SCT tire size adjustment

[NosMan]

If my tires are 34.5" inches tall what do I set my SCT tire size too?

I don't understand the minus/plus system on my Livewire. Thanks for the help

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[redsmoke]

I dont have the livewire but I set my X3 up by putting tape on my tire and on the ground. Then pull foreward till the piece of tape on you tire has gone a full revolution and is back to the ground. Mark that spot and measure back to you first piece of tape on the ground then divide that into 63360. I got the same size tires you do and I get 615. So that is what I set mine to.

[NosMan]

Thanks much appreciated...

Seems like a lot of work, why not make it easier for us like Superchips flash paq. You just select the tire size you have on your truck (ie 34.5") and it does the rest.

Don't get me wrong, I like everything about the SCT except this option.

[Goose350]

Or you could just Google a tire size calculator.

[Dave]

Originally Posted by Goose350

Or you could just Google a tire size calculator.

Yup thats easier. Google a revolutions per mile calculator or go to the tire manufacturer website and see what their specs sheet says for that tire and size.

The reason SCT doesnt do it like superchips is the fact that not all 34.5 inch tires are actually the same size

[tmanscrew]

Do you have to play with the numbers on the SCT to get the speedo calibrated when you change tire size? I have had to do this on the Edge Evo when I changed tire sizes and used the circumference of the tire, which is what the Edge uses, I had to play with the numbers to get the speedo to match my GPS.

[Dave]

The SCT does not effect speedometer calibration. And I dont believe the edge did either.

[tmanscrew]

Maybe is doesn't on a 250, but the Edge does on the 150, I know for a fact because I have done it on an Edge Evo on my 150. If it doesn't affect your speedo, what is the use in having a tire size adjustment on the SCT? I am not trying to be a smarta$$, just wondering why you would need to change it if it doesn't affect the speedo?

[Goose350]

Originally Posted by tmanscrew

Maybe is doesn't on a 250, but the Edge does on the 150, I know for a fact because I have done it on an Edge Evo on my 150. If it doesn't affect your speedo, what is the use in having a tire size adjustment on the SCT? I am not trying to be a smarta$$, just wondering why you would need to change it if it doesn't affect the speedo?

It corrects the shifting for different tire sizes.

[tmanscrew]

Gotcha, Goose, wasn't thinking about that! At what size does that become a real big issue. I am going from stock 275/65-20's which is 34.1 to a 315/70-17, which is a 34.6" tire. Seems like I read somewhere where it becomes critical when you get above 35's.