Diablo Intune speedo help

swollpatrol · February 5, 2016

Hey guys I just bought and tuned my truck with the Diablo Intune in running 35/12.50 on 20s but when I put that in my speed adjustment and re program it my speedometer reads 40 when I'm going like 60 does anyone know the magic number for the tires I'm running to ge it correct

SILVER SLED · February 6, 2016

From what I remember, you can enter the tire size two ways. For example, 275/65 20 "traditional" measurement style, or you can just enter the tire height. If your in the tradional tire size screen and enter 35/12.5 20, it will obviously not be correct. You need to go to the actual height section and enter 35". And keep in mind a 35 advertised tire is not always 35", but it's usually pretty close.

Johnnynovo · February 6, 2016

I ended up taking a tape measure and measure the tires on my truck. I checked it with a gps speed app on my phone. This got me very close. It was further off when I used the factory height

swollpatrol · February 6, 2016

Ok so you think either measure my tire from or put in 35 in there and see how close it gets

Johnnynovo · February 7, 2016

Yep. You can try either one. Easy way to check is with gps or download a speedo app to your phone. My tires specs 34.1" from the manufacturer but only measure 33.5 on the truck. The 33.5 got me right on when I checked. The 34.1" was a little off at highway speeds. Only by 1 or 2 mph

SILVER SLED · February 7, 2016

^^^^

What he said. Tirerack.com is a good source for a tire spec. The slight diff in the spec vs actual is probably due to the tire squat once installed and on the ground.

CNC237 · February 8, 2016

Your most accurate is to mark the tire and the ground then move truck one tire rotation. Now measure from the original mark too the mark on the tire. This it's the circumference. Now c=pi*d so diameter=circumference/PI

This is the exact number to enter.