Tylerl66

I received my SCT X4 yesterday and my 5 Star custom tuning today.
When I selected my tune of choice I was still given the option to change tire size, idle rpm etc etc.... Which is fine. But I noticed my tire size was still at "stock" according to the custom tune I selected.

I sent my info in via the required form stating my new tire size.

Is this the case for everyone or was it just me?

rplatt2189

If you think it is incorrect insert your correct size

Tylerl66

I will when I reload the tune again.

I just don't understand why it would be if someone is already writing my tunes with my info

RLXXI

I think the option is there incase you decide to upgrade to a different size tire in the future, the main thing the tune does is change the timing and fuel control maps.

Tylerl66

Ok that makes more sense!

cfree

OP, I noticed the same thing when I loaded my tune yesterday. I went ahead and put in my actual rear-end ratio and bigger tire size just in case and the speedometer is almost spot on.

Tylerl66

I just did the same thing in my speedometer is between one and 2 mph off
But from what I learned on a thread the other day is ford sets your speedo to show your going faster than you really are so I'm not complaining

RLXXI

When I went up from a 30" tire to a 32" tire I compared the speedo to gps and it was dead on accurate, when I reflected the change using the tuner as well as IDS it made the speedo off by 2mph. So I changed it back, I like to know exactly how fast I'm traveling.

Per Ford docs: The speedo can be + or - 6mph to be considered within spec.
.

Tylerl66

I've tried above and below revs per mile and it either 4 slow or 2 slow
I wish I could get it dead on

RLXXI

Yeah the tuner does have a gap in revs/mi, When I ordered my custom tunes I specified stock for tire size.

Are your new tires 2" larger than stock? If so you could request a revision in your tune to that stock spec and then the speedo might be dead on like mine is.

I used IDS to reset mine but there again, my tune was written with the stock size to begin with.
.