Need help with speedo being off

[Notorious2409]

Looking for some help with getting my speedo to read correctly after uploading a tune. so far i have tried 11 different rev/mile combinations with my gear ratio setting and still cant get this damn thing to read correctly.

The best i can manage is getting my speedo to within 5 MPH off but using the 3:55 gear ratio setting at 750 rev/mile setting. i looked at a rev/mile calculator online after punching in my rear tire size 295/30/20 it gave me a setting 748.2. i used 750 in my SCT (because you cant select 748 number) with my correct gear ratio of 3:31 and that put my speedo at 10 MPH off. How i am judging my MPH is by using a GPS MPH app on my iphone.

Is this something i am just going to have to try every single rev/mile setting in my SCT tuner with every single gear ratio setting until i find the "fix" ?

Thanks in advance for any help.

 

[01yellercobra]

Is the overall diameter of your current tires taller or shorter then stock? Have you looked on the manufacturer's website to see what they say the revs/miles are? They might have a different number then the calculator you're using.

 

[ctgreddy]

When I put that tire size into the calculator I use I got 771 rev per mile. I'd try and up your revs and see how close it gets.