DoorKicker is getting installed.

 

I tend to agree with your opinion. My truck is brand spankin new. I want to start off right.
Plus, I figured that if I DON"T re-program, and then have a problem down the line, the dealer might be more likely to blame it on the tires.
If I had changed from the tire that comes on the 20's to these, I wouldn't see a reason to change anything, but remember my truck had even smaller tires that come on the 17" rim. Way too small a tire IMO

Thanks guys

 

Check your speedometer with a GPS unit or another car if possible. I put 35x12.5R20s on my truck and the speedometer is only off by 1mph at 75 going by my nav unit reading.

 

Well I had it done today. $90 bucks later and I feel better about it and even if I do think I paid too much for the labor. My truck reacts different now too. More responsive to the pedel like when I had the smaller tires. I would reccomend it to anyone with larger tires. Unless you have some type of tuner.
I think I made the right descision.
Thanks for the input

 

i am sure the dealer is happy with your desion as well...

 

They are definetly happy that I made this descision AND that I chose their dealership to have it done too.
It was the third dealership that I went to and they seemed the most eager to do the "Work" i.e. plug up their computer and push some buttons, and knew exactly what I was talking about when I mentioned it.
The other two said it would take like three hours minimum, and wanted me to make an apointment. This particular one said it was very simple, and that they only charged a diognostic fee! I guess they don't touch a PSD for less than $90 bucks??
I chalk it up to a bit of a pricey piece of mind.....maybe it wasn't nessicary, but I feel better having it done.