fredlo69

I went from 17inch wheels to 20 inch rims, do I need to adjust anything.
I have a C&L cai and diablo predator tune. Do I need to adjust the speedo.

teksp0rt

it depends upon wheel tire combo i guess. if your overall diameter of the tire changed then you might want to consider it..

check out this site: http://www.1010tires.com/TireSizeCalculator.asp

it will give you an approximate speed difference based on overall diameter / circumference of the wheel.

fredlo69

thanks,
Now What do i need to do to adjust the speed?

fredlo69

If I recall is there something i can adjust with the predator so i can get the right speed reading?

thanks all for input!

Scotty07

I'm not familiar with what the Predator can do, but I do know the SCT can adjust for both rear gear changes and tire rev's per mile. The tire manufacturer usually shows rev's per mileon their spec chart. The taller the tire, the lower the rev's per mile.

chronism

Is this something that can be done at a Ford dealership?

Stkjock

yup!

fredlo69

Thanks- fellas,
I used the predator and adjusted the speedo it was a bit behind about 6 mph.
Used the rev per mile adjustment. Work liked a charm.

fredlo69

chronism

So can one use one of these "predator" or other to adjust a non tuned, factory system to fix a speedo registering too fast? If so, will that fix the odometer that is turning more than actual due to speedo? Where would I buy one?

fredlo69

Its costlly if you just want it to fix the speedo.
Ford can probably fix for a lot less.